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Proposed Rule

National Emission Standards for Hazardous Air Pollutants: Proposed Standards for Hazardous Air Pollutants for Hazardous Waste Combustors (Phase I Final Replacement Standards and Phase II)

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Information about this document as published in the Federal Register.

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AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

This action proposes national emission standards for hazardous air pollutants (NESHAP) for hazardous waste combustors. These combustors include hazardous waste burning incinerators, cement kilns, lightweight aggregate kilns, industrial/commercial/institutional boilers and process heaters, and hydrochloric acid production furnaces, known collectively as hazardous waste combustors (HWCs). EPA has identified these HWCs as major sources of hazardous air pollutant (HAP) emissions. These proposed standards will, when final, implement section 112(d) of the Clean Air Act (CAA) by requiring hazardous waste combustors to meet HAP emission standards reflecting the application of the maximum achievable control technology (MACT).

The HAP emitted by facilities in the incinerator, cement kiln, lightweight aggregate kiln, industrial/commercial/institutional boiler, process heater, and hydrochloric acid production furnace source categories include arsenic, beryllium, cadmium, chromium, dioxins and furans, hydrogen chloride and chlorine gas, lead, manganese, and mercury. Exposure to these substances has been demonstrated to cause adverse health effects such as irritation on the lung, skin, and mucus membranes, effects on the central nervous system, kidney damage, and cancer. The adverse health effects associated with the exposure to these specific HAP are further described in the preamble. In general, these findings have only been shown with concentrations higher than those typically in the ambient air.

This action also presents our tentative decision regarding the February 28, 2002, petition for rulemaking submitted by the Cement Kiln Recycling Coalition to the Administrator, relating to EPA's implementation of the so-called omnibus permitting authority under section 3005(c) of the Resource Conservation and Recovery Act (RCRA), which requires that each permit issued under RCRA contain such terms and conditions as are determined necessary to protect human health and the environment. In that petition, the Cement Kiln Recycling Coalition requests that we repeal the existing site-specific risk assessment policy and technical guidance for hazardous waste combustors and that we promulgate the policy and guidance as rules in accordance with the Administrative Procedure Act if we continue to believe that site-specific risk assessments may be necessary.

DATES:

Submit comments on or before July 6, 2004.

ADDRESSES:

Submit your comments, identified by Docket ID No. OAR-2004-0022 by one of the following methods:

  • Federal eRulemaking Portal: http://www.regulations.gov. Follow the on-line instructions for submitting comments.
  • Agency Web site: http://www.epa.gov/​edocket. EDOCKET, EPA's electronic public docket and comment system, is EPA's preferred method for receiving comments. Follow the on-line instructions for submitting comments.
  • E-mail: http://www.epa.gov/​edocket.
  • Fax: 202-566-1741.
  • Mail: OAR Docket, Environmental Protection Agency, Mailcode: B102, 1200 Pennsylvania Ave., NW., Washington, DC 20460. Please include a total of 2 copies.
  • Hand Delivery: EPA/DC, EPA West, Room B102, 1301 Constitution Ave., NW., Washington, DC. Such deliveries are only accepted during the Docket's normal hours of operation, and special arrangements should be made for deliveries of boxed information.

Instructions: Direct your comments to Docket ID No. OAR-2004-0022. EPA's policy is that all comments received will be included in the public docket without change and may be made available online at http://www.epa.gov/​edocket, including any personal information provided, unless the comment includes information claimed to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Do not submit information that you consider to be CBI or otherwise protected through EDOCKET, regulations.gov, or e-mail. The EPA EDOCKET and the federal regulations.gov Web sites are “anonymous access” systems, which means EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an e-mail comment directly to EPA without going through EDOCKET or regulations.gov, your e-mail address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the Internet. If you submit an electronic comment, EPA recommends that you include your name and other contact information in the body of your comment and with any disk or CD-ROM you submit. If EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, EPA may not be able to consider your comment. Electronic files should avoid the use of special characters, any form of encryption, and be free of any defects or viruses. For additional information about EPA's public docket visit EDOCKET on-line or see the Federal Register of May 31, 2002 (67 FR 38102).

For additional instructions on submitting comments, go to unit II of the SUPPLEMENTARY INFORMATION section of this document.

Docket: All documents in the docket are listed in the EDOCKET index at http://www.epa.gov/​edocket. Although listed in the index, some information is not publicly available, i.e., CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the Internet and will be publicly available only in hard copy form. Publicly available docket materials are available either electronically in EDOCKET or in hard copy at the OAR Docket, EPA/DC, EPA West, Room B102, 1301 Constitution Ave., NW., Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The telephone number for the Public Reading Room is (202) 566-1744, and the telephone number for the OAR Docket is (202) 566-1742.

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FOR FURTHER INFORMATION CONTACT:

For general information, call the RCRA Call Center at 1-800-424-9346 or TDD 1-800-553-7672 (hearing impaired). Callers within the Washington Metropolitan Area must dial 703-412-9810 or TDD 703-412-3323 (hearing impaired). The RCRA Call Center is open Monday-Friday, 9 a.m. to 4 p.m., eastern standard time. For more information about this proposal, contact Michael Galbraith at 703-605-0567, or galbraith.michael@epa.gov.

End Further Info End Preamble Start Supplemental Information

SUPPLEMENTARY INFORMATION:

I. Regulated Entities

The promulgation of the proposed rule would affect the following North Start Printed Page 21199American Industrial Classification System (NAICS) and Standard Industrial Classification (SIC) codes:

CategoryNAICS codeSIC codeExamples of potentially regulated entities
Any industry that combusts hazardous waste as defined in the proposed rule5622114953Incinerator, hazardous waste.
3273103241Cement manufacturing, clinker production.
3279923295Ground or treated mineral and earth manufacturing.
32528Chemical Manufacturers.
32429Petroleum Refiners.
33133Primary Aluminum.
33338Photographic equipment and supplies.
488, 561, 56249Sanitary Services, N.E.C.
42150Scrap and waste materials.
42251Chemical and Allied Products, N.E.C.
512, 541, 561, 81273Business Services, N.E.C.
512, 514, 541, 71189Services, N.E.C.
92495Air, Water and Solid Waste Management.

This table is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be regulated by this action. This table lists examples of the types of entries EPA is now aware could potentially be regulated by this action. Other types of entities not listed could also be affected. To determine whether your facility, company, business, organization, etc., is regulated by this action, you should examine the applicability criteria in Part II of this preamble. If you have any questions regarding the applicability of this action to a particular entity, consult the person listed in the preceding FOR FURTHER INFORMATION CONTACT section.

II. What Should I Consider as I Prepare My Comments for EPA?

1. Submitting CBI. Do not submit this information to EPA through EDOCKET, regulations.gov or e-mail. Clearly mark the part or all of the information that you claim to be CBI. For CBI information in a disk or CD-ROM that you mail to EPA, mark the outside of the disk or CD-ROM as CBI and then identify electronically within the disk or CD-ROM the specific information that is claimed as CBI). In addition to one complete version of the comment that includes information claimed as CBI, a copy of the comment that does not contain the information claimed as CBI must be submitted for inclusion in the public docket. Information so marked will not be disclosed except in accordance with procedures set forth in 40 CFR part 2.

2. Tips for Preparing Your Comments. When submitting comments, remember to:

A. Identify the rulemaking by docket number and other identifying information (subject heading, Federal Register date and page number).

B. Follow directions—The agency may ask you to respond to specific questions or organize comments by referencing a Code of Federal Regulations (CFR) part or section number.

C. Explain why you agree or disagree; suggest alternatives and substitute language for your requested changes.

D. Describe any assumptions and provide any technical information and/or data that you used.

E. If you estimate potential costs or burdens, explain how you arrived at your estimate in sufficient detail to allow for it to be reproduced.

F. Provide specific examples to illustrate your concerns, and suggest alternatives.

G. Explain your views as clearly as possible, avoiding the use of profanity or personal threats.

H. Make sure to submit your comments by the comment period deadline identified.

Outline

Part One: Background and Summary

I. Background Information

A. What Criteria Are Used in the Development of NESHAP?

B. What Is the Regulatory Development Background of the Source Categories in the Proposed Rule?

C. What Is the Statutory Authority for this Standard?

D. What Is the Relationship Between the Proposed Rule and Other MACT Combustion Rules?

E. What Are the Health Effects Associated with Pollutants Emitted by Hazardous Waste Combustors?

II. Summary of the Proposed Rule

A. What Source Categories Are Affected by the Proposed Rule?

B. What HAP Are Emitted?

C. Does Today's Proposed Rule Apply to My Source?

D. What Emissions Limitations Must I Meet?

E. What Are the Testing and Initial Compliance Requirements?

F. What Are the Continuous Compliance Requirements?

G. What Are the Notification, Recordkeeping, and Reporting Requirements?

Part Two: Rationale for the Proposed Rule

I. How Did EPA Determine Which Hazardous Waste Combustion Sources Would Be Regulated?

A. How Are Area Sources Regulated?

B. What Hazardous Waste Combustors Are Not Covered by this Proposal?

C. How Would Sulfuric Acid Regeneration Facilities Be Regulated?

II. What Subcategorization Considerations Did EPA Evaluate?

A. What Subcategorization Options Did We Consider for Incinerators?

B. What Subcategorization Options Did We Consider for Cement Kilns?

C. What Subcategorization Options Did We Consider for Lightweight Aggregate Kilns?

D. What Subcategorization Options Did We Consider for Boilers?

E. What Subcategorization Options Did We Consider for Hydrochloric Acid Production Furnaces?

III. What Data and Information Did EPA Consider to Establish the Proposed Standards?

A. Data Base for Phase I Sources

B. Data Base for Phase II Sources

C. Classification of the Emission Data

D. Invitation to Comment on Data Base

IV. How Did EPA Select the Format for the Proposed Rule?

A. What Is the Rationale for Generally Selecting an Emission Limit Format Rather than a Percent Reduction Format?

B. What Is the Rationale for Selecting a Hazardous Waste Thermal Emissions Format for Some Standards, and an Emissions Concentration Format for Others?

C. What Is the Rationale for Selecting Surrogates to Control Multiple HAP?

D. What Is the Rationale for Requiring Compliance with Operating Parameter Limits to Ensure Compliance with Emission Standards?

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V. How Did EPA Determine the Proposed Emission Limitations for New and Existing Units?

A. How Did EPA Determine the Proposed Emission Limitations for New Units?

B. How Did EPA Determine the Proposed Emission Limitations for Existing Units?

VI. How Did EPA Determine the MACT Floor for Existing and New Units?

A. What MACT Methodology Approaches Are Used to Identify the Best Performers for the Proposed Floors, and When Are They Applied?

B. How Did EPA Select the Data to Represent Each Source When Determining Floor Levels?

C. How Did We Evaluate Whether It Is Appropriate to Issue Separate Emissions Standards for Various Subcategories?

D. How Did We Rank Each Source's Performance Levels to Identify the Best Performing Sources for the Three MACT Methodologies?

E. How Did EPA Calculate Floor Levels That Are Achievable for the Average of the Best Performing Sources?

F. Why Did EPA Default to the Interim Standards When Establishing Floors?

G. What Other Options Did EPA Consider?

VII. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste Burning Incinerators?

A. What Are the Proposed Standards for Dioxin and Furan?

B. What Are the Proposed Standards for Mercury?

C. What Are the Proposed Standards for Particulate Matter?

D. What Are the Proposed Standards for Semivolatile Metals?

E. What Are the Proposed Standards for Low Volatile Metals?

F. What Are the Proposed Standards for Hydrogen Chloride and Chlorine Gas?

G. What Are the Standards for Hydrocarbons and Carbon Monoxide?

H. What Are the Standards for Destruction and Removal Efficiency?

VIII. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste Burning Cement Kilns?

A. What Are the Proposed Standards for Dioxin and Furan?

B. What Are the Proposed Standards for Mercury?

C. What Are the Proposed Standards for Particulate Matter?

D. What Are the Proposed Standards for Semivolatile Metals?

E. What Are the Proposed Standards for Low Volatile Metals?

F. What Are the Proposed Standards for Hydrogen Chloride and Chlorine Gas?

G. What Are the Standards for Hydrocarbons and Carbon Monoxide?

H. What Are the Standards for Destruction and Removal Efficiency?

IX. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste Burning Lightweight Aggregate Kilns?

A. What Are the Proposed Standards for Dioxin and Furan?

B. What Are the Proposed Standards for Mercury?

C. What Are the Proposed Standards for Particulate Matter?

D. What Are the Proposed Standards for Semivolatile Metals?

E. What Are the Proposed Standards for Low Volatile Metals?

F. What Are the Proposed Standards for Hydrogen Chloride and Chlorine Gas?

G. What Are the Standards for Hydrocarbons and Carbon Monoxide?

H. What Are the Standards for Destruction and Removal Efficiency?

X. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste Burning Solid Fuel-Fired Boilers?

A. What Is the Rationale for the Proposed Standards for Dioxin and Furan?

B. What Is the Rationale for the Proposed Standards for Mercury?

C. What Is the Rationale for the Proposed Standards for Particulate Matter?

D. What Is the Rationale for the Proposed Standards for Semivolatile Metals?

E. What Is the Rationale for the Proposed Standards for Low Volatile Metals?

F. What Is the Rationale for the Proposed Standards for Total Chlorine?

G. What Is the Rationale for the Proposed Standards for Carbon Monoxide or Hydrocarbons?

H. What Is the Rationale for the Proposed Standard for Destruction and Removal Efficiency?

XI. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste Burning Liquid Fuel-Fired Boilers?

A. What Are the Proposed Standards for Dioxin and Furan?

B. What Is the Rationale for the Proposed Standards for Mercury?

C. What Is the Rationale for the Proposed Standards for Particulate Matter?

D. What Is the Rationale for the Proposed Standards for Semivolatile Metals?

E. What Is the Rationale for the Proposed Standards for Chromium?

F. What Is the Rationale for the Proposed Standards for Total Chlorine?

G. What Is the Rationale for the Proposed Standards for Carbon Monoxide or Hydrocarbons?

H. What Is the Rationale for the Proposed Standard for Destruction and Removal Efficiency?

XII. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste Burning Hydrochloric Acid Production Furnaces?

A. What Is the Rationale for the Proposed Standards for Dioxin and Furan?

B. What Is the Rationale for the Proposed Standards for Mercury, Semivolatile Metals, and Low Volatile Metals?

C. What Is the Rationale for the Proposed Standards for Total Chlorine?

D. What Is the Rationale for the Proposed Standards for Carbon Monoxide or Hydrocarbons?

E. What Is the Rationale for the Proposed Standard for Destruction and Removal Efficiency?

XIII. What Is the Rationale for Proposing An Alternative Risk-Based Standard for Total Chlorine in Lieu of the MACT Standard?

A. What Is the Legal Authority to Establish Risk-Based Standards?

B. What Is the Rationale for the National Exposure Standards?

C. How Would You Determine if Your Total Chlorine Emission Rate Meets the Eligibility Requirements Defined by the National Exposure Standards?

D. What Is the Rationale for Caps on the Risk-Based Emission Limits?

E. What Would Your Risk-Based Eligibility Demonstration Contain?

F. When Would You Complete and Submit Your Eligibility Demonstration?

G. How Would the Risk-Based HCl-Equivalent Emission Rate Limit Be Implemented?

H. How Would You Ensure that Your Facility Remains Eligible for the Risk-Based Emission Limit?

I. Request for Comment on an Alternative Approach: Risk-Based National Emission Standards

XIV. How Did EPA Determine Testing and Monitoring Requirements for the Proposed Rule?

A. What Is the Rationale for the Proposed Testing Requirements?

B. What Are the Dioxin/Furan Testing Requirements for Boilers that Would Not Be Subject to a Numerical Dioxin/Furan Emission Standard?

C. What Are the Proposed Test Methods?

D. What Is the Rationale for the Proposed Continuous Monitoring Requirements?

E. What Are the Averaging Periods for the Operating Parameter Limits, and How Are Performance Test Data Averaged to Calculate the Limits?

F. How Would Sources Comply with Emissions Standards Based on Normal Emissions?

G. How Would Sources Comply with Emission Standards Expressed as Hazardous Waste Thermal Emissions?

H. What Happens if My Thermal Emissions Standard Limits Emissions to Below the Detection Limit of the Stack Test Methods?

I. Are We Concerned About Possible Negative Biases Associated With Making Hydrogen Chloride Measurements in High Moisture Conditions?

J. What Are the Other Proposed Compliance Requirements?

XV. How Did EPA Determine Compliance Times for this Proposed Rule?

XVI. How Did EPA Determine the Required Records and Reports for the Proposed Rule?

A. Summary of Requirements Currently Applicable to Incinerators, Cement Kilns, and Lightweight Aggregate Kilns and that Would Be Applicable to Boilers and Hydrochloric Acid Production Furnaces

B. Why Is EPA Proposing Notification of Intent to Comply and Compliance Progress Report Requirements?

XVII. What Are the Title V and RCRA Permitting Requirements for Phase I and Phase II Sources?

A. What Is the General Approach to Permitting Hazardous Waste Combustion Sources?

B. How Will the Replacement Standards Affect Permitting for Phase I Sources?

C. What Permitting Requirements Is EPA Proposing for Phase II Sources?

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D. How Would this Proposal Affect the RCRA Site-Specific Risk Assessment Policy?

XVIII. What Alternatives to the Particulate Matter Standard Is EPA Proposing or Requesting Comment On?

A. What Alternative to the Particulate Matter Standard Is EPA Proposing for Incinerators, Liquid Fuel-Fired Boilers, and Solid Fuel-Fired Boilers?

B. What Alternative to the Particulate Matter Standard Is EPA Requesting Comment On?

XIX. What Are the Proposed RCRA State Authorization and CAA Delegation Requirements?

A. What Is the Authority for this Rule?

B. Are There Any Changes to the CAA Delegation Requirements for Phase I Sources?

C. What Are the Proposed CAA Delegation Requirements for Phase II Sources?

Part Three: Proposed Revisions to Compliance Requirements

I. Why Is EPA Proposing to Allow Phase I Sources to Conduct the Initial Performance Test to Comply with the Replacement Rules 12 Months After the Compliance Date?

II. Why Is EPA Requesting Comment on Requirements Promulgated as Interim Standards or as Final Amendments?

A. Interim Standards Amendments to the Startup, Shutdown, and Malfunction Plan Requirements

B. Interim Standards Amendments to the Compliance Requirements for Ionizing Wet Scrubbers

C. Why Is EPA Requesting Comment on the Fugitive Emission Requirements?

D. Why Is EPA Requesting Comment on Bag Leak Detector Sensitivity?

E. Final Amendments Waiving Operating Parameter Limits during Testing without an Approved Test Plan

III. Why Is EPA Requesting Comment on Issues and Amendments that Were Previously Proposed?

A. Definition of Research, Development, and Demonstration Source

B. Identification of an Organics Residence Time that Is Independent of, and Shorter than, the Hazardous Waste Residence Time

C. Why Is EPA Not Proposing to Extend APCD Controls after the Residence Time Has Expired when Sources Operate under Alternative Section 112 or 129 Standards?

D. Why Is EPA Proposing to Allow Use of Method 23 as an Alternative to Method 0023A for Dioxin/Furan?

E. Why Is EPA Not Proposing the “Matching the Profile” Alternative Approach to Establish Operating Parameter Limits?

F. Why Is EPA Not Proposing to Allow Extrapolation of OPLs?

G. Why Is EPA Proposing to Delete the Limit on Minimum Combustion Chamber Temperature for Dioxin/Furan for Cement Kilns?

H. Why Is EPA Requesting Additional Comment on Whether to Add a Maximum pH Limit for Wet Scrubbers to Control Mercury Emissions?

I. How Is EPA Proposing to Ensure Performance of Electrostatic Precipitators, Ionizing Wet Scrubbers, and Fabric Filters?

IV. Other Proposed Compliance Revisions

A. What Is the Proposed Clarification to the Public Notice Requirement for Approved Test Plans?

B. What Is the Proposed Clarification to the Public Notice Requirement for the Petition to Waive a Performance Test?

Part Four: Impacts of the Proposed Rule

I. What Are the Air Impacts?

II. What Are the Water and Solid Waste Impacts?

III. What Are the Energy Impacts?

IV. What are the Control Costs?

V. Can We Achieve the Goals of the Proposed Rule in a Less Costly Manner?

VI. What are the Economic Impacts?

A. Market Exit Estimates

B. Quantity of Waste Reallocated

C. Employment Impacts

VII. What Are the Benefits of Reductions in Particulate Matter Emissions?

VIII. What are the Social Costs and Benefits of the Proposed Rule?

A. Combustion Market Overview

B. Baseline Specification

C. Analytical Methodology and Findings—Social Cost Analysis

D. Analytical Methodology and Findings—Benefits Assessment

IX. How Does the Proposed Rule Meet the RCRA Protectiveness Mandate?

A. Background

B. Assessment of Risks

Part Five: Administrative Requirements

I. Executive Order 12866: Regulatory Planning and Review

II. Paperwork Reduction Act

III. Regulatory Flexibility Act

IV. Unfunded Mandates Reform Act

V. Executive Order 13132: Federalism

VI. Executive Order 13175: Consultation and Coordination with Indian Tribal Governments

VII. Executive Order 13045: Protection of Children from Environmental Health and Safety Risks

VIII. Executive Order 13211: Actions that Significantly Affect Energy Supply, Distribution, or Use

IX. National Technology Transfer and Advancement Act

X. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations

XI. Congressional Review

Abbreviations and Acronyms Used in This Document

acfm—actual cubic feet per minute

Btu—British thermal units

CAA—Clean Air Act

CFR—Code of Federal Regulations

DRE—destruction and removal efficiency

dscf—dry standard cubic foot

dscm—dry standard cubic meter

EPA—Environmental Protection Agency

FR—Federal Register

gr/dscf—grains per dry standard cubic foot

HAP—hazardous air pollutant(s)

ICR—Information Collection Request

kg/hr—kilograms per hour

kW-hour—kilo Watt hour

MACT—Maximum Achievable Control Technology

mg/dscm—milligrams per dry standard cubic meter

MMBtu—million British thermal unit

ng/dscm—nanograms per dry standard cubic meter

NESHAP—national emission standards for HAP

ng—nanograms

POHC—principal organic hazardous constituent

ppmv—parts per million by volume

ppmw—parts per million by weight

Pub. L.—Public Law

RCRA—Resource Conservation and Recovery Act

SRE—system removal efficiency

TEQ—toxicity equivalence

ug/dscm—micrograms per dry standard cubic meter

U.S.C.—United States Code

Part One: Background and Summary

I. Background Information

A. What Criteria Are Used in the Development of NESHAP?

1. What Information Is Covered in This Preamble and How Is It Organized?

In this preamble, EPA summarizes the important features of these proposed standards that apply to hazardous waste burning incinerators, cement kilns, lightweight aggregate kilns, boilers, and hydrochloric acid production furnaces, known collectively as HWCs. This preamble describes: (1) The environmental, energy, and economic impacts of these proposed standards; (2) the basis for each of the decisions made regarding the proposed standards; (3) requests public comments on certain issues; and (4) discusses administrative requirements relative to this action.

2. Where in the Code of Federal Regulations Will These Standards Be Codified?

The Code of Federal Regulations (CFR) is a codification of the general and permanent rules published in the Federal Register by the Executive departments and agencies of the Federal Government. The code is divided into 50 titles that represent broad areas subject to Federal regulation. These proposed rules would be published in Title 40, Protection of the Environment, Part 63, Subpart EEE: National Emission Standards for Hazardous Air Pollutants From Hazardous Waste Combustors.

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3. What Criteria Are Used in the Development of NESHAP?

Section 112 of the Clean Air Act (CAA) requires EPA to promulgate regulations for the control of HAP emissions from each source category listed by EPA under section 112(c). The statute requires the regulations to reflect the maximum degree of reduction in emissions of HAP that is achievable taking into consideration the cost of achieving the emission reduction, any nonair quality health and environmental impacts, and energy requirements. This level of control is commonly referred to as MACT (i.e., maximum achievable control technology). The MACT regulation can be based on the emission reductions achievable through application of measures, processes, methods, systems, or techniques including, but not limited to: (1) Reducing the volume of, or eliminating emissions of, such pollutants through process changes, substitutions of materials, or other modifications; (2) enclosing systems or processes to eliminate emissions; (3) collecting, capturing, or treating such pollutants when released from a process, stack, storage or fugitive emission point; (4) design, equipment, work practices, or operational standards as provided in subsection 112(h); or (5) a combination of the above. See section 112(d)(2) of the CAA.

For new sources, MACT standards cannot be less stringent than the emission control achieved in practice by the best-controlled similar source. See section 112(d)(3) of the Act. The MACT standards for existing sources can be less stringent than standards for new sources, but they cannot be less stringent than the average emission limitation achieved by the best-performing 12 percent of existing sources for categories and subcategories with 30 or more sources, or the best-performing 5 sources for categories or subcategories with fewer than 30 sources. Id. This level of control is usually referred to as the MACT “floor”, the term used in the Legislative History.

In essence, MACT standards ensure that all major sources of air toxic (i.e., HAP) emissions achieve the level of control already being achieved by the better-controlled and lower-emitting sources in each category. This approach provides assurance to citizens that each major source of toxic air pollution will be required to effectively control its emissions of air toxics. At the same time, this approach provides a level playing field, ensuring that facilities that employ cleaner processes and good emission controls are not disadvantaged relative to competitors with poorer controls.

B. What Is the Regulatory Development Background of the Source Categories in the Proposed Rule?

Today's notice proposes standards for controlling emissions of HAP from hazardous waste combustors. Hazardous waste combustors comprise several categories of sources that burn hazardous waste: incinerators, cement kilns, lightweight aggregate kilns, boilers and hydrochloric acid production furnaces. We call incinerators, cement kilns, and lightweight aggregate kilns Phase I sources because we have already promulgated standards for those source categories. We call boilers and hydrochloric acid production furnaces Phase II sources because we intended to promulgate MACT standards for those source categories after promulgating MACT standards for Phase I sources. The regulatory background of Phase I and Phase II source categories is discussed below.

1. Phase I Source Categories

Phase I combustor sources are regulated under the Resource Conservation and Recovery Act (RCRA), which establishes a “cradle-to-grave” regulatory structure overseeing the safe treatment, storage, and disposal of hazardous waste. We issued RCRA rules to control air emissions from incinerators in 1981, 40 CFR parts 264 and 265, subpart O, and from cement kilns and lightweight aggregate kilns that burn hazardous waste in 1991, 40 CFR part 266, subpart H. These rules rely generally on risk-based standards to achieve the RCRA protectiveness mandate.

The Phase I source categories are also subject to standards under section 112(d) of the Clean Air Act. We promulgated standards for Phase I sources on September 30, 1999 (64 FR 52828). This final rule is referred to as the Phase I rule or 1999 final rule. These emission standards created a technology-based national cap for hazardous air pollutant emissions from the combustion of hazardous waste in these devices. The rule regulates emissions of numerous hazardous air pollutants: dioxin/furans, other toxic organics (through surrogates), mercury, other toxic metals (both directly and through a surrogate), and hydrogen chloride and chlorine gas. Where necessary, section 3005(c)(3) of RCRA provides the authority to impose additional conditions in a RCRA permit to protect human health and the environment.

A number of parties, representing interests of both industrial sources and of the environmental community, sought judicial review of the Phase I rule. On July 24, 2001, the United States Court of Appeals for the District of Columbia Circuit (the Court) granted portions of the Sierra Club's petition for review and vacated the challenged portions of the standards. Cement Kiln Recycling Coalition v. EPA, 255 F. 3d 855 (D.C. Cir. 2001). The Court held that EPA had not demonstrated that its calculation of MACT floors met the statutory requirement of being no less stringent than (1) the average emission limitation achieved by the best performing 12 percent of existing sources and (2) the emission control achieved in practice by the best controlled similar source for new sources. 255 F.3d at 861, 865-66. As a remedy, the Court, after declining to rule on most of the issues presented in the industry petitions for review, vacated the “challenged regulations,” stating that: “[W]e have chosen not to reach the bulk of industry petitioners' claims, and leaving the regulations in place during remand would ignore petitioners' potentially meritorious challenges.” Id. at 872. Examples of the specific challenges the Court indicated might have merit were provisions relating to compliance during start up/shut down and malfunction events, including emergency safety vent openings, the dioxin/furan standard for lightweight aggregate kilns, and the semivolatile metal standard for cement kilns. Id. However, the Court stated, “[b]ecause this decision leaves EPA without standards regulating [hazardous waste combustor] emissions, EPA (or any of the parties to this proceeding) may file a motion to delay issuance of the mandate to request either that the current standards remain in place or that EPA be allowed reasonable time to develop interim standards.” Id.

Acting on this invitation, all parties moved the Court jointly to stay the issuance of its mandate for four months to allow EPA time to develop interim standards, which would replace the vacated standards temporarily, until final standards consistent with the Court's mandate are promulgated. The interim standards were published on February 13, 2002 (67 FR 6792). EPA did not justify or characterize these standards as conforming to MACT, but rather as an interim measure to prevent the adverse environmental and other consequences that would result from the regulatory gap resulting from no standards being in place. Id. at 6795-96.

The motion also indicates that EPA will issue final standards which comply Start Printed Page 21203with the Court's opinion by June 14, 2005, and it indicates that EPA and Petitioner Sierra Club intend to enter into a settlement agreement requiring us to promulgate final rules by that date, and that date be judicially enforceable. EPA and Sierra Club entered into that settlement agreement on March 4, 2002.

The joint motion also details other actions we agreed to take, including issuing a one-year extension to the September 30, 2002, compliance date (66 FR 63313, December 6, 2001), and promulgating several of the compliance and implementation amendments to the rule which we proposed on July 3, 2001 (66 FR 35126). These final amendments were published on February 14, 2002 (67 FR 6968).

2. Phase II Source Categories

Phase II combustors—boilers and hydrochloric acid production furnaces—are also regulated under the Resource Conservation and Recovery Act (RCRA) pursuant to 40 CFR part 266, subpart H, and (for reasons discussed below) are also subject to the MACT standard setting process in section 112(d) of the CAA. We delayed promulgating MACT standards for these source categories pending reevaluation of the MACT standard setting methodology following the Court's decision to vacate the standards for the Phase I source categories. We have also entered into a judicially enforceable consent decree with Sierra Club which requires EPA to promulgate MACT standards for the Phase II sources by June 14, 2005—the same date that (for independent reasons) is required for the replacement standards for Phase I sources.

C. What Is the Statutory Authority for This Standard?

Section 112 of the Clean Air Act requires that the EPA promulgate regulations requiring the control of HAP emissions from major and certain area sources. The control of HAP is achieved through promulgation of emission standards under sections 112(d) and (in a second round of standard setting) (f) and, in appropriate circumstances, work practice standards under section 112(h).

EPA's initial list of categories of major and area sources of HAP selected for regulation in accordance with section 112(c) of the Act was published in the Federal Register on July 16, 1992 (57 FR 31576). Incinerators, cement kilns, lightweight aggregate kilns, industrial/commercial/institutional boilers and process heaters, and hydrochloric acid production furnaces are among the listed 174 categories of sources. The listing was based on the Administrator's determination that they may reasonably be anticipated to emit several of the 188 listed HAP in quantities sufficient to designate them as major sources.

D. What Is the Relationship Between the Proposed Rule and Other MACT Combustion Rules?

The proposed amendments to the subpart EEE, part 63, standards for hazardous waste combustors would apply to the source categories that are currently subject to that subpart—incinerators, cement kilns, and lightweight aggregate kilns that burn hazardous waste. Today's proposed rule, however, would also amend subpart EEE to establish MACT standards for the Phase II source categories—those boilers and hydrochloric acid production furnaces that burn hazardous waste.

Generally speaking, you are an affected source pursuant to subpart EEE if you combust, or have previously combusted, hazardous waste in an incinerator, cement kiln, lightweight aggregate kiln, boiler, or hydrochloric acid production furnace. You continue to be an affected source until you cease burning hazardous waste and initiate closure requirements pursuant to RCRA. See § 63.1200(b). If you never previously combusted hazardous waste, or have ceased burning hazardous waste and initiated RCRA closure requirements, you are not subject to subpart EEE. Rather, EPA has promulgated or proposed separate MACT standards for sources that do not burn hazardous waste within the following source categories: commercial and industrial solid waste incinerators (40 CFR part 60, subparts CCCC and DDDD); Portland cement manufacturing facilities (40 CFR part 63, subpart LLL); industrial/commercial/institutional boilers and process heaters (40 CFR part 63, proposed subpart DDDDD); and hydrochloric acid production facilities (40 CFR part 63, subpart NNNNN). In addition, EPA considered whether to establish MACT standards for lightweight aggregate manufacturing facilities that do not burn hazardous waste, and determined that they are not major sources of HAP emissions. Thus, EPA has not established MACT standards for lightweight aggregate manufacturing facilities that do not burn hazardous waste.

Note that non-stack emissions points are not regulated under subpart EEE.[1] Emissions attributable to storage and handling of hazardous waste prior to combustion (i.e., emissions from tanks, containers, equipment, and process vents) would continue to be regulated pursuant to either RCRA subpart AA, BB, and CC or an applicable MACT that applies to the before-mentioned material handling devices. Emissions unrelated to the hazardous waste operations may be regulated pursuant to other MACT rulemakings. For example, Portland cement manufacturing facilities that combust hazardous waste are subject to both subpart EEE and subpart LLL, and hydrochloric acid production facilities that combust hazardous waste may be subject to both subpart EEE and subpart NNNNN.[2] In these instances subpart EEE controls HAP emissions from the cement kiln and hydrochloric acid production furnace stack, while subparts LLL and NNNNN would control HAP emissions from other operations that are not directly related to the combustion of hazardous waste (e.g., clinker cooler emissions for cement production facilities, and hydrochloric acid product transportation and storage for hydrochloric acid production facilities).

Note that if you temporarily cease burning hazardous waste for any reason, you remain an affected source and are still subject to the applicable Subpart EEE requirements. However, even as an affected source, the proposed emission standards or operating limits derived from the hazardous waste combustors do not apply if: (1) Hazardous waste is not in the combustion chamber and you elect to comply with other MACT (or CAA section 129) standards that otherwise would be applicable if you were not burning hazardous waste, e.g., the nonhazardous waste burning Portland Cement Kiln MACT (subpart LLL); or (2) you are in a startup, shutdown, or malfunction mode of operation.

E. What Are the Health Effects Associated With Pollutants Emitted by Hazardous Waste Combustors?

Today's proposed rule protects air quality and promotes the public health by reducing the emissions of some of the HAP listed in section 112(b)(1) of the CAA. Emissions data collected in the development of this proposed rule show that metals, particulate matter, hydrogen chloride and chlorine gas, dioxins and furans, and other organic compounds are emitted from hazardous waste combustors. The HAP that would Start Printed Page 21204be controlled with this rule are associated with a variety of adverse health affects. These adverse health effects include chronic health disorders (e.g., irritation of the lung, skin, and mucus membranes and effects on the blood, digestive tract, kidneys, and central nervous system), and acute health disorders (e.g., lung irritation and congestion, alimentary effects such as nausea and vomiting, and effects on the central nervous system). Provided below are brief descriptions of risks associated with HAP that are emitted from hazardous waste combustors. Note that a more detailed discussion of the risks associated with these emissions is included in Part Four.

Antimony

Antimony occurs at very low levels in the environment, both in the soils and foods. Higher concentrations, however, are found at antimony processing sites, and in their hazardous wastes. The most common industrial use of antimony is as a fire retardant in the form of antimony trioxide. Chronic occupational exposure to antimony (generally antimony trioxide) is most commonly associated with “antimony pneumoconiosis,” a condition involving fibrosis and scarring of the lung tissues. Studies have shown that antimony accumulates in the lung and is retained for long periods of time. Effects are not limited to the lungs, however, and myocardial effects (effects on the heart muscle) and related effects (e.g., increased blood pressure, altered EKG readings) are among the best-characterized human health effects associated with antimony exposure. Reproductive effects (increased incidence of spontaneous abortions and higher rates of premature deliveries) have been observed in female workers exposed in antimony processing facilities. Similar effects on the heart, lungs, and reproductive system have been observed in laboratory animals.

EPA recently assessed the carcinogenicity of antimony and found the evidence for carcinogenicity to be weak, with conflicting evidence from inhalation studies with laboratory animals, equivocal data from the occupational studies, negative results from studies of oral exposures in laboratory animals, and little evidence of mutagenicity or genotoxicity.[3] As a consequence, EPA concluded that insufficient data are available to adequately characterize the carcinogenicity of antimony and, accordingly, the carcinogenicity of antimony cannot be determined based on available information. However, IARC (International Agency for Research on Cancer) in an earlier evaluation, concluded that antimony trioxide is “possibly carcinogenic to humans” (Group 2B).

Arsenic

Acute (short-term) high-level inhalation exposure to arsenic dust or fumes has resulted in gastrointestinal effects (nausea, diarrhea, abdominal pain), and central and peripheral nervous system disorders. Chronic (long-term) inhalation exposure to inorganic arsenic in humans is associated with irritation of the skin and mucous membranes. Human data suggest a relationship between inhalation exposure of women working at or living near metal smelters and an increased risk of reproductive effects, such as spontaneous abortions. Inorganic arsenic exposure in humans by the inhalation route has been shown to be strongly associated with lung cancer, while ingestion or inorganic arsenic in humans has been linked to a form of skin cancer and also to bladder, liver, and lung cancer. EPA has classified inorganic arsenic as a Group A, human carcinogen.

Beryllium

Beryllium is a hard, grayish metal naturally found in minerals, rocks, coal, soil, and volcanic dust. Beryllium dust enters the air from burning coal and oil. This beryllium dust will eventually settle over the land and water. It enters water from erosion of rocks and soil, and from industrial waste. Some beryllium compounds will dissolve in water, but most stick to particles and settle to the bottom. Most beryllium in soil does not dissolve in water and remains bound to soil. Beryllium does not accumulate in the food chain.

Beryllium can be harmful if you breathe it. The effects depend on how much you are exposed to and for how long. If beryllium air levels are high enough, an acute condition can result. This condition resembles pneumonia and is called acute beryllium disease. Long-term exposure to beryllium can increase the risk of developing lung cancer.

Cadmium

The acute (short-term) effects of cadmium inhalation in humans consist mainly of effects on the lung, such as pulmonary irritation. Chronic (long-term) inhalation or oral exposure to cadmium leads to a build-up of cadmium in the kidneys that can cause kidney disease. Cadmium has been shown to be a developmental toxicant in animals, resulting in fetal malformations and other effects, but no conclusive evidence exists in humans. An association between cadmium exposure and an increased risk of lung cancer has been reported from human studies, but these studies are inconclusive due to confounding factors. Animal studies have demonstrated an increase in lung cancer from long-term inhalation exposure to cadmium. EPA has classified cadmium as a Group B1, probable carcinogen.

Chlorine Gas

Acute exposure to high levels of chlorine in humans can result in chest pain, vomiting, toxic pneumonitis, and pulmonary edema. At lower levels chlorine is a potent irritant to the eyes, the upper respiratory tract, and lungs. Chronic exposure to chlorine gas in workers has resulted in respiratory effects including eye and throat irritation and airflow obstruction. Animal studies have reported decreased body weight gain, eye and nose irritation, nonneoplastic nasal lesions, and respiratory epithelial hyperplasia from chronic inhalation exposure to chlorine. No information is available on the carcinogenic effects of chlorine in humans from inhalation exposure. We have not classified chlorine for potential carcinogenicity.

Chromium

Chromium may be emitted in two forms, trivalent chromium (chromium III) or hexavalent chromium (chromium VI). The respiratory tract is the major target organ for chromium VI toxicity, for acute (short-term) and chronic (long-term) inhalation exposures. Shortness of breath, coughing, and wheezing have been reported from acute exposure to chromium VI, while perforations and ulcerations of the septum, bronchitis, decreased pulmonary function, pneumonia, and other respiratory effects have been noted from chronic exposure. Limited human studies suggest that chromium VI inhalation exposure may be associated with complications during pregnancy and childbirth, while animal studies have not reported reproductive effects from inhalation exposure to chromium VI. Human and animal studies have clearly established that inhaled chromium VI is a carcinogen, resulting in an increased risk of lung cancer. EPA has classified chromium VI as a Group A, human carcinogen.

Chromium III is less toxic than chromium VI. The respiratory tract is also the major target organ for Start Printed Page 21205chromium III toxicity, similar to chromium VI. Chromium III is an essential element in humans, with a daily intake of 50 to 200 micrograms per day recommended for an adult. The body can detoxify some amount of chromium VI to chromium III. EPA has not classified chromium III with respect to carcinogenicity.

Cobalt

Cobalt is a relatively rare metal that is produced primarily as a by-product during refining of other metals, primarily copper. Cobalt has been widely reported to cause respiratory effects in humans exposed by inhalation, including respiratory irritation, wheezing, asthma, and pneumonia. Cardiomyopathy (or damage to the heart muscle) has also been reported, although this effect is better known from oral exposure. Other effects of oral exposure in humans are polycythemia (an abnormally high number of red blood cells) and the blocking of uptake of iodine by the thyroid. In addition, cobalt is a sensitizer in humans by any route of exposure. Sensitized individuals may react to inhalation of cobalt by developing asthma or to ingestion or dermal contact with cobalt by developing dermatitis. Cobalt is a vital component of vitamin B12, though there is no evidence that intake of cobalt is ever limiting in the human diet.

A number of epidemiological studies have found that exposures to cobalt are associated with an increased incidence of lung cancer in occupational settings. The International Agency for Research on Cancer (IARC, part of the World Health Organization) classifies cobalt and cobalt compounds as “possibly carcinogenic to humans” (Group 2B). The American Conference of Governmental Industrial Hygienists (ACGIH) has classified cobalt as a confirmed animal carcinogen with unknown relevance to humans (category A3). An EPA assessment concludes that under EPA's 1986 guidelines, cobalt would be classified as a probable human carcinogen (group B1) based on limited evidence of carcinogenicity in humans and sufficient evidence of carcinogenicity in animals, as evidenced by an increased incidence of alveolar/bronchiolar tumors in recent studies of both rats and mice. Under EPA's proposed cancer guidelines, cobalt is considered likely to be carcinogenic to humans.[4]

Dioxins and Furans

Exposures to 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) at levels 10 times or less above those modeled to approximate average background exposure have resulted in adverse non-cancer health effects in animals. These effects include changes in hormone systems, alterations in fetal development, reduced reproductive capacity, and immunosuppression. Effects that may be linked to dioxin and furan exposures at low dose in humans include changes in markers of early development and hormone levels. Dioxin and furan exposures are associated with altered liver function and lipid metabolism changes in activity of various liver enzymes, depression of the immune system, and endocrine and nervous system effects. EPA in its 1985 dioxin assessment classified 2,3,7,8-TCDD as a probable human carcinogen. The International Agency for Research on Cancer (IARC) concluded in 1997 that the overall weight of the evidence was sufficient to characterize 2,3,7,8-TCDD as a known human carcinogen.[5] In 2001 the U.S. Department of Health and Human Services National Toxicology Program in their 9th Report on Carcinogens classified 2,3,7,8-TCDD as a known human carcinogen.[6]

Hydrogen Chloride/Hydrochloric Acid

Hydrogen chloride, also called hydrochloric acid, is corrosive to the eyes, skin, and mucous membranes. Acute (short-term) inhalation exposure may cause eye, nose, and respiratory tract irritation and inflammation and pulmonary edema in humans. Chronic (long-term) occupational exposure to hydrochloric acid has been reported to cause gastritis, bronchitis, and dermatitis in workers. Prolonged exposure to low concentrations may also cause dental discoloration and erosion. No information is available on the reproductive or developmental effects of hydrochloric acid in humans. In rats exposed to hydrochloric acid by inhalation, altered estrus cycles have been reported in females and increased fetal mortality and decreased fetal weight have been reported in offspring. EPA has not classified hydrochloric acid for carcinogenicity.

Lead

Lead is a very toxic element, causing a variety of effects at low dose levels. Brain damage, kidney damage, and gastrointestinal distress may occur from acute (short-term) exposure to high levels of lead in humans. Chronic (long-term) exposure to lead in humans results in effects on the blood, central nervous system (CNS), blood pressure, and kidneys. Children are particularly sensitive to the chronic effects of lead, with slowed cognitive development, reduced growth and other effects reported. Reproductive effects, such as decreased sperm count in men and spontaneous abortions in women, have been associated with lead exposure. The developing fetus is at particular risk from maternal lead exposure, with low birth weight and slowed postnatal neurobehavioral development noted. Human studies are inconclusive regarding lead exposure and cancer, while animal studies have reported an increase in kidney cancer from lead exposure by the oral route. EPA has classified lead as a Group B2, probable human carcinogen.

Manganese

Health effects in humans have been associated with both deficiencies and excess intakes of manganese. Chronic (long-term) exposure to low levels of manganese in the diet is considered to be nutritionally essential in humans, with a recommended daily allowance of 2 to 5 milligrams per day (mg/d). Chronic exposure to high levels of manganese by inhalation in humans results primarily in central nervous system (CNS) effects. Visual reaction time, hand steadiness, and eye-hand coordination were affected in chronically-exposed workers. Manganism, characterized by feelings of weakness and lethargy, tremors, a mask-like face, and psychological disturbances, may result from chronic exposure to higher levels. Impotence and loss of libido have been noted in male workers afflicted with manganism attributed to inhalation exposures. EPA has classified manganese in Group D, not classifiable as to carcinogenicity in humans.

Mercury

Mercury exists in three forms: elemental mercury, inorganic mercury compounds (primarily mercuric chloride), and organic mercury compounds (primarily methyl mercury). Each form exhibits different health effects. Various sources may release elemental or inorganic mercury; environmental methyl mercury is Start Printed Page 21206typically formed by biological processes after mercury has precipitated from the air.

Acute (short-term) exposure to high levels of elemental mercury in humans results in central nervous system (CNS) effects such as tremors, mood changes, and slowed sensory and motor nerve function. High inhalation exposures can also cause kidney damage and effects on the gastrointestinal tract and respiratory system. Chronic (long-term) exposure to elemental mercury in humans also affects the CNS, with effects such as increased excitability, irritability, excessive shyness, and tremors. EPA has not classified elemental mercury with respect to cancer.

Acute exposure to inorganic mercury by the oral route may result in effects such as nausea, vomiting, and severe abdominal pain. The major effect from chronic exposure to inorganic mercury is kidney damage. Reproductive and developmental animal studies have reported effects such as alterations in testicular tissue, increased embryo resorption rates, and abnormalities of development. Mercuric chloride (an inorganic mercury compound) exposure has been shown to result in forestomach, thyroid, and renal tumors in experimental animals. EPA has classified mercuric chloride as a Group C, possible human carcinogen.

Nickel

Nickel is a commonly used industrial metal, and is frequently associated with iron and copper ores. Contact dermatitis is the most common effect in humans from exposure to nickel, whether via inhalation, oral, or dermal exposure. Cases of nickel-contact dermatitis have been reported following occupational and non-occupational exposure, with symptoms of itching of the fingers, wrists, and forearms. Many studies have also demonstrated dermal effects in sensitive humans from ingested nickel, invoking an eruption or worsening of eczema. Chronic inhalation exposure to nickel in humans results in direct respiratory effects, such as asthma due to primary irritation, or an allergic response and an increased risk of chronic respiratory tract infections.

Animal studies have reported a variety of inflammatory effects on the lungs, as well as effects on the kidneys and immune system from inhalation exposure to nickel. Significant differences in inhalation toxicity among the various forms of nickel have been documented, with soluble nickel compounds being more toxic to the respiratory tract than less soluble compounds (e.g., nickel oxide). Animal studies have also reported effects on the respiratory and gastrointestinal systems, heart, blood, liver, kidney, and body weight from oral exposure to nickel, as well as to the fetus.

EPA currently classifies nickel refinery dust and nickel subsulfide (a major component of nickel refinery dust) as class A human carcinogens based on increased risks of lung and nasal cancer in human epidemiological studies of occupational exposures to nickel refinery dust, increased tumor incidences in animals by several routes of administration in several animal species, and positive results in genotoxicity assays. More recently, a pair of inhalation studies performed under the auspices of the National Toxicology Program (NTP) of the National Institutes of Health concluded that there was no evidence of carcinogenic activity of soluble nickel salts in rats or mice and that there was some evidence of carcinogenic activity of nickel oxide in male and female rats based on increased incidence of alveolar/bronchiolar adenoma or carcinoma and increased incidence of benign or malignant pheochromocytoma (a tumor of the adrenal gland) and equivocal evidence in mice based on marginally increased incidence of alveolar/bronchiolar adenoma or carcinoma in females and no evidence in males. The Tenth Annual Report on Carcinogens classifies nickel compounds as “known to be human carcinogens.” [7] This is consistent with the International Agency for Cancer Research (IARC) which classifies nickel compounds as Group 1 human carcinogens.

Organic HAP

Organic HAPs include halogenated and nonhalogenated organic classes of compounds such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). Both PAHs and PCBs are classified as potential human carcinogens, and are considered toxic, persistent and bioaccumulative. They include compounds such as benzene, methane, propane, chlorinated alkanes and alkenes, phenols and chlorinated aromatics. Adverse health effects of HAPs include damage to the immune system, as well as neurological, reproductive, developmental, respiratory and other health problems.

Particulate Matter [8]

Atmospheric PM is composed of sulfate, nitrate, ammonium, and other ions, elemental carbon, particle-bound water, a wide variety of organic compounds, and a large number of elements contained in various compounds, some of which originate from crustal materials and others from combustion sources. Combustion sources are the primary origin of trace metals found in fine particles in the atmosphere. Ambient PM can be of primary or secondary origin.[9]

A large body of evidence exists from epidemiological studies that demonstrates a relationship between ambient particulate matter (PM) and mortality and morbidity in the general population and, when combined with evidence from other studies (e.g., clinical and animal studies), indicates that exposure to PM is a probable contributing cause to the adverse human health effects that have been observed. For example, many different studies report that increased cardiovascular and respiratory-related mortality risks are significantly associated with various measures (both long-term and short-term) of ambient PM. Some studies suggest that a portion of the increased mortality may be associated with concurrent exposures to PM and other criteria pollutants, such as SO2. Much evidence exists of positive associations between ambient PM concentrations and increased respiratory-related hospital admissions, emergency room, and other medical visits. Additional findings implicate PM as likely associated with an increased occurrence of chronic bronchitis and a contributing factor in the exacerbation of asthmatic conditions. Recent reports from prospective cohort studies of long-term ambient PM exposures provide substantial evidence of an association between increased risk of lung cancer and PM, especially exposure to fine PM or its components.

PM has other effects, beyond the health effects to human beings. The major effect of atmospheric PM on ecosystems is indirect and occurs through the deposition of nitrates and sulfates and the acidifying effects of the associated hydrogen ions contained in Start Printed Page 21207wet and dry deposition.[10] Acidification of surface waters can have long-term adverse effects on aquatic ecosystems, including effects on fish populations, macro invertebrates, species richness, and zooplankton abundance. In the soil environment, acid deposition has the potential to inhibit nutrient uptake, alter the ecological processes of energy flow and nutrient cycling, change ecosystem structure, and affect ecosystem biodiversity. In addition, ambient fine particles are well known as the major cause of visibility impairment. Visibility impairment (or haziness) is widespread in the U.S. and is greatest in the eastern United States and southern California. In addition, PM exerts important effects on materials, such as soiling, corrosion, and degradation of surfaces, and accelerates weathering of man-made and natural materials.

A large body of evidence exists from epidemiological studies that demonstrates a relationship between ambient particulate matter (PM) and mortality and morbidity in the general population and, when combined with evidence from other studies (e.g., clinical and animal studies), indicates that exposure to PM is a probable contributing cause to the adverse human health effects that have been observed. For example, many different studies report that increased cardiovascular and respiratory-related mortality risks are significantly associated with various measures (both long-term and short-term) of ambient PM. Some studies suggest that a portion of the increased mortality may be associated with concurrent exposures to PM and other criteria pollutants, such as SO2. Much evidence exists of positive associations between ambient PM concentrations and increased respiratory-related hospital admissions, emergency room, and other medical visits. Additional findings implicate PM as likely associated with an increased occurrence of chronic bronchitis and a contributing factor in the exacerbation of asthmatic conditions. Recent reports from prospective cohort studies of long-term ambient PM exposures provide substantial evidence of an association between increased risk of lung cancer and PM, especially exposure to fine PM or its components.

PM has other effects, beyond the health effects to human beings. The major effect of atmospheric PM on ecosystems is indirect and occurs through the deposition of nitrates and sulfates and the acidifying effects of the associated hydrogen ions contained in wet and dry deposition.[11] Acidification of surface waters can have long-term adverse effects on aquatic ecosystems, including effects on fish populations, macro invertebrates, species richness, and zooplankton abundance. In the soil environment, acid deposition has the potential to inhibit nutrient uptake, alter the ecological processes of energy flow and nutrient cycling, change ecosystem structure, and affect ecosystem biodiversity. In addition, ambient fine particles are well known as the major cause of visibility impairment. Visibility impairment (or haziness) is widespread in the U.S. and is greatest in the eastern United States and southern California. In addition, PM exerts important effects on materials, such as soiling, corrosion, and degradation of surfaces, and accelerates weathering of man-made and natural materials.

Selenium

Selenium occurs naturally in soils, is associated with copper refining, and several industrial processes, and has been used in pesticides. It is an essential element and bioaccumulates in certain plant species, and has been associated with toxic effects in livestock (blind staggers syndrome). Soils containing high levels of selenium (seleniferous soils can lead to high concentration of selenium in certain plants, and pose a hazard to livestock and other species. Bioaccumulation and magnification of selenium has also been observed in aquatic organisms and has been shown to be toxic to piscivorous fish. In humans, selenium partitions to the kidneys and liver, and is excreted through the urine and feces. Selenium intoxication in humans causes a syndrome known as selenosis. The condition is characterized by chronic dermatitis, fatigue, anorexia, gastroenteritis, hepatic degeneration, enlarged spleen and increased concentrations of Se in the hair and nails. Clinical signs of selenosis include a characteristic “garlic odor” of excess selenium excretion in the breath and urine, thickened and brittle nails, hair and nail loss, lowered hemoglobin levels, mottled teeth, skin lesions and CNS abnormalities (peripheral anesthesia, acroparesthesia and pain in the extremities). Aquatic birds are extremely sensitive to selenium; toxic effects include teratogenesis. Based on available data, both aquatic birds and aquatic mammals are sensitive ecological receptors.

II. Summary of the Proposed Rule

A. What Source Categories Are Affected by the Proposed Rule?

1. Incinerators That Burn Hazardous Waste

A hazardous waste burning incinerator is defined under § 63.1201(a) as a device that meets the definition of an incinerator in 40 CFR part 260.10 and that burns hazardous waste at any time. Hazardous waste incinerators are currently subject to the emission standards of part 63, subpart EEE.[12] Hazardous waste incinerator design types include rotary kilns, liquid injection incinerators, fluidized bed incinerators, and fixed hearth incinerators. Most incinerators have air pollution control equipment to capture particulate matter (and nonvolatile metals) and scrubbing equipment for the capture of acid gases. At least four incinerators are equipped with activated carbon injection systems or carbon beds to control dioxin/furan emissions (as well as other HAP emissions).

Incinerators can be further classified as either commercial or onsite. Commercial incinerators accept and treat, for a tipping fee, wastes that have been generated off-site. The purpose of commercial incinerators is to generate profit from treating hazardous wastes. On-site facilities treat only wastes that have been generated at the facility to avoid the costs of off-site treatment. In 2003, there were approximately 107 hazardous waste incinerators in operation, 15 of which were commercial facilities, the remaining being on-site facilities.

2. Cement Kilns That Burn Hazardous Waste

A hazardous waste burning cement kiln is defined under § 63.1201(a). Cement kilns that burn hazardous waste are currently subject to the emission standards of part 63, subpart EEE.[13] Cement kilns are long, cylindrical, slightly inclined rotating furnaces that are lined with refractory brick to protect the steel shell and retain heat within the Start Printed Page 21208kiln. Cement kilns are designed to calcine, or expel carbon dioxide by roasting, a blend of raw materials such as limestone, shale, clay, or sand to produce Portland cement. The raw materials enter the kiln at the elevated end, and the combustion fuels generally are introduced into the lower end of the kiln where the clinker product is discharged. The materials are continuously and slowly moved to the lower end by rotation of the kiln. As they move down the kiln, the raw materials are changed to cementitious minerals as a result of increased temperatures within the kiln.

Portland cement is a fine powder, usually gray in color, that consists of a mixture of minerals comprising primarily calcium silicates, aluminates, and aluminoferrites, to which small amounts of gypsum have been added during the finish grinding operations. Portland cement is the key ingredient in Portland cement concrete, which is used in almost all construction applications.

Cement kilns covered by this proposal burn hazardous waste-derived fuels to replace some or all of normal fossil fuels, typically coal. Most kilns burn liquid waste; however, cement kilns also may burn solids and small containers containing viscous or solid hazardous waste fuels. The annual hazardous waste fuel replacement rate varies considerably across sources from approximately 25 to 85 percent.

In 2003, there were 14 Portland cement plants in nine states operating a total of 25 hazardous waste burning kilns. All cement kilns use either bag houses or electrostatic precipitators to control particulate matter emissions.

3. Lightweight Aggregate Kilns That Burn Hazardous Waste

A hazardous waste burning lightweight aggregate kiln is defined under § 63.1201(a). Lightweight aggregate kilns that burn hazardous waste are currently subject to the emission standards of part 63, subpart EEE.[14] Raw materials such as shale, clay, and slate are crushed and introduced at the upper end of the rotary kiln. In passing through the kiln, the materials reach temperatures of 1,900-2,100 ° F. Heat is provided by a burner at the lower end of the kiln where the product is discharged. As the raw material is heated, it melts into a semi-plastic state and begins to generate gases that serve as the bloating or expanding agent. As temperatures reach their maximum, the semi-plastic raw material becomes viscous and entraps the expanding gases. This bloating action produces small, unconnected gas cells, which remain in the material after it cools and solidifies. Lightweight aggregate kilns are designed to expand the raw material by thermal processing into a coarse aggregate used in the production of lightweight concrete products such as concrete block, structural concrete, and pavement.

The lightweight aggregate kilns affected by this proposal burn hazardous waste-derived fuels to replace some or all of normal fossil fuels. Two of the facilities burn only liquid hazardous wastes, while the third facility burns both liquid and solid wastes. The annual hazardous waste fuel replacement rate is 100 percent.

In 2003, there were three lightweight aggregate kiln facilities in two states operating a total of seven hazardous waste-fired kilns. All lightweight aggregate kilns use baghouses to control particulate matter and one facility also uses a venturi scrubber to control acid gas emissions.

4. Boilers That Burn Hazardous Waste

Boilers that burn hazardous waste are currently regulated under RCRA at part 266, subpart H. We propose to use the RCRA definition of boiler under 40 CFR 260.10 for purposes of today's rulemaking for simplicity and continuity. This definition includes industrial, commercial, and institutional boilers as well as thermal units known in industry as process heaters. We propose to subcategorize boilers based on the type of fuel that is burned, which would result in separate emission standards for solid fuel-fired boilers and liquid fuel-fired boilers. We discuss subcategorization options in more detail in Part Two, Section II.

Boilers are typically described by either their design or type of fuel burned. Hazardous waste burning boilers comprise two basic different boiler designs—watertube and firetube. The choice of which design to use depends on factors such as the desired steam quality, thermal efficiency, size, economics, fuel type, and responsiveness. Watertube boilers are those that flow the water through tubes running the length of the boiler. The hot combustion gas surrounds these tubes, causing the water inside to get hot. Most hazardous waste burning boilers use this design. Watertube boilers can also burn a variety of fuel types including coal, oil, gas, wood, and municipal or industrial wastes. Firetube boilers are similar to watertube type, except the placement of the water and combustion gas is reversed. Here the hot combustion gas flows through the tubes, while the water surrounds the tubes. This design does have some disadvantages, however, in that they work well with only gas and liquid fuels.

Process heaters are similar to boilers (as conventionally defined), except they heat a fluid other than water. This fluid is often an oil or some other fluid with more suitable heating properties. Process heaters are often used in circumstances where the amount of heat needed is greater than what can be delivered by steam. For the purposes of this rulemaking and consistent with current RCRA regulations, process heaters would be classified as boilers.

Descriptions of liquid and solid fuel-fired boilers that burn hazardous waste are provided below.

a. Liquid Fuel-Fired Boilers. A liquid fuel-fired boiler is a device that meets the definition of a boiler under 40 CFR 260.10 and that burns any combination of liquid and gas fuels, but no solids. See proposed definition in § 63.1201(a). A liquid fuel is defined as a fuel that is pumpable (e.g., liquid wastes, sludges, or slurries). Most liquid hazardous waste burning boilers co-fire natural gas, fuel oil, or process gases to achieve the proper combustion temperatures and a consistent steam supply.

There are approximately 104 liquid fuel-fired boilers that burn hazardous waste, 85 of which have not installed back-end air pollution control equipment. The rest of the liquid boilers use either a wet scrubber, electrostatic precipitator, or fabric filter. These boilers co-fire liquid hazardous waste with either natural gas or heating oil at heat input rates of 10% to 100%.

b. Solid Fuel-Fired Boilers. A solid fuel-fired boiler is a device that meets the definition of a boiler under 40 CFR 260.10 and that burns solid fuels, including both pulverized and stoker coal.[15] See proposed definition in § 63.1201(a). Boilers that co-fire solid fuel with liquid or gaseous fuels are solid fuel-fired boilers.

There are 12 solid fuel-fired boilers that burn hazardous waste. These boilers co-fire liquid hazardous waste with coal at heat input rates of 6% to 33%. Nine of these boilers are stoker-fired, and three burn pulverized coal. Two boilers are equipped with fabric filters to control particulate matter and Start Printed Page 21209metals, and 10 are equipped with electrostatic precipitators.

5. Hydrochloric Acid Production Furnaces That Process Hazardous Waste

Hydrochloric acid production furnaces that burn hazardous waste are currently regulated under RCRA at part 266, subpart H. We propose to use the RCRA definition of hydrochloric acid production furnace under 40 CFR 260.10 for purposes of today's rulemaking for simplicity and continuity. See proposed definition in § 63.1201(a).

Hydrochloric acid production furnaces burn chlorinated hazardous wastes to make an aqueous hydrochloric acid for on-site use as an ingredient in a manufacturing process. The hazardous waste feedstocks have a chlorine content of over 20% by weight. The hydrochloric acid produced by burning the chlorinated byproducts dissolves in the scrubber water to produce an acid product containing hydrochloric acid greater than 3% by weight. There are 17 hazardous waste burning hydrochloric acid production furnaces currently in operation.

Chlorine-bearing feedstreams, wastes, and auxiliary fuels (usually natural gas) are burned in these hydrochloric acid production furnaces in a refractory lined chamber similar to a liquid waste incinerator chamber. Combustion is maintained at a high temperature, with adequate excess hydrogen to ensure the conversion of chlorine in the feedstreams to hydrogen chloride in the combustion gases. Many furnaces also have waste heat boilers, similar to those used by some incinerators, to recover heat and return it to the production process. Others use a water spray quench to cool the combustion gases.

The cooled combustion flue gas is routed to an acid recovery system, consisting of multiple wet scrubbing absorption units. These units are usually packed tower or film tray scrubbers which operate with an acidic scrubbing solution. The scrubbing solution is recycled to concentrate the acid until it reaches the desired concentration level, at which point it is recovered for use as a valuable product. A final polishing scrubber, operated with a caustic liquid solution, is used to control emissions of hydrogen chloride and chlorine gas.

B. What HAP Are Emitted?

Incinerators, cement kilns, lightweight aggregate kilns, and hydrochloric acid production furnaces that burn hazardous waste can emit high levels of dioxin/furans depending on the design and operation of the emission control equipment, and, for incinerators, whether a waste heat recovery boiler is used. Our data base shows that boilers that burn hazardous waste generally do not emit high levels of dioxin/furans.

All hazardous waste combustors can emit high levels of other organic HAP if they are not designed, operated, and maintained to operate under good combustion conditions.

Hazardous waste combustors can also emit high levels of metal HAP, depending on the level of metals in the waste feed and the design and operation of air emissions control equipment. Hydrochloric acid production furnaces, however, generally feed and emit low levels of metal HAP.

Hazardous waste combustors can also emit high levels of particulate matter, except that hydrochloric acid production furnaces generally feed wastes with low ash content and emit low levels of particulate matter.[16] The majority of particulate matter emissions from hazardous waste combustors is in the form of fine particulate (i.e., 50% or more of the particulate matter emitted is 2.5 microns in diameter or less).[17] Particulate emissions from incinerators and liquid fuel-fired boilers depend on the ash content of the waste feed and the design and operation of air emission control equipment. Particulate emissions from cement kilns and lightweight aggregate kilns are not significantly affected by the ash content of the hazardous waste fuel because uncontrolled particulate emissions are attributable primarily to raw material entrained in the combustion gas. Thus, particulate emissions from kilns depend on operating conditions that affect entrainment of raw material, and the design and operation of the emission control equipment.

C. Does Today's Proposed Rule Apply to My Source?

The following sources that burn hazardous waste are considered to be affected sources subject to today's proposed rule: Incinerators, cement kilns, lightweight aggregate kilns, boilers, and hydrochloric acid production furnaces. Affected sources do not include: (1) Sources exempt from regulation under 40 CFR part 266, subpart H, because the only hazardous waste they burn is listed under 40 CFR 266.100(c); (2) research, development, and demonstration sources exempt under § 63.1200(b); and (3) boilers exempt from regulation under 40 CFR part 266, subpart H, because they meet the definition of small quantity burner under 40 CFR 266.108. See § 63.1200(b).

Affected sources also do not include emission points that are unrelated to the combustion of hazardous waste (e.g., cement kiln clinker cooler stack emissions, hydrochloric acid production facility emissions originating from product or waste storage tanks and transfer operations, etc.). This is because subpart EEE only controls HAP emission points that are directly related to the combustion of hazardous waste. Under separate rulemakings, the Agency has or will establish MACT standards, where warranted, to control HAP emissions from non-hazardous waste related emission points.

Hazardous waste combustors are affected sources irrespective of whether they are major sources or area sources. As discussed in Part Two, Section I.A, we are proposing to subject area sources of boilers and hydrochloric acid production furnaces to the major source MACT standards for mercury, dioxin/furans, carbon monoxide/hydrocarbons, and destruction and removal efficiency pursuant to section 112(c)(6). As promulgated in the 1999 rule, both area source and major source incinerators, cement kilns, and lightweight aggregate kilns will continue to be subject to the full suite of Subpart EEE emission standards.

D. What Emissions Limitations Must I Meet?

Under today's proposal, you would have to comply with the emission limits in Tables 1 and 2. Note that these emission limitations are discussed in greater detail for each source category (and subcategory) in Part Two, Section VII thru XII. Note also that we are proposing several alternative emission standards: (1) You may elect to comply with an alternative to the particulate matter standard for incinerators and liquid fuel-fired boilers that would limit emissions of total metal HAP; and (2) you may elect to comply with an alternative to the total chlorine standard applicable to all source categories, except hydrochloric acid production furnaces, under which you may establish site-specific, risk-based emission limits for hydrogen chloride and chlorine gas based on national Start Printed Page 21210exposure standards. These alternative standards are discussed in Part Two, Section XVIII and Section XIII, respectively.

Table 1.—Proposed Standards for Existing Sources

IncineratorsCement kilnsLightweight aggregate kilnsSolid fuel-fired boilers 1Liquid fuel-fired boilers 1Hydrochloric acid production furnaces 1
Dioxin/Furans ( ng TEQ/dscm)0.28 for dry APCD and WHB sources; 6 0.40 for others0.20 or 0.40 + 400°F at APCD inlet0.40CO or THC standard as a surrogate0.40 for dry APCD sources; CO or HC standard as surrogate for others0.40
Mercury130 ug/dscm64 ug/dscm 267 ug/dscm 210 ug/dscm3.7E-6 lb/MMBtu 2, 5Total chlorine standard as surrogate
Particulate Matter0.015 gr/dscf 80.028 gr/dscf0.025 gr/dscf0.030 gr/dscf 80.032 gr/dscf 8Total chlorine standard as surrogate
Semivolatile Metals (lead + cadmium)59 ug/dscm4.0E-4 lbs/MMBtu 53.1E-4 lb/MMBtu 5 and 250 ug/dscm 3170 ug/dscm1.1E-5 lb/MMBtu 2, 5Total chlorine standard as surrogate
Low Volatile Metals (arsenic + beryllium + chromium)84 ug/dscm1.4E-5 lbs/MMBtu 59.5E-5 lbs/MMBtu 5 and 110 ug/dscm 3210 ug/dscm1.1E-4 lb/MMBtu 4, 5Total chlorine standard as surrogate
Total Chlorine (hydrogen chloride + chlorine gas)1.5 ppmv 7110 ppmv 7600 ppmv 7440 ppmv 72.5E-2 lb/MMBtu 5, 714 ppmv or 99.9927% system removal efficiency
Carbon Monoxide (CO) or Hydrocarbons HWC100 ppmv CO or 10 ppmv HWCSee Part Two, Section VIII100 ppmv CO or 20 ppmv HWC(2) 100 ppmv CO or 10 ppmv HWC
Destruction and Removal Efficiency (DRE)99.99% for each principal organic hazardous pollutant. For sources burning hazardous wastes F020, F021, F022, F023, F026, or F027, however, 99.9999% for each principal organic hazardous pollutant.
Notes:
1 Particulate matter, semivolatile metal, low volatile, and total chlorine standards apply to major sources only for solid fuel-fired boilers, liquid fuel-fired boilers, and hydrochloric acid production furnaces.
2 Standard is based on normal emissions data.
3 Sources must comply with both the thermal emissions and emission concentration standards.
4 Low volatile metal standard for liquid fuel-fired boilers is for chromium only. Arsenic and beryllium are not included in the low volatile metal total for liquid fuel-fired boilers.
5 Standards are expressed as mass of pollutant contributed by hazardous waste per million Btu contributed by the hazardous waste.
6 APCD denotes “air pollution control device”, WHB denotes “waste heat boiler”.
7 Sources may elect to comply with site-specific, risk-based emission limits for hydrogen chloride and chlorine gas based on national exposure standards. See Part Two, Section XIII.
8 Sources may elect to comply with an alternative to the particulate matter standard. See Part Two, Section XVIII.

Table 2.—Proposed Standards for New Sources

IncineratorsCement kilnsLightweight aggregate kilnsSolid fuel boilers 1Liquid fuel boilers 1Hydrochloric acid production furnaces 1
Dioxin/Furans ( ng TEQ/dscm)0.11 for dry APCD or WHBs 5; 0.2 for others0.20 or 0.40 + 400°F at inlet to particulate matter control device0.40Carbon monoxide (CO) or hydrocarbon (HC) as a surrogate0.015 or 400°F at the inlet to particulate matter control device for dry APCD; CO or HC standard as surrogate for others0.40
Mercury8 ug/dscm35 ug/dscm 267 ug/dscm 210 ug/dscm3.8E-7 lb/MMBtu 2, 4Tcl as surrogate
Particulate matter0.00070 gr/dscf 70.0058 gr/dscf0.0099 gr/dscf0.015 gr/dscf70.0076 gr/dscf7TCL as surrogate
Semivolatile Metals (lead + cadmium)6.5 ug/dscm6.2E-5 lb/MMBtu 42.4E-5 lb/MMBtu 4170 ug/dscm4.3E-6 lb/MMBtu 2, 4TCL as surrogate
Low Volatile Metals (arsenic + beryllium + chromium)8.9 ug/dscm1.4E-5 lb/MMBtu 43.2E-5 lb/MMBtu 4190 ug/dscm3.6E-5 lb/MMBtu in HW 3, 4TCL as surrogate
Total Chlorine (Hydrogen chloride + chlorine gas)0.18 ppmv678 ppmv6600 ppmv673 ppmv67.2E-4 lb/MMBtu 4, 61.2 ppmv or 99.99937% SRE
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Carbon monoxide CO or Hydrocarbons (HWC)100 ppmv (CO) or 10 ppmv HWCSee Part Two, Section VIII100 ppmv CO or 20 ppmv HWC100 ppmv CO or 10 ppmv HWC
Destruction and Removal Efficiency99.99% for each principal organic hazardous pollutant. For sources burning hazardous wastes F020, F021, F022, F023, F026, or F027, however, 99.9999% for each principal organic hazardous pollutant.
Notes:
1 Particulate matter, semivolatile metal, low volatile metal, and total chlorine standards apply to major sources only for solid fuel-fired boilers, liquid fuel-fired boilers, and hydrochloric acid production furnaces.
2 Standard is based on normal emissions data.
3 Low volatile metal standard for liquid fuel-fired boilers is for chromium only. Arsenic and beryllium are not included in the low volatile metal total for liquid fuel-fired boilers.
4 Standards are expressed as mass of pollutant contributed by hazardous waste per million Btu contributed by the hazardous waste.
5 APCD denotes “air pollution control device”, WHB denotes “waste heat boiler”.
6 Sources may elect to comply with site-specific, risk-based emission limits for hydrogen chloride and chlorine gas based on national exposure standards. See Part Two, Section XIII.
7 Sources may elect to comply with an alternative to the particulate matter standard. See Part Two, Section XVIII.

E. What Are the Testing and Initial Compliance Requirements?

We are proposing testing and initial compliance requirements for solid fuel-fired boilers, liquid fuel-fired boilers and hydrochloric acid production furnaces that are identical to those that are applicable to incinerators, cement kilns, and lightweight aggregate kilns already in place at §§ 63.1206, 63.1207, and 63.1208. Please note also that in Part Three of today's preamble we request comment on, or propose revisions to, several testing and initial compliance requirements. Any amendments to the testing and compliance requirements that we promulgate as a result of those discussions would be applicable to all hazardous waste combustors.

In addition, we are proposing to revise the existing initial compliance requirements for incinerators, cement kilns, and lightweight aggregate kilns. Under the proposed revision, owners and operators of incinerators, cement kilns, and lightweight aggregate kilns would be required to conduct the initial comprehensive performance test to document compliance with the replacement standards proposed today (§§ 63.1219, 63.1220, and 63.1221) within 12 months of the compliance date. Owners and operators of solid fuel-fired boilers, liquid fuel-fired boilers and hydrochloric acid production furnaces would be required to conduct an initial comprehensive performance test within six months of the compliance date, and periodic comprehensive performance tests every five years. The purpose of the comprehensive performance test is to document compliance with the emission standards, document that continuous monitoring systems meet performance requirements, and establish limits on operating parameters that would be monitored by continuous monitoring systems.

Owners and operators of liquid fuel-fired boilers equipped with a dry air pollution control device and hydrochloric acid production furnaces would be required to conduct a dioxin/furan confirmatory performance test 2.5 years after each comprehensive performance test (i.e., midway between comprehensive performance tests). The purpose of the dioxin/furan confirmatory performance test is to document compliance with the dioxin/furan standard when operating within the range of normal operations. Owners and operators of solid fuel-fired boilers, and liquid fuel-fired boilers that are not subject to a numerical dioxin/furan emission standard (i.e., liquid fuel-fired boilers other than those equipped with an electrostatic precipitator or fabric filter), would be required to conduct a one-time dioxin/furan test to enable the Agency to evaluate the effectiveness of the carbon monoxide/hydrocarbon standard and destruction and removal efficiency standard in controlling dioxin/furan emissions for those sources. The Agency would use those emissions data when reevaluating the MACT standards under section 112(d)(6) and when determining whether to develop residual risk standards for these sources pursuant to CAA section 112(f)(2).

Owners and operators of solid fuel-fired boilers, liquid fuel-fired boilers and hydrochloric acid production furnaces would be required to use the following stack test methods to document compliance: (1) Method 29 for mercury, semivolatile metals, and low volatile metals; and (2) Method 26A for hydrogen chloride and chlorine gas; (3) either Method 0023A or Method 23 for dioxin/furans; and (4) either Method 5 or 5i for particulate matter.

The following is a proposed time-line for testing and initial compliance requirements for owners and operators of solid fuel-fired boilers, liquid fuel-fired boilers and hydrochloric acid production furnaces: (1) The compliance date is three years from publication of the final rule; (2) you must place in the operating record a Documentation of Compliance by the compliance date identifying that the operating parameter limits you have determined using available information will ensure compliance with the emission standards; (3) you must commence the initial comprehensive performance test within six months of the compliance date; (4) you must complete the initial comprehensive performance test within 60 days of commencing the test; and (5) you must submit a Notification of Compliance within 90 days of completing the test documenting compliance with emission standards and CMS requirements.

F. What Are the Continuous Compliance Requirements?

We are proposing continuous compliance requirements for solid fuel-fired boilers, liquid fuel-fired boilers and hydrochloric acid production furnaces that are identical to those already in place at § 63.1209 and applicable to incinerators, cement kilns, and lightweight aggregate kilns. Please note, however, that in Part Three of today's preamble we request comment on, or propose revisions to, several continuous compliance requirements. Any amendments to the continuous compliance requirements that we promulgate as a result of those discussions would be applicable to all hazardous waste combustors.

Start Printed Page 21212

Owners and operators of solid fuel-fired boilers, liquid fuel-fired boilers and hydrochloric acid production furnaces would be required to use carbon monoxide or hydrocarbon continuous emissions monitors (as well as an oxygen continuous emissions monitor to correct the carbon monoxide or hydrocarbon values to 7% oxygen) to ensure compliance with the carbon monoxide or hydrocarbon emission limits.

Owners and operators of solid fuel-fired boilers, liquid fuel-fired boilers and hydrochloric acid production furnaces would also be required to establish limits on the feedrate of metals, chlorine, and (for some source categories) ash, key combustor operating parameters, and key operating parameters of the control device based on operations during the comprehensive performance test. You must continuously monitor these parameters with continuous monitoring systems. See Part Two, Section XIV.C for a discussion of the specific parameters for which you must establish limits.

G. What Are the Notification, Recordkeeping, and Reporting Requirements?

We are proposing notification, recordkeeping, and reporting requirements for solid fuel-fired boilers, liquid fuel-fired boilers and hydrochloric acid production furnaces that are identical to those already in place at §§ 63.1210 and 63.1211 and applicable to incinerators, cement kilns, and lightweight aggregate kilns. Please note, however, that we are proposing a new requirement applicable to all hazardous waste combustors that would require you to submit a Notification of Intent to Comply and a Compliance Progress Report. See Part Two, Section XVI.B.

The proposed notification, recordkeeping, and reporting requirements are summarized in Part Two, Section XVI.

Part Two: Rationale for the Proposed Rule

I. How Did EPA Determine Which Hazardous Waste Combustion Sources Would Be Regulated

A. How Are Area Sources Regulated?

We are proposing to subject area source boilers and hydrochloric acid production furnaces to the major source MACT standards for mercury, dioxin/furan, carbon monoxide/hydrocarbons, and destruction and removal efficiency pursuant to section 112(c)(6).[18] Both area source and major source incinerators, cement kilns, and lightweight aggregate kilns will continue to be subject to the full suite of Subpart EEE emission standards.[19]

Section 112(c)(6) of the CAA requires EPA to list and promulgate section 112(d)(2) or (d)(4) standards (i.e., standards reflecting MACT) for categories and subcategories of sources emitting seven specific pollutants. Four of those listed pollutants are emitted by boilers and hydrochloric acid production furnaces: mercury, 2,3,7,8-tetrachlorodibenzofuran, 2,3,7,8-tetrachlorodibenzo-p-dioxin, and polycyclic organic matter. EPA must assure that source categories accounting for not less than 90 percent of the aggregated emissions of each enumerated pollutant are subject to MACT standards. Congress singled out the pollutants in section 112(c)(6) as being of “specific concern” not just because of their toxicity but because of their propensity to cause substantial harm to human health and the environment via indirect exposure pathways (i.e., from the air through other media, such as water, soil, food uptake, etc.). Furthermore, these pollutants have exhibited special potential to bioaccumulate, causing pervasive environmental harm in biota and, ultimately, human health risks.

We estimate that approximately 1,800 pounds of mercury are emitted annually in aggregate from hazardous waste burning boilers in the United States.[20] Also, we estimate that hazardous waste burning boilers and hydrochloric acid production furnaces emit in aggregate approximately 1.1 and 1.6 grams TEQ per year of dioxin/furan, respectively. The Agency has already counted on the control of these pollutants from area sources in the industrial/commercial/institutional boiler source category when we accounted for at least 90 percent of the emissions of these hazardous air pollutants as being subject to standards under section 112(c)(6). See 63 FR 17838; April 10, 1998. Therefore, we are proposing to subject boiler and hydrochloric acid furnace area sources to the major source MACT standards for mercury, dioxin/furan, carbon monoxide/hydrocarbons, and destruction and removal efficiency pursuant to section 112(c)(6).

We are proposing that only major source boilers and hydrochloric acid furnaces would be subject to the full suite of subpart EEE emission standards we propose today. Section 112(c)(3) of the CAA requires us to subject area sources to the full suite of standards applicable to major sources if we find “a threat of adverse effects to human health or the environment” that warrants such action. We cannot make this finding for area source boilers and halogen acid production furnaces.[21] Consequently, area sources in these categories would be subject to the MACT standards for mercury, dioxin/furan, carbon monoxide/hydrocarbons, and destruction and removal efficiency standards only to control the HAP listed under section 112(c)(6). RCRA standards under Part 266, Subpart H for particulate matter, metals other than mercury, and hydrogen chloride and chlorine gas would continue to apply to these area sources unless an area source elects to comply with the major source standards in lieu of the RCRA standards. See proposed § 266.100(b)(3) and the proposed revisions to §§ 270.22 and 270.66.

B. What Hazardous Waste Combustors Are Not Covered by This Proposal?

1. Small Quantity Burners

Boilers that are exempt from the RCRA hazardous waste-burning boilers rule under 40 CFR 266.108 because they burn small quantities of hazardous waste fuel would also be exempt from today's proposed rule. Those boilers would be subject, however, to the MACT standards the Agency has proposed for industrial/commercial/institutional boilers. See 68 FR 1660, January 13, 2003.

The type and concentration of HAP emissions from boilers that co-fire small quantities of hazardous waste fuel with other fuels under § 266.108 should be characterized more by the metals and chlorine levels in the primary fuels and the effect of combustion conditions on the primary fuels than by the composition and other characteristics of the hazardous waste fuel. Under § 266.108, boilers that burn small quantities of hazardous waste fuel cannot fire hazardous waste at any time at a rate greater than 1 percent of the Start Printed Page 21213total fuel requirements for the boiler. In addition, a boiler with a stack height of 20 meters or less cannot fire more than 84 gallons of hazardous waste fuel a month, which would equate to an average firing rate of 0.5 quarts per hour. Finally, the hazardous waste fuel must have a heating value of 5,000 Btu/lb to ensure it is a bonafide fuel, and cannot contain hazardous wastes that are listed because they contain chlorinated dioxins/furans. Given these restrictions, we believe that HAP emissions are not substantially related to the hazardous waste fuels these boilers burn. Thus, these boilers are more appropriately regulated under the MACT standards proposed at part 63, subpart DDDDD, than the MACT standards proposed today for hazardous waste combustors.

Boilers that burn small quantities of hazardous waste fuel under § 266.108 would become subject to part 63, subpart DDDDD, three years after publication of the final rule for hazardous waste combustors (i.e., the rules we are proposing today). Subpart DDDDD exempts “a boiler or process heater required to have a permit under section 3005 of the Solid Waste Disposal Act [i.e., RCRA] or covered by 40 CFR part 63, subpart EEE (e.g., hazardous waste combustors).” See 40 CFR 63.7491(d). Boilers that burn small quantities of hazardous waste fuel under § 266.108 are exempt from the substantive emission standards of part 266, subpart H, and the permit requirements of 40 CFR part 270 (establishing RCRA permit requirements). In addition, owners and operators of such boilers would not know whether they are covered by part 63, subpart EEE, until we promulgate the final rule for hazardous waste combustors. Thus, it is appropriate to require that these boilers begin complying with subpart DDDDD three years after we publish the final rule for hazardous waste combustors.

2. Sources Exempt From RCRA Emission Regulation Under 40 CFR Part 266.100(c)

Consistent with the Phase I Hazardous Waste Combustor MACT rule promulgated in 1999, we would not subject boilers and hydrochloric acid production furnaces to today's proposed requirements if the only hazardous waste combusted is exempt from regulation pursuant to § 266.100(c), including certain types of used oil, landfill gas, and otherwise exempt or excluded waste. This is appropriate because HAP emissions from sources that qualify for this exemption would not be significantly impacted by the combustion of hazardous waste. Thus, emissions from these sources would be more appropriately regulated by other promulgated MACT standards that specifically address emissions from these sources.

3. Research, Development, and Demonstration Sources

Consistent with the Phase I Hazardous Waste Combustor MACT rule promulgated in 1999, we would not subject boilers and hydrochloric acid production furnaces that are research, development, and demonstration sources to today's proposed requirements. We explained at promulgation of the Phase I MACT standards that the hazardous waste combustor emission standards may not be appropriate for research, development, and demonstration sources because of their typically intermittent operations and small size. See 64 FR at 52839. Given that emissions from these sources are addressed under RCRA on case-by-case basis pursuant to § 270.65, we continue to believe this is appropriate, and we are today proposing the same exemption for boilers and hydrochloric acid production furnaces.

C. How Would Sulfuric Acid Regeneration Facilities Be Regulated?

Sulfuric acid regeneration facilities burn spent sulfuric acid and sulfur-bearing hazardous wastes or hazardous waste fuel to produce sulfuric acid and are subject to 40 CFR part 266, subpart H, (i.e., the RCRA Boiler and Industrial Furnace Rule) as a listed industrial furnace. We are not proposing MACT standards for these sources because EPA did not list sulfuric acid regeneration facilities as a category of major sources of HAP emissions. See 57 FR 31576 (July 16, 1992). We obtained emissions and other data on these sources and confirmed that they emit very low levels of HAP.[22] Accordingly, these combustors will remain subject to RCRA regulations under part 266, subpart H.

II. What Subcategorization Considerations Did EPA Evaluate?

CAA section 112(d)(1) allows us to distinguish amongst classes, types, and sizes of sources within a category when establishing floor levels. Subcategorization typically reflects “differences in manufacturing process, emission characteristics, or technical feasibility.” See 67 FR 78058. A classic example, provided in the legislative history to CAA 112(d), is of a different process leading to different emissions and different types of control strategies—the specific example being Soderberg and prebaked anode primary aluminum processes. See “A Legislative History of the Clean Air Act Amendments of 1990,” vol. 1 at 1138-39 (floor debates on Conference Report). If we determine, for instance, that a given source category includes sources that are designed differently such that the type or concentration of HAP emissions are different we may subcategorize these sources and issue separate standards.

We have determined that it is appropriate to subcategorize sources that combust hazardous waste from those sources that do not. EPA published an initial list of categories of major and area sources of HAP selected for regulation in accordance with section 112(c) of the Act on July 16, 1992 (57 FR 31576). Hazardous waste incineration, Portland cement manufacturing, clay products manufacturing (including lightweight aggregate manufacturing), industrial/commercial/institutional boilers and process heaters, and hydrochloric acid production are among the listed 174 categories of sources. Although some cement kilns, lightweight aggregate kilns, boilers and process heaters, and hydrochloric acid production furnaces burn hazardous waste, EPA did not list hazardous waste burning sources as separate source categories. Nonetheless, we generally believe that hazardous waste combustion sources can emit different types or concentrations of HAP emissions because hazardous waste combustors: (1) Have different fuel HAP concentrations; (2) use different control techniques (e.g., feed control); and (3) have a different regulatory history given that their toxic emissions were regulated pursuant to RCRA standards. As a result, we believe it is appropriate to subcategorize each source category listed above to define sources that burn hazardous waste as a separate classes of combustors. We also assessed if further subdividing each class of hazardous waste burning combustors is warranted using both engineering judgement and statistical analysis. In our proposed approach, we first use engineering information and principles to identify potential subcategorization options. We then determine if there is a statistical difference in the emission characteristics between these options. See Part Two, Section VI.C for a discussion of this statistical analysis. Finally, we review the results of the statistical analysis to determine whether they are an appropriate basis for Start Printed Page 21214subcategorization.[23] We describe below the subcategorization options we considered for each source category.

A. What Subcategorization Options Did We Consider for Incinerators?

We considered whether to propose separate standards for three hazardous waste incinerator subcategory options. First, we assessed whether government-owned incinerator facilities had different emission characteristics when compared to non-government facilities for the mercury, semivolatile metal, low volatile metal, particulate matter, and total chlorine floors. After evaluating the data, we determined that emission characteristics from these two subcategories are not statistically different, and, therefore are not proposing separate emission standards.

Second, we assessed whether liquid injection incinerators emitted significantly different levels of metals and particulate matter compared to incinerators that feed solid wastes (e.g., rotary kilns, fluid bed units, and hearth fired units). We define liquid injection units as those incinerators that exclusively feed pumpable waste streams and solid feed units as those that feed a combination of liquid and solid wastes. We determined that emissions of metal HAP from these potential subcategories are not statistically different.[24] We, therefore, are not proposing separate emission standards for metal HAP. The statistical analysis for particulate matter shows that emissions from liquid feed injection incinerators are higher than emissions from solid feed injection units. However, we believe that separate standards for particulate matter are not warranted because the difference in emissions was more a factor of the types of back-end air pollution devices used by the sources rather than incinerator design. We would expect particulate emissions to be potentially higher for solid feed units, not lower, because solid feed units have higher ash feedrates and air pollution control device inlet particulate matter loadings. Therefore, we must conclude that the difference is the product of less effective back-end air pollution control.

Third, we assessed whether incinerators equipped with dry air pollution control devices and/or waste heat boilers have different dioxin/furan emission characteristics when compared to other sources, i.e., sources with either wet air pollution control or no air pollution control devices. Our statistical analysis determined that dioxin/furan emissions from sources equipped with waste heat boilers and/or dry air pollution control devices are higher.[25] We believe use of wet air pollution control systems (and use of no air pollution control system) can result in different dioxin/furan emission characteristics because they have different post-combustion particle residence times and temperature profiles, which can affect dioxin/furan surface catalyzed formation reaction rates. As a result, we believe that it is appropriate to subcategorize these different types of combustors.

Note that we do not subcategorize based on the type of air pollution control device used. See 69 FR 394 (January 5, 2004). Dioxin/furan emission characteristics are unique in that they are not typically fed into the combustion device, but rather are formed in the combustor or post combustion within ductwork, a heat recovery boiler, or the air pollution control system. Wet and dry air pollution control systems are generally not considered to be dioxin/furan control systems because their primary function is to remove metals and/or total chlorine from the combustion gas. They generally do not remove dioxin/furans from the incinerator flue gas unless they are used in tandem with carbon injection systems or carbon beds. (In contrast, carbon injection systems and carbon beds are considered to be dioxin/furan air pollution control systems). Thus, the differences in dioxin formation here reflect something more akin to a process difference resulting in different emission characteristics, rather than a difference in pollution-capture efficiencies among pollution control devices. We thus are not proposing to subcategorize based on whether a source is equipped with a dioxin/furan control system.

We also considered whether to further subcategorize based on the presence of a waste heat boiler or dry air pollution control device. Our analysis determined that dioxin/furan emissions from incinerators with waste heat boilers are not statistically different from those equipped with dry air pollution control devices.[26] We conclude that further subcategorization is not necessary. See Part Two, Section VII.A for more discussion on the proposed dioxin/furan standards for incinerators.

B. What Subcategorization Options Did We Consider for Cement Kilns?

We considered subdividing hazardous waste burning cement kilns by the clinker manufacturing process: wet process kilns without in-line raw mills versus preheater/precalciner kilns with in-line raw mills. All cement kilns that burn hazardous waste use one of these clinker manufacturing processes. Based on available emissions data, we evaluated design and operating features of each process to determine if the features could have a significant impact on emissions. For the reasons discussed below, we believe that subcategorization is not warranted.

In the wet process, raw materials are ground, wetted, and fed into the kiln as a slurry. Twenty-two of the 25 cement kilns that burn hazardous waste use the wet process to manufacture clinker. In the preheater/precalciner kilns, raw materials are ground dry in a raw mill and fed into the kiln dry. The remaining three of the 25 cement kilns burning hazardous waste use preheater/precalciner kilns with in-line raw mills.

Combustion gases and raw materials move in a counterflow direction inside a cement kiln for both processes. The kiln is inclined, and raw materials are fed into the upper end while fuels are typically fired into the lower end. Combustion gases move up the kiln counter to the flow of raw materials. The raw materials get progressively hotter as they travel down the length of the kiln. The raw materials begin to soften and fuse at temperatures between 2,250 and 2,700 °F to form the clinker product.

Wet process kilns are longer than the preheater/precalciner kilns in order to facilitate evaporation of the water from the slurried raw material. The preheater/precalciner kilns begin the calcining process—heating of the limestone to drive off carbon dioxide to obtain lime (calcium oxide)—before the raw materials are fed into the kiln. This is accomplished by routing the flue gases from the kiln up through the preheater tower while the raw materials are passing down the preheater tower. Start Printed Page 21215The heat of the flue gas is transferred to the raw material as they interact in the preheater tower. The precalciner is a secondary firing system—typically fired with coal—located at the base of the preheater tower.

Though not necessary in a wet process kiln, a preheater/precalciner kiln uses an alkali bypass designed to divert a portion of the flue gas to remove problematic volatile constituents such as alkalies (potassium and sodium oxides), chlorides, and sulfur that, if not removed, can lead to operating problems. In addition, removal of the alkalies is necessary so that their concentrations are below maximum acceptable levels in the clinker. An alkali bypass diverts between 10-30% of the kiln off-gas before it reaches the lower cyclone stages of the preheater tower. Without use of a bypass, the high concentration of volatile constituents at the lower cyclone stage of the preheater tower would create operational problems. Bypass gases are quenched and sent to a dedicated particulate matter control device to capture and remove the volatile constituents.

All preheater/precalciner kilns that burn hazardous waste use the hot flue gases to dry the raw materials as they are being ground in the in-line raw mill. Typically, the raw mill is operating or “on” approximately 85% of the time. The kilns with in-line raw mills must operate both in the “on” mode—gases are routed through the raw mill supporting raw material drying and preparation—and in the “off” mode—necessary down time for raw mill maintenance. Given that there are few preheater/precalciner cement kilns that burn hazardous waste, we had limited emissions data to evaluate to see if there was a significant difference in emissions. Moreover, we do not have any data from a preheater/precalciner kiln operating under similar operating conditions (e.g., metals and chlorine feed concentrations) both for the “on” mode and “off” mode.

We evaluated whether there was a significant difference in HAP emissions between wet process kilns without in-line raw mills versus preheater/precalciner kilns with in-line raw mills. We found a statistically significant difference in mercury emissions between wet process kilns and preheater/precalciner kilns in the “off” mode.[27] But, we conclude that there is no significant difference in emissions of dioxin/furans, particulate matter, semivolatile metals, low volatile metals, and total chlorine between these types of kiln systems.[28]

For wet process cement kilns without in-line raw mills, mercury remains in the vapor phase at the typical operating temperatures in the kiln and particulate matter control equipment, and exits the kiln as volatile stack emissions with only a small fraction partitioning to the clinker or cement kiln dust. In the preheater/precalciner kilns with in-line raw mill, we believe that a significant portion of the volatilized mercury condenses on to the surfaces of the cooler raw material in the operating raw mill. The raw material with adsorbed mercury ends up in the raw material storage bin which will eventually be fed to the kiln and re-volatilized. During the periods that the in-line raw mill is “on”, mercury is effectively captured in the raw mill essentially establishing an internal recycle loop of mercury that builds-up within the system. Eventually, when the in-line raw mill switches to the “off” mode, the re-volatilized mercury exits the kiln as volatile stack emissions. Notwithstanding the apparent removal of mercury during periods that the in-line raw mill is “on” in a preheater/precalciner kiln, over time the mercury is emitted eventually as volatile stack emissions because system removal efficiencies for mercury are essentially zero. Thus, over a longer period of time (e.g., one month), the mass of mercury emitted by a wet process kiln without an in-line raw mill and a preheater/precalciner kiln with an in-line raw mill (assuming identical mercury-containing feedstreams) would be the same. However, at any given point in time, the stack gas concentration of mercury of the two types of kilns could be significantly different.

As noted above, our data base shows a significant difference in mercury emissions between preheater/precalciner kilns when operating in the “off” mode and emissions both from wet process kilns and preheater/precalciner kilns in the “on” mode. In spite of this difference, we don't believe it is technically justified to subcategorize cement kilns for mercury.[29]

In conclusion, we propose not to subcategorize the hazardous waste burning class of cement kilns by wet process kilns and preheater/precalciner kilns with in-line raw mills.

C. What Subcategorization Options Did We Consider for Lightweight Aggregate Kilns?

Following promulgation of the September 1999 Final Rule, Solite Corporation filed a Petition for Review challenging the total chlorine standard for new kilns. For new sources, the Clean Air Act states that the MACT floor cannot be “less stringent than the emission control that is achieved by the best controlled similar source.” Solite Corporation challenged the standard on the ground that Norlite Corporation, another hazardous waste-burning lightweight aggregate kiln source, should not be the best controlled similar source because they are designed to burn for purposes of treatment hazardous wastes containing high levels of chlorine and high mercury. Solite states that Norlite's superior emission control equipment is designed to control the chlorine and mercury in these wastes that are burned for treatment, rather than primarily as fuel for lightweight aggregate production. Thus, Solite states that Norlite's sources should be considered a separate class of lightweight aggregate kilns.

Though we believe that subcategorizing by the concentrations of HAP in the hazardous waste is not appropriate, we considered subdividing hazardous waste burning lightweight aggregate kilns by the types of hazardous waste they combust: low Btu wastes with higher concentrations of chlorine and mercury and high Btu wastes with lower concentrations of chlorine and mercury. We believe, however, that separate emission standards for lightweight aggregate kilns based on the types of hazardous waste they burn are unnecessary because the floor levels would not differ significantly under either approach.

Analysis of available total chlorine emissions from compliance testing indicates that the emissions are significantly different for sources burning hazardous waste with high levels of chlorine compared to sources burning wastes with much lower levels of chlorine. Total chorine emissions range from 14 to 116 ppmv for sources feeding higher concentrations of chlorine but using a venturi scrubber to control emissions and range from 500 to 2,400 ppmv for sources feeding waste with lower levels of chlorine and not using a wet scrubber. However, when we identify floor levels for these potential subcategories (both for existing and new sources), the calculated floor Start Printed Page 21216level would be less stringent than the interim emission standard sources are currently achieving. Because all sources are achieving the more stringent interim standard, the interim standard becomes the default floor level. Therefore, subdividing would not affect the proposed floor level.

We have compliance test mercury emissions data representing maximum emissions for only one source, and we have snap-shot mercury emissions data within the range of normal emissions for all sources. Snap-shot mercury emissions range from: (1) 11 to 20 ug/dscm for sources with the potential to feed higher concentrations of mercury because they use a venturi scrubber to control emissions; and (2) 1 to 47 ug/dscm for sources that typically feed lower mercury containing wastes and do not use a wet scrubber to control mercury. We performed a statistical test and confirmed that there is no statistically significant difference in the snap-shot mercury emissions between sources that have the potential to feed higher levels of mercury because they are equipped with a wet scrubber and with other sources. Therefore, it appears that subcategorization for mercury is not warranted.[30]

D. What Subcategorization Options Did We Consider for Boilers?

We discuss below the rationale for proposing to subcategorize boilers by the physical form of the fuels they burn—solid fuel-fired boilers and liquid fuel-fired boilers. We also discuss further subcategorization options we considered for each of those subcategories and explain why we believe that further subcategorization is not warranted.

1. Subcategorization by Physical Form of Fuels Burned

There are substantial design differences and emission characteristics among boilers that cofire hazardous waste primarily with coal versus oil or gas. Because of these differences, it is appropriate to subcategorize boilers by the physical form of the fuel burned. We note that the Agency has already proposed that industrial/commercial/institutional boilers and process heaters that do not burn hazardous waste should be subcategorized by the physical form of fuels fired.[31]

Twelve boilers cofire hazardous waste with coal. These boilers are designed to handle high ash content solid fuels, including the relatively large quantities of boiler bottom ash and particulate matter that are entrained in the combustion gas. The coal also contributes to emissions of metal HAP. Approximately 104 boilers co-fire hazardous waste with natural gas or fuel oil. These units are not designed to handle the high ash loadings that are associated with coal-fired units, and the primary fuels for these boilers contribute little to HAP emissions. See “Draft Technical Support Document for HWC MACT Replacement Standards, Volume I: Description of Source Categories” (Chapter 2.4) and “Volume III: Selection of MACT Standards” (Chapter 4) for a discussion of the design differences between liquid and coal fuel-fired boilers.

Because the type of primary fuel burned dictates the design of the boiler and emissions control systems, and can affect the concentration of HAP, it is appropriate to subcategorize boilers by the physical form of the fuel.

2. Subcategorization Considerations Among Solid Fuel Boilers

We considered whether to subcategorize solid fuel-fired boilers to establish separate particulate matter standards. All 12 of the solid fuel-fired boilers co-fire hazardous waste with coal. Three of the 12 boilers burn pulverized coal while the remaining nine are stoker-fired boilers. Pulverized coal-fired boilers have higher uncontrolled emissions than stoker-fired boilers because the coal is pulverized to a talcum powder consistency and burned in suspension. Stoker-fired boilers burn lump coal partially or totally on a grate. Thus, much more of the coal ash is entrained in the combustion gas for pulverized coal-fired boilers than for stoker-fired boilers.

Although the pulverized coal-fired boilers have higher uncontrolled particulate matter emissions (i.e., at the inlet to the emission control device), controlled emissions from the pulverized coal-fired boilers are not statistically different than emissions from the stoker-fired boilers, primarily because all solid fuel-fired boilers are equipped with either a baghouse or electrostatic precipitator.[32] Accordingly, we conclude that it is not appropriate to establish separate particulate matter standards for pulverized coal-fired boilers versus stoker-fired boilers. This is consistent with the proposal for industrial/institutional/commercial boilers and process heaters that do not burn hazardous waste.

3. Subcategorization Considerations for Liquid Fuel Boilers

We believe it is appropriate to combine liquid and gas fuel boilers into one subcategory because emissions from gas fuel boilers are within the range of emissions one finds from liquid fuel boilers. Also, most of the hazardous waste burning liquid fuel boilers, in fact, burn gas fossil fuels to supplement the liquid hazardous waste fuel. Even though there are no hazardous waste gas burning boilers currently in operation, today we propose to subject hazardous waste gas burning boilers that may begin operating in the future to the standards for liquid fuel-fired boilers. See proposed definition of liquid boiler in § 63.2101(a).

We also assessed whether liquid fuel-fired boilers equipped with dry air pollution control devices had different dioxin/furan emission characteristics when compared to other sources, i.e., sources with either wet air pollution control devices or no air pollution control device. Our statistical analysis indicated that dioxin/furan emissions from sources equipped with dry air pollution control devices are higher.[33] We believe use of wet air pollution control systems (and use of no air pollution control system) can result in different dioxin/furan emission characteristics because they have different post-combustion particle residence times and temperature profiles, which can affect dioxin/furan surface catalyzed formation reaction rates. As a result, we believe that it is appropriate to have different subcategories for these different types of combustors. As discussed previously for incinerators in Part Two, Section II.A, the differences in dioxin formation here reflect something more akin to a process difference resulting in different emission characteristics, rather than a difference in pollution-capture efficiencies among pollution control devices. We thus are not subcategorizing based on whether a source is equipped with a dioxin/furan control system.

E. What Subcategorization Options Did We Consider for Hydrochloric Acid Production Furnaces?

Consistent with our incinerator subcategorization analysis (see Section A of this Part), we also considered whether to establish separate floor emission standards for dioxin/furans for Start Printed Page 21217hydrochloric acid production furnaces equipped with waste heat recovery boilers versus those without boilers. As discussed below, we conclude that there is no significant statistical difference in dioxin/furan emissions between furnaces equipped with boilers and those without them. As a result we do not propose to have different subcategories for these sources.

Ten of the 16 hydrochloric acid production furnaces are equipped with waste heat recovery boilers, and all hydrochloric acid production furnaces are equipped with wet scrubbers that quench the combustion gas immediately after it exits the furnace or boiler. We have dioxin/furan emissions data for eight of the ten furnaces with boilers. Two furnaces have low dioxin/furan emissions—approximately 0.1 ng TEQ/dscm, while the other six furnaces have emissions ranging from 0.5 to 6.8 ng TEQ/dscm. We have dioxin/furan emissions data for five of the six furnaces without boilers. Dioxin/furan emissions for four furnaces are below 0.15 ng TEQ/dscm. But, one furnace has dioxin/furan emissions of 1.7 ng TEQ/dscm.

It appears that dioxin/furan emissions from hydrochloric acid production furnaces may not be governed by whether the furnace is equipped with a waste heat recovery boiler. We performed a statistical test and confirmed that there is no statistically significant difference in dioxin/furan emissions between furnaces equipped with boilers and those without boilers.[34] Thus, we conclude that it is not appropriate to establish separate dioxin/furan emission standards for furnaces with boilers and those without boilers.

III. What Data and Information Did EPA Consider To Establish the Proposed Standards?

The proposed standards are based on our hazardous waste combustor data base. The data base contains general facility information, stack gas emissions data, combustor design information, composition and feed concentration data for the hazardous waste, fossil fuel, and raw materials, combustion unit operating conditions, and air pollution control device operating information. We gathered the emissions data and information from test reports submitted by hazardous waste combustor facilities to EPA Regional Offices or State agencies. Many of the test reports were prepared as part of the compliance demonstration process for the current RCRA standards, and may include results from trial burns, certification of compliance demonstrations, annual performance tests, mini-burns, and risk burns.

A. Data Base for Phase I Sources

The current data base for Phase I sources contain test results for over 100 incinerators, 26 cement kilns, and 9 lightweight aggregate kilns. In many cases, especially for cement and lightweight aggregate kilns, the data base contain test reports from multiple testing campaigns. For example, our data base includes results for a cement kiln that conducted emissions testing for the years 1992, 1995, and 2000.

We first compiled a data base for hazardous waste burning incinerators, cement kilns, and lightweight aggregate kilns to support the proposed MACT standards in 1996 (61 FR 17358, April 19, 1996). Based on public comments, a revised Phase I data base was published for public comment (62 FR 960, January 7, 1997). The data base was again revised based on public comments, and we used this data base to develop the Phase I MACT standards promulgated in 1999 (64 FR 52828, September 30, 1999).

Following promulgation of the interim standards, we initiated a data collection effort in early 2002 to obtain additional test reports. The effort focused on obtaining test reports from sources for which we had no information, obtaining data from more recent testing, and updating the list of operating Phase I sources. Sources once identified as hazardous waste combustors, but that have since ceased operations as a hazardous waste combustor, were removed from the data base. This revised data base was noticed for public comment in July 2002 (67 FR 44452, July 2, 2002) and updated based on public comments. See USEPA “Draft Technical Support Document for HWC MACT Replacement Standards, Volume II: HWC Emissions Data Base,” March 2004, Appendix A for comments and responses.

In comments on the data base notice, industry stakeholders question whether emissions data obtained for some sources are appropriate to use to identify MACT floor for today's proposed replacement standards. Stakeholders suggest that it is inappropriate to use emissions data from sources that tested after retrofitting their emission control systems to meet the emission standards promulgated in September 1999 (and since vacated and replaced by the February 2002 Interim Standards). Stakeholders refer to this as MACT-on-MACT: establishing MACT floor based on sources that already upgraded to meet the 1999 standards. Stakeholders identified emissions data from only approximately three of the Phase I sources (all incinerators) as being obtained after the source upgraded to meet the 1999 standards. None of these incinerator sources are consistently identified as a best performer when establishing the proposed MACT standards.

Notwithstanding stakeholder concerns, we believe it is appropriate to consider all of the data collected in the 2002 effort.[35] First, section 112(d)(3) states that floor standards for existing sources are to reflect the average emission achieved by the designated per cent of best performing sources “for which the Administrator has emissions information” (emphasis added). Second, the motivation for a source's performance is legally irrelevant in developing MACT floor levels. National Lime Ass'n v. EPA, 233 F. 3d at 640. In any case, it would be problematic to identify sources that upgraded their facilities (and reduced their emissions) for purposes of complying with the 1999 standards versus for other purposes (e.g., normal replacement schedule). Moreover, the MACT-on-MACT formulation is not correct. Although the Interim Standards did result in reduction of emissions from many sources, those standards are not MACT standards, and do not purport to be. See February 13, 2002, Interim Standards Rulemaking, 67 FR at 7693. Finally, we note that, although we were prepared to use the same data base for today's proposed rules as we used for the September 1999 rule to save the time and resources required to collect new data, industry stakeholders wanted to submit new emissions data for us to consider in developing the replacement standards. Rather than allowing industry stakeholders to submit potentially selected emissions data, however, we agreed to undertake a substantial data collection effort in 2002. It is unfortunate that industry stakeholders now suggest that some portion of the new data is not appropriate for establishing MACT.

Notwithstanding our view that all of the 2002 data base should be considered in establishing MACT standards, we Start Printed Page 21218specifically request comment on: (1) Whether emissions data should be deleted from the data base that were obtained from sources that owners and operators assert were upgraded to meet the 1999 rule; and (2) whether, because it may be problematic to identify such data, we should identify MACT using the original 1999 data base.

Stakeholders have also raised concerns that the Agency may be considering inappropriately emissions data in its MACT analyses based on the language of section 112(d)(3)(A) of the Clean Air Act. Section 112(d)(3)(A) says emissions standards for existing sources shall not be less stringent, and may be more stringent than—

the average emission limitation achieved by the best performing 12 percent of the existing sources (for which the Administrator has emissions information), excluding those sources that have, within 18 months before the emission standard is proposed or within 30 months before such standard is promulgated, whichever is later, first achieved a level of emission rate or emission reduction which complies, or would comply if the source is not subject to such standard, with the lowest achievable emission rate (as defined by section 171) applicable to the source category and prevailing at the time, in the category or subcategory for categories and subcategories with 30 or more sources,

Section 171 pertains to nonattainment areas for a particular pollutant. The lowest achievable emission rate (LAER) for a pollutant in a nonattainment area is the most stringent emission limitation which is contained in the implementation plan of any State, or the most stringent emission limitation which is achieved in practice. Given that stakeholders neither identified any lowest achievable emission rates for any pollutants applicable to nonattainment areas nor identified any sources that are subject to such lowest achievable emission rates, we conclude that there are no sources to exclude.

B. Data Base for Phase II Sources

Phase II sources are comprised of boilers and hydrochloric acid production furnaces that burn hazardous waste. The data base for Phase II sources was initially compiled by EPA in 1999. In developing this data base, we collected the most recent test report available for each source that included test results under compliance test operating conditions. The most recent test report, however, may have also included data used for other purposes (e.g., risk burn to obtain data for a site-specific risk assessment), which are also included in the data base. In nearly all instances, the dates of the test reports collected were either 1998 or 1999.

After the initial compilation, we published the Phase II data base for public comment in June 2000 (65 FR 39581, June 27, 2000). Since the June 2000 notice, we have not collected additional emissions data for Phase II sources; however, we revised the data base to address public comments received in response to the June 2000 notice. We noticed the Phase II data base (together with the one for Phase I sources) for public comment in July 2002 (67 FR 44452, July 2, 2003) and revised the data base based on comments received. The current data base for Phase II sources contains test reports for over 115 boilers and 17 hydrochloric acid production furnaces. See USEPA “Draft Technical Support Document for HWC MACT Replacement Standards, Volume II: HWC Emissions Data Base,” March 2004.

C. Classification of the Emission Data

The hazardous waste combustor data base [36] comprises emissions data from tests conducted for various purposes, including compliance testing, risk burns, annual performance testing, and research testing. Therefore, some emissions data represent the highest emissions the source has emitted in each of its compliance demonstrations, some data represent normal or typical operating conditions and emissions, and some data represent operating conditions and emissions during compliance testing in a test campaign where there are other compliance tests with higher emissions.

Hazardous waste combustors generally emit their highest emissions during RCRA compliance testing while demonstrating compliance with emission standards. For real-time compliance assurance, sources are required to establish limits on particular operating parameters that are representative of operating levels achieved during compliance testing. Thus, the emission levels achieved during these compliance tests are typically the highest emission levels a source emits under reasonably anticipable circumstances. To ensure that these operating limits do not impede normal day-to-day operations, sources generally take measures to operate during compliance testing under conditions that are at the extreme high end of the range of normal operations. For example, sources often feed ash, metals, and chlorine during compliance testing at substantially higher than normal levels (e.g., by spiking the waste feed) to maximize the feed concentration, and they often detune the air pollution control equipment to establish operating limits on the control equipment that provide operating flexibility. By designing the compliance test to generate emissions at the extreme high end of the normal range of emissions, sources can establish operating limits that account for variability in operations (e.g., composition and feedrate of feedstreams, as well as variability of pollution control equipment efficiency) and that do not impede normal operations.

The data base also includes normal emissions data that are within the range of typical operations. Sources will sometimes measure emissions of a pollutant during a compliance test even though the test is not designed to establish operating limits for that pollutant (i.e., it is not a compliance test for the pollutant). An example is a trial burn where a lightweight aggregate kiln measures emissions of all RCRA metals, but uses the Tier I metals feedrate limit to comply with the mercury emission standard.[37] Other examples of emissions data that are within the range of normal emissions are annual performance tests that some sources are required to conduct under State regulations, or RCRA risk burns. Both of these types of tests are generally performed under normal operating conditions, and would not necessarily reflect day-to-day emission variability. However, such data may be appropriate to use to evaluate long-term average performance.

Other emissions tests may generate emissions in-between normal and the highest compliance test emissions. An example is a compliance test designed to demonstrate compliance with the particulate matter standard where: (1) The air pollution control equipment is detuned; and (2) the source measured lead and cadmium emissions even though it elected to comply with RCRA Tier 1 feedrate limits for those metals and, thus, does not spike those metals. We would conclude that lead and cadmium emissions—together they comprise the semivolatile metals—are between normal and the highest compliance test emissions. Emissions are not likely to be as high as Start Printed Page 21219compliance test emissions because the source did not use the test to demonstrate compliance with emission standards for the metals (and so did not spike the metals). However, emissions of the metals are likely to be higher than normal because the air pollution control equipment was detuned.

To distinguish between normal and compliance test data, we classified emissions data for each pollutant for each test condition as compliance test (CT); normal (N); in between (IB); or not applicable (NA).[38] These classifications apply on a HAP-by-HAP basis. For example, some HAP measured during a test condition may be classified as representing compliance test emissions for those HAP, while other HAP measured during the test condition may be classified as representing normal emissions. See USEPA “Draft Technical Support Document for HWC MACT Replacement Standards, Volume II: HWC Emissions Data Base,” March 2004, Chapter 2, for additional details.

D. Invitation To Comment on Data Base

As previously discussed, we updated the data base based on comments received since it was last made publicly available. We believe the data base used to determine today's proposed standards is complete and accurate. However, given the complexity of the data base, we believe it is appropriate to once again solicit comments on the accuracy of the data. If you find errors, please submit the pages from the test report that document the missing or incorrect entries and the cover page of the test report as a reference. In addition, we identified several sources that are no longer burning hazardous waste and removed their emissions data and related information from the data base. We encourage owners and operators of hazardous waste combustors to review our list of operating combustors to ensure its accuracy. See USEPA “Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards and Technologies,” March 2004.

IV. How Did EPA Select the Format for the Proposed Rule?

The proposed rule includes emission limits for dioxin/furans, mercury, particulate matter, semivolatile metals, low volatile metals, hydrogen chloride/chlorine gas, and carbon monoxide or hydrocarbons. We also propose percent reduction standards for: (1) Destruction and removal efficiency [39] for organic HAP; and (2) total chlorine control for hydrochloric acid production furnaces. Finally, sources would be required to establish operating parameter limits under prescribed procedures to ensure continuous compliance with the emission standards.

We discuss below the rationale for: (1) Selecting an emission limit format rather than a percent reduction format in most cases; (2) selecting a hazardous waste thermal emissions format for the emission limit in some cases, and an emissions concentration format in others; (3) selecting surrogates to control multiple HAP; and (4) using operating parameter limits to ensure compliance with emission standards.

A. What Is the Rationale for Generally Selecting an Emission Limit Format Rather Than a Percent Reduction Format?

Using emission limits as the format for most of the proposed standards provides flexibility for the regulated community by allowing a regulated source to choose any control technology or technique to meet the emission limits, rather than requiring each unit to use a prescribed method that may not be appropriate in each case. (See CAA section 112(h), relating to authority to adopt work place standards). Although a percent reduction format would allow flexibility in choosing the control technology to achieve the reduction, a percent reduction technology does not allow the option of achieving the standard by feed control—minimizing the feed of metals or chlorine. Consequently, we propose percent reduction standards only in special circumstances.

We are proposing a percent reduction standard for boilers and hydrochloric acid production furnaces, i.e., a destruction and removal efficiency standard for organic HAP, because all sources currently comply with such a standard under RCRA and RCRA implementing rules. Further, we do not have emissions data on trace levels of organic HAP that would be needed to establish emission limits for particular compounds.

We also propose a total chlorine percent reduction standard as a compliance option for hydrochloric acid production furnaces in lieu of the proposed stack gas concentration limit because a stack gas concentration limit may ultimately result in limiting the feed of chlorine to furnaces with MACT emission control equipment. Given that these furnaces produce hydrochloric acid from chlorinated feedstocks, limiting the feed of chlorine is inappropriate. See Part Two, Section VI.A and XII for more discussion on the total chlorine standard for hydrochloric acid production furnaces.

B. What Is the Rationale for Selecting a Hazardous Waste Thermal Emissions Format for Some Standards, and an Emissions Concentration Format for Others?

We are proposing numerical emission limits in two formats: hazardous waste thermal emissions, and stack gas emissions concentrations. Hazardous waste thermal emissions are expressed as mass of pollutant contributed by hazardous waste per million Btu of heat contributed by hazardous waste. Emission concentration based standards are expressed as mass of pollutant (from all feedstocks) per unit of stack gas (e.g., μg/dscm).

1. What Is the Rationale for the Hazardous Waste Thermal Emissions Format?

In the 1999 rule, we assessed hazardous waste feed control levels for metals and chlorine by evaluating each source's maximum theoretical emission concentration (MTEC) using the “aggregate MTEC” approach. See 64 FR at 52854. MTEC is defined as the metals or chlorine feedrate divided by the gas flow rate, and is expressed in μg/dscm. We used MTECs to assess feed control levels because it normalizes metal and chlorine feedrates across sources of different sizes. Industry stakeholders have claimed that use of MTECs to assess feed control levels for energy recovery units (e.g., cement kilns) when establishing floor standards inappropriately penalizes sources that burn hazardous waste fuels at high firing rates (i.e., percent of heat input from hazardous waste). This is because hazardous waste fuels generally have higher levels of metals and chlorine than the fossil fuels they displace, thus metal and chlorine feedrates and emissions may increase as the hazardous waste firing rate increases.

Although we are not using the aggregate MTEC approach to evaluate feed control in today's proposal, the SRE/Feed approach explained in Part Two, Section VI.A, does assess each source's metal and chlorine hazardous waste feed control levels. In order to avoid the hazardous waste firing rate bias discussed above for energy recovery Start Printed Page 21220units, we believe it is appropriate to instead assess feed control for energy recovery units by ranking each source's thermal feed concentration, which is equivalent to the mass of metal or chlorine in the hazardous waste per million BTUs hazardous waste fired to the combustion unit. This approach not only normalizes metal and chlorine feedrates across sources of different sizes, but also normalizes these feedrates across energy recovery units with different hazardous waste firing rates. For example, a kiln that feeds hazardous waste with a given metal concentration to fulfill 100% of its energy demand would be an equally ranked feed control source when compared to an identical kiln that fulfills 50% of its energy demand from coal and 50% from hazardous waste with an identical metal concentration.

Similarly, it is our preference to express today's proposed emission standards for metals and chlorine in units of hazardous waste thermal emissions as opposed to expressing the standards in units of stack gas concentrations. As previously discussed, hazardous waste thermal emission standards are expressed as mass of HAP emissions attributable to the hazardous waste per million Btu hazardous waste fired to combustor. As with thermal feed concentration, thermal emissions normalizes emissions across energy recovery units with different hazardous waste firing rates. The hazardous waste thermal emissions format addresses two concerns. First, it avoids the above discussed bias against sources that burn hazardous waste fuels at high firing rates. We prefer not to discourage energy recovery from hazardous waste as opposed to potentially establishing standards that effectively restrict the hazardous waste firing rate in an energy recovery combustor. (See, for example, the requirement in CAA section 112(d)(2) to take energy considerations into account when promulgating MACT standards, as well as the objective in RCRA section 1003(b)(6) to encourage properly conducted recycling and reuse of hazardous waste).

Second, because the hazardous waste thermal emissions approach controls only emissions attributable to the hazardous waste feed (see discussion in following section), the rule can be simplified by not including waivers for sources that cannot meet the standard because of metals or chlorine contributed by nonhazardous waste feedstreams. To ensure that hazardous waste combustors will be able to achieve the standards if they use MACT control for metals and chlorine attributable to the hazardous waste feed, but irrespective of metals and chlorine in nonhazardous waste feedstreams, current MACT standards for cement and lightweight aggregate kilns that burn hazardous waste provide alternative standards that sources can request under a petitioning procedure. See § 63.1206(b)(9-10). These alternative standards would be unnecessary under the hazardous waste thermal emissions approach because, by definition, the approach controls only hazardous waste-derived metals and chlorine.

2. Which Standards Would Use the Hazardous Waste Thermal Emissions Format?

We propose a hazardous waste thermal emissions format for mercury, semivolatile metals, low volatile metals, and total chlorine (i.e., the HAPs found in hazardous waste fuels) for source categories that burn hazardous waste fuels where we have data to calculate a hazardous waste thermal emissions limit. Cement kilns, lightweight aggregate kilns and liquid-fuel fired boilers burn hazardous waste fuels and are thus candidates for the hazardous waste thermal emission standards. Incinerators and solid fuel-fired boilers are not candidates for thermal emission standards because some sources within these source categories do not combust hazardous waste for energy recovery, i.e., they burn low heating value hazardous waste for the purpose of treating the waste.[40] Consequently, these sources could not duplicate a hazardous waste thermal emissions standard based on emissions from sources that burn hazardous waste fuels, even though their stack gas emission concentrations could be as low or lower than emissions from a best performing source under the hazardous waste thermal emissions approach.

We propose a hazardous waste thermal emissions format for all HAP for which we can apportion emissions between the hazardous waste fuel feed and other feedstreams. Under this approach, we apportion total stack emissions between hazardous waste fuel and other feedstreams using the ratio of the feedrate contribution from hazardous waste to the total feedrate of the pollutant. Thus, the particulate matter, metals, and total chlorine standards are candidates because we often have data on hazardous waste and total feedrates of these pollutants.

We believe, however, that a hazardous waste thermal emissions format is not appropriate for particulate matter for cement and lightweight aggregate kilns because particulate matter emissions from cement and lightweight aggregate kilns are primarily entrained raw material, not ash contributed by the hazardous waste fuel. There is therefore no correlation between particulate matter emissions and hazardous waste thermal input rate.

In addition, please note that we could have expressed the proposed particulate matter standard for liquid boilers in units of hazardous waste thermal emissions since (unlike the case of kilns just discussed) particulate matter emissions are attributable to the hazardous waste fuel. However, for consistency, we elected to use the same format for all the particulate matter standards. We invite comment as to whether the particulate matter standard for liquid boilers should be expressed in units of hazardous waste thermal emissions.

We do not have adequate data to establish hazardous waste thermal emissions-based standards for several cases. An example is when we have only normal feedrate and emissions data (e.g., the mercury standard for cement kilns). We prefer to establish emission standards under the hazardous waste thermal emissions format using compliance test data because the metals and chlorine feedrate information from compliance tests that we use to apportion emissions to calculate emissions attributable to hazardous waste are more reliable than feedrate data measured during testing under normal, typical operations.[41] Thus, as a general rule, we prefer to express emission standards for energy recovery units using the hazardous waste thermal emissions format only when we have sufficient compliance test feed data.[42] These situations are discussed below in more detail in Part Two, Sections VIII, IX, and XI where we discuss the rationale for the proposed emission standards for energy recovery units.

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3. How Are Emissions From Other Feedstreams Regulated Under the Hazardous Waste Thermal Emissions Format?

Under the thermal emissions format, only emissions of HAP contributed by the hazardous waste are directly regulated by today's proposed standards. Non-mercury metal HAP emissions from raw materials and fossil fuels would be subject to MACT standards, even though it may not be feasible to directly control their feedrate. We are proposing standards for particulate matter as surrogates to control these HAP metals contributed by raw materials and fossil fuel.

C. What Is the Rationale for Selecting Surrogates To Control Multiple HAP?

HWCs can emit a wide variety of HAP, depending on the types and concentrations of pollutants in the hazardous waste feed. Because of the large number of HAP potentially present in emissions, we propose to use several surrogates to control multiple HAP. This will reduce the burden of implementation and compliance on both regulators and the regulated community.

1. Surrogates for Metal HAP

We are proposing to control metal HAP emissions attributable to the hazardous waste by subjecting sources to metal and particulate matter emission limitations.[43] We grouped metal HAP according to their volatility because volatility is a primary consideration when selecting an emission control technology.[44] We then considered the following to identify metals that would be “enumerated” and directly controlled with an emission limit: (1) The amount of available data for the metal HAP; (2) the potential for hazardous waste to contain substantial levels of a metal; and (3) the toxicity of the metal. Other, “nonenumerated” metal HAP would be controlled using particulate matter as a surrogate.

Mercury is highly volatile, especially toxic, and may not be controllable by the same air pollution control mechanisms as the other HAP metals, so we are proposing a standard for mercury individually. Two semivolatile metals can be prevalent in hazardous waste and are particularly hazardous: lead and cadmium. We group these two metals together and propose an emission standard for these metals, combined. The combined emissions of lead and cadmium cannot exceed the semivolatile metal emission limit. Three low volatile metals can be prevalent in hazardous waste and are particularly hazardous: arsenic, beryllium, and chromium. We group these three metals together and propose an emission standard for these metals, combined. The combined emissions of arsenic, beryllium, and chromium cannot exceed the low volatile metal emission limit.

The particulate matter standard generally serves as a surrogate to control non-enumerated metals in the hazardous waste as well as a surrogate to control relevant metal HAP in non-hazardous waste feed streams. We generally chose not to propose numerical metal HAP emission standards that would have accounted for all metal HAP for two reasons (note that such an approach would be in lieu of a proposed particulate matter standard because particulate matter is not a listed HAP). We generally do not have as much compliance test emissions information in our database for the nonenumerated metal HAP compared to the enumerated metal HAP. Thus it would be more difficult to assess the control levels for these additional metals. We also believe that a particulate matter standard, in lieu of emission standards that directly regulate all the metals, simplifies compliance activities in that sources would not have to monitor feed control levels of these nonenumerated metals on a continuous basis.

Note that particulate matter is not an appropriate surrogate where standards are based, in part (or in whole) on feedrate control. This is because, unlike the case where HAP metals are controlled by air pollution control devices, HAP metal reductions in hazardous waste feedrate are not necessarily correlated with particulate matter reductions, i.e., hazardous waste feedrate reductions could reduce HAP metal emissions without a correlated reduction in particulate matter emissions. (See National Lime, 233 F. 3d at 639 noting this possibility.) Moreover, particulate matter that is emitted generally contain greater percentages of HAP metals when the metal concentrations in the hazardous waste feed increase. Thus, low particulate matter emissions do not necessarily guarantee low metal HAP emissions, especially in instances where the hazardous waste feeds are highly concentrated with metal HAP.

We do not believe that the proposed emission standards for semivolatile and low volatile metals serve as adequate surrogate control for the nonenumerated metal HAP. Compliance with the semivolatile and low volatile metal emission standards does not ensure that sources are using MACT back-end control devices because they could be achieving compliance by primarily implementing hazardous waste feed control for the enumerated metals. Thus, if a source uses superior feed control only for the enumerated metals, the nonenumerated metal emissions would not be controlled to MACT levels if it were not using a MACT particulate matter control device. The proposed semivolatile and low volatile metal standards are also inappropriate surrogates for controlling nonmercury metal HAP in the nonhazardous waste feedstreams for kilns and solid fuel-fired boilers for the same reason. These sources may comply with the proposed semivolatile and low volatile metal emission standards by implementing hazardous waste feed control. This would not assure that the nonmercury metal HAP emissions attributable to the nonhazardous waste feedstreams are controlled to MACT levels. A particulate matter standard provides this assurance.

Note that we are proposing that incinerators and liquid boilers that emit particulate matter at levels higher than the proposed standard but do not emit significant levels of non-mercury metal HAP can elect to comply with an alternative standard. Under the proposed alternative standard, these sources would be required to: (1) Limit emissions of all semivolatile metals, including nonenumerated semivolatile metals, to the emission limit for semivolatile metals; and (2) limit emissions of all low volatile metals, including nonenumerated low volatile metals, to the emission limit for low volatile metals. See Part Two, Section XVIII for more discussion on this alternative.

2. Surrogates for Organic HAP

For Phase II sources, we propose two standards as surrogates to control emissions of organic HAP: carbon monoxide or hydrocarbons, and destruction and removal efficiency.[45] Both of these standards control organic HAP by ensuring combustors are operating under good combustion Start Printed Page 21222practices that should result in destruction of the organic HAP. Note that boilers and hydrochloric acid production furnaces that burn hazardous waste are currently subject to RCRA requirements that regulate carbon monoxide or hydrocarbon emissions and destruction and removal efficiency standard under RCRA regulations. We propose to control dioxin/furans by a separate standard because dioxin/furan can also be formed post-combustion in ductwork, waste heat recovery boilers, or dry air pollution control devices (e.g., electrostatic precipitators and fabric filters).

Hydrocarbon emissions are a direct measure of many organic compounds, including organic HAP. Carbon monoxide emissions are a more conservative indicator of hydrocarbon and organic HAP emissions because the presence of carbon monoxide at elevated levels is indicative of incomplete oxidation of organic compounds. Sources generally choose to comply with the carbon monoxide standard because carbon monoxide continuous emissions monitors are less expensive and easier to maintain than hydrocarbon monitors.

We also propose to use the destruction and removal efficiency standard to help ensure boilers and hydrochloric acid production furnaces operate under good combustion conditions. We propose to adopt the standard and implementation procedures that currently apply to these sources under RCRA regulations at § 266.104. We propose, however, to require a one-time only compliance requirement for destruction and removal efficiency, unless a source changes its design or operation in a manner that could adversely affect its ability to meet the destruction and removal efficiency standard. Further, previous destruction and removal efficiency testing performed under RCRA could be used to document the one-time compliance.

D. What Is the Rationale for Requiring Compliance With Operating Parameter Limits To Ensure Compliance With Emission Standards?

In addition to meeting emission limits, today's proposal would require sources to establish limits on key operating parameters for the combustor and emission control devices. Each source would establish site-specific limits for the parameters based on operations during the comprehensive performance test, using prescribed procedures for calculating the limits. The operating parameter limits would reasonably ensure that the combustor and emission control devices continue to operate in a manner that will achieve the same level of control as during the comprehensive performance test.

We selected the operating parameters for which sources would establish limits because: (1) The parameters can substantially affect emissions of HAP; (2) they are feasible to monitor continuously; (3) they are currently used to monitor performance under the Interim Standards Rule for incinerators, cement kilns, and lightweight aggregate kilns that burn hazardous waste; and (4) this is the same general compliance approach that is currently applicable to all hazardous waste combustion sources pursuant to the RCRA emission standard requirements.

V. How Did EPA Determine the Proposed Emission Limitations for New and Existing Units?

A. How Did EPA Determine the Proposed Emission Limitations for New Units?

All standards established pursuant to section 112 of the CAA must reflect MACT, the maximum degree of reduction in emissions of air pollutants that the Administrator, taking into consideration the cost of achieving such emission reduction, and any non-air quality health and environmental impacts and energy requirements, determines is achievable for each category. The CAA specifies that the degree of reduction in emissions that is deemed achievable for new hazardous waste combustors must be at least as stringent as the emissions control that is achieved in practice by the best-controlled similar unit (as noted earlier, this specified level of minimum stringency is referred to as the MACT floor, the term used when the statutory provision was first introduced in Congress). However, EPA may not consider costs or other impacts in determining the MACT floor. EPA may adopt a standard that is more stringent than the floor (i.e., a beyond-the-floor standard) if the Administrator considers the standard to be achievable after considering cost, environmental, and energy impacts.

B. How Did EPA Determine the Proposed Emission Limitations for Existing Units?

For existing sources, MACT can be less stringent than standards for new sources, but cannot be less stringent than the average emission limitation achieved by the best-performing 12 percent of existing sources for categories and subcategories with 30 or more sources. EPA may not consider costs or other impacts in determining the MACT floor. The EPA may require a control option that is more stringent than the floor (beyond-the-floor) if the Administrator considers the cost, environmental, and energy impacts to be reasonable.

It has been argued that EPA is limited in the level of performance it can evaluate in assessing which are the 12 percent existing best performing sources to standards codified in permits, or other regulatory limitations. The argument is based on use of the term “emission limitation” in section 112 (d) (3), the argument being that “emission limitation” is a term defined in section 302 (k) to mean “a requirement established by the State or the Administrator which limits the quantity, rate, or concentration of air pollutants * * *”. EPA does not accept this argument, and indeed doubts that such an interpretation of the statute is even permissible. In brief:

(i) Statutory text indicates that MACT floors for existing sources is to based on actual performance. Section 112 (d) (3) (A) speaks to the actual performance of sources, and requires that the floor for existing sources reflect actual performance. The key statutory phrase is not just “emission limitation” but “emission limitation achieved”, a phrase referring to actual performance, not just a limit simply set out in a permit or regulation. The floor is to be calculated using “emissions information”, a reference again to actual performance. The provision likewise states that certain sources achieving a lowest achievable emission rate (LAER) level of performance without being subject to LAER (a regulatory limit) are not to be considered in assessing best performers, redundant language if only regulatory limits could be considered.

In fact, it is clear from context when Congress used the term “emission limitation” to refer to regulatory limits, and when it uses the term to refer to a level of performance actually achieved. Compare CAA section 111(b)(1)(B) (EPA is to consider “emissions limitations and percent reductions achieved in practice” when considering whether to revise new source performance standards) with section 110(a)(2)(A) (State Implementation Plans must contain “enforceable emission limitations”).

(ii) The argument leads to absurd and illegal results. The argument that existing source MACT floors can only be based on regulatory limits leads to results that are illegal, absurd, or both. Congress enacted section 112 to assure technology-based control of HAP which had heretofore gone unregulated due to the vagaries and glacial pace of Start Printed Page 21223implementing the previous risk-based regime for HAP. 1 Legislative History at 790, 860; 2 Legislative History at 3174-78, 3340-42. The result, at the time of the 1990 amendments is that there were widespread regulatory limits for only one of the 190 listed HAPs (lead, for which there was a National Ambient Air Quality Standard) plus NESHAPs for a half dozen other HAPs. Thus, “emission limitations”, in the sense used in the argument, did not exist for most HAPs. This would lead necessarily to the result of no existing source floors because no “emission limitations” exist. This result is illegal. National Lime v. EPA, 233 F. 3d 625, 634 (D.C. Cir. 2000). Where regulatory limits are higher than actual performance levels, existing source floors likewise would be higher than performance levels, a result both absurd and illegal. Sierra Club v. EPA, 167 F. 3d 658, 662-63 (D.C. Cir. 1999). In fact, at the time of the 1999 rule for this source category (hazardous waste combustion), RCRA regulatory limits were higher than the level of performance achieved even by the very worst performing source in the category (for some HAPs, by orders of magnitude). Yet under the argument, the floor for existing sources would have to be higher than even this worst performing single source.

(iii) Legislative History shows that Congress intended the existing source floor to reflect actual best performance. The legislative history to the MACT floor provision for existing sources likewise makes clear that the standard was to reflect actual performance, not regulatory limits. 2 Legislative History pp. 2887, 2898; 3353; 1 Legislative History p. 870. The legislative history to the parallel provision for municipal waste combusters in section 129(a)(2) (which floor requirement reads identically to section 112(d)(3)) is equally clear, stating that the floor for such sources is to reflect emission limitations which either have been achieved in practice or are reflected in permit limitations, whichever is more stringent. See Sierra Club v. EPA, 167 F. 3d at 662 (noting this legislative history.)

(iv) The argument has already been rejected in litigation. The D.C. Circuit, in the three cases dealing with MACT floors, has held in all three cases that the floor standard must reflect actual performance. Sierra Club, 167 F. 3d at 162-63; National Lime, 233 F. 3d at 632; Cement Kiln Recycling Coalition, 255 F. 3d at 865-66.

For these reasons, we reject the argument that existing source floors are compelled to reflect only regulatory limits. Such limits may be a permissible means of establishing existing source floors, but only if regulatory limits “are a reasonable means of estimating the performance of the top 12 percent of [sources] in each [category or subcategory].” Sierra Club, 167 F. 3d at 661.

Somewhat ironically, there is a regulatory limit which is relevant in establishing floors for incinerators, cement kilns and lightweight aggregate kilns. The interim standards fix a level of performance for all of these sources. Thus, any floor standard can be no less stringent than this standard (see National Lime 233 F. 3d at 640 (reason for which a level of performance is being achieved is irrelevant in ascertaining MACT floors)). Based on actual performance, however, floors may be more stringent.

VI. How Did EPA Determine the MACT Floor for Existing and New Units?

We followed five basic steps to calculate the proposed MACT floors. First, we determined which MACT methodology approach is most appropriate to apply to the given pollutant for each source category. Second, we selected which of the available emissions data best represent each source's performance. Third, we evaluated whether it is appropriate to issue separate emissions standards for various subcategories. Fourth, we identified the best performing sources based on the chosen methodology and data. Finally, we calculated floor levels for new and existing sources. The following sections include a description of each of these steps. Please note that we are also proposing to invoke CAA section 112(d)(4) to establish risk-based standards on a site-specific basis for total chlorine for hazardous waste combustors (except for hydrochloric acid production furnaces). Under the proposed approach, sources may elect to comply with either risk-based standards or section 112(d) MACT standards. See Part Two, Section XIII for more details.

A. What MACT Methodology Approaches Are Used To Identify the Best Performers for the Proposed Floors, and When Are They Applied?

A MACT methodology approach is a set of procedures used to define and identify the best performing sources consistent with CAA section 112(d)(3). We have developed and used the following three different MACT methodologies to identify the best performing sources for the full suite of proposed floor standards for new and existing sources: (1) System Removal Efficiency (SRE)/Feed approach; (2) Air Pollution Control Technology Approach; and (3) Emissions-Based approach. These three methodologies, together with their rationales and when they are used, are described in the following sections. Note that each methodology described below assesses best performing sources for each pollutant or pollutant group independently, often resulting in different best performers for each pollutant. For a more detailed description of these methodologies and when they are applied, see USEPA “Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards,” March 2004, Chapters 7 through 15.

1. What Is SRE/Feed Approach, and When Are We Proposing To Apply It?

The SRE/Feed MACT approach defines best performers as those sources with the best combined front-end hazardous waste feed control and back-end air pollution control efficiency as defined by our ranking procedure. The approach is applicable to HAP whose emissions can be controlled by controlling the hazardous waste feed of the HAP: metals and chlorine.[46]

These two parameters—feedrate of metals and chlorine in hazardous waste, and performance of the emission control device measured by system removal efficiency [47] determine emissions of metals and chlorine contributed by the hazardous waste feed. Back-end air pollution control is evaluated by assessing each source's pollutant system removal efficiency, which is a measure of the percentage of HAP that is emitted compared to the amount fed to the unit. In identifying system removal efficiency as a measure of best performing, the Agency is rejecting the notion that “best performing” must mean a source with the lowest absolute rate of emission of a HAP. A source emitting 300 pounds of a HAP, but removing that HAP at a rate of 99.9% from its emissions, can logically be considered a better performing source than one emitting 100 pounds of the same HAP but Start Printed Page 21224removing it at an efficiency of only 50 percent.

Use of feedrate and system removal efficiency as measures of performance is appropriate because these parameters incorporate the effects of the myriad factors that can indirectly affect emissions, such as level of maintenance of the combustor or emission control equipment, and operator training, as well as design and operating parameters that directly affect performance of the emission control device (e.g., air to cloth ratio and bag type for a fabric filter; use of a power controller on an electrostatic precipitator). For example, an incinerator with a well-designed and operated fabric filter would have a higher performance rating measured by system removal efficiency than an identical incinerator equipped with the same fabric filter which is, in addition, poorly maintained because of inadequate operator training. Also, although feedrate of metals and chlorine in nonhazardous waste feedstreams such as raw materials and fossil fuels fed to a cement kiln can affect HAP emissions substantially, those emissions can be feasibly controlled only by back-end control (measured here by system removal efficiency).[48] This is because neither fuel switching nor raw material switching is practicable for production facilities such as cement and lightweight aggregate kiln facilities. Thus, feedrate of metals and chlorine contributed by the hazardous waste—the only controllable feed parameter for these sources—is an appropriate metric.

For incinerators and solid fuel-fired boilers, feed control is evaluated by assessing each source's hazardous waste pollutant maximum theoretical emission concentration.[49] Feed control for energy recovery units (cement kilns, lightweight aggregate kilns, and liquid fuel-fired boilers) are evaluated by assessing each source's hazardous waste pollutant thermal feed concentration when possible (i.e., when EPA has sufficient data to make the calculation).

We rank each source's pollutant hazardous waste feed control level against all the other source's feed control level, assigning a relative rank of 1 to the source with the lowest, i.e., best, feed control level and assigning the highest ranking score to the source with the highest, i.e., worst, feed control level. We do the same with each source's system removal efficiency. We rank each source's pollutant system removal efficiency against all the other sources' system removal efficiencies, assigning a relative rank of 1 to the source with the highest, i.e., best, system removal efficiency and assigning the highest ranking score to the source with the lowest, i.e., worst, system removal efficiency. We then add each source's feed control ranking score and system removal efficiency ranking score to yield an SRE/Feed aggregated score. Each source's aggregated score is arrayed and ranked from lowest to highest, i.e., best to worst, and, for existing sources, the best performers are the sources at the 12th percentile aggregate score and below. Floor levels are then calculated by using the emissions from these best performing sources. The SRE/Feed-based standards are expressed in units of hazardous waste thermal emissions when possible for energy recovery units.

Please note that the SRE/Feed approach can occasionally identify a floor level for new sources that is higher than the floor level for existing sources, as discussed below in Sections VII to XII. This is because the source with the best SRE/Feed aggregate score, and thus, the single best performing source under this approach, does not always achieve the lowest emissions among the best performing sources after accounting for emissions variability. In two cases only, the emissions for the best performing SRE/Feed source, after accounting for emissions variability, are higher than the average of the best performing five (or 12%) of sources—the floor for existing sources—after considering emissions variability.[50] For example, the single best performing SRE/Feed source may have both higher emissions and run variability than other best performing sources. This source's emissions are averaged with the other best performers to identify the floor level, and its run variability is dampened when we calculate the floor for existing sources by pooling run variability across the best performing sources. When the single best performer's emissions are evaluated individually, however, a relatively high run variability is not dampened. In those few situations where the best performing SRE/Feed source has higher emissions, after accounting for emissions variability (i.e., the potential floor for new sources), than the floor for existing sources, we default to the floor for existing sources to identify the floor for new sources. We request comment on whether it would be more appropriate to identify the floor for new sources under the SRE/Feed approach by selecting the source with the lowest emissions among the best performing existing sources, after considering run variability, rather than the lowest SRE/Feed aggregate score.

The SRE/Feed methodology is generally applied only to HAP where we can accurately assess each source's relative hazardous waste feed control and back-end air pollution control: mercury, semivolatile metals, low volatile metals, and total chlorine. Dioxin/furans are not considered to be feed control HAP because they generally are not fed into the combustor; rather, they are formed in the combustor and post combustion. Also, whereas particulate matter (for all source categories) and total chlorine (for hydrochloric acid production furnaces) could be considered to be feed-controlled and back-end controlled pollutants, we do not believe it is appropriate to assess feed control as a control mechanism for these situations for reasons discussed below in Section 2 (largely dealing with the inability to control HAP in raw material feed or in fossil fuel). As a result, we did not apply the SRE/Feed approach to these pollutants.

Finally, the SRE/Feed approach is also not applied when we do not have sufficient compliance test data to accurately assess each source's relative back-end control efficiency. This occurs in a limited number of circumstances when the majority of the emissions data reflect normal operations. The mercury and semivolatile metal standard for liquid boilers are examples of when we do not believe we possess sufficient data to accurately assess each source's back end control efficiency because we are concerned that the normal feed data are too sensitive to sampling and measurement error to provide a reliable Start Printed Page 21225system removal efficiency that would be used reliably in the ranking procedure. Our preference is to use system removal efficiencies that are based on compliance testing because sources typically spike the pollutant feeds during these compliance tests to known elevated levels, resulting in calculated system removal efficiencies that are more reliable.

2. What Are the Air Pollution Control Technology Approaches, and When Are They Applied?

The air pollution control technology approach is applied in two situations where we consider it inappropriate to directly assess hazardous waste feed control—the particulate matter standard for all sources categories and the total chlorine standard for hydrochloric acid production furnaces. We apply slightly different methodologies to each of these situations, as discussed below.

a. What Methodology Was Used To Identify the Best Performing Sources for the Particulate Matter Floors? The best performing sources for the proposed particulate matter floor levels are determined using a methodology that is conceptually similar to that used in the Industrial Boiler MACT proposal. See 68 FR at 1660. We call this methodology the “air pollution control technology” approach because it defines best performers as those that use the best type of back-end air pollution control technology.

This methodology first assesses all the back-end control technologies used by all the sources within the source category, and ranks the general effectiveness of these control technologies from best to worst using engineering information and principles. For example, for particulate matter control, high efficiency particulate air filters may be ranked as the best air pollution control device, followed by baghouses, electrostatic precipitators, and high energy wet scrubbers. In this example, all sources equipped with a high efficiency particulate air (i.e., HEPA) filter would get the best ranking (e.g., “1”), and all sources equipped with high energy wet scrubbers would get the worst ranking (e.g., 4).

The sources are arrayed and ranked from best to worst based on their control technology rankings. For existing sources, MACT control is defined as the control technology or technologies used by the best 12 percent of these sources. For example, using the previous particulate matter control rankings, if more than 12 percent of the sources within the source category were using high efficiency particulate air filters, then MACT control would be defined to be high efficiency particulate air filters. If 10 percent of all the sources were equipped with high efficiency particulate air filters, and 4 percent were equipped with baghouses, then MACT control would be defined as both high efficiency particulate air filters and baghouses.

After the MACT control technology or technologies are determined, the MACT floor levels are calculated using emissions data from those sources using MACT control. See Part Two, Section IV.D.3 for more discussion on the ranking procedure that is used to identify the best performing sources under this approach. Also see USEPA “Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards,” March 2004, Chapter 9, for more information. This methodology consequently focuses on performance of the best pollution control device, but does not assess further control that might result from lower HAP feedrates.[51]

We believe it is appropriate to identify the best performing sources using particulate matter emissions from those using MACT back-end control without considering hazardous waste ash feedrate control. For cement kilns, lightweight aggregate kilns, and solid fuel-fired boilers, particulate emissions are largely contributed by non-hazardous waste feedstreams (i.e., entrained raw material for kilns, and entrained coal ash for solid fuel-fired boilers). Thus, hazardous waste feed control is an inappropriate factor to consider when assessing particulate matter control efficiency. Assessment of, and control of, total ash feedrate (i.e., hazardous waste plus raw materials and nonhazardous waste fuel ash feed) would also be inappropriate because, as discussed below, total ash feedrate may not be a reliable indicator of a source's emission control level for metal HAP, and could inappropriately result in a methodology that assesses (and controls) raw material and/or nonhazardous waste fuel input.

Although particulate matter emissions for incinerators and liquid fuel-fired boilers are more directly related to these devices' hazardous waste ash feedrate, the hazardous waste ash feedrate for these sources may not be a reliable indicator of a source's feedrate (and emissions) of nonenumerated metal HAP given that the ash feed into the combustor may contain high or low concentrations of regulated metal HAP. A source that feeds low levels of ash thus may not be a best performing source for metal HAP emissions if its metal concentration levels in its ash are relatively high. Such a source could be identified as a best performing source because its particulate matter emissions and ash feed is low, even though its metal HAP emissions are relatively high. This result would also inappropriately assess and control elements of the hazardous waste ash feed that are not regulated HAP (e.g., silica input). For these reasons, using the air pollution control technology approach to establish particulate matter floors without explicitly considering ash feedrate is appropriate since it focuses on the control technology (i.e., back-end air pollution control technology) that is known to control metal HAP emissions.[52]

b. What Methodology Is Used To Identify the Best Performing Sources for the Total Chlorine Floor for Hydrochloric Acid Production Furnaces? We apply the air pollution control technology approach to total chlorine for hydrochloric acid production furnaces differently. For this floor calculation, we are proposing to use the same methodology that the Agency used for the hydrochloric acid production MACT final rule for sources that do not burn hazardous waste. See 68 FR at 19076. This methodology defines best performers as those sources with the best total chlorine system removal efficiency. Each source's total chlorine system removal efficiency is arrayed and ranked from highest to lowest, and the best existing performers are the sources at the 12th percentile ranking and below. We calculate the system removal efficiency floor level using the total chlorine system removal efficiencies achieved by these best performing sources. Consistent with the non hazardous waste hydrochloric acid production MACT final rule, we also propose to allow sources to comply with a total chlorine stack gas concentration limit that is calculated by multiplying the highest hazardous waste chlorine maximum theoretical emission concentration in the data base by 1 minus the MACT system removal efficiency. This ensures that a source Start Printed Page 21226complying with the alternative concentration-based standard would not emit higher levels of total chlorine than a source equipped with wet scrubbers that achieve MACT system removal efficiency. We believe this alternative standard is appropriate because it gives sources the option of complying with the floor by implementing hazardous waste feed control.[53]

We believe this methodology is appropriate even though it does not directly assess hazardous waste total chlorine feed control because these sources are in the business of feeding highly chlorinated hazardous wastes so that they can recover the chlorine for use in their production process. Requiring these sources to minimize hazardous waste chlorine feed would be directly regulating their raw material and would directly affect their ability to produce their product. Again, in this situation, we believe it is appropriate to use a methodology approach that solely focuses on back-end control, since back-end control assures removal of the target pollutant without inappropriately requiring a source to control feedstreams in a manner that affects its ability to produce its intended product.

3. What Is the Emissions-Based Approach, and When Is It Applied?

The emissions-based approach defines best performers as those sources with the lowest emissions in our database. We array and rank each source's pollutant emission levels from lowest to highest. The best existing performers are the sources at the 12th percentile ranking and below. We calculate floor levels using the emission levels from these best performing sources. We express the emissions-based standards in units of hazardous waste thermal emissions when possible for energy recovery units, and use the approach whenever the SRE/Feed or air pollution control technology approaches are not used. Specifically, we use the emissions-based approach for the dioxin/furan floors for all source categories, and for the mercury and semivolatile metal floors for liquid fuel-fired boilers.

The SRE/Feed and air pollution technology-based approaches cannot be used for the dioxin/furan floors because dioxin/furans are generated in the combustor or post-combustion within the air pollution control device. Since dioxin/furans are generally not fed to the units, the SRE/Feed methodology would not properly assess dioxin/furan emission control performance. In theory, the technology-based approach for particulate matter could be applied to the dioxin/furan floors. However, such a technology approach would, for the most part, identify the same best performers as the emissions-based approach because there is only one primary control technology being used by all the sources—temperature control at the inlet to the dry air pollution control device.

The SRE/Feed approach cannot be used for the mercury and semivolatile metal floors for the liquid fuel-fired boilers because we do not have sufficient compliance test data to accurately assess each source's back-end control efficiency. The technology-based approach is also not appropriate because sources within this source category control these HAP both by feed control and by back-end control. As a result, a methodology that considers only one of the two primary control techniques may not be appropriate.

4. Why Doesn't EPA Simply Apply the Emissions-Based Approach to All Source Categories and HAP?

Under the most simplistic interpretation of CAA 112(d), we would apply the emissions-based approach to all source categories and HAP in calculating floors for existing sources. We considered proposing this option. As described later in Part Two, Section VI.G, it was one of three options for which we conducted a complete economics analysis. We discuss below, however, why we believe the air pollution control technology and SRE/Feed approaches more reasonably ascertains the performance of the average of the best 12 percent of existing sources.

a. Why Do We Prefer the SRE/Feed Approach Over the Emissions-Based Approach? We believe the SRE/Feed approach is a reasonable and appropriate MACT methodology for the hazardous waste combustion source categories because it better estimates the performance of the average of the 12 percent best performing sources, and (as a necessary corollary) assures that the floor standards would be achievable by such sources. As previously discussed, we apply the SRE/Feed approach to HAP that are actively controlled (via floor controls) by both hazardous waste feed control and back-end air pollution control. There are only two ways to control emissions of these HAP from these sources—limit the feedrate of metal and chlorine and remove them prior to venting the exhaust gas out the stack. These two control mechanisms are used simultaneously by all sources in this category at varying levels.

We do not believe the lowest emission levels in our data base in fact represent the full range of emissions achieved in practice by the best performing sources. Indeed, it would be unlikely if this were the case, since these data are necessarily “snapshots” of emissions from the source, obtained in one-time testing events.[54] Notwithstanding that such testing seeks to encompass much of the variability in system performance, no single test can be expected to do so. Thus, inherent variability such as feedrate fluctuation over time due to production process changes, uncertainties associated with correlations between operating parameter levels and emissions, precision and accuracy differences in different testing crews and analytical laboratories, and changes in emission of materials (SO2 being an example) that may cause test method interferences. See generally 64 FR at 52857and 52587-59.

An emissions-based approach for cement kilns, lightweight aggregate kilns, and solid fuel-fired boilers that assesses performance based on stack gas concentrations (as opposed to hazardous waste thermal emissions) may not appropriately estimate the performance of the average of the 12 percent best performing sources given that those best performers may have low emissions in part because their raw material and/or fossil fuels contained low levels of HAP during the emissions test. We do not believe feed control of HAP in raw material and fossil fuel should be assessed as a MACT floor control primarily because it could result in floor levels that are not replicable by the best performing sources, nor duplicable by other sources. See Part Two, Section VI.A.1.

Moreover, although the emissions-based approach is not facially inconsistent with section 112 of the Act, there are serious questions as to whether its applicability here leads to limits that could be achieved even by the average of the best performing sources (under the emissions-based approach). The alternative emissions-based floor Options 1 and 2 discussed in Part Two, Section VI.G result in floor levels across all HAP that are achievable simultaneously by fewer than 6% of the sources for the cement kiln, incinerator, and liquid fuel-fired boiler source Start Printed Page 21227categories.[55] See USEPA “Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards,” March 2004, Chapters 10 and 19, for a summary of the simultaneous achievability analysis. A reason the floors which would result from this methodology are so low is that there already have been at least one and, for many of the sources, two rounds of regulatory reduction of emissions from these sources (under the RCRA rules, and then under the Interim Standards MACT rules for incinerators and kilns). The emissions-based approach thus yields results more akin to new source standards, confirmation being that the levels are not even achievable as a whole by the average of the 12 percent best performing sources. The simultaneous achievability of today's proposed floors, for which we use the SRE/Feed approach for certain HAP preferentially over the emissions-based approach, is substantially better (but not dramatically more than 6%) for cement kilns and liquid fuel-fired boilers than the achievability under the emissions-based approach.

There are other reasons why the emissions-based approach results in such low simultaneous achievability percentages. If the emissions-based approach is applied to feed-controlled HAP, the best performers are defined as those sources that are either: (1) The lowest feeders; (2) the best back-end controlled units; or (3) the best combination of front-end control or back-end control. The emissions-based approach selects the lowest emitters from the previous three categories and does not necessarily account for the full range of emissions that are achieved in practice by well designed and operated feed control units, well designed and operated back-end controlled units, or well designed and operated combination of both front-end and back-end controlled units. As explained below, the SRE/Feed methodology better accounts for the range of emissions from these well designed and operated sources.[56]

For example, assume we have 100 sources in a hypothetical source category, and source A is the 5th best feed controlled source and the 30th best back-end controlled source. Source B, on the other hand, is the 30th best feed controlled source and the 5th best back-end controlled source. The SRE/Feed ranking procedure would score these two sources equally, even though their emissions may be different. Let's also assume that these two sources are among the best performers for the SRE/Feed approach. We would not expect their emission levels to be dramatically different under the SRE/Feed approach because source A is a superior front-end controlled source with a relatively poorer back-end control device, and source B is a superior back-end controlled source with relatively poorer feed control. Even though sources A and B do not have the same emissions, they are both considered to be well designed and operated sources because they both use a superior combination of front-end and back-end control. The difference in emissions merely reflects the range of emissions from well designed and operated sources.

If the emissions-based approach was applied in the source A and B example, the source with the higher emissions would have a worse emission ranking, and thus may not be identified as a best performer. Thus, even though we would consider this higher emitting source under the SRE/Feed approach to be a well-designed and operated source, it would not be capable of achieving the calculated floor level. We believe this outcome may be problematic, for example, because sources that are already operating with a well-designed and operated back-end control unit should not have to upgrade its back-end control technology simply because it is not achieving a floor level driven, in part, by other sources within the source category that are implementing lower feed control rates that are impractical for it to achieve.[57] It may be questionable to require these well controlled back-end units to implement better feed control to achieve this emission-based floor level because: (1) they may not be capable of implementing feed control without sending/diverting the waste elsewhere—yet these units are providing a needed and required service in treating hazardous waste; and (2) it could be argued that hazardous waste containing high levels of metals and chlorine should in fact be treated in the well-designed and operated back-end controlled units (see RCRA sections 3004 (d) to (m), requiring advanced treatment of hazardous waste before the waste can be land disposed).

Similarly, sources that are already achieving superior feedrate control should not necessarily have to upgrade their feedrate control further simply because they are not achieving a floor level driven, in part, by sources with superior back-end control. Improving already superior feedrate control may be problematic simply because they may not be capable of implementing additional feed control (e.g., source reduction) at their facility, or having generators implement further feedrate control. EPA believes that hazardous waste feed control is an important element of what constitutes “best performing” sources from this source category, and does not wish to structure the rule to discourage the practice by developing standards which do not directly take this means of control into account. See CAA section 112(d)(2)(A) (feed control is an explicit means of achieving MACT); and see also the pollution prevention and waste minimization goals of both the CAA (sections 112(d) (2) and 101(c) and RCRA (section 1003(b)). The SRE/Feed approach thus better preserves the opportunity for sources to achieve the floor levels if they are using either superior front-end control or back-end control (or superior combination of both). At the same time, it addresses both means by which sources in this category can control their HAP emissions: hazardous waste feed control and back-end air pollution capture through control technology.

The example in the previous paragraph of the source using superior feed control is clearly applicable to incinerators and boilers that combust hazardous waste. These are somewhat unique source categories in that they are comprised of many different industrial sectors that may not be capable of achieving/duplicating the same metal and chlorine feedrate control levels of other sources within their respective source category given that hazardous waste feed control levels are directly influenced by amount of HAP that are generated in their specific production process. Similarly, other sources that comprise commercial hazardous waste combustors (i.e., kilns and commercial incinerators) are subject to the feed control levels that are governed Start Printed Page 21228primarily by third parties (i.e., the generators or fuel blenders). The emissions-based approach identifies the best performers as those sources with the lowest emissions and does not consider differences in emission characteristics across all the industrial sectors that combust hazardous waste. We contemplated whether we should assess if subcategorization is appropriate based on the various industrial sectors that combust hazardous waste. We believe, however, that such an assessment would be difficult given the vast number of industrial sectors that generate hazardous waste which is treated by combustion.

The emissions-based approach could be identifying a suite of floor levels across HAP that would require sources to operate at feedrate control levels in the aggregate that are in theory achieved by few, if any, well-operated and designed feed controlled sources. For example, the best performing sources for the emissions-based approach for the incinerator semivolatile and low volatile metal floors are entirely different. This may occur because sources have different relative feed control levels for mercury, semivolatile metals, low volatile metals, and total chlorine (e.g., a source could have superior semivolatile metal feed control but only moderate low volatile metal feed control).

Finally, the emissions-based approach may result in low simultaneous achievability percentages because a back-end control technology for one pollutant may not control the emissions of another pollutant as efficiently. For example, wet air pollution control systems may control total chlorine emissions very well, but are not as efficient at limiting particulate matter emissions when compared to a baghouse. Thus, best performers under the emissions-based floor approach for total chlorine could be driven by sources with wet air pollution control systems, and the particulate matter floor could be driven by sources equipped with baghouses, resulting in a combined set of floors that are conceivably achieved by few sources, a result confirmed, as noted above, in that less than 6% of existing sources would be achieving floor standards developed using the emission-based approach.[58,] [59]

We thus believe that using the SRE/Feed approach preferentially over the emissions-based approach and technology based approach is appropriate because use of the SRE/Feed approach results in floor levels that better reflect the range of emissions from well-designed and operated sources and also results in floor levels across all HAP that are achievable simultaneously by at least 6 percent of the sources within each source category.

b. Why Do We Prefer the Air Pollution Control Technology Approach Over the Emissions-Based Approach? As previously discussed, we apply the air pollution control technology approach in two situations where we consider it inappropriate to directly assess hazardous waste feed control using an SRE/Feed type approach: the particulate matter standard for all source categories; and, the total chlorine standard for hydrochloric acid production furnaces. We discuss below why the emissions-based approach is not our preferred methodology for these standards.

For particulate matter, the emissions-based approach identifies the lowest emitters as best performers, irrespective of the types of controls that were used. This would not necessarily reflect emissions that are in fact capable of being achieved by sources using MACT back-end control technology as defined by the air pollution control technology approach because, as discussed above, our data are “snapshots” of emissions from each source, obtained in one-time testing events. As a result, the particulate matter floors that are based on the emissions-based approach would not necessarily account for inherent variability such as ash feedrate fluctuation over time due to production process changes,[60] uncertainties associated with correlations between operating parameter levels and emissions, precision and accuracy differences in different testing crews and analytical laboratories, and changes in emission of materials (SO 2 being an example) that may cause test method interferences. The air pollution control technology approach may better account for this inherent variability because it assesses the emissions ranges from those sources that utilize the defined back-end MACT control devices, as opposed to merely selecting the lowest emitters irrespective of the type of control it uses.

Also, using the emissions-based approach for incinerators and liquid boilers (for the particulate matter standard) and hydrochloric acid production furnaces (for the total chlorine standard) is not our preferred approach because it assesses in part, hazardous waste ash and chlorine feed control. As discussed above, the emissions-based approach defines best performers as those sources with the lowest emissions, and thus inherently accounts for and assesses hazardous waste ash and chlorine feed control in that sources with lower ash feedrates and chlorine feedrates may have lower emissions.[61] This is not our preferred way of establishing floors for these HAP for the reasons discussed above in Section A.2.

B. How Did EPA Select the Data To Represent Each Source When Determining Floor Levels?

After we determine which MACT methodology is appropriate for a given pollutant and source category, we select which of the available emissions data to use for each source to: (1) Determine if subcategorization is warranted; (2) Start Printed Page 21229identify the best performing sources; and (3) calculate the floor levels. Our emissions data base is complex because it includes, in part, compliance test data, emissions data that is representative of the normal operating range of the source, and, for the Phase I sources, multiple emission test data that have been collected over a number of years. See Part Two, Section III for more discussion on data base issues.

We follow a general “data hierarchy” to determine which of these data types to use to represent each source's performance (with the performance being reassessed for each HAP). First, we prefer to explicitly use compliance test data rather than data representative of normal operations because compliance test data best reflect the upper range of emissions from each source and thus best accounts for day-to-day emissions variability. Use of compliance test data allows us to express emission floors as “short-term limits” (e.g., hourly or twelve hour rolling averages), which is consistent with the current interim MACT standard format for incinerators, cement kilns, and lightweight aggregate kilns. Short-term limits are also consistent with the RCRA emission standards currently applicable to boilers and hydrochloric acid production furnaces. Finally, we prefer to use compliance test data because the majority of the available data are compliance test data.

Absent sufficient compliance test data for sources within the source category to calculate floor levels, we default to explicitly using data that are representative of the source's operating range under conditions not designed to assess performance variability. Since these so-called normal data do not typically reflect the upper range of emissions from each source, we believe it is necessary to account for emissions variability (in part) by expressing floors that are based on normal data as long-term, annual average emission limits (since the snap-shot data, by definition, do not reflect short-term variability).

We considered using all available emissions data to calculate the floors, irrespective of whether they were normal or compliance test data. We believe, however, that it is inappropriate to mix such dissimilar data when calculating floor levels because it would bring into question how to account for day-to-day emissions variability when setting the format of the standard. For example, if a floor were calculated using 50% percent normal data and 50% compliance data, should the standard be expressed as a long-term limit or short-term limit? This is critical because the averaging period associated with the numerical emission limitation affects the stringency of the standard. It is also unclear how mixing dissimilar data would affect the statistical variability factor we apply to each floor to assure that floor levels are achievable by the average of the best performing sources. As discussed in Part Two, Section VI.E, we apply the statistical variability factor to the floor levels to assure that the average of the best performing sources would be able to replicate the emission test results that were used to calculate the floor levels. Mixing dissimilar data not only complicates the analyses, but also could result in inconsistent evaluation of data (hence inconsistent results), primarily because the ratio of normal data to compliance data differs across HAP within each source and across all sources. We therefore believe it is appropriate to assess “like data” explicitly to assure results are consistent across HAP and source categories.

We prefer to use the most recent compliance test data to represent each source in situations where we have data from multiple test campaigns that were collected at different times. For example, we typically have multiple test campaign emission information for cement kilns and lightweight aggregate kilns because: (1) We conducted a comprehensive data collection effort for these sources to update the data base that was used to support the 1999 final rule; and (2) these sources, prior to receiving their RCRA permit, are required to conduct emissions tests every three years.

We believe it is appropriate to only use the most recent compliance test data for a source because those data best reflect current operations and emission levels. Older compliance test data may not be representative of current emissions because: (1) Permitted feed and air pollution control device operating levels may have been changed/upgraded; (2) combustion unit and associated air pollution control equipment design may have been changed/upgraded; and (3) standard operating practices that relate to maintenance and upkeep may have been changed/upgraded. As a result, we believe that a source's most recent compliance data best reflect a source's upper range of emissions. We considered using all of the sources historical compliance emissions data to perhaps better account for day-to-day emissions variability. We believe, however, that it is not appropriate to consider older compliance emission test data to account for day-to-day emission variability because: (1) The older compliance data may reflect varying emissions merely because the source was previously operating with poorer control levels, which is not an appropriate factor to consider when assessing day-to-day emission variability; and (2) the most recent compliance test data adequately accounts for day-to-day variability because the operating levels demonstrated during the most recent compliance test generally represent the maximum upper range of operations and emissions.[62]

We do not apply the concept of using the most recent emissions test information to normal emissions data (as previously discussed, we use normal emission data to calculate floor levels only in situations where we do not have sufficient compliance test data). We instead use all normal emissions data that are available because we are concerned that a source's most recent normal emissions may not be representative of its average emissions. The most recent normal emissions data could reflect emissions at the upper range of normal operations or the lower end of normal operations. If we were to use only the most recent normal emissions information, we may identify as best performers those sources that were operating below their average levels. This would be inappropriate because the floor level may be unachievable by the best performing sources.

Finally, for liquid fuel-fired and solid fuel-fired boilers, we eliminated emission test runs from the MACT analysis when we had information that the source conducted sootblowing during that emission test run. Boilers that burn fuels with high ash content are designed to blow the soot off the tubes periodically to maintain proper heat transfer. The soot can contain metal HAP, and emissions of these HAP can increase during sootblowing. Although the current RCRA particulate matter and metals emissions standards for these sources at §§ 266.105 and 266.106 do not require sootblowing during compliance testing, we have provided guidance recommending that sources blow soot during one of the three runs of a compliance test condition and calculate average emissions considering the frequency and duration of sootblowing.[63] We conclude that these sootblowing run data should not be Start Printed Page 21230considered when establishing MACT floor, however, for several reasons. We do not know if all sources that blow soot followed the guidance to blow soot during a run of the test condition. If they did not, they could be identified as a best performer but may not be able to achieve the floor level when blowing soot. In addition, several boilers that blew soot during a run of the test condition did not use our recommended approach to calculate time-weighted average emissions considering the frequency and duration of sootblowing. For these sources, we cannot calculate time-weighted average emissions. We also note that, for sources with emission control equipment, emissions during sootblowing runs are not significantly higher than when not blowing soot. This is because soot particles are relatively large and easily controlled. For sources with no emission control equipment, sootblowing increased particulate matter emissions for some sources, but not others. In addition, we could not use the sootblowing run to help address emissions variability by evaluating run variability because the (in some cases) higher emissions during sootblowing are unrelated to the factors affecting run variability that we are evaluating (e.g., method precision and other largely uncontrollable factors that affect run-to-run emissions during a test condition). Finally, we note that the Agency did not propose to require sootblowing to demonstrate compliance with the MACT standards for industrial, commercial, and institutional boilers and process heaters.[64] Although for these reasons we conclude that it is appropriate not to consider sootblowing run data to establish the MACT floor, we request comment on alternative views.[65]

Because we do not consider sootblowing when establishing floor levels, sootblowing would not be required during performance testing to demonstrate compliance with the standards for particulate matter and semivolatile and low volatile metals.[66]

C. How Did We Evaluate Whether It Is Appropriate To Issue Separate Emissions Standards for Various Subcategories?

The third step we use to calculate MACT floor levels evaluates subcategorization options. CAA section 112(d)(1) allows us to distinguish among classes, types, and sizes of sources within a category when establishing floor levels. Subcategorization typically reflects “differences in manufacturing process, emission characteristics, or technical feasibility.” See 67 FR 78058.

We use both engineering principles and a statistical analysis to assess whether it is appropriate to subcategorize and issue separate emission standards. We first use engineering principles to determine potential subcategory options. These subcategory options are discussed in more detail in Part Two Section II for each source category. As discussed in greater detail below, we then determine if there is a statistical difference in the emission characteristics between these potential subcategory options. Finally, we conduct a technical analysis to determine if the statistical analysis results are consistent with sound engineering judgement.

“Analysis of Variance” (ANOVA) is the statistical test used to cross-check these engineering judgements. ANOVA, a conventional statistical method, evaluates whether there are differences in the mean of HAP emissions levels from two or more different potential subcategories (i.e., do the different subcategories of HAP data come from distinctly different populations). Subcategories are considered significantly different using a 95% confidence level. ANOVA is used in combination with engineering principles to sequentially identify significant differences between various different combinations of potential subcategories. See U.S. EPA “Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards,” March 2004, Chapter 4, for detailed steps and results of the ANOVA evaluation process.

D. How Did We Rank Each Source's Performance Levels To Identify the Best Performing Sources for the Three MACT Methodologies?

The fourth step used in determining the MACT floor levels involves ranking each source's performance level to identify the best performers. Below we discuss the general ranking procedure used for each of the three MACT methodologies and the statistical methodology used to perform the ranking process.

1. Emissions-Based Methodology Ranking Procedure

As previously discussed in Part Two, Section VI.A, the emissions-based approach defines best performers as those sources with the lowest emissions in our database. Each source's emission test runs are first converted to an upper 99% confidence level in order to rank performance not only on the average emission levels each source achieves, but also on the emissions variability each source demonstrates during the emissions tests. We believe this is appropriate because a source's ability to consistently control its emissions below the MACT floor levels is important in determining whether a source is in fact a well designed and operated source.[67] We then array and rank each source by its 99% upper confidence emission levels from best to worst (i.e., lowest to highest). For existing source floors, we identify the best performers as either sources at the 12th percentile ranking and below or the lowest 5 ranked sources values if we have data from less than 30 sources. The best performing source for the new source floor is simply the source with the single lowest ranked 99% upper confidence emission level.

2. SRE/Feed Ranking Procedure

As previously discussed, the SRE/Feed methodology approach defines best performers as those sources with the best combined front-end hazardous waste feed control and back-end air pollution control efficiency as defined by our ranking procedure. The first step involves ranking each source's feed control level. As with the emissions-based approach, we first convert each source's feed control run levels (i.e., hazardous waste maximum theoretical emission concentration level or thermal feed concentrations) to an upper 99% confidence level. We then array each source's 99% upper confidence feed control levels from best to worst (i.e., lowest to highest). Next we assign a feed control ranking score to each source. The source with the lowest feed control value gets a ranking of 1, and the source with highest feed control value receives the highest numerical ranking.

The second step ranks each source's system removal efficiency, which is a measure of the percent of metal or Start Printed Page 21231chlorine that is emitted as compared to the amount fed to the combustion unit. Again, we first convert each source's system removal efficiency run values to an upper 99% confidence level value. We then array each source's 99% upper confidence levels from best to worst (i.e., highest to lowest). Next we assign a system removal efficiency ranking score to each source. The source with the best system removal efficiency gets a ranking of 1, and the source with the worst system removal efficiency receives the highest numerical ranking.

As with the emissions ranking procedure discussed above, our feed control and system removal efficiency ranking procedure measures performance not only on the average feed control and system removal efficiency level each source achieves, but also on the feed and system removal efficiency variability each source demonstrates during the emissions tests. This is appropriate because a source's ability to consistently regulate its control mechanisms to achieve MACT emissions is important in determining whether a source is in fact a well designed and operated source.

Third, we add each source's feed control ranking score and system removal efficiency ranking score together in order to calculate an aggregated SRE/Feed score. We then array and rank each source's aggregated score from best to worst (i.e., lowest to highest). For existing source floors, we identify the best performers as sources at the 12th percentile aggregate ranking and below or sources with the lowest 5 aggregated scores if we have data from less than 30 sources. The best performing source for the new source floor is simply the source with the single lowest aggregated score.

3. Technology Approach Ranking Procedure for the Particulate Matter Standard

As previously discussed in Part Two, Section VI.A.2.a, the best performing sources for the particulate matter proposed floor levels are determined from a pool of sources that use the MACT-defining back-end control technology. We assess only the emissions from those sources equipped with the MACT-defining control technology (or technologies), and, as with the previously discussed methodologies, we convert each source's emission run values to an upper 99% confidence level value. Emissions information from each source is then grouped based on the type of MACT control each source uses. The first group contains emissions information from sources equipped with the best ranked MACT control device; the second group includes emissions information from sources equipped with the second best ranked MACT control technology (if there is more than MACT control technology), and so on.

We then array and rank each source's 99% upper confidence emission levels from best to worst (i.e., lowest to highest) within each of these groups. If there is only one defined MACT control technology, the best performing sources are those sources with the lowest 99% upper confidence emission levels amongst the sources using this MACT control technology. The lowest emitting sources are added to a list of best performers up until the number of sources that are included in this list is representative of 12 percent of sources within the source category (for the existing source floor determination). If there is more than one defined MACT control technology, the list of best performers first considers sources with the lowest 99% upper confidence emission levels that are equipped with the best ranked control device up until the number of sources that are included in this list is representative of 12 percent of sources within the sources category. If additional sources need to be added to this list to appropriately represent 12% of the sources within the source category, then sources with the lowest emissions that are equipped with the second best MACT control device are added until the appropriate number of best performing sources are obtained.[68] For the new source floor, the best performer is simply the single source equipped with the best ranked MACT control device with the lowest 99% upper confidence emission level.

4. Technology Approach Ranking Procedure for the Total Chlorine Floor for Hydrochloric Acid Production Furnaces

As previously discussed in Part Two, Section VI.A.2.b, the technology approach used to determine the total chlorine floor levels for hydrochloric acid production furnaces defines best performers as those sources with the best total chlorine system removal efficiency. The ranking procedure used for this methodology is identical to that used in the emissions-based approach with the exception that system removal efficiencies are ranked instead of emissions. Each source's total chlorine system removal efficiency run values are first converted to an upper 99% confidence level. We then array and rank each source's 99% upper confidence system removal efficiencies from best to worst (i.e., highest to lowest). For existing source floors, we define best performers as either: (1) Sources at the 12th percentile ranking and below; or (2) sources with the lowest 5 rankings if we have data from less than 30 sources. The best performing source for the new source floor is simply the source with the single highest 99% upper confidence system removal efficiency.

5. Description of the Statistical Procedures Used To Identify the 99% Confidence Levels

As previously discussed, each source's performance level is first converted to an upper 99% confidence level in order to rank performance not only on the average performance level each source achieves, but also on the emissions variability each source demonstrates during the emissions tests. We believe this is appropriate because a source's ability to consistently control its emissions below the MACT floor levels is important in determining whether a source is in fact a well designed and operated source.

Sources are ranked based on their projected “upper 99% confidence limit” (or lower 99% confidence limit for system removal efficiency). For emissions and feedrates, upper 99% confidence limits are determined using a “prediction limit” calculation procedure. The prediction limit is an estimate of the level which will capture 99 out of 100 future test condition averages (where each average comprise three individual test runs). HAP emissions data within each source are determined to be normally distributed. The prediction limit is calculated for each source based on the average, standard deviation, and number of individual test runs.

For system removal efficiencies, the lower 99% confidence limit is determined using the “two parameter Beta distribution”. The beta distribution is used for modeling proportions, i.e., system removal efficiencies, is highly robust, and appropriately bounded by zero and 1. Beta distribution modeling parameters are determined based on the “method of moments” using the average and standard deviation of the individual source data. The lower 99% estimate comes directly from the Beta distribution model. See USEPA “Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards,” Start Printed Page 21232March 2004, Chapter 8, for further discussion.

E. How Did EPA Calculate Floor Levels That Are Achievable for the Average of the Best Performing Sources?

The emissions data we used to establish MACT floor were obtained by manual sampling of stack gas. To ensure that the average of the best performing sources can routinely achieve the floor during future performance testing under the MACT standards, we must account for emissions variability.

We account for long-term emissions variability by: (1) Using compliance test emissions data, when available, to establish floors; (2) when other than compliance test data must be used to establish the floor, basing compliance on an annual average. In addition, we add a statistically-derived variability factor to the floor to account for run-to-run variability. This variability factor ensures that the average of the best performing sources can achieve the floor level in 99 of 100 future tests if the best performing sources replicate the operating conditions and other factors that affect the emissions we use to represent the performance of those sources.

1. How Does Using Compliance Test Data Account for Variability?

We use RCRA compliance test emissions data, when available, to establish the floors because compliance test data largely account for emissions variability. Under RCRA compliance testing, sources must establish operating limits based on operating conditions demonstrated during the test. Each source designs the compliance test such that the operating limits it establishes account for the variability of operating parameter levels it expects to encounter during its normal operations (e.g., feedrate of metals and chlorine; air pollution control device operating parameters, production rate). Thus, operating conditions during these tests generally reflect the upper range of emissions from these sources. Using a source's compliance test emissions to establish the floor accounts largely for long-term emissions variability. However, this does not necessarily account for factors that affect variability. As previously discussed, our snap-shot data base emissions information does not necessarily account for inherent variability such as feedrate fluctuation over time due to production process changes, uncertainties associated with correlations between operating parameter levels and emissions, precision and accuracy differences that may result from using different stack sampling crews and analytical laboratories, and changes in emission of materials (SO2 being an example) that may cause test method interferences.

Use of compliance test data also does not account for run-to-run variability. We thus use a statistically-derived variability factor to account for the variability in emissions that would result if the best performing sources were to replicate their compliance tests, as discussed below.[69]

In addition, use of compliance test data may not account for long-term variability of particulate matter emissions from sources equipped with a fabric filter. Accordingly, we also use a statistically-derived variability factor to account for this variability, as discussed below.

2. How Does Using Long-Term Averaging Account for Emissions Variability When Using Other Than Compliance Test Data?

RCRA compliance test emissions data are not available for some metals (mercury in particular) for some source categories. In these cases, we use other emissions test data to establish the floor. These other test data are snap shots of emissions within the range of normal emissions. To largely account for emissions variability when using emissions data assumed to represent the average of normal emissions, we propose to express the floor as a long-term, yearly, average. Sources would comply with the floor by establishing limits on metal feedrate and air pollution control device operating parameters. Compliance with the metal feedrate limits would be based on an annual average feedrate, while compliance with the air pollution control device operating limits would be based on short-term limits (e.g., hourly rolling average). We propose short-term averages for air pollution control device operating parameters because the parameters may not correlate with emissions linearly; emissions resulting when an air pollution control device parameter is above the limit thus may not be offset by emissions resulting when the air pollution control device parameter is below the limit. See 1999 rule, 64 FR at 52920.

As discussed above, we also use a statistically derived variability factor to account for the variability in emissions that would result if the best performing sources were to replicate the emissions tests we use to establish the floor, as discussed below.

We use the normal emissions data to represent the average emissions from a source even though we do not know where the emissions may fall within the range of normal emissions; the emissions may be at the high end, low end, or close to the average emissions. It may be reasonable to assume the emissions represent average emissions, given that we have emissions data from several sources, and that emissions for these sources in the aggregate could be expected to fall anywhere within the range of normal emissions. Note that, as previously discussed, we have not applied the concept of using the most recent emissions test information to normal emissions data because we are concerned a source's most recent normal emissions may not be representative of a source's true average emissions. These emissions could reflect emissions at the upper range of normal operations, or instead, could reflect emissions at the lower end of normal operations. If we were to use only the most recent normal emissions information, the MACT standard setting process may identify best performers as those sources that operate below their normal levels. This may be inappropriate because the floor level may be unachievable even by the best performing sources. We invite comment as to whether floors that are based on normal data are in fact achievable by the best performing sources, and whether there is perhaps a more appropriate method to identify floors that are based on normal data.

3. What Statistical Procedures Did EPA Use To Calculate Floor Levels?

In order to calculate a floor that would be achievable by the average of the best performing sources, we considered the variability in emissions across runs of the test conditions of the best performing sources. We also use statistical procedures to account for long-term variability in particulate matter emissions for sources equipped with fabric filters. We discuss these procedures and the rationale for using them below.

a. Run-to-Run Variability. The MACT floor level is determined by modeling a normally distributed population that has an average and variability that are equal to that of the “average” of the best performing MACT pool sources. The MACT floor is calculated using a Start Printed Page 21233modified prediction limit procedure. The prediction limit is designed to capture 99 out of 100 future three-run averages from the “average” of the best performing MACT sources.

Specifically, the modified prediction limit for calculating the MACT floor is the sum of the average of the best performing sources and the “pooled” variability of the best performing sources. The pooled variability term accounts for the expected variability in future measurements due to variations resulting from system operation and measurement activities. The pooled variability term is based in part on the observed variance of individual runs within test conditions from the best performing MACT pool sources. The pooled variability term assumes that variability from the individual best performing sources are independent (not related), and thus are additive (and not averaged). The pooled variability term is a function of the variances of the individual MACT pool sources, the number of MACT pool sources, the desired 99% confidence level, and the number of future test runs for demonstrating compliance (assumed to be 3). See USEPA “Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards,” March 2004, Chapter 7, for discussion of the detailed steps and prediction limit formula used to calculate the MACT floors.

b. Particulate Matter Variability for Fabric Filters. Compliance test emissions of particulate matter from sources that are equipped with a fabric filter may not account for long-term variability because it is difficult to maximize emissions during the compliance test.[70] Fabric filters control particulate matter emissions generally to the same concentration irrespective of the particulate matter loading at the inlet to the fabric filter. Because there are no operating parameters that can be readily changed to increase emissions, it is difficult to maximize emissions of particulate matter from a fabric filter during compliance testing.[71]

To address long-term variability in particulate matter emissions for fabric filters we developed a universal variability factor (UVF). The UVF represents the standard deviation of the pooled runs from multiple compliance tests for a source, and is imputed as a function of the source's emission concentration. We use the UVF to account for both long-term and run-to-run variability to calculate the floor using the procedures discussed above in lieu of the pooled variability term for the most-recent test condition run variability.

To develop the data base to calculate the UVF, we considered each best performing source that is equipped with a fabric filter and for which we have two or more compliance tests for particulate matter. We considered all compliance test particulate matter emissions data for these sources, including those test conditions we previously labeled as “IB” (representing in-between), indicating that emissions levels are lower than for another test condition of the compliance test campaign. We include historical test campaign data where available for incinerators, cement kilns, and lightweight aggregate kilns. Considering historical compliance test data and compliance test data labeled IB is appropriate because any differences in emission levels (over time or among compliance test results for a test campaign) should be indicative of emissions variability given that fabric filters generally produce constant emission concentrations and are difficult to detune to increase emissions for compliance testing. Finally, we combined test conditions for multiple on-site sources where both the combustor and fabric filter have similar design and operating characteristics. Combining the test conditions for such sources as if they represent emissions from a single source better accounts for emissions variability.

To calculate the UVF, we calculated the pooled standard deviation of the runs for each source for which we have data for two or more compliance tests and plotted this standard deviation versus particulate matter emission concentration for all such sources. It is reasonable to aggregate the data for sources across all source categories given that there is no reason to believe that the standard deviation/emissions relationship would vary from source category to source category. We then identified the best-fit curve for the data. The best fit curve is a power function that achieved a R2 of 0.83, indicating a good power function correlation between standard deviation and emission concentration.[72]

We use the best-fit curve to impute a standard deviation for each best performing source (that is equipped with a fabric filter) as a function of the source's particulate matter emissions. We use the source's average compliance test emissions (i.e., including historical compliance test emissions that we label in the data base as “WC” and “IB”) to represent average emissions.

F. Why Did EPA Default to the Interim Standards When Establishing Floors?

When we calculate floor levels for several standards for the Phase I sources, the floor levels would be higher than the currently applicable interim standards at §§ 63.1203, 63.1204, and 63.1205. As explained earlier, we conclude that today's proposed floor levels can be no higher than the interim standards because all sources, not just the best performing sources, are achieving the interim standards. The most recent emissions data in our data base are from compliance testing in 2001 and do not represent emissions tests from sources used to demonstrate compliance with the interim standards, thus the data we used to calculate the proposed floor levels generally does not reflect the control upgrades necessary for compliance with the interim standards. The fact that we are “capping” the floor at the interim standard level does not mean our proposed methodology is less conservative than the methodology used in the 1999 rule. Our calculated floor levels can be higher than the interim standards for several reasons. As a result of our data collection effort, we have compiled more emissions information from some source categories that result in higher calculated floor levels (e.g., dioxin/furans for lightweight aggregate Start Printed Page 21234kilns). Some of the instances where we “capped” the floor at the interim standard level occurred when the interim standard was a beyond-the-floor standard promulgated in 1999 (e.g., semivolatile metals for lightweight aggregate kilns). Finally, some standards are “capped” because we used different types of data to calculate the proposed floors (e.g., the 1999 rule generally considered normal mercury data to establish the mercury floor for incinerators, whereas today's proposed approach used compliance test data to calculate the mercury floor).

G. What Other Options Did EPA Consider?

We considered five other alternative approaches to establish the full suite of floor levels for each source category. The first two alternative options use different combinations of the three main methodology options to determine the proposed floors. Note that we also conducted a complete economics and benefits analysis for these first two alternative options. See USEPA “Draft Technical Support Document for HWC MACT Replacement Standards, Volume V: Emission Estimates and Engineering Costs,” March, 2004 for more information. The third option identifies best performing sources by considering emissions of metals and particulate matter simultaneously, instead of pollutant by pollutant. The fourth option is an approach recommended by the Environmental Treatment Council. Finally, the fifth option identifies best performing sources as those sources with the best back-end control efficiencies, as measured by their associated system removal efficiencies. After review of comments we may use one or more of these approaches in toto or part to establish final standards. We explain below how these approaches work and the rationale for considering them.

1. What Is Alternative Option 1, and What Is the Rationale?

Under alternative option 1, we do not use the SRE/Feed methodology to calculate any floors. We use the emissions-based approach to establish all the floors, other than the exceptions that are explained below. We express emission standards for energy recovery units in units of hazardous waste thermal emissions when appropriate. All other emission standards under this approach are expressed as stack gas emission concentrations. The two exceptions under this option uses the technology-based approach for the particulate matter standard (for all source categories) and the total chlorine standard for hydrochloric acid production furnaces, as was done for today's proposed standards.

We evaluated this option because it is simpler and more straightforward to use than the SRE/Feed Approach. The best performing sources simply are those with the lowest emissions in our data base, irrespective of the level of feed control or back-end control a source achieves. The advantages of using the air pollution control technology approach and expressing emission standards using the hazardous waste thermal emissions format for energy recovery units are retained. Although we have doubts that standards based on these limits are achievable even by the best performing sources (as noted earlier) and that this approach could be based on unrepresentatively low hazardous waste feedrates, we invite comment as to whether this approach is appropriate. We present the results of using alternative option 1 to identify floor levels for existing sources in Table 3 below. See U.S. EPA “Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards,” March 2004, Chapters 16, 17, and 18 for documentation of the floor levels.

Table 3.—Floor Levels for Existing Sources Under Alternative Option 1

IncineratorsCement kilnsLightweight aggregate kilnsSolid fuel-fired boilers 1Liquid fuel-fired boilers 1Hydrochloric acid production furnaces 1
Dioxin/Furans (ng TEQ/dscm)0.28 for dry APCD and WHB sources,6 0.20 or 0.40 + 400°F at APCD inlet for others.70.20 or 0.40 + 400°F at APCD inlet.70.20 or 400°F at kiln outlet.7CO or THC standard as a surrogate3.0 or 400°F at APCD inlet for dry APCD sources; CO or THC standard as surrogate for othersCO or THC standard as a surrogate.
Mercury130 μg/dscm 731 μg/dscm 219 μg/dscm 210 μg/dscm3.7E-6 lb/MMBtu 2, 5Total chlorine standard as surrogate.
Particulate Matter0.015 gr/dscf 70.028 gr/dscf0.025 gr/dscf 70.063 gr/dscf0.032 gr/dscfTotal chlorine standard as surrogate.
Semivolatile Metals (lead +cadmium)19 μg/dscm1.3E-4 lb/MMBtu 53.1E-4 lb/MMBtu 5 and 250 μg/dscm.3170 μg/dscm1.1E-5 lb/MMBtu 2, 5Total chlorine standards as surrogate.
Low Volatile Metals (arsenic + beryllium + chromium)14 μg/dscm1.1E-5 lbs/MMBtu 59.5E-5 lb/MMBtu 5 and 100 μg/dscm.3210 μg/dscm7.7E-5 lb/MMBtu 4, 5Total chlorine standard as surrogate.
Total Chlorine (hydrogen chloride + chlorine gas)0.93 ppmv41 ppmv600 ppmv 7440 ppmv5.7E-3 lb/MMBtu 514 ppmv or 99.9927% system removal efficiency.
Notes:
1 Particulate matter, semivolatile metal, low volatile metal, and total chlorine standards apply to major sources only for solid fuel-fired boilers, liquid fuel-fired boilers, and hydrochloric acid production furnaces.
2 Standard is based on normal emissions data.
3 Sources must comply with both the thermal emissions and emission concentration standards.
4 Low volatile metal standard for liquid fuel-fired boilers is for chromium only. Arsenic and beryllium are not included in the low volatile metal total for liquid fuel-fired boilers.
5 Standards are expressed as mass of pollutant contributed by hazardous waste per million Btu contributed by the hazardous waste.
6 APCD denotes “air pollution control device,” WHB denotes “waste heat boiler.”
7 Floor level represents the “capped interim standard level,” which means the floor level determined by the associated methodology was less stringent than the interim standard level.

2. What Is Alternative Option 2, and What Is the Rationale?

Under alternative option 2, we use the emissions-based approach to establish all floors and there are no exceptions. All floor levels are expressed in units of stack gas concentrations (we do not express any floors for energy recovery units in terms of thermal emissions). The best performing sources for all floors are those with the lowest emissions, on a stack gas concentration basis.

We are not proposing this alternative option because it has the disadvantages that the more complicated provisions of Option 1 (and to some extent Option 2) address: (1) By not using the SRE/Feed Approach for metals and total chlorine, it does not ensure that sources could use either feedrate control or back-end control to achieve the floor; (2) the approach may be inappropriately biased against sources that burn hazardous waste fuel at high firing rates because it does not express the standards in units of hazardous waste thermal emissions; (3) it inappropriately considers feed control for particulate matter and for hydrochloric acid production furnaces by not using the Air Pollution Control Device Approach for those floors; and (4) it may not appropriately estimate the performance of the average of the 12 percent best performing sources given that those best performers may have low emissions in part because their raw material and/or fossil fuels contained low levels of HAP during the emissions test (and because we do not believe feed control of HAP in raw material and fossil fuel should be assessed as a MACT floor control because it could result in floor levels that are not replicable by the best performing sources, nor duplicable by other sources).

We invite comment as to whether this alternative approach is appropriate, noting the doubts we have voiced above. We present the results of using this alternative option 2 to identify floor levels for existing sources in Table 4 below. See USEPA “Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards,” March 2004, Chapter 16, for more information.

Table 4.—Floor Levels for Existing Sources Under Alternative Option 2

IncineratorsCement kilnsLightweight aggregate kilnsSolid fuel-fired boilers 1Liquid fuel-fired boilers 1Hydrochloric acid production furnaces 1
Dioxin/Furans (ng TEQ/dscm)0.28 for dry APCD and WHB sources; 5 0.20 or 0.40 + 400°F at APCD inlet for others.60.20 or 0.40 + 400°F at APCD inlet.60.20 or 400°F at kiln outlet.6CO or THC standard as a surrogate3.0 or 400°F at APCD inlet for dry APCD sources; CO or THC standard as surrogate for othersCO or THC standard as a surrogate.
Mercury130 μg/dscm 631 μg/dscm 219 μg/dscm 210 μg/dscm0.47 μg/dscm 2Total chlorine standard as surrogate.
Particulate Matter0.0040 gr/dscf0.016 gr/dscf0.025 gr/dscf 60.065 gr/dscf0.0028 gr/dscfTotal chlorine standard as surrogate.
Semivolatile Metals (lead + cadmium)19 μg/dscm68 μg/dscm130 μg/dscm170 μg/dscm8.7 μg/dscm 2Total chlorine standard as surrogate.
Low Volatile Metals (arsenic + beryllium + chromium)14 μg/dscm8.9 μg/dscm82 μg/dscm210 μg/dscm28 μg/dscm 4Total chlorine standards as surrogate.
Total Chlorine (hydrogen chloride + chlorine gas)0.93 ppmv41 ppmv600 ppmv 6440 ppmv2.4 ppmv2.0 ppmv.
Notes:
1 Particulate matter, semivolatile metal, low volatile metal, and total chlorine standards apply to major sources only for solid fuel-fired boilers, liquid fuel-fired boilers, and hydrochloric acid production furnaces.
2 Standard is based on normal emissions data.
3 Sources must comply with both the thermal emissions and emission concentration standards.
4 Low volatile metal standard for liquid fuel-fired boilers is for chromium only. Arsenic and beryllium are not included in the low volatile metal total for liquid fuel-fired boilers.
5 APCD denotes “air pollution control device”, WHB denotes “waste heat boiler'.
6 Floor level represents the “capped interim standard level”, which means the floor level determined by the associated methodology was less stringent than the interim standard level.

3. What Is Alternative Option 3, and What Is the Rationale?

Under alternative option 3, we evaluated an approach to identify the best performing sources for particulate matter, semivolatile metals, and low volatile metals that considers how well a source is controlling these pollutants simultaneously. Simultaneous control of these pollutants is an appropriate consideration because these pollutants are controlled by the same emission control device, the particulate matter control device (e.g., a wet scrubber, electrostatic precipitator, or fabric filter). We call this alternative approach the Simultaneous Achievability for Particulates (SAP) Approach. See USEPA, “Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards,” March 2004, Chapters 10 and 19.

Start Printed Page 21236

We evaluated semivolatile metal and low volatile metal emissions for energy recovery sources—cement kilns, lightweight aggregate kilns, and liquid fuel-fired boiler—under two emissions-based SAP alternatives: hazardous waste thermal emissions, and stack gas concentrations. The hazardous waste thermal emissions option assesses semivolatile metal and low volatile metal thermal emissions for energy recovery units, while assessing particulate matter using the emissions-based stack gas concentration approach. The emissions-based stack-gas concentration approach assesses stack gas concentrations (as opposed to thermal emissions) for all HAP. Note that we did not evaluate hydrochloric acid production furnaces under this SAP approach because we propose to use the total chlorine standard as a surrogate to control emissions of particulate matter and metals for these sources.

Under the SAP approach, we rank emissions for each pollutant across the sources for which we have emissions data for that pollutant. For ranking, we use the upper 99% confidence interval for the average of the runs of the test condition for a source. For example, if we have semivolatile metal emissions data for 15 sources, the lowest semivolatile metal emissions level is ranked one and the highest is ranked 15. To identify the best performing sources for all three pollutants simultaneously, we calculate an aggregate rank score for each source. For example, if source A has a rank of 5 for particulate matter, a rank of 10 for semivolatile metals, a rank of 15 for low volatile metals, the aggregate rank score for that source is 10, the average rank across the pollutants. If we do not have emissions data for a pollutant for a source, there is no rank score for that pollutant, and that pollutant is not considered in the aggregate rank score for the source.

To identify the best performing sources in the aggregate, we rank the aggregate rank scores for the sources from lowest to highest. If we have emissions data for all three pollutants for all sources, the 5 (or 12% if we have data for more than 30 sources) sources with the lowest aggregate rank scores are the best performing sources. If we have incomplete data sets for some sources for a source category, the best performing sources for a pollutant (i.e., particulate matter, semivolatile metals, or low volatile metals) are the sources with the lowest aggregate rank scores and for which we have emissions data.

We present the alternative MACT floors for existing sources under the SAP approach in Table 5 below.

Table 5.—Floor Levels for Existing Sources Under the SAP Approach

Source categoryEmissions-based approachParticulate matter floor (gr/dscf)Semivolatile metals floorLow volatile metals floor
IncineratorsStack Gas Conc.0.004053 μg/dscm50 μg/dscm.
Cement KilnsThermal Emissions0.027190 lb/trillion Btu20 lb/trillion Btu.
Stack Gas Con.0.015103 μg/dscm14 μg/dscm.
Lightweight Aggregate KilnsThermal Emissions0.019300 lb/trillion Btu95 lb/trillion Btu.
Stack Gas Conc.0.019120 μg/dscm89 μg/dscm.
Solid Fuel-Fired BoilersStack Gas Conc.0.090180 μg/dscm230 μg/dscm.
Liquid Fuel-Fired BoilersThermal Emissions0.003981 lb/trillion Btu180 lb/trillion Btu.
Stack Gas Conc.0.003926 μg/dscm210 μg/dscm.

We request comment on this alternative approach for identifying MACT floors. If we use this approach in the final rule to identify MACT floors, we would promulgate a beyond-the-floor standard for particulate matter of 0.030 gr/dscf for existing solid fuel-fired boilers for the same reasons we are proposing today a beyond-the-floor standard. See Part Two, Section X.C for a discussion of today's proposed beyond-the-floor particulate matter standard for solid fuel-fired boilers.

See USEPA, “Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards,” March 2004, Chapters 10 and 19, for a more detailed explanation of this SAP analysis.

4. What Is Alternative Option 4, and What Is the Rationale?

The Environmental Technology Council (ETC) recommends an approach to calculate floor levels for metals and chlorine that uses a low feedrate screen and addresses emissions variability differently than the options we evaluated.[73] We may use this approach in total or in part to support a final rule, and therefore request comment on the approach.

Under ETC's approach, test conditions are screened from further consideration if metals or chlorine were not fed at levels that challenge the emissions control system.[74] Feedrates of metals and chlorine in hazardous waste are normalized to account for size of the combustor by converting feedrates to maximum theoretical emissions concentrations. A low maximum theoretical emissions concentration filter is used to screen out emissions from low feed test conditions, where the filter is the lower 99% confidence limit of the mean of the maximum theoretical emissions concentrations for all test conditions for all sources within a source category.

ETC's approach also excludes specialty units, defined as sources that burn munitions and radiological waste (i.e., Department of Defense and Department of Energy sources). ETC believes that these sources burn wastes with atypical concentrations of ash and metals that may inappropriately skew the calculation of floor levels. Under this approach, we would either subcategorize and issue separate emission standards for these specialty units, or omit these speciality units from the MACT analysis and require the specialty units to comply with the floor levels that are determined from emissions of the non-specialty units.

After applying the low maximum theoretical emissions concentration filter and excluding specialty units, this approach identifies the best performing sources by ranking emissions from Start Printed Page 21237lowest to highest.[75] Run variability is not considered at this point. For incinerators, cement kilns, and lightweight aggregate kilns where we may have historical compliance test emissions from several test campaigns for a source, test conditions from the campaign with the lowest compliance test emissions are used to identify the best performers.

The average of the emissions from the best performing sources are used to calculate the floor, and an emissions variability factor is added. For incinerators, cement kilns, and lightweight aggregate kilns where we may have historical compliance test emissions data from several test campaigns for a source, three approaches are considered to select representative emissions for each best performing source: (1) The highest compliance test emissions from any test campaign; (2) the average of the highest compliance test emissions from all test campaigns; and (3) the highest emissions during the most recent compliance test campaign. By identifying the best performers based on compliance test emissions from the test campaign with the lowest emissions and calculating the floor using compliance test emissions under these alternative approaches, emissions variability is addressed in part.[76]

Emissions variability is accounted for by adding an emissions variability factor to the average emissions for the best performing sources. The variability factor is a measure of the average run-to-run variability for the test conditions for the best performing sources. The variability factor is determined as the upper confidence limit (calculated at the 99% confidence interval) around the mean of the runs for each test condition for each best performer. (For sources with more than one compliance test condition, the variability factor for each source is first determined as the average of the variabilities associated with each compliance test condition).[77] The upper confidence limits are averaged across the best performing sources, and the average confidence limit is added to the average emissions from the best performers to identify the floor.

We invite comment as to whether this alternative approach is appropriate. We calculated alternative floor levels for new and existing sources with minor adjustments.[78] We present the results of applying that approach in Table 6 below. See USEPA “Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards,” March 2004, Chapters 12 and 21, for more information on how we applied this approach to our data base.

Table 6.—Floor Levels for Existing Sources Under the Modified ETC Approach

Data baseIncineratorsCement kilnsLightweight aggregate kilnsSolid fuel-fired boilersLiquid fuel-fired boilers
AllExcluding speciality units
Mercury (μg/dscm)Avg of historical CT data130 (308) 1130 (308) 14837
Most recent CT data130 (308) 1130 (308) 14031144.8
Highest of historical CT data130 (308) 1130 (308) 16845
Particulate Matter (gr/dscf)Avg of historical CT data0.00430.00430.0250.017
Most recent CT data0.00430.00430.0250.0170.110.0090
Highest of historical CT data0.00430.00430.030 (0.032) 10.017
Semivolatile Metals (μg/dscm)Avg of historical CT data5332230250 (901) 1
Most recent CT data5332160250 (746) 12308.2
Highest of historical CT data5332300250 (1208) 1
Low Volatile Metals (μg/dscm)Avg of historical CT data394651110 (119) 1
Most recent CT data393642110 (129) 132052
Highest of historical CT data395656 1110 (133) 1
Total Chlorine (ppmv)Avg of historical CT data1.41.885600 (1655) 1
Most recent CT data1.41.886600 (1811) 14103.2
Highest of historical CT data1.41.889600 (1823) 1
Notes: “CT” means Compliance Test.
1 Floor would be capped by the Interim Standards. Number in parentheses represents the calculated floor level, the number preceding is the “capped” interim standard level.

5. What Is Alternative Option 5, and What Is the Rationale?

Alternative Option 5 would use system removal efficiency (SRE) to identify the best performing sources for the mercury, semivolatile metals, low volatile metals, and total chlorine floor levels. This is similar to the approach we propose to establish the total chlorine standard for hydrochloric acid production furnaces. See discussion in Part Two, Section VI.A.2.b.

Floor levels would be expressed as an SRE or an emission concentration where the emission concentration is based on the emissions achieved by the best performing SRE sources.[79] A source could elect to comply with either floor. An emissions floor as an alternative to the SRE floor is appropriate because a source may be achieving emission levels lower than those achieved by the best performing SRE sources even though it may not be achieving MACT floor SRE. For example, a source may be achieving low emissions without achieving MACT SRE by using superior feedrate control.

The SRE floor is an SRE that the average of the best performing SRE sources could be expected to achieve in 99 of 100 future tests when operating under the conditions used to establish the SRE.[80] The emissions floor is a stack gas concentration, or thermal emission concentration for source categories that burn hazardous waste fuels, that the average of the best performing SRE sources could be expected to achieve in 99 of 100 future tests when operating under the conditions used to establish the SRE and emission level.

We note that this approach is not applicable for situations where sources in a source category do not use back-end control to control metals or total chlorine. For example, cement kilns do not use back-end control to control mercury or total chlorine.[81]

This approach is also not applicable for situations where our data base is comprised of normal emissions data. As discussed previously, SREs calculated from normal test conditions may be unreliable because a small error in the feedrate calculation at low feedrates can have a substantial impact on the calculated SRE.

In situations where this SRE-based approach is not applicable, we would use an alternative approach to identify MACT floor, such as the Emissions approach.

Floor levels for existing sources under this approach are presented in Table 7.

We also investigated a variation of this approach where sources with atypically high feedrates for metals or chlorine are excluded from the calculation of the alternative emission level. This variation may be appropriate to ensure that sources with high feedrates do not drive the alternative emission concentration-based floor inappropriately high even though the source may be a best performing SRE source. Under this variation, note that sources with high feedrates are used, however, to identify the best performing SRE sources and MACT SRE. This is because sources with the highest feedrates may employ the best performing back-end control systems to meet current standards or otherwise control emissions. As a measure of atypically high feedrates, we use the 99th upper percentile feedrate around the mean of feedrate data in the data set available for the analysis. To ensure that we continue to use 5 sources or 12 percent of sources to calculate the emission concentration-based floor under this variation, we replace a best performing SRE source that is screened out of the concentration-based floor analysis because of high feedrates with the source with the next best SRE.[82]

Floor levels for existing sources under this feedrate-screened variation are presented in Table 8.

We invite comment on these alternative floor approaches. For more information on how the approach would work, see USEPA “Draft Technical Support Document for HWC MACT Replacement Standards, Volume III: Selection of MACT Standards,” March 2004, Chapters 13 and 22.

Start Printed Page 21239

Table 7.—Floor Levels for Existing Sources Under Alternative Option 5

Source categoryMercurySemivolatile metalsLow volatile metalsTotal chlorine
SRE 1EmissionsSRE 1Emission concentrationSRE 1Emission concentrationSRE 1Emission concentration
Stack gas 2Thermal 3Stack gas 2Thermal 3Stack gas 2Thermal 3Stack gas 2Thermal 3
Incinerators2720,000 9n/a 899.8974n/a 899.96933n/a 899.9903.1n/a 8
Cement Kilnsn/a 4, 599.9667114099.9891122n/a 4, 5
Lightweight Aggregate Kilnsn/a 4, 699.7833031099.8910095n/a 4, 6
Solid Fuel-Fired Boilers11n/a 899.78180n/a 897.9230n/a 8n/a 4, 5
Liquid Fuel-Fired Boilersn/a 4n/a 490.4 727 745 799.702555
1 SRE is system removal efficiency expressed as a percent.
2 Stack gas concentration is expressed in μg/dscm for all except total chlorine, which is expressed as ppmv.
3 Thermal emission is expressed in lb/trillion Btu, except total chlorine which is expressed in lb/billion Btu.
4 Unable to determine SRE due to normal feedrate data.
5 No SRE due to no reliable back-end control.
6 Only one source has back-end control.
7 LVM Standards for liquid fuel-fired boilers are for Chromium, only.
8 Thermal emissions not appropriate for source categories with sources that do not burn hazardous waste fuels.
9 We believe this methodology yields inappropriate MACT mercury floors for incinerators because we have only 11 compliance test conditions, and the best performers spiked uncharacteristically high levels of mercury during their compliance test.

Table 8.—Floor Levels for Existing Sources Under Alternative Option 5 With High Feedrate Screen

Source categoryMercurySemivolatile metalsLow volatile metalsTotal chlorine
SRE 1EmissionsSRE 1Emission concentrationSRE 1Emission concentrationSRE 1Emission concentration
Stack gas 2Thermal 3Stack gas 2Thermal 3Stack gas 2Thermal 3Stack gas 2Thermal 3
Incinerators277,500 9n/a 899.8964n/a 899.96929n/a 899.9901.3n/a 8
Cement Kilnsn/a 4, 599.9666513099.9891118n/a 4, 5
Lightweight Aggregate Kilnsn/a 4, 699.7833031099.8910095n/a 4, 6
Solid Fuel-Fired Boilers11n/a 899.78180n/a 897.9230n/a 8n/a 4, 5
Liquid Fuel-Fired Boilersn/a 4n/a 490.4 727 7110 799.702355
1 SRE is system removal efficiency expressed as a percent.
2 Stack gas concentration is expressed in μg/dscm for all except total chlorine, which is expressed as ppmv.
3 Thermal emission is expressed in lb/trillion Btu, except total chlorine which is expressed in lb/billion Btu.
4 Unable to determine SRE due to normal feedrate data.
5 No SRE due to no reliable back-end control.
6 Only one source has back-end control.
7 LVM Standards for liquid fuel-fired boilers are for Chromium, only.
8 Thermal emissions not appropriate for source categories with sources that do not burn hazardous waste fuels.
9 We believe this methodology yields inappropriate MACT mercury floors for incinerators because we have only 11 compliance test conditions, and the best performers spiked uncharacteristically high levels of mercury during the their compliance test.
Start Printed Page 21240

VII. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste Burning Incinerators?

The proposed standards for existing and new incinerators that burn hazardous waste are summarized in the table below. See proposed § 63.1219.

Proposed Standards for Existing and New Incinerators

Hazardous air pollutant or surrogateEmission standard 1
Existing sourcesNew sources
Dioxin and furan—sources equipped with waste heat boilers or dry air pollution control system 20.28 ng TEQ/dscm0.11 ng TEQ/dscm.
Dioxin and furan—sources not equipped with waste heat boilers or dry air pollution control system 20.2 ng TEQ/dscm; or 0.40 ng TEQ/dscm and temperature at inlet to the initial particulate matter control device ≤400°F0.20 ng TEQ/dscm.
Mercury130 μg/dscm8.0 μg/dscm.
Particulate matter34 mg/dscm (0.015 gr/dscf)1.6 mg/dscm (0.00070 gr/dscf).
Semivolatile metals59 μg/dscm6.5 μg/dscm.
Low volatile metals84 μg/dscm8.9 μg/dscm.
Hydrogen chloride and chlorine gas 31.5 ppmv or the alternative emission limits under § 63.12150.18 ppmv or the alternative emission limits under § 63.1215.
Hydrocarbons 4,510 ppmv (or 100 ppmv carbon monoxide)10 ppmv (or 100 ppmv carbon monoxide).
Destruction and removal efficiencyFor existing and new sources, 99.99% for each principal organic hazardous constituent (POHC). For sources burning hazardous wastes F020, F021, F022, F023, F026, or F027, however, 99.9999% for each POHC.
1 All emission standards are corrected to 7% oxygen dry basis.
2 A wet air pollution system followed by a dry air pollution control system is not considered to be a dry air pollution control system for purposes of this standard. A dry air pollution systems followed a wet air pollution control system is considered to be a dry air pollution control system for purposes of this standard.
3 Combined standard, reported as a chloride (Cl(−)) equivalent.
4 Sources that elect to comply with the carbon monoxide standard must demonstrate compliance with the hydrocarbon standard during the comprehensive performance test.
5 Hourly rolling average. Hydrocarbons reported as propane.

A. What Are the Proposed Standards for Dioxin and Furan?

The proposed standards for dioxin/furan for sources equipped with dry air pollution control devices and/or waste heat boilers are 0.28 ng TEQ/dscm for existing sources and 0.11 ng TEQ/dscm for new sources. For incinerators using either wet air pollution control or no air pollution control devices, the proposed standards for dioxin/furan are 0.20 ng TEQ/dscm or 0.40 ng TEQ/dscm while limiting the temperature at the inlet to the particulate matter control device to less than 400 °F for existing sources and 0.20 ng TEQ/dscm for new sources.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Dioxin and furan emissions for existing incinerators are currently limited by § 63.1203(a)(1) to 0.20 ng TEQ/dscm; or 0.40 ng TEQ/dscm provided that the combustion gas temperature at the inlet to the initial particulate matter control device is limited to 400 °F or less. (For purposes of compliance, operation of a wet air pollution control system is presumed to meet the 400 °F or lower requirement.) This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796, February 13, 2002).

Since promulgation of the September 1999 final rule, we have obtained additional dioxin/furan emissions data. We now have dioxin/furan emissions data for over 55 sources. The emissions in our data base range from less than 0.001 to 34 ng TEQ/dscm.

As discussed in Part Two, Section II, we assessed whether incinerators equipped with dry air pollution control devices and/or waste heat boilers have statistically different emissions than sources with either wet air pollution control or no air pollution control equipment.[83] Our statistical analysis indicates dioxin/furan emissions between these types of incinerators are significantly different. (As we explained there, these differences relate to differences in dioxin/furan formation mechanisms, not pollution control device efficiency.) Therefore, we believe subcategorization is warranted for this emission standard and we are proposing separate floor levels.

To identify the floor level for incinerators equipped with dry air pollution control equipment and/or waste heat boilers, we evaluated the compliance test emissions data associated with the most recent test campaign using the Emissions Approach described in Part Two, Section VI. The calculated floor is 0.28 ng TEQ/dscm, which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. The calculated floor level of 0.28 ng TEQ/dscm is based on five best performing sources that achieved this floor level either by the use of temperature control at the inlet to dry air pollution control device and good combustion or by the use of activated carbon injection. The single best performer is equipped with a dry air pollution control system and a waste heat boiler, and uses activated carbon injection, good combustion, and temperature control to control dioxin/furan emissions. The remaining four Start Printed Page 21241best performers are equipped with dry air pollution systems but do not have waste heat recovery boilers. Two of these sources use activated carbon, good combustion, and temperature control to control dioxin/furan emissions.[84] The other two without waste heat recovery boilers use a combination of good combustion and temperature control to control emissions.

We then judged the relative stringency of the calculated floor level to the interim standard to determine if the proposed floor level needed to be “capped” by the current interim standard to ensure the proposed floor level is not less stringent than an existing federal emission standard. A comparison of the calculated floor level of 0.28 ng TEQ/dscm to the interim standard—0.20 ng TEQ/dscm or 0.40 ng TEQ/dscm provided that the combustion gas temperature at the inlet to the initial particulate matter control device is limited to less than 400 °F—indicates that a floor level of 0.28 ng TEQ/dscm is more stringent than the current interim standard. This judgment is based on our belief that the majority of these incinerators are currently complying with the 0.40 ng TEQ/dscm and temperature limitation portion of the interim standard.[85] We estimate that this emission level is being achieved by 71% of sources and would reduce dioxin/furan emissions by 0.28 grams per year.

We also considered whether to further subcategorize based on whether the incinerator is equipped with a waste heat recovery boiler or dry air pollution control device. Our analysis determined that the dioxin/furan emissions from incinerators with waste heat recovery boilers are not statistically different from those equipped with dry air pollution control systems. We propose, therefore, that further subcategorization is not necessary given that incinerators using either waste heat recovery boilers or dry air pollution control systems can readily achieve the calculated floor level using control technologies demonstrated by the best performing sources.

For sources with either wet air pollution control systems or no air pollution control equipment, but are not equipped with a heat recovery boiler, we contemplated identifying an emission limit but instead rely on surrogates for control of organic HAP, namely good combustion practices, to be demonstrated by complying with the carbon monoxide or hydrocarbon emissions standard and compliance with the destruction and removal efficiency standard.[86] We believe that it would be inappropriate to establish a numerical dioxin/furan floor level for sources with wet or no air pollution control systems because the floor emission level would not be replicable by the best performing sources nor duplicable by other sources. Dioxin/furan formation mechanisms are complex. Sources with wet or no air pollution control devices may have difficulty complying with a numerical dioxin/furan limit that is based on the lowest emitting dioxin/furan sources within this subcategory because there is not a demonstrated floor control technology that these sources can use to “dial in” to achieve a given emission level. Moreover, dioxin/furan emissions could result from operation under poor combustion conditions and formation on particulate matter surfaces in duct work, on heat recovery boiler tubes, and on particulates entrained in the combustion gas stream. As a result, we would instead identify floor control for these sources to be operating under good combustion practices by complying with the destruction and removal efficiency and carbon monoxide/hydrocarbon standards.

Though MACT floor for these units is operating under good combustion practices, there is a regulatory limit which is relevant in identifying the floor level. Hazardous waste incinerators are complying with an interim standard for dioxin/furan—an emission limit of 0.20 ng TEQ/dscm or, alternatively, 0.40 ng TEQ/dscm provided that the combustion gas temperature at the inlet to the initial particulate matter control device is limited to 400 °F or less—that fixes a level of performance for the source category. Given that all sources are meeting this interim standard and that the interim standard is judged as more stringent than a MACT floor of “good combustion practices,” the dioxin/furan floor level can be no less stringent than the current regulatory limit.[87] Therefore, the proposed floor level for incinerators with either wet air pollution control systems or no air pollution control equipment that are not equipped with a heat recovery boiler is either 0.20 ng TEQ/dscm or 0.40 ng TEQ/dscm provided that the combustion gas temperature at the inlet to the initial particulate matter control device is limited to 400 °F or less. This emission level is currently being achieved by all sources because the interim standard is an enforceable standard currently in effect.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We evaluated beyond-the-floor standards based on the use of control technology which removes dioxin/furan, namely use of an activated carbon injection system or a carbon bed system as beyond-the-floor control for further reduction of dioxin/furan emissions. Activated carbon is currently used at three incinerators to control dioxin/furan. We evaluated a beyond-the-floor level of 0.10 ng TEQ/dscm for all incinerators, which represents a 65-75% reduction in dioxin/furan emissions from the floor level. We selected this level because it represents a level that is considered routinely achievable with activated carbon.[88]

For incinerators equipped with dry air pollution control equipment and/or waste heat boilers, the national incremental annualized compliance cost for these sources to meet the beyond-the-floor level rather than comply with the floor controls would be approximately $2.2 million and would provide an incremental reduction in dioxin/furan emissions beyond the floor level controls of 0.5 grams TEQ per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between activated carbon injection and carbon beds and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of hazardous waste generated by 1,500 tons per year in addition to using an additional 3 million kW-hours per year beyond the requirements to achieve the floor level. The costs associated with these hazardous waste treatment/disposal and energy impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $4.4 million per Start Printed Page 21242additional gram of dioxin/furan removed, we are not proposing a beyond-the-floor standard based on activated carbon injection and carbon bed systems.

For sources with either wet air pollution control systems or no air pollution control equipment that are not equipped with a heat recovery boiler, the national incremental annualized compliance cost for these sources to meet the beyond-the-floor level would be approximately $3.9 million and would provide an incremental reduction in dioxin/furan emissions beyond the MACT floor controls of 0.35 grams TEQ per year. Nonair quality health and environmental impacts and energy effects were also evaluated. We estimate that this beyond-the-floor option would increase the amount of hazardous waste generated by 700 tons per year. The option would also require sources to use an additional 2 million kW-hours per year and 70 million gallons of water beyond the requirements to achieve the floor level. Therefore, based on these factors and costs of approximately $11 million per additional gram of dioxin/furan removed, we are not proposing a beyond-the-floor standard based on activated carbon injection and carbon bed systems.

3. What Is the Rationale for the MACT Floor for New Sources?

Dioxin and furan emissions for new incinerators are currently limited by § 63.1203(b)(1) to 0.20 ng TEQ/dscm. This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796, February 13, 2002).

For incinerators equipped with dry air pollution control equipment and/or waste heat boilers, the calculated floor level is 0.11 ng TEQ/dscm, which considers variability. This is an emission level that the single best performing source identified using the Emissions Approach could be expected to achieve in 99 out of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained.

For sources with either wet air pollution control systems or no air pollution control equipment that are not equipped with a heat recovery boiler, as previously discussed for existing sources, we believe that it would be inappropriate to establish numerical dioxin/furan emission for these sources. We would instead identify floor control for these sources to be operating under good combustion practices by complying with the destruction and removal efficiency and carbon monoxide/hydrocarbon standards.

Though MACT floor for these units is operating under good combustion practices, there is a regulatory limit which is relevant in identifying the floor level. New hazardous waste incinerators are subject to an interim emission standard for dioxin/furan of 0.20 ng TEQ/dscm. Given that the interim standard is judged more stringent than a MACT floor of “good combustion practices,” the dioxin/furan floor level can be no less stringent than the current regulatory limit. Therefore, the proposed floor level for incinerators with either wet air pollution control systems or no air pollution control equipment that are not equipped with a heat recovery boiler is 0.20 ng TEQ/dscm. Therefore, we are proposing the current interim standard of 0.20 ng TEQ/dscm as the floor level for new sources.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We evaluated beyond-the-floor standards based on the use of a carbon bed system to achieve additional removal of dioxin/furan. Given the relatively low dioxin/furan levels at the floor, we made a conservative assumption that the use of a carbon bed will provide an additional 50% dioxin/furan control. We applied this removal efficiency to the dioxin/furan floor levels to identify the beyond-the-floor levels.

For a new incinerator with average gas flowrate equipped with dry air pollution control equipment and/or a waste heat boiler, the national incremental annualized compliance cost to meet the beyond-the-floor level of 0.06 ng TEQ/dscm rather than comply with the floor controls would be approximately $0.22 million and would provide an incremental reduction in dioxin/furan emissions beyond the floor level controls of 0.013 grams TEQ per year. Nonair quality health and environmental impacts and energy effects were evaluated. Therefore, based on these factors and costs of approximately $17 million per additional gram of dioxin/furan removed, we are not proposing a beyond-the-floor standard based on activated carbon bed systems.

For a source with either a wet air pollution control system or no air pollution control equipment that is not equipped with a heat recovery boiler, the national incremental annualized compliance cost for a new incinerator with an average gas flowrate to meet a beyond-the-floor level of 0.10 ng TEQ/dscm would be approximately $0.22 million and would provide an incremental reduction in dioxin/furan emissions beyond the MACT floor controls of 0.024 grams TEQ per year. Considering the nonair quality health and environmental impacts and energy effects in addition to costs of approximately $9.3 million per additional gram of dioxin/furan removed, we are not proposing a beyond-the-floor standard based on a carbon bed system.

B. What Are the Proposed Standards for Mercury?

We are proposing to establish standards for existing and new incinerators that limit emissions of mercury to 130 μg/dscm and 8 μg/dscm, respectively.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Mercury emissions for existing incinerators are currently limited to 130 μg/dscm by § 63.1203(a)(2). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796).

We have both normal and compliance test emissions data for over 50 sources. For several sources, we have emissions data from more than one test campaign. The mercury stack emissions in our data base range from less than 1 to 35,000 μg/dscm, which are expressed as mass of mercury per unit volume of stack gas.

To identify the floor level, we evaluated the compliance test emissions data associated with the most recent test campaign using the SRE/Feed Approach. The calculated floor is 610 μg/dscm, which considers emissions variability. Even though all sources have recently demonstrated compliance with the interim standard of 130 μg/dscm, all the mercury emissions data in our data base precede initial compliance with these interim standards. As a result, the calculated floor level of 610 μg/dscm is less stringent than the interim standard, which is a regulatory limit relevant in identifying the floor level (so as to avoid any backsliding from a current level of performance achieved by all incinerators, and hence, the level of minimal stringency at which EPA could calculate the MACT floor). Therefore, we are proposing the floor level as the current emission standard of 130 μg/dscm. This emission level is currently being achieved by all sources.

We invite comment on an alternative approach to identify the floor level using available normal emissions data instead of the compliance test data. For reasons we discussed above in Part Two, our floor-setting methodology favors compliance test data over normal emissions data. However, there are available more mercury emissions data Start Printed Page 21243characterized as normal—over 40 test conditions—than the eleven compliance test results. Given that the data base includes considerably more normal emissions than compliance test data, we invite comment on whether the floor analysis should be based on the normal emissions data instead of the compliance test data. The floor level considering the normal data using the Emissions Approach is 7.8 μg/dscm, which considers emissions variability. If we were to adopt such an approach, we would require sources to comply with the limit on an annual basis because the floor analysis is based on normal emissions data. Under this approach, compliance would not be based on the use of a total mercury continuous emissions monitoring system because these monitors have not been adequately demonstrated as a reliable compliance assurance tool at all types of incinerator sources. Instead, a source would maintain compliance with the mercury standard by establishing and complying with short-term limits on operating parameters for pollution control equipment and annual limits on maximum total mercury feedrate in all feedstreams.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We identified two potential beyond-the-floor techniques for control of mercury: (1) Activated carbon injection; and (2) control of mercury in the hazardous waste feed.

Use of Activated Carbon Injection. We evaluated activated carbon injection as beyond-the-floor control for further reduction of mercury emissions. Activated carbon injection is currently being used at three incinerators and has been demonstrated for controlling mercury and has achieved efficiencies ranging from 80% to greater than 90% depending on various factors such as injection rate, mercury speciation in the flue gas, flue gas temperature, and carbon type. Given the limited experience at hazardous waste combustion systems, we made a conservative assumption that the use of activated carbon will provide 70% mercury control. We evaluated a beyond-the-floor level of 39 μg/dscm.

The national incremental annualized compliance cost for incinerators to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $7.1 million and would provide an incremental reduction in mercury emissions beyond the MACT floor controls of 0.39 tons per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between activated carbon injection and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of hazardous waste generated by 1,800 tons per year and would require sources to use an additional 5.8 million kW-hours per year beyond the requirements to achieve the floor level. The costs associated with these hazardous waste treatment/disposal and energy impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $18 million per additional ton of mercury removed, we are not proposing a beyond-the-floor standard based on activated carbon injection.

Feed Control of Mercury in the Hazardous Waste. We also evaluated a beyond-the-floor level of 100 μg/dscm, which represents a 20% reduction from the floor level. We chose a 20% reduction as a level that represents the practicable extent that additional feedrate control of mercury in hazardous waste (beyond feedrate control that may be necessary to achieve the floor level) can be used and still achieve modest emissions reductions.[89] The national incremental annualized compliance cost for incinerators to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $1.8 million and would provide an incremental reduction in mercury emissions beyond the MACT floor controls of 0.11 tons per year. Nonair quality health and environmental impacts and energy effects were also evaluated. Therefore, based on these factors and costs of approximately $17 million per additional ton of mercury removed, we are not proposing a beyond-the-floor standard based on feed control of mercury in the hazardous waste.

For the reasons discussed above, we propose a mercury emissions standard of 130 μg/dscm for existing incinerators.

3. What Is the Rationale for the MACT Floor for New Sources?

Mercury emissions from new incinerators are currently limited to 45 μg/dscm by § 63.1203(b)(2). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796).

The MACT floor for new sources for mercury would be 8 μg/dscm, which considers emissions variability. This is an emission level that the single best performing source identified with the SRE/Feed Approach considering compliance test data could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the test conditions during which the emissions data were obtained.

As we did for existing sources, we also invite comment on basing the floor analysis on the normal emissions data using the Emissions Approach. The floor level using the normal data is 0.70 μg/dscm, which considers emissions variability. If we were to adopt such an approach, we would require sources to comply with the limit on an annual basis because it is based on normal emissions data.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We identified two potential beyond-the-floor techniques for control of mercury: (1) Use of a carbon bed; and (2) control of mercury in the hazardous waste feed.

Carbon Bed System. We evaluated a carbon bed system as beyond-the-floor control for further reduction of mercury emissions. Given the relatively low floor level, we made a conservative assumption that the use of a carbon bed system would provide 50% mercury control. The incremental annualized compliance cost for a new incinerator with average gas flow rate to meet a beyond-the-floor level of 4 μg/dscm, rather than comply with the floor level, would be approximately $0.22 million and would provide an incremental reduction in mercury emissions of approximately 2.1 pounds per year. Nonair quality health and environmental impacts and energy effects are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $200 million per additional ton of mercury removed, we are not proposing a beyond-the-floor standard based on a carbon bed system.

Feed Control of Mercury in the Hazardous Waste. We also believe that the expense for a reduction in mercury emissions based on further control of mercury concentrations in the Start Printed Page 21244hazardous waste is not warranted. A beyond-the-floor level of 6.4 μg/dscm, which represents a 20% reduction from the floor level, would result in a small incremental reduction in mercury emissions. For similar reasons discussed above for existing sources, we likewise conclude that a beyond-the-floor standard based on controlling the mercury in the hazardous waste feed would not be justified because of the costs and emission reductions. Therefore, we propose a mercury standard of 8 μg/dscm for new sources.

C. What Are the Proposed Standards for Particulate Matter?

We are proposing to establish standards for existing and new incinerators that limit emissions of particulate matter to 0.015 and 0.00070 gr/dscf, respectively.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Particulate matter emissions for existing incinerators are currently limited to 0.015 gr/dscf (34 mg/dscm) by § 63.1203(a)(7). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796). The particulate matter standard is a surrogate control for the hazardous air pollutant metals antimony, cobalt, manganese, nickel, and selenium.

We have compliance test emissions data for most incinerators. For some sources, we have compliance test emissions data from more than one compliance test campaign. Our data base of particulate matter stack emission concentrations range from 0.0002 to 0.078 gr/dscf.

To identify the MACT floor for incinerators, we evaluated the compliance test emissions data associated with the most recent test campaign using the Air Pollution Control Technology Approach. The calculated floor is 0.020 gr/dscf (46 mg/dscm), which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. The calculated floor level of 0.020 gr/dscf is less stringent than the interim standard of 0.015 gr/dscf, which is a regulatory limit relevant in identifying the floor level (so as to avoid any backsliding from a current level of performance achieved by all incinerators, and hence, the level of minimal stringency at which EPA could calculate the MACT floor). Therefore, we are proposing the floor level as the current emission standard of 0.015 gr/dscf. This emission level is currently being achieved by all sources.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We evaluated improved particulate matter control to achieve a beyond-the-floor standard of 17 mg/dscm (0.0075 gr/dscf). For an existing incinerator that needs a significant reduction in particulate matter emissions, we assumed and costed a new baghouse to achieve the beyond-the-floor level. If little or modest emissions reductions were needed, then improved control was costed as design, operation, and maintenance modifications of the existing particulate matter control equipment.

The national incremental annualized compliance cost for incinerators to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $3.9 million and would provide an incremental reduction in particulate matter emissions beyond the MACT floor of 48 tons per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the nonair quality health and environmental impacts between further improvements to control particulate matter and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of hazardous waste generated by 48 tons per year and would also require sources to use an additional 2.7 million kW-hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $81,000 per additional ton of particulate matter removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control.

3. What Is the Rationale for the MACT Floor for New Sources?

Particulate matter emissions from new incinerators are currently limited to 0.015 gr/dscf (34 mg/dscm) by § 63.1203(b)(7). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796).

The MACT floor for new sources for particulate matter would be 1.6 mg/dscm (0.00070 gr/dscf), which considers emissions variability. This is an emission level that the single best performing source identified with the Air Pollution Control Technology Approach could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the test conditions during which the emissions data were obtained.

As discussed in Part Two, Section II, we considered whether to propose separate standards (subcategorize) for particulate matter for several different potential subcategories such as government-owned versus non-government incinerators and liquid injection versus solid fuel-fired incinerators. We determined that the emission characteristics from these potential subcategories are not statistically different, and, therefore, separate standards for particulate matter are not warranted. We request comment on whether these subcategorization considerations capture the appropriate differences in manufacturing process, emission characteristics, or technical feasibility for particulate matter. We note, for example, the single best performing source, which is the basis of the floor level for new incinerators, is an incinerator used to decontaminate scrap metal. Though we believe these sources are best performers because they use highly efficient baghouses for the capture of particulate matter, and, therefore, appropriate for inclusion in the analysis, we invite comment on whether we have considered the appropriate subcategories for particulate matter. We note that a floor level based on the second best performing incinerator source would be 0.0021 gr/dscf.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We evaluated improved emissions control based on a state-of-the-art baghouse using a high quality fabric filter bag material to achieve a beyond-the-floor standard of 1.2 mg/dscm (0.0005 gr/dscf). The incremental annualized compliance cost for a new incinerator to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $80,000 and would provide an incremental reduction in particulate matter emissions of approximately 0.15 tons per year. Nonair quality health and environmental impacts and energy effects were also evaluated and are accounted for in the national annualized compliance cost estimates. We estimate that this option would require a new source to use an additional 0.2 million kW-hours per year. For these reasons and a cost-effectiveness of $0.53 million per ton of particulate matter removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control for new incinerators. Therefore, we propose a particulate Start Printed Page 21245matter standard of 1.6 mg/dscm for new sources.

D. What Are the Proposed Standards for Semivolatile Metals?

We are proposing to establish standards for existing and new incinerators that limit emissions of semivolatile metals (cadmium and lead) to 59 ug/dscm and 6.5 ug/dscm, respectively.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Semivolatile metals emissions from existing incinerators are currently limited to 240 ug/dscm by § 63.1203(a)(3). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796). Incinerators control emissions of semivolatile metals with air pollution control equipment and/or by controlling the feed concentration of semivolatile metals in the hazardous waste.

We have compliance test emissions data for nearly 30 incinerators. Semivolatile metal stack emissions range from approximately 4 to 29,000 ug/dscm. These emissions are expressed as mass of semivolatile metals per unit volume of stack gas. Lead was usually the most significant contributor to semivolatile emissions during compliance test conditions.

To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the SRE/Feed Approach. The calculated floor is 59 ug/dscm, which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 52% of sources. The floor level would reduce semivolatile metals emissions by 0.43 tons per year.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We identified two potential beyond-the-floor techniques for control of semivolatile metals: (1) Improved particulate matter control; and (2) control of semivolatile metals in the hazardous waste feed.

Improved Particulate Matter Control. Controlling particulate matter also controls emissions of semivolatile metals. We evaluated a beyond-the-floor level of 30 μg/dscm, which is a 50% reduction from the floor level, based on additional reductions of particulate matter emissions by operating and maintaining existing control equipment to have improved collection efficiency. The national incremental annualized compliance cost for incinerators to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $3.0 million and would provide an incremental reduction in semivolatile metals emissions beyond the MACT floor controls of 190 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between further improvements to control particulate matter and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of hazardous waste generated by 50 tons per year and would require sources to use an additional 3.4 million kW-hours per year beyond the requirements to achieve the floor level. The costs associated with these hazardous waste treatment and energy impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $31 million per additional ton of semivolatile metals removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control.

Feed Control of Semivolatile Metals in the Hazardous Waste. We also evaluated a beyond-the-floor level of 47 μg/dscm, which represents a 20% reduction from the floor level. We chose a 20% reduction as a level that represents the practicable extent that additional feedrate control of semivolatile metals in the hazardous waste can be used and still achieve modest emissions reductions. The national incremental annualized compliance cost for incinerators to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $1.7 million and would provide an incremental reduction in semivolatile metals emissions beyond the MACT floor of 90 pounds per year. Nonair quality health and environmental impacts and energy effects were also evaluated and are accounted for in the national annualized compliance cost estimates. For these reasons and costs of approximately $39 million per additional ton of semivolatile metals removed, we are not proposing a beyond-the-floor standard based on feed control of semivolatile metals in the hazardous waste.

For the reasons discussed above, we propose to establish the emission standard for existing incinerators at 59 μg/dscm.

3. What Is the Rationale for the MACT Floor for New Sources?

Semivolatile metals emissions from new incinerators are currently limited to 120 μg/dscm by § 63.1203(b)(3). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796).

The MACT floor for new sources for semivolatile metals would be 6.5 μg/dscm, which considers emissions variability. This is an emission level that the single best performing source identified with the SRE/Feed Approach could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the test conditions during which the emissions data were obtained.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We identified two potential beyond-the-floor techniques for control of semivolatile metals: (1) Improved control of particulate matter; and (2) control of semivolatile metals in the hazardous waste feed.

Improved Particulate Matter Control. We evaluated a standard of 3.3 μg/dscm, which is a 50% reduction from the floor level, based on a state-of-the-art baghouse using a high quality fabric filter bag material as beyond-the-floor control for further reductions in semivolatile metals emissions. The incremental annualized compliance cost for a new incinerator with an average gas flow rate to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $80,000 and would provide an incremental reduction in semivolatile metals emissions of approximately 2 pounds per year. Nonair quality health and environmental impacts and energy effects were also evaluated and are included in the cost estimates. We estimate that this option would require a new source to use an additional 0.2 million kW-hours per year. For these reasons and costs of $94 million per ton of semivolatile metals removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control for new sources.

Feed Control of Semivolatile Metals in the Hazardous Waste. We also believe that the expense for a reduction in semivolatile metals emissions based on further control of semivolatile metals concentrations in the hazardous waste is not warranted. A beyond-the-floor level of 5.2 μg/dscm, which represents a 20% reduction from the floor level, would result in little additional semivolatile metals reductions. For similar reasons discussed above for existing sources, we Start Printed Page 21246judge that a beyond-the-floor standard based on controlling the semivolatile metals in the hazardous waste feed would not be justified because of the costs and expected emission reductions. Therefore, we propose a semivolatile metals standard of 6.5 μg/dscm for new sources.

E. What Are the Proposed Standards for Low Volatile Metals?

We are proposing to establish standards for existing and new incinerators that limit emissions of low volatile metals (arsenic, beryllium, and chromium) to 84 μg/dscm and 8.9 μg/dscm, respectively.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Low volatile metals emissions from existing incinerators are currently limited to 97 μg/dscm by § 63.1203(a)(4). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796). Incinerators control emissions of low volatile metals with air pollution control equipment and/or by controlling the feed concentration of low volatile metals in the hazardous waste.

We have compliance test emissions data for nearly 30 incinerators. Low volatile metal stack emissions range from approximately 1 to 4,300 μg/dscm. These emissions are expressed as mass of low volatile metals per unit volume of stack gas.

To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the SRE/Feed Approach. The calculated floor is 84 μg/dscm, which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 85% of sources and would reduce low volatile metals emissions by 56 pounds per year.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We identified two potential beyond-the-floor techniques for control of low volatile metals: (1) Improved particulate matter control; and (2) control of low volatile metals in the hazardous waste feed.

Improved Particulate Matter Control. Controlling particulate matter also controls emissions of low volatile metals. We evaluated a beyond-the-floor level of 42 μg/dscm, which is a 50% reduction from the floor level, based on additional reductions of particulate matter emissions by operating and maintaining existing control equipment to have improved collection efficiency. The national incremental annualized compliance cost for incinerators to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $0.88 million and would provide an incremental reduction in low volatile metals emissions beyond the MACT floor controls of 365 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between further improvements to control particulate matter and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of hazardous waste generated by 100 tons per year and would require sources to use an additional 0.7 million kW-hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $4.8 million per additional ton of low volatile metals removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control.

Feed Control of Low Volatile Metals in the Hazardous Waste. We also evaluated a beyond-the-floor level of 67 μg/dscm, which represents a 20% reduction from the floor level. We chose a 20% reduction as a level that represents the practicable extent that additional feedrate control of low volatile metals in the hazardous waste can be used and still achieve modest emissions reductions. The national incremental annualized compliance cost for incinerators to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $0.25 million and would provide an incremental reduction in low volatile metals emissions beyond the MACT floor controls of 0.11 tons per year. Nonair quality health and environmental impacts and energy effects were also evaluated and are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $2.2 million per additional ton of low volatile metals removed, we are not proposing a beyond-the-floor standard based on feed control of low volatile metals in the hazardous waste.

For the reasons discussed above, we propose to establish the emission standard for existing incinerators at 84 μg/dscm.

3. What Is the Rationale for the MACT Floor for New Sources?

Low volatile metal emissions from new incinerators are currently limited to 97 μg/dscm by § 63.1203(b)(4). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796).

The MACT floor for new sources for low volatile metals would be 8.9 μg/dscm, which considers emissions variability. This is an emission level that the single best performing source identified with the SRE/Feed Approach could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the test conditions during which the emissions data were obtained.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We identified two potential beyond-the-floor techniques for control of low volatile metals: (1) Improved control of particulate matter; and (2) control of low volatile metals in the hazardous waste feed.

Improved Particulate Matter Control. We evaluated a standard of 4.5 μg/dscm, which is a 50% reduction from the floor level, based on a state-of-the-art baghouse using a high quality fabric filter bag material as beyond-the-floor control for further reductions in low volatile metals emissions. The incremental annualized compliance cost for a new incinerator with average gas flowrate to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $80,000 and would provide an incremental reduction in low volatile metals emissions of approximately 2.3 pounds per year. Nonair quality health and environmental impacts and energy effects were also evaluated and are included in the cost estimates. For these reasons and costs of $69 million per ton of low volatile metals removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control for new sources.

Feed Control of Low Volatile Metals in the Hazardous Waste. We also believe that the expense associated with a reduction in low volatile metals emissions based on further control of low volatile metals concentrations in the hazardous waste is not warranted. A beyond-the-floor level of 7.1 μg/dscm, which represents a 20% reduction from the floor level, would result in little additional low volatile metals reductions. For similar reasons discussed above for existing sources, we Start Printed Page 21247judge that a beyond-the-floor standard based on controlling the low volatile metals in the hazardous waste feed would not be cost-effective or otherwise appropriate. Therefore, we propose a low volatile metals standard of 8.9 μg/dscm for new sources.

F. What Are the Proposed Standards for Hydrogen Chloride and Chlorine Gas?

We are proposing to establish standards for existing and new incinerators that limit total chlorine emissions (hydrogen chloride and chlorine gas, combined, reported as a chloride equivalent) to 1.5 and 0.18 ppmv, respectively. However, we are also proposing to establish alternative risk-based standards, pursuant to CAA section 112(d)(4), which a source could elect to comply with by in lieu of the MACT emission standards for total chlorine. The emission limits would be based on national exposure standards that ensure protection of public health with an ample margin of safety. See Part Two, Section XIII for additional details.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Total chlorine emissions from existing incinerators are limited to 77 ppmv by § 63.1203(a)(6). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796). Incinerators control emissions of total chlorine with air pollution control equipment and/or by controlling the feed concentration of chlorine in the hazardous waste.

We have compliance test emissions data for most incinerators. Total chlorine emissions range from less than 1 ppmv to 460 ppmv.

To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the SRE/Feed Approach. The calculated floor is 1.5 ppmv, which considers emissions variability. This is an emission level that the best performing feed control sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 11% of sources and reductions to the floor level would reduce total chlorine emissions by 286 tons per year.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We identified two potential beyond-the-floor techniques for control of total chlorine: (1) Improved control with wet scrubbing; and (2) control of chlorine in the hazardous waste feed.

Use of Wet Scrubbing. We evaluated a beyond-the-floor level of 0.8 ppmv based on improved wet scrubbers that would include increasing the liquid to gas ratio, increasing the liquor pH, and replacing the existing packing material with new more efficient packing material. We made a conservative assumption that an improved wet scrubber will provide 50% total chlorine control beyond the controls needed to achieve the floor level given the low total chlorine levels at the floor. Applying this wet scrubbing removal efficiency to the total chlorine floor level of 1.5 ppmv leads to a beyond-the-floor level 0.8 ppmv. The national incremental annualized compliance cost for incinerators to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $1.7 million and would provide an incremental reduction in total chlorine emissions beyond the MACT floor controls of 6 tons per year. We also evaluated nonair quality health and environmental impacts and energy effects between improved wet scrubbers and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of waste water generated by 270 million gallons per year. The option would also require sources to use an additional 3.2 million kW-hours per year and 270 million gallons of water beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $0.29 million per additional ton of total chlorine removed, we are not proposing a beyond-the-floor standard based on improved wet scrubbing.

Feed Control of Chlorine in the Hazardous Waste. We also evaluated a beyond-the-floor level of 1.2 ppmv, which represents a 20% reduction from the floor level. We chose a 20% reduction as a level that represents the practicable extent that additional feedrate control of chlorine in hazardous waste can be used and still achieve appreciable emissions reductions. The national incremental annualized compliance cost for incinerators to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $0.69 million and would provide an incremental reduction in total chlorine emissions beyond the MACT floor controls of 2.5 tons per year. Nonair quality health and environmental impacts and energy effects were also evaluated and are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $0.28 million per additional ton of total chlorine removed, we are not proposing a beyond-the-floor standard based on feed control of chlorine in the hazardous waste.

For the reasons discussed above, we propose to establish the emission standard for existing incinerators at 1.5 ppmv.

3. What Is the Rationale for the MACT Floor for New Sources?

Total chlorine emissions from incinerators are currently limited to 21 ppmv by § 63.1203(b)(6). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796). The MACT floor for new sources for total chlorine would be 0.18 ppmv, which considers emissions variability. This is an emission level that the single best performing source identified with the SRE/Feed Approach could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the test conditions during which the emissions data were obtained.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We identified similar potential beyond-the-floor techniques for control of total chlorine for new sources: (1) Use of improved wet scrubbers; and (2) control of chlorine in the hazardous waste feed.

Use of Wet Scrubbing. We evaluated a beyond-the-floor level of 0.1 ppmv using wet scrubbers as beyond-the-floor control for further reductions in total chlorine emissions. We made a conservative assumption that an improved wet scrubber will provide 50% total chlorine reductions beyond the controls needed to achieve the floor level given the low total chlorine levels at the floor. The incremental annualized compliance cost for a new incinerator with an average gas flowrate to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $0.2 million and would provide an incremental reduction in total chlorine emissions of approximately 35 pounds per year. Nonair quality health and environmental impacts and energy effects were also evaluated and are included in the cost estimates. We estimate that this option would increase the amount of wastewater generated by 50 million gallons per year and would require a new source to use an additional 0.5 million kW-hours per year beyond the requirements to achieve the floor level. For these reasons and Start Printed Page 21248costs of $12 million per ton of chlorine removed, we are not proposing a beyond-the-floor standard based on improved wet scrubbing control for new sources.

Feed Control of Chlorine in the Hazardous Waste. We also believe that the expense associated with a reduction in chlorine emissions based on further control of chlorine concentrations in the hazardous waste is not warranted. We considered a beyond-the-floor level of 0.14 ppmv, which represents a 20% reduction from the floor level. For similar reasons discussed above for existing sources, we judge that a beyond-the-floor standard based on controlling the chlorine in the hazardous waste feed would not be cost-effective or otherwise appropriate. Therefore, we propose a chlorine standard of 0.18 ppmv for new sources.

G. What Are the Standards for Hydrocarbons and Carbon Monoxide?

Hydrocarbon and carbon monoxide standards are surrogates to control emissions of organic hazardous air pollutants for existing and new incinerators. The standards limit hydrocarbons and carbon monoxide concentrations to 10 ppmv or 100 ppmv. See §§ 63.1203(a)(5) and (b)(5). Existing and new incinerators can elect to comply with either the hydrocarbon limit or the carbon monoxide limit on a continuous basis. Sources that comply with the carbon monoxide limit on a continuous basis must also demonstrate compliance with the hydrocarbon standard during the comprehensive performance test. However, continuous hydrocarbon monitoring following the performance test is not required. The rationale for these decisions are discussed in the September 1999 final rule (64 FR at 52900). We view the standards for hydrocarbons and carbon monoxide as unaffected by the Court's vacature of the challenged regulations in its decision of July 24, 2001. We therefore are not proposing these standards for incinerators, but rather are mentioning them here for the reader's convenience.

H. What Are the Standards for Destruction and Removal Efficiency?

The destruction and removal efficiency (DRE) standard is a surrogate to control emissions of organic hazardous air pollutants other than dioxin/furans. The standard for existing and new incinerators requires 99.99% DRE for each principal organic hazardous constituent, except that 99.9999% DRE is required if specified dioxin-listed hazardous wastes are burned. See §§ 63.1203(c). The rationale for these decisions are discussed in the September 1999 final rule (64 FR at 52902). We view the standards for DRE as unaffected by the Court's vacature of the challenged regulations in its decision of July 24, 2001. We therefore are not proposing these standards for incinerators, but rather are mentioning them here for the reader's convenience.

VIII. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste Burning Cement Kilns?

In this section, the basis for the proposed emission standards is discussed. See proposed § 63.1220 The proposed emission limits apply to the kiln stack gases, in-line kiln raw mill stack gases if combustion gases pass through the in-line raw mill, and kiln alkali bypass stack gases if discharged through a separate stack.[90] The proposed standards for existing and new cement kilns that burn hazardous waste are summarized in the table below:

Proposed Standards for Existing and New Cement Kilns

Hazardous air pollutant or surrogateEmission standard 1
Existing sourcesNew sources
Dioxin and furan 10.20 ng TEQ/dscm; or 0.40 ng TEQ/dscm and control of flue gas temperature not to exceed 400°F at the inlet to the particulate matter control device.
Mercury 264 ug/dscm35 ug/dscm.
Particulate Matter65 mg/dscm (0.028 gr/dscf)13 mg/dscm (0.0058 gr/dscf).
Semivolatile metals 34.0 x 10−4 lb/MMBtu6.2 x 10−5 lb/MMBtu.
Low volatile metals 31.4 x 10−5 lb/MMBtu1.4 x 10−5 lb/MMBtu.
Hydrogen chloride and chlorine gas 4110 ppmv or the alternative emission limits under § 63.121578 ppmv or the alternative emission limits under § 63.1215.
Hydrocarbons: kilns without bypass 5,620 ppmv (or 100 ppmv carbon monoxide) 5Greenfield kilns: 20 ppmv (or 100 ppmv carbon monoxide and 50 ppmv 7 hydrocarbons). All others: 20 ppmv (or 100 ppmv carbon monoxide) 5.
Hydrocarbons: kilns with bypass; main stack 6,8No main stack standard50 ppmv 7.
Hydrocarbons: kilns with bypass; bypass duct and stack 5,6,810 ppmv (or 100 ppmv carbon monoxide)10 ppmv (or 100 ppmv carbon monoxide).
Destruction and removal efficiencyFor existing and new sources, 99.99% for each principal organic hazardous constituent (POHC). For sources burning hazardous wastes F020, F021, F022, F023, F026, or F027, however, 99.9999% for each POHC.
1 All emission standards are corrected to 7% oxygen, dry basis. If there is a separate alkali bypass stack, then both the alkali bypass and main stack emissions must be less than the emission standard.
2 Mercury standard is an annual limit.
3 Standards are expressed as mass of pollutant stack emissions attributable to the hazardous waste per million British thermal unit heat input of the hazardous waste.
4 Combined standard, reported as a chloride (Cl(-)) equivalent.
5 Sources that elect to comply with the carbon monoxide standard must demonstrate compliance with the hydrocarbon standard during the comprehensive performance test.
6 Hourly rolling average. Hydrocarbons reported as propane.
7 Applicable only to newly-constructed cement kilns at greenfield sites (see 64 FR at 52885). The 50 ppmv standard is a 30-day block average limit.
8 Measurement made in the bypass sampling system of any kiln (e.g., alkali bypass of a preheater/precalciner kiln; midkiln gas sampling system of a long kiln).

A. What Are the Proposed Standards for Dioxin and Furan?

We are proposing to establish standards for existing and new cement kilns that limit emissions of dioxin and furans to either 0.20 ng TEQ/dscm or 0.40 ng TEQ/dscm and control of flue gas temperature not to exceed 400°F at the inlet to the particulate matter control device.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Dioxin and furan emissions for existing cement kilns are currently limited by § 63.1204(a)(1) to 0.20 ng TEQ/dscm or 0.40 ng TEQ/dscm and control of flue gas temperature not to exceed 400°F at the inlet to the particulate matter control device. This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796, February 13, 2002).

Since promulgation of the 1999 final rule, we have obtained additional dioxin/furan emissions data. We now have compliance test emissions data for all but one cement kiln that burns hazardous waste. The compliance test dioxin/furan emissions in our data base range from approximately 0.004 to 20 ng TEQ/dscm.[91] Cement kilns control dioxin by quenching kiln gas temperatures so that gas temperatures at the inlet to the particulate matter control device are below the range of optimum dioxin/furan formation.

To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the Emissions Approach described in Part Two, Section VI.C above. The calculated floor is 0.22 ng TEQ/dscm, which considers emissions variability. These best performing sources controlled inlet temperatures to the particulate matter control device from 380°-475°F. Although some best performing sources had inlet temperatures to the particulate matter control device within the optimum temperature range (i.e., >400°F) for formation of dioxin/furan, their emissions were lower than other non-best performing sources. Our data base shows that these other non-best performing sources, when operating within a temperature range up to 475°F, had emissions of dioxin/furan as high as 1.2 ng TEQ/dscm. We cannot explain why some sources emit dioxin/furan at significantly lower levels than other sources operating at similar control device inlet temperatures. As noted earlier, there are many uncertainties and imperfectly understood complexities relating to dioxin/furan formation.

The data generally support the relationship between inlet temperature to the particulate matter control device and dioxin/furan emissions: When inlet temperatures are below the optimum range of formation, dioxin/furan emissions are lower. However, the converse may not hold: When inlet temperatures are within the optimum range of formation, dioxin/furan emissions may or may not be higher (but in most cases are higher). Moreover, we are concerned that a floor level of 0.22 ng TEQ/dscm is not replicable by all sources using temperature control because we have emissions data from sources operating below the optimum temperature range of dioxin/furan formation that is higher than the calculated floor level of 0.22 ng TEQ/dscm. As a result of this concern, we would identify the floor level as 0.22 ng TEQ/dscm or controlling the inlet temperature to the particulate matter control device.

Allowing a source to comply with a temperature limit alone, however, absent a numerical dioxin/furan emission limit, is less stringent than the current interim standard of 0.20 ng TEQ/dscm, or 0.40 ng TEQ/dscm and control of flue gas temperature not to exceed 400°F at the inlet to the particulate matter control device. The current interim standard is a regulatory limit that is relevant in identifying the floor level because it fixes a level of performance for the source category. Given that all sources are achieving this interim standard and that the interim standard is judged as more stringent than the calculated MACT floor, the dioxin/furan floor level can be no less stringent than the current regulatory limit. We are, therefore, proposing the dioxin/furan floor level as 0.20 ng TEQ/dscm or 0.40 ng TEQ/dscm and control of flue gas temperature not to exceed 400°F at the inlet to the particulate matter control device. This emission level is being achieved by all sources because it is the current required interim standard.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We evaluated activated carbon injection as beyond-the-floor control for further reduction of dioxin/furan emissions. Activated carbon has been demonstrated for controlling dioxin/furans in various combustion applications. However, currently no cement kiln that burns hazardous waste uses activated carbon injection. We evaluated a beyond-the-floor level of 0.10 ng TEQ/dscm, which represents a 75% reduction in dioxin/furan emissions from the floor level. We selected this level because it represents a level that is considered routinely achievable with activated carbon injection. In addition, we assumed for costing purposes that cement kilns needing activated carbon injection to achieve the beyond-the-floor level would install the activated carbon injection system after the existing particulate matter control device and add a new, smaller baghouse to remove the injected carbon with the adsorbed dioxin/furan. We chose this costing approach to address potential concerns that injected carbon may interfere with cement kiln dust recycling practices.

The national incremental annualized compliance cost for cement kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $21 million and would provide an incremental reduction in dioxin/furan emissions beyond the MACT floor controls of 3.4 grams TEQ per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between activated carbon injection and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of solid waste [92] generated by 7,800 tons per year and would require sources to use an additional 2.6 million kW-hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $6.2 million per additional gram of dioxin/furan removed, we are not proposing a Start Printed Page 21250beyond-the-floor standard based on use of activated carbon injection.

3. What Is the Rationale for the MACT Floor for New Sources?

Dioxin and furan emissions for new cement kilns are currently limited by § 63.1204(b)(1) to either 0.20 ng TEQ/dscm or 0.40 ng TEQ/dscm and control of flue gas temperature not to exceed 400°F at the inlet to the particulate matter control device. This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796).

The calculated MACT floor for new sources would be 0.21 ng TEQ/dscm, which considers emissions variability. This is an emission level that the single best performing source identified by the Emissions Approach could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the test conditions during which the emissions data were obtained. As discussed for existing sources, we are concerned that a floor level of 0.21 ng TEQ/dscm would not be reproducible by all sources using temperature control because we have emissions data from sources operating below the optimum temperature range of dioxin/furan formation that is higher than the calculated floor level of 0.21 ng TEQ/dscm. As a result of this concern, we would identify the MACT floor as 0.21 ng TEQ/dscm or controlling the inlet temperature to the particulate matter control device.

Allowing a source to comply with a temperature limit alone, however, absent a numerical dioxin/furan emission limit, is less stringent than the current interim standard of 0.20 ng TEQ/dscm, or 0.40 ng TEQ/dscm and control of flue gas temperature not to exceed 400°F at the inlet to the particulate matter control device. The current interim standard is a regulatory limit that is relevant in identifying the floor level because it fixes a level of performance for new cement kilns. Given that all sources are achieving this interim standard and that the interim standard is judged as more stringent than the calculated MACT floor, the dioxin/furan floor level can be no less stringent than the current regulatory limit. We are, therefore, proposing the dioxin/furan floor level as 0.20 ng TEQ/dscm or 0.40 ng TEQ/dscm and control of flue gas temperature not to exceed 400°F at the inlet to the particulate matter control device.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We evaluated activated carbon injection as beyond-the-floor control for further reduction of dioxin/furan emissions. We evaluated a beyond-the-floor level of 0.10 ng TEQ/dscm, which represents a 75% reduction in dioxin/furan emissions from the floor level. We selected this level because it represents a level that is considered routinely achievable with activated carbon injection. In addition, we assumed for costing purposes that a new cement kiln will install the activated carbon injection system after the existing particulate matter control device and add a new, smaller baghouse to remove the injected carbon with the adsorbed dioxin/furan. The incremental annualized compliance cost for a new cement kiln to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $1.0 million and would provide an incremental reduction in dioxin/furan emissions of approximately 0.17 grams TEQ per year, for a cost-effectiveness of $5.8 million per gram of dioxin/furan removed. Nonair quality health and environmental impacts and energy effects were not significant factors. For these reasons, we are not proposing a beyond-the-floor standard based on activated carbon injection for new cement kilns. Therefore, we are proposing the standard as 0.20 ng TEQ/dscm or 0.40 ng TEQ/dscm or control of flue gas temperature not to exceed 400°F at the inlet to the particulate matter control device.

B. What Are the Proposed Standards for Mercury?

We are proposing to establish standards for existing and new cement kilns that limit emissions of mercury to 64 and 35 μg/dscm, respectively. If we were to adopt these standards, then sources would comply with the limit on an annual basis because the standards are based on normal emissions data.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Mercury emissions for existing cement kilns are currently limited to 120 μg/dscm by § 63.1204(a)(2).[93] This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796). None of the cement kilns burning hazardous waste use a dedicated control device to remove mercury from the gas stream; however, kilns control the feed concentration of mercury in the hazardous waste.

We have emissions data for all sources. All of these data are best classified as from normal operations, although, as explained below, there is a substantial range within these data. For most sources, we have normal emissions data from more than one test campaign. The normal mercury stack emissions in our data base range from less than 2 to 118 μg/dscm. These emissions are expressed as mass of mercury (from all feedstocks) per unit volume of stack gas.

To identify the MACT floor, we evaluated all normal emissions data using the SRE/Feed Approach. We considered normal emissions data from all test campaigns.[94] For example, one source in our data base has normal emissions data for three different testing campaigns: 1992, 1995, and 1998. Under this approach we would consider the emissions data from the three separate years or campaigns. We believe this approach better captures the range of average emissions for a source than only considering the most recent normal emissions. Given that no cement kilns burning hazardous waste use a control device which captures mercury from the flue gas stream, for purposes of this analysis we assumed all sources achieved a SRE of zero. The effect of this assumption is that the sources with the lowest mercury concentrations in the hazardous waste were identified as the best performing sources.

The calculated floor is 64 μg/dscm, which considers emissions variability, based on a hazardous waste maximum theoretical emissions concentration (MTEC) of 26 μg/dscm. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 59% of sources and would reduce mercury emissions by 0.23 tons per year. If we were to adopt such a floor level, we are proposing that sources comply with the limit on an annual basis because it is based on normal emissions data. Under this approach, Start Printed Page 21251compliance would not be based on the use of a total mercury continuous emissions monitoring system because these monitors have not been adequately demonstrated as a reliable compliance assurance tool at cement kiln sources. Instead, a source would maintain compliance with the mercury standard by establishing and complying with short-term limits on operating parameters for pollution control equipment and annual limits on maximum total mercury feedrate in all feedstreams.

We did not use the stack emissions data of preheater/precalciner kilns in the floor analysis because we believe the mercury emissions are biased low when the in-line raw mill is on-line and biased high when the in-line raw mill is off-line. (See earlier discussion on why we are proposing not to subcategorize hazardous waste burning cement kilns for mercury between wet process kilns and preheater/precalciner kilns with in-line raw mills.) For either case, we believe the normal mercury data are not representative of average emissions and, therefore, not appropriate to include in the floor analysis. We request comment on this data handling decision.

In the September 1999 final rule, we acknowledged that a cement kiln using properly designed and operated MACT control technologies, including controlling the levels of metals in the hazardous waste, may not be capable of achieving a given emission standard because of mineral and process raw material contributions that might cause an exceedance of the emission standard. To address this concern, we promulgated a provision that allows kilns to petition for alternative standards provided they submit site-specific information that shows raw material hazardous air pollutant contributions to the emissions prevent the source from complying with the emission standard even though the kiln is using MACT control. See § 63.1206(b)(10).

Today's proposed floor of 64 μg/dscm, which was based on a hazardous waste MTEC of 26 μg/dscm, may likewise necessitate such an alternative because contributions of mercury in the raw materials and fossil fuels at some sources may cause an exceedance of the emission standard. The Agency intends to retain a source's ability to comply with an alternative standard, and we request comment on two approaches to accomplish this. The first approach would be to structure the alternative standard similar to the petitioning process used under § 63.1206(b)(10). In the case of mercury for an existing cement kiln, MACT would be defined as a hazardous waste feedrate corresponding to an MTEC of 26 μg/dscm. If we were to adopt this approach, we would require sources, upon approval of the petition by the Administrator, to comply with this hazardous waste MTEC on an annual basis because it is based on normal emissions data. Under the second approach, we would structure the alternative standard similar to the framework used for the alternative interim standards for mercury under § 63.1206(b)(15). The operating requirement would be an annual MTEC not to exceed 26 μg/dscm. We also request comment on whether there are other approaches that would more appropriately provide relief to sources that cannot achieve a total stack gas concentration standard because of emissions attributable to raw material and nonhazardous waste fuels.

In June 2003, the Cement Kiln Recycling Coalition (CKRC) [95] submitted to EPA information on actual mercury concentrations in the hazardous waste burn tanks of all 14 cement facilities for a three year period covering 1999 to 2001. In general, the information shows the mercury concentration (in parts per million) in the hazardous waste for each burn tank.[96] In total, approximately 20,000 mercury burn tank concentration data points are included in CKRC's submission.[97] The data show that approximately 50% of the individual burn tank measurements are 0.6 ppmw or less, 75% are less than 1.1 ppmw, 88% are less than 2 ppmw, and 97% of all burn tank measurements are less than 5 ppmw. For a hypothetical wet process cement kiln that gets 50% of its required heat input from hazardous waste, a hazardous waste with a mercury concentration of 0.6 ppmw equates approximately to an uncontrolled (i.e., a system removal efficiency of zero) stack gas concentration of 24 μg/dscm. This estimated stack gas concentration, of course, does not include contributions to emissions from other mercury-containing feedstocks including raw materials and fossil fuels. Mercury concentrations of 1.1, 2, and 5 ppmw in the hazardous waste equate to uncontrolled stack gas concentrations of approximately 43, 79, and 196 μg/dscm.[98]

We compared the concentration of mercury in the hazardous waste associated with the normal emissions data in our data base to the 3-year historical burn tank concentration data to estimate whether the normal data in our data base—the basis of today's proposed floor of 64 μg/dscm—are likely to represent the high end, low end, or close to average emissions. Mercury feed concentration information is not available for every test condition; however, the mercury concentrations in the hazardous waste burned by the best performing sources during the tests that generated the normal emissions ranged from 0.1 to 0.44 ppmw. For the best performing sources comprising the MACT pool for which we can make a comparison, it appears that the normal concentrations in the hazardous waste during testing represent the low end (15th percentile or less) of average mercury concentrations. We invite comment on whether the normal emissions data in our data base are representative of average emissions in practice and whether evaluating the data to identify a floor level is appropriate.

In addition, we request comment on how to identify a floor level using the 3-year hazardous waste mercury concentration data. One potential approach would be to establish a hazardous waste feed concentration standard expressed in ppmw. To identify a floor level expressed as a hazardous waste feed concentration in ppmw, we identified and evaluated the 3-year historical burn tank concentration data of the five best performing facilities (those sources with the lowest mean concentration considering variability). The calculated alternative floor level is 2.2 ppmw in the hazardous waste. To put this in context for a hypothetical wet process cement kiln that gets 50% of its required heat input from hazardous waste, a mercury concentration of 2.2 ppmw in the hazardous waste equates approximately to an uncontrolled stack gas concentration of 86 μg/dscm.[99] This Start Printed Page 21252estimated stack gas concentration, of course, does not include contributions to emissions from other mercury-containing feedstocks such as raw materials and fossil fuels. If we were to adopt such an approach, we would require sources to comply with the feed concentration standard on a short term basis (e.g., 12 hour average).

We also invite comment on whether we should judge an annual limit of 64 μg/dscm as less stringent than either the current emission standard of 120 μg/dscm or the hazardous waste MTEC of mercury of 120 μg/dscm for cement kilns (so as to avoid any backsliding from a current level of performance achieved by all sources, and hence, the level of minimal stringency at which EPA could calculate the MACT floor). In order to comply with the current emission standard, generally a source must conduct manual stack sampling to demonstrate compliance with the mercury emission standard and then establish a maximum mercury feedrate limit based on operations during the performance test. Following the performance test, the source complies with a limit on the maximum total mercury feedrate in all feedstreams on a 12-hour rolling average (not an annual average). Alternatively, a source can elect to comply with a hazardous waste MTEC of mercury of 120 μg/dscm that would require the source to limit the mercury feedrate in the hazardous waste on a 12-hour rolling average. The floor level of 64 μg/dscm proposed today would allow a source to feed more variable mercury-containing feedstreams (e.g., a hazardous waste with an mercury MTEC greater than 120 μg/dscm) than the current 12-hour rolling average because today's proposed floor level is an annual limit. For example, we estimated a hazardous waste MTEC for each burn tank measurement associated with the 3-year historical concentration data submitted by CKRC. We found that approximately 5% of burn tank measurements would exceed a hazardous waste MTEC of 120 μg/dscm, including sources upon which the proposed floor is based.[100]

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We identified three potential beyond-the-floor techniques for control of mercury: (1) Activated carbon injection; (2) control of mercury in the hazardous waste feed; and (3) control of mercury in the raw materials and auxiliary fuels. For reasons discussed below, we are not proposing a beyond-the-floor standard for mercury.

Use of Activated Carbon Injection. We evaluated activated carbon injection as beyond-the-floor control for further reduction of mercury emissions. Activated carbon has been demonstrated for controlling mercury in several combustion applications; however, currently no cement kiln that burns hazardous waste uses activated carbon injection. Given this lack of experience using activated carbon injection, we made a conservative assumption that the use of activated carbon injection will provide 70% mercury control and evaluated a beyond-the-floor level of 19 μg/dscm. In addition, for costing purposes we assumed that cement kilns needing activated carbon injection to achieve the beyond-the-floor level would install the activated carbon injection system after the existing particulate matter control device and add a new, smaller baghouse to remove the injected carbon with the adsorbed mercury. We chose this costing approach to address potential concerns that injected carbon may interfere with cement kiln dust recycling practices.

The national incremental annualized compliance cost for cement kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $16.8 million and would provide an incremental reduction in mercury emissions beyond the MACT floor controls of 0.41 tons per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between activated carbon injection and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of solid waste generated by 4,400 tons per year and would require sources to use an additional 21 million kW-hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $41 million per additional ton of mercury removed, we are not proposing a beyond-the-floor standard based on activated carbon injection.

Feed Control of Mercury in the Hazardous Waste. We also evaluated a beyond-the-floor level of 51 μg/dscm, which represents a 20% reduction from the floor level. We chose a 20% reduction as a level representing the practicable extent that additional feedrate control of mercury in hazardous waste (beyond feedrate control that may be necessary to achieve the floor level) can be used and still achieve modest emissions reductions.[101] The national incremental annualized compliance cost for cement kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $3.7 million and would provide an incremental reduction in mercury emissions beyond the MACT floor controls of 180 pounds per year. Nonair quality health and environmental impacts and energy effects were also evaluated. Therefore, based on these factors and costs of approximately $42 million per additional ton of mercury removed, we are not proposing a beyond-the-floor standard based on feed control of mercury in the hazardous waste.

Feed Control of Mercury in the Raw Materials and Auxiliary Fuels. Cement kilns could achieve a reduction in mercury emissions by substituting a raw material containing lower levels of mercury for a primary raw material with a higher level. We believe that this beyond-the-floor option would be even less cost-effective than either of the options discussed above, however. Given that sources are sited near the supply of the primary raw material, transporting large quantities of an alternate source of raw materials is likely to be cost-prohibitive, especially considering the small expected emissions reductions that would result.

We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of mercury would be an appropriate control option for sources. Given that most cement kilns burning hazardous waste also burn coal as a fuel, we considered switching to natural gas as a potential beyond-the-floor option. We are concerned about the availability of natural gas to all cement kilns because natural gas pipelines are not available in all regions of the United States. See 68 FR 1673. Moreover, even where pipelines provide access to natural gas, supplies of natural gas may not be adequate. For example, it is common practice in cities during winter months (or periods of peak demand) to prioritize natural gas usage for residential areas before industrial usage. Requiring cement kilns to switch to natural gas would place an even greater strain on natural gas resources. Consequently, even where pipelines exist, some sources may not be able to use natural gas during times of limited Start Printed Page 21253supplies. Thus, natural gas may not be a viable control option for some sources. Therefore, we are not proposing a beyond-the-floor standard based on limiting mercury in the raw material feed and auxiliary fuels.

For the reasons discussed above, we propose not to adopt a beyond-the-floor standard for mercury and propose to establish the emission standard for existing cement kilns at 64 μg/dscm. If we were to adopt such a standard, we are proposing that sources comply with the standard on an annual basis because it is based on normal emissions data.

3. What Is the Rationale for the MACT Floor for New Sources?

Mercury emissions from new cement kilns are currently limited to 120 μg/dscm by § 63.1204(b)(2). New cement kilns can comply with an alternative mercury standard that limits the hazardous waste maximum theoretical emissions concentration or MTEC of mercury of 120 μg/dscm. This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796).

The MACT floor for new sources for mercury would be 35 μg/dscm, which considers emissions variability, based on a hazardous waste MTEC of 5.1 μg/dscm. This is an emission level that the single best performing source identified with the SRE/Feed Approach could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the test conditions during which the emissions data were obtained. As for existing sources, we assumed all sources equally achieved a SRE of zero. The effect of this assumption is that the single source with the lowest mercury concentration in the hazardous waste was identified as the best performing source. We also invite comment on whether we should judge an annual limit of 35 μg/dscm as less stringent than either the current emission standard of 120 μg/dscm or the hazardous waste MTEC of mercury of 120 μg/dscm for cement kilns (so as to avoid any backsliding from a current level of performance achieved by all sources).

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We identified the same three potential beyond-the-floor techniques for control of mercury: (1) Use of activated carbon; (2) control of mercury in the hazardous waste feed; and (3) control of the mercury in the raw materials and auxiliary fuels.

Use of Activated Carbon Injection. We evaluated activated carbon injection as beyond-the-floor control for further reduction of mercury emissions. We made a conservative assumption that the use of activated carbon injection will provide 70% mercury control and evaluated a beyond-the-floor level of 11 μg/dscm. The incremental annualized compliance cost for a new cement kiln to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $1.0 million and would provide an incremental reduction in mercury emissions of approximately 88 pounds per year. We also estimate that this option would increase the amount of solid waste generated by 400 tons per year and would require sources to use an additional 1.9 million kW-hours per year. Nonair quality health and environmental impacts and energy effects are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of $23 million per ton of mercury removed, we are not proposing a beyond-the-floor standard based on activated carbon injection for new cement kilns.

Feed Control of Mercury in the Hazardous Waste. We also believe that the expense for further reduction in mercury emissions based on further control of mercury concentrations in the hazardous waste is not warranted. A beyond-the-floor level of 28 ug/dscm, which represents a 20% reduction from the floor level, would result in little additional mercury reductions. For similar reasons discussed above for existing sources, we conclude that a beyond-the-floor standard based on controlling the mercury in the hazardous waste feed would not be justified because of the costs coupled with estimated emission reductions.

Feed Control of Mercury in the Raw Materials and Auxiliary Fuels. Cement kilns could achieve a reduction in mercury emissions by substituting a raw material containing lower levels of mercury for a primary raw material with a higher level. For a new source at an existing cement plant, we believe that this beyond-the-floor option would not be cost-effective due to the costs of transporting large quantities of an alternate source of raw materials to the cement plant. Given that the plant site already exists and sited near the source of raw material, replacing the raw materials at the plant site with lower mercury-containing materials would be the source's only option. For a new cement kiln constructed at a new site—a greenfield site [102] —we are not aware of any information and data from a source that has undertaken or is currently located at a site whose raw materials are low in mercury which would consistently decrease mercury emissions. Further, we are uncertain as to what beyond-the-floor standard would be achievable using a lower, if it exists, mercury-containing raw material. Although we are doubtful that selecting a new plant site based on the content of metals in the raw material is a realistic beyond-the-floor option considering the numerous additional factors that go into such a decision, we solicit comment on whether and what level of a beyond-the-floor standard based on controlling the level of mercury in the raw materials is appropriate.

We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of mercury would be an appropriate control option for sources. We considered using natural gas in lieu of a fossil fuel such as coal containing higher concentrations of mercury as a potential beyond-the-floor option. As discussed for existing sources, we are concerned about the availability of the natural gas infrastructure in all regions of the United States and believe that using natural gas would not be a viable control option for all new sources. Therefore, we are not proposing a beyond-the-floor standard based on limiting mercury in the raw material feed and auxiliary fuels.

Therefore, we propose a mercury standard of 35 ug/dscm for new sources. If we were to adopt such a standard, we are proposing that sources comply with the standard on an annual basis because it is based on normal emissions data.

C. What Are the Proposed Standards for Particulate Matter?

We are proposing to establish standards for existing and new cement kilns that limit emissions of particulate matter to 65 mg/dscm (0.028 gr/dscf) and 13 mg/dscm (0.0058 gr/dscf), respectively.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Particulate matter emissions for existing cement kilns are currently limited to 0.15 kilograms of particulate matter per megagram dry feed [103] and 20% opacity by § 63.1204(a)(7). This standard was promulgated in the Interim Standards Rule (See 67 FR at Start Printed Page 212546796). The particulate matter standard is a surrogate control for the metals antimony, cobalt, manganese, nickel, and selenium in the hazardous waste and all HAP metals in the raw materials and auxiliary fuels which are controllable by particulate matter control. All cement kilns control particulate matter with baghouses and electrostatic precipitators.

We have compliance test emissions data for all cement kiln sources. For most sources, we have compliance test emissions data from more than one compliance test campaign. Our data base of particulate matter stack emission concentrations range from 0.0008 to 0.063 gr/dscf.

To identify the floor level, we evaluated the compliance test emissions data associated with the most recent test campaign using the Air Pollution Control Technology Approach. The calculated floor is 65 mg/dscm (0.028 gr/dscf), which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 44% of sources and would reduce particulate matter emissions by 43 tons per year.

We are also proposing to delete the current opacity standard in conjunction with revisions to the compliance assurance requirements for particulate matter for cement kilns. These proposed compliance assurance amendments include requiring a cement kiln source using a baghouse to comply with the same bag leak detection system requirements that are currently applicable to all other hazardous waste combustors (see § 63.1209(m)). A cement kiln source using an ESP has the option either to (1) use a particulate matter emissions detector as a process monitor in lieu of complying with operating parameter limits, as we are proposing for all other hazardous waste combustor sources; or (2) establish site-specific, enforceable operating parameter limits that are linked to the automatic waste feed cutoff system. See Part Three, Section III for a discussion of the proposed changes.

We also request comment on whether the particulate matter standard should be expressed on a concentration basis (as proposed today) or on a production-based format. A concentration-based standard is expressed as mass of particulate matter per dry standard volume of gas (e.g., mg/dscm as proposed today) while a production-based standard is expressed as mass of particulate matter emitted per mass of dry raw material feed to the kiln (e.g., the format of the interim standard). We evaluated the compliance test production-based data associated with the most recent test campaign to determine what the floor level would be under this approach. The calculated floor would be 0.10 kilograms of particulate matter per megagram dry feed. We note that a concentration format can be viewed as penalizing more energy efficient kilns, which burn less fuel and produce less kiln exhaust gas per megagram of dry feed. This is because with a concentration-based standard the more energy-efficient kilns would be restricted to a lower level of particulate matter emitted per unit of production.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We evaluated improved particulate matter control to achieve a beyond-the-floor standard of 32 mg/dscm (0.014 gr/dscf), which is a 50% reduction from MACT floor emissions.[104] For an existing source that needs a significant reduction in particulate matter emissions, we assumed and estimated costs for a new baghouse to achieve the beyond-the-floor level. If little or modest emissions reductions were needed, then improved control was costed as design, operation, and maintenance modifications of the existing particulate matter control equipment.

The national incremental annualized compliance cost for cement kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $4.8 million and would provide an incremental reduction in particulate matter emissions beyond the MACT floor controls of 385 tons per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between further improvements to control particulate matter and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of solid waste generated by 385 tons per year and would require sources to use an additional 15 million kW-hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $12,400 per additional ton of particulate matter removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control.

3. What Is the Rationale for the MACT Floor for New Sources?

Particulate matter emissions from new cement kilns are currently limited to 0.15 kilograms of particulate matter per megagram dry feed and 20% opacity by § 63.1204(b)(7). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796).

The MACT floor for new sources for particulate matter would be 13 mg/dscm (0.0058 gr/dscf), which considers emissions variability. This is an emission level that the single best performing source identified with the Air Pollution Control Technology Approach could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the test conditions during which the emissions data were obtained. We are also proposing to delete the current opacity standard in conjunction with revisions to the compliance assurance requirements for particulate matter for cement kilns. See Part Three, Section III for details.

As discussed for existing sources, we also request comment on whether the particulate matter standard should be expressed on a concentration basis or on a production-based format. We evaluated the compliance test production-based data associated with the most recent test campaign to determine what the floor level would be under this approach. The calculated floor would be 0.028 kilograms of particulate matter per megagram dry feed.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We evaluated improved emissions control based on a state-of-the-art baghouse using a high quality fabric filter bag material to achieve a beyond-the-floor standard of 6.7 mg/dscm (0.0029 gr/dscf). This reduction represents a 50% reduction in particulate matter emissions from MACT floor levels. The incremental annualized compliance cost for a new cement kiln to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $0.38 million and would provide an incremental reduction in particulate matter emissions of approximately 2.6 tons per year. We estimate that this Start Printed Page 21255beyond-the-floor option would increase the amount of solid waste generated by less than 6 tons per year and would require sources to use an additional 1.8 million kW-hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $61,400 per additional ton of particulate matter removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control for new cement kilns. Therefore, we propose a particulate matter standard of 13 mg/dscm for new sources.

D. What Are the Proposed Standards for Semivolatile Metals?

We are proposing to establish standards for existing cement kilns that limit emissions of semivolatile metals (cadmium and lead, combined) to 4.0 × 10−4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. The proposed standard for new sources is 6.2 × 10−5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Semivolatile metals emissions from existing cement kilns are currently limited to 330 μg/dscm by § 63.1204(a)(3). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796). Cement kilns control emissions of semivolatile metals with baghouses or electrostatic precipitators and/or by controlling the feed concentration of semivolatile metals in the hazardous waste.

We have compliance test emissions data for all cement kiln sources. For most sources, we have compliance test emissions data from more than one compliance test campaign. Semivolatile metal stack emissions range from approximately 1 to 2,800 μg/dscm. These emissions are expressed as mass of semivolatile metals (from all feedstocks) per unit volume of stack gas. Hazardous waste thermal emissions range from 3.0 × 10−6 to 3.7 × 10−3 lbs per million Btu. Hazardous waste thermal emissions represent the mass of semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. Lead was the most significant contributor to semivolatile emissions during compliance test conditions.

To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the SRE/Feed Approach. The calculated floor is 4.0 × 10−4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 81% of sources and would reduce semivolatile metals emissions by 1 ton per year.

To put the proposed floor level in context for a hypothetical wet process cement kiln that gets 50% of its required heat input from hazardous waste, a thermal emissions level of 4.0 × 10−4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste equates approximately to a stack gas concentration of 180 μg/dscm. This estimated stack gas concentration does not include contributions to emission from other semivolatile metals-containing materials such as raw materials and fossil fuels. The additional contribution to stack emissions of semivolatile metals in an average raw material and coal is estimated to range as high as 20 to 50 μg/dscm. Thus, for the hypothetical wet process cement kiln the thermal emissions floor level of 4.0 × 10−4 lbs semivolatile metals attributable to the hazardous waste per million Btu heat input of the hazardous waste is estimated to be less than 230 μg/dscm, which is less than the current interim standard of 330 μg/dscm. Given that comparing the proposed floor level to the interim standard requires numerous assumptions (as just illustrated) including hazardous waste fuel replacement rates, heat input requirements per ton of clinker, concentrations of semivolatile metals in the raw material and coal, and system removal efficiency, we have a more detailed analysis in the background document.[105] Our detailed analysis indicates the proposed floor level is at least as stringent as the interim standard (so as to avoid any backsliding from a current level of performance achieved by all cement kilns, and hence, the level of minimal stringency at which EPA could calculate the MACT floor). Thus, we conclude that a dual standard—the semivolatile metals standard as both the calculated floor level, expressed as a hazardous waste thermal emissions level, and the current interim standard—is not needed for this standard.

In the September 1999 final rule, we acknowledged that a cement kiln using properly designed and operated MACT control technologies, including controlling the levels of metals in the hazardous waste, may not be capable of achieving a given emission standard because of mineral and process raw material contributions that might cause an exceedance of the emission standard. To address this concern, we promulgated a provision that allows kilns to petition for alternative standards provided that they submit site-specific information that shows raw material hazardous air pollutant contributions to the emissions prevent the source from complying with the emission standard even though the kiln is using MACT control. See § 63.1206(b)(10). If we were to adopt the semivolatile (and low volatile) metals standard using a thermal emissions format, then there would be no need for these alternative standard provisions for semivolatile metals (since, as explained earlier, that standard is based solely on semivolatile metals contributions from hazardous waste fuels). Therefore, we would delete the provisions of § 63.1206(b)(10) as they apply to semivolatile (and low volatile) metals. We invite comment on this approach.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We identified three potential beyond-the-floor techniques for control of semivolatile metals: (1) Improved particulate matter control; (2) control of semivolatile metals in the hazardous waste feed; and (3) control of the semivolatile metals in the raw materials and fuels. For reasons discussed below, we are not proposing a beyond-the-floor standard for semivolatile metals.

Improved Particulate Matter Control. Controlling particulate matter also controls emissions of semivolatile metals. Our data show that all cement kilns are already achieving greater than 98.6% system removal efficiency for semivolatile metals, with most attaining 99.9% removal. Thus, additional controls of particulate matter are likely to result in only modest additional reductions of semivolatile metals emissions. We evaluated a beyond-the-floor level of 2.0 × 10−4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which Start Printed Page 21256represents a 50% reduction in emissions from MACT floor levels. The national incremental annualized compliance cost for cement kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $2.7 million and would provide an incremental reduction in semivolatile metals emissions beyond the MACT floor controls of 1.2 tons per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between further improvements to control particulate matter and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of solid waste generated by 300 tons per year and would also require sources to use an additional 5.7 million kW-hours of energy per year to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $2.3 million per additional ton of semivolatile metals removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control.

Feed Control of Semivolatile Metals in the Hazardous Waste. We also evaluated a beyond-the-floor level of 3.2 × 10−4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which represents a 20% reduction from the floor level. We chose a 20% reduction as a level representing the practicable extent that additional feedrate control of semivolatile metals in hazardous waste can be used and still achieve appreciable emissions reductions. The national incremental annualized compliance cost for cement kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $0.30 million and would provide an incremental reduction in semivolatile metals emissions beyond the MACT floor controls of 0.36 tons per year. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the national compliance cost estimates. Therefore, based on these factors and costs of approximately $0.84 million per additional ton of semivolatile metals removed, we are not proposing a beyond-the-floor standard based on feed control of semivolatile metals in the hazardous waste.

Feed Control of Semivolatile Metals in the Raw Materials and Auxiliary Fuels. Cement kilns could achieve a reduction in semivolatile metal emissions by substituting a raw material containing lower levels of lead and/or cadmium for a primary raw material with higher levels of these metals. We believe that this beyond-the-floor option would even be less cost-effective than either of the options discussed above, however. Given that cement kilns are sited near the primary raw material supply, acquiring and transporting large quantities of an alternate source of raw materials is likely to be cost-prohibitive. Therefore, we are not proposing a beyond-the-floor standard based on limiting semivolatile metals in the raw material feed. We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of semivolatile metals would be an appropriate control option for sources. Given that most cement kilns burning hazardous waste also burn coal as a fuel, we considered switching to natural gas as a potential beyond-the-floor option. For the same reasons discussed for mercury, we judge a beyond-the-floor standard based on fuel switching as unwarranted.

For the reasons discussed above, we propose to establish the emission standard for existing cement kilns at 4.0 × 10−4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste.

3. What Is the Rationale for the MACT Floor for New Sources?

Semivolatile metals emissions from new cement kilns are currently limited to 180 μg/dscm by § 63.1204(b)(3). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796).

The MACT floor for new sources for semivolatile metals would be 6.2 × 10−5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which considers emissions variability. This is an emission level that the single best performing source identified with the SRE/Feed Approach could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the test conditions during which the emissions data were obtained.

To put the proposed floor level in context for a hypothetical wet process cement kiln that gets 50% of its required heat input from hazardous waste, a thermal emissions level of 6.2 × 10−5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste equates approximately to a stack gas concentration of 80 μg/dscm, including contributions from typical raw materials and coal. Thus, for the hypothetical wet process cement kiln the thermal emissions floor level of 6.2 × 10−5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste is estimated to be less than the current interim standard for new sources of 180 μg/dscm.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We identified the same three potential beyond-the-floor techniques for control of semivolatile metals: (1) Improved control of particulate matter; (2) control of semivolatile metals in the hazardous waste feed; and (3) control of semivolatile metals in the raw materials and fuels.

Improved Particulate Matter Control. Controlling particulate matter also controls emissions of semivolatile metals. We evaluated improved control of particulate matter based on a state-of-the-art baghouse using a high quality fabric filter bag material as beyond-the-floor control for further reductions in semivolatile metals emissions. We evaluated a beyond-the-floor level of 2.5 × 10−5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. The incremental annualized compliance cost for a new cement kiln with an average gas flow rate to meet this beyond-the-floor level, rather than to comply with the floor level, would be approximately $0.38 million and would provide an incremental reduction in semivolatile metals emissions of approximately 144 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the cost estimates. For these reasons and costs of $5.3 million per ton of semivolatile metals removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control for new cement kilns.

Feed Control of Semivolatile Metals in the Hazardous Waste. We also believe that the expense for further reduction in semivolatile metals emissions based on further control of semivolatile metals concentrations in the hazardous waste is not warranted. We also evaluated a beyond-the-floor level of 5.0 × 10−5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which represents a 20% reduction from the floor level. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the compliance cost estimates. For similar Start Printed Page 21257reasons discussed above for existing sources, we conclude that a beyond-the-floor standard based on controlling the concentration of semivolatile metals levels in the hazardous waste feed would not be justified because of the costs coupled with estimated emission reductions.

Feed Control of Semivolatile Metals in the Raw Materials and Auxiliary Fuels. Cement kilns could achieve a reduction in semivolatile metals emissions by substituting a raw material containing lower levels of cadmium and lead for a primary raw material with a higher level. For a new source at an existing cement plant, we believe that this beyond-the-floor option would not be cost-effective due to the costs of transporting large quantities of an alternate source of raw materials to the cement plant. Given that the plant site already exists and sited near the source of raw material, replacing the raw materials at the plant site with lower semivolatile metals-containing materials would be the source's only option. For a cement kiln constructed at a new greenfield site, we are not aware of any information and data from a source that has undertaken or is currently located at a site whose raw materials are inherently lower in semivolatile metals that would consistently achieve reduced semivolatile metals emissions. Further, we are uncertain as to what beyond-the-floor standard would be achievable using a lower, if it exists, semivolatile metals-containing raw material. Although we are doubtful that selecting a new plant site based on the content of metals in the raw material is a realistic beyond-the-floor option considering the numerous additional factors that go into such a decision, we solicit comment on whether and what level of a beyond-the-floor standard based on controlling the level of semivolatile metals in the raw materials is appropriate.

We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of semivolatile metals would be an appropriate control option for sources. Given that most cement kilns burning hazardous waste also burn coal as a fuel, we considered switching to natural gas as a potential beyond-the-floor option. For the same reasons discussed for mercury, we judge a beyond-the-floor standard based on fuel switching as unwarranted.

For the reasons discussed above, we propose to establish the emission standard for new cement kilns at 6.2 × 10−5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste.

E. What Are the Proposed Standards for Low Volatile Metals?

We are proposing to establish standards for existing and new cement kilns that limit emissions of low volatile metals (arsenic, beryllium, and chromium, combined) to 1.4 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Low volatile metals emissions from existing cement kilns are currently limited to 56 μg/dscm by § 63.1204(a)(4). This standard was promulgated in the Interim Standards Rule (see 67 FR at 6796). Cement kilns control emissions of low volatile metals with baghouses or electrostatic precipitators and/or by controlling the feed concentration of low volatile metals in the hazardous waste.

We have compliance test emissions data for all cement kiln sources. For most sources, we have compliance test emissions data from more than one compliance test campaign. Low volatile metal stack emissions range from approximately 1 to 100 μg/dscm. These emissions are expressed as mass of low volatile metals (from all feedstocks) per unit volume of stack gas. Hazardous waste thermal emissions range from 9.2 × 10−7 to 1.0 × 10−5 lbs per million Btu. Hazardous waste thermal emissions represent the mass of low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. For nearly every cement kiln, chromium was the most significant contributor to low volatile emissions.

To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the SRE/Feed Approach. The calculated floor is 1.4 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 52% of sources and would reduce low volatile metals emissions by 0.10 tons per year.

To put the proposed floor level in context for a hypothetical wet process cement kiln that gets 50% of its required heat input from hazardous waste, a thermal emissions level of 1.4 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste equates approximately to a stack gas concentration of 7 μg/dscm. This estimated stack gas concentration does not include contributions to emission from other low volatile metals-containing materials such as raw materials and fossil fuels. The additional contribution to stack emissions of low volatile metals in an average raw material and coal is estimated to range from less than 1 to 15 μg/dscm. Thus, for the hypothetical wet process cement kiln the thermal emissions floor level of 1.4 × 10−5 lbs low volatile metals attributable to the hazardous waste per million Btu heat input of the hazardous waste is estimated to be less than 22 μg/dscm, which is less than the current interim standard of 56 μg/dscm. Given that comparing the proposed floor level to the interim standard requires numerous assumptions (as just illustrated) including hazardous waste fuel replacement rates, heat input requirements per ton of clinker, concentrations of low volatile metals in the raw material and coal, and system removal efficiency, we have included a more detailed analysis in the background document.[106] Our detailed analysis indicates the proposed floor level is as least as stringent as the interim standard (so as to avoid any backsliding from a current level of performance achieved by all cement kilns, and hence, the level of minimal stringency at which EPA could calculate the MACT floor). Thus, we conclude that a dual standard—the low volatile metals standard as both the calculated floor level, expressed as a hazardous waste thermal emissions level, and the current interim standard—is not needed for this standard.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We identified three potential beyond-the-floor techniques for control of low volatile metals: (1) Improved particulate matter control; (2) control of low volatile metals in the hazardous waste feed; and (3) control of the low volatile metals in the raw materials. For reasons discussed below, we are not proposing a beyond-the-floor standard for low volatile metals.

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Improved Particulate Matter Control. Controlling particulate matter also controls emissions of low volatile metals. Our data show that all cement kilns are already achieving greater than 99.9% system removal efficiency for low volatile metals, with most attaining 99.99% removal. Thus, additional control of particulate matter emissions is likely to result in only a small increment in reduction of low volatile metals emissions. We evaluated a beyond-the-floor level of 7.0 × 10−6 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which represents a 50% reduction in emissions from MACT floor levels. The national incremental annualized compliance cost for cement kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $3.7 million and would provide an incremental reduction in low volatile metals emissions beyond the MACT floor controls of 120 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between further improvements to control particulate matter and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of solid waste generated by 72 tons per year and would also require sources to use an additional 1.2 million kW-hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $63 million per additional ton of low volatile metals removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control.

Feed Control of Low Volatile Metals in the Hazardous Waste. We also evaluated a beyond-the-floor level of 1.1 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which represents a 20% reduction from the floor level. We chose a 20% reduction as a level representing the practicable extent that additional feedrate control of mercury in hazardous waste can be used and still achieve appreciable emissions reductions. The national incremental annualized compliance cost for cement kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $1.2 million and would provide an incremental reduction in low volatile metals emissions beyond the MACT floor controls of 38 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the cost estimates. Therefore, based on these factors and costs of approximately $64 million per additional ton of low volatile metals removed, we are not proposing a beyond-the-floor standard based on feed control of low volatile metals in the hazardous waste.

Feed Control of Low Volatile Metals in the Raw Materials and Auxiliary Fuels. Cement kilns could achieve a reduction in low volatile metal emissions by substituting a raw material containing lower levels of arsenic, beryllium, and/or chromium for a primary raw material with higher levels of these metals. We believe that this beyond-the-floor option would even be less cost-effective than either of the options discussed above, however. Given that cement kilns are sited near the primary raw material supply, acquiring and transporting large quantities of an alternate source of raw materials is likely to be cost-prohibitive. Therefore, we are not proposing a beyond-the-floor standard based on limiting low volatile metals in the raw material feed. We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of low volatile metals would be an appropriate control option for sources. Given that most cement kilns burning hazardous waste also burn coal as a fuel, we considered switching to natural gas as a potential beyond-the-floor option. For the same reasons discussed for mercury, we judge a beyond-the-floor standard based on fuel switching as unwarranted.

For the reasons discussed above, we propose to establish the emission standard for existing cement kilns at 1.4 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste.

3. What Is the Rationale for the MACT Floor for New Sources?

Low volatile metals emissions from new cement kilns are currently limited to 54 μg/dscm by § 63.1204(b)(4). This standard was promulgated in the Interim Standards Rule (see 67 FR at 6796, February 13, 2002).

The floor level for new sources for low volatile metals would be 1.4 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which considers emissions variability. This is an emission level that the single best performing source identified with the SRE/Feed Approach could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the test conditions during which the emissions data were obtained.

To put the proposed floor level in context for a hypothetical wet process cement kiln that gets 50% of its required heat input from hazardous waste, a thermal emissions level of 1.4 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste equates approximately to a stack gas concentration of 22 μg/dscm, including contributions from typical raw materials and coal. Thus, for the hypothetical wet process cement kiln the thermal emissions floor level of 6.2 × 105 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste is estimated to be more stringent than the current interim standard for new sources of 54 μg/dscm.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We identified the same three potential beyond-the-floor techniques for control of low volatile metals: (1) Improved control of particulate matter; (2) control of low volatile metals in the hazardous waste feed; and (3) control of low volatile metals in the raw materials and fuels.

Improved Particulate Matter Control. Controlling particulate matter also controls emissions of low volatile metals. We evaluated improved control of particulate matter based on a state-of-the-art baghouse using a high quality fabric filter bag material as beyond-the-floor control for further reductions in low volatile metals emissions. We evaluated a beyond-the-floor level of 6.0 × 10−6 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. The incremental annualized compliance cost for a new cement kiln to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $0.38 million and would provide an incremental reduction in low volatile metals emissions of approximately 33 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the cost estimates. For these reasons and costs of $23.5 million per ton of low volatile metals removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control for new cement kilns.

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Feed Control of Low Volatile Metals in the Hazardous Waste. We also evaluated a beyond-the-floor level of 1.1 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which represents a 20% reduction from the floor level. We believe that the expense for further reduction in low volatile metals emissions based on further control of low volatile metals concentrations in the hazardous waste is not warranted given the costs, nonair quality health and environmental impacts, and energy effects.

Feed Control of Low Volatile Metals in the Raw Materials and Auxiliary Fuels. Cement kilns could achieve a reduction in low volatile metals emissions by substituting a raw material containing lower levels of low volatile metals for a primary raw material with a higher level. For a new source at an existing cement plant, we believe that this beyond-the-floor option would not be cost-effective due to the costs of transporting large quantities of an alternate source of raw materials to the cement plant. Given that the plant site already exists and sited near the source of raw material, replacing the raw materials at the plant site with lower low volatile metals-containing materials would be the source's only option. For a cement kiln constructed at a new greenfield site, we are not aware of any information and data from a source that has undertaken or is currently located at a site whose raw materials are inherently lower in low volatile metals that would consistently achieve reduced low volatile metals emissions. Further, we are uncertain as to what beyond-the-floor standard would be achievable using a lower, if it exists, low volatile metals-containing raw material. Although we are doubtful that selecting a new plant site based on the content of metals in the raw material is a realistic beyond-the-floor option considering the numerous additional factors that go into such a decision, we solicit comment on whether and what level of a beyond-the-floor standard based on controlling the level of low volatile metals in the raw materials is appropriate.

We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of low volatile metals would be an appropriate control option for sources. Given that most cement kilns burning hazardous waste also burn coal as a fuel, we considered switching to natural gas as a potential beyond-the-floor option. For the same reasons discussed for mercury, we judge a beyond-the-floor standard based on fuel switching as unwarranted.

Therefore, we are proposing a low volatile metals standard of 1.4 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste.

F. What Are the Proposed Standards for Hydrogen Chloride and Chlorine Gas?

We are proposing to establish standards for existing and new cement kilns that limit total chlorine emissions (hydrogen chloride and chlorine gas, combined, reported as a chloride equivalent) to 110 and 83 ppmv, respectively. However, we are also proposing to establish alternative risk-based standards, pursuant to CAA section 112(d)(4), which could be elected by the source in lieu of the MACT emission standards for total chlorine. The emission limits would be based on national exposure standards that ensure protection of public health with an ample margin of safety. See Part Two, Section XIII for additional details.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Total chlorine emissions from existing cement kilns are limited to 130 ppmv by § 63.1204(a)(6). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796). None of the cement kilns burning hazardous waste use a dedicated control device, such as a wet scrubber, to remove total chlorine from the gas stream. However, the natural alkalinity in some of the raw materials is highly effective at removing chlorine from the gas stream. Our data base shows that the majority of the system removal efficiency (SRE) data of total chlorine—over 80%—indicate a SRE greater than 95%. This scrubbing effect, though quite effective, varies across different sources and also at individual sources over time due to differences in raw materials, operating conditions, cement kiln dust recycle rates, and production requirements. Likewise, our data show that total chlorine emissions from a given source can vary over a considerable range. Based on these data, we conclude that the best (highest) SRE achieved at a given source is not duplicable or replicable.

The majority of the chlorine fed to the cement kiln during a compliance test comes from the hazardous waste.[107] In all but a few cases the hazardous waste contribution to the total amount of chlorine fed to the kiln represented at least 75% of the total chlorine loading to the kiln. As we identified in the September 1999 final rule, the proposed MACT floor control for total chlorine is based on controlling the concentration of chlorine in the hazardous waste. The chlorine concentration in the hazardous waste will affect emissions of total chlorine at a given SRE because emissions increase as the chlorine loading increases.

We have compliance test emissions data for all cement kiln sources. For most sources, we have compliance test emissions data from more than one compliance test campaign. Total chlorine emissions range from less than 1 ppmv to 192 ppmv.

To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using a variant of the SRE/Feed Approach because of concerns about a cement kiln's ability to replicate a given SRE. To identify the floor level we first evaluated the chlorine feed level in the hazardous waste for all sources. The best performing sources had the lowest maximum theoretical emissions concentration or MTEC, considering variability. We then applied a SRE of 90% to the best performing sources' total MTEC (i.e., includes chlorine contributions to emissions from all feedstreams such as raw material and fossil fuels) to identify the floor level. Given our concerns about the reproducibility of SREs of total chlorine, we selected a SRE of 90% because our data base shows that all sources have demonstrated this SRE at least once (and often several times) during a compliance test. The calculated floor is 110 ppmv, which considers emissions variability. This is an emission level that the best performing feed control sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 93% of sources and would reduce total chlorine emissions by 64 tons per year.

We also invite comment on an alternative approach to establish a floor level expressed as a hazardous waste thermal feed concentration.[108] A hazardous waste thermal feed concentration is expressed as mass of chlorine in the hazardous waste per Start Printed Page 21260million Btu heat input contributed by the hazardous waste. The floor would be based on the best five performing sources with the lowest thermal feed concentration of chlorine in the hazardous waste considering each source's most recent compliance test data. One advantage of this approach is that the uncertainty surrounding the capture (SRE) of chlorine in a kiln is removed. The calculated floor level would be 2.4 lbs chlorine in the hazardous waste per million Btu in the hazardous waste, which considers variability. For a hypothetical wet process cement kiln that gets 50% of its required heat input from hazardous waste, a hazardous waste with a chlorine concentration of 2.4 lbs chlorine per million Btu and achieving 90% SRE equates approximately to a stack gas concentration of 75 ppmv. This estimated stack gas concentration does not include contributions to emission from other chlorine-containing materials such as raw materials and fossil fuels. The additional contribution to stack emissions of total chlorine in an average raw material and coal is estimated to range from less than 1 to 35 ppmv. Thus, for the hypothetical wet process cement kiln this floor level is estimated to be less than 110 ppmv, which is less than the current interim standard of 130 ppmv.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We identified three potential beyond-the-floor techniques for control of total chlorine: (1) Use of wet scrubbers; (2) control of chlorine in the hazardous waste feed; and (3) control of the chlorine in the raw materials. For reasons discussed below, we are not proposing a beyond-the-floor standard for total chlorine.

Use of Wet Scrubbers. We evaluated the use of wet scrubbers as beyond-the-floor control for further reduction of mercury emissions. Wet scrubbers are not currently being used at any hazardous waste burning cement kilns to capture hydrogen chloride. We evaluated a beyond-the-floor level of 55 ppmv. The national incremental annualized compliance cost for cement kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $3.4 million and would provide an incremental reduction in total chlorine emissions beyond the MACT floor controls of 370 tons per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between wet scrubbing and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of water usage and waste water generated by 1.5 billion gallon per year. The option would also require sources to use an additional 12 million kW-hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $9,300 per additional ton of total chlorine removed, we are not proposing a beyond-the-floor standard based on wet scrubbing.

Feed Control of Chlorine in the Hazardous Waste. We also evaluated a beyond-the-floor level of 88 ppmv, which represents a 20% reduction from the floor level. We chose a 20% reduction as a level that represents the practicable extent that additional feedrate control of chlorine in the hazardous waste can be used and still achieve modest emissions reductions. The national incremental annualized compliance cost for cement kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $1.1 million and would provide an incremental reduction in total chlorine emissions beyond the MACT floor controls of 100 tons per year. Nonair quality health and environmental impacts and energy effects were also evaluated and are included in the compliance cost estimates. Therefore, based on these factors and costs of approximately $11,000 per additional ton of total chlorine, we are not proposing a beyond-the-floor standard based on feed control of chlorine in the hazardous waste.

Feed Control of Chlorine in the Raw Materials and Auxiliary Fuels. Cement kilns could achieve a reduction in total chlorine emissions by substituting a raw material containing lower levels of chlorine for a primary raw material with higher levels of chlorine. We believe that this beyond-the-floor option would even be less cost-effective than either of the options discussed above because most chlorine feed to the kiln is in the hazardous waste. In addition, given that cement kilns are sited near the primary raw material supply, acquiring and transporting large quantities of an alternate source of raw materials is likely to be cost-prohibitive. Therefore, we are not proposing a beyond-the-floor standard based on limiting chlorine in the raw material feed. We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of chlorine would be an appropriate control option for kilns. Given that most cement kilns burning hazardous waste also burn coal as a fuel, we considered switching to natural gas as a potential beyond-the-floor option. For the same reasons discussed for mercury, we judge a beyond-the-floor standard based on fuel switching as unwarranted.

For the reasons discussed above, we propose not to adopt a beyond-the-floor standard for total chlorine and propose to establish the emission standard for existing cement kilns at 110 ppmv.

3. What Is the Rationale for the MACT Floor for New Sources?

Total chlorine emissions from new cement kilns are currently limited to 86 ppmv by § 63.1204(b)(6). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6796). The MACT floor for new sources for total chlorine would be 78 ppmv, which considers emissions variability. This is an emission level that the single best performing source identified with the SRE/Feed Approach could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the test conditions during which the emissions data were obtained.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We identified similar potential beyond-the-floor techniques for control of total chlorine for new sources: (1) Use of wet scrubbing; (2) control of chlorine in the hazardous waste feed; and (3) control of chlorine in the raw materials and fuels.

Use of Wet Scrubbers. We considered wet scrubbing as beyond-the-floor control for further reductions in total chlorine emissions and evaluated a beyond-the-floor level of 39 ppmv. The incremental annualized compliance cost for a new cement kiln to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $1.2 million and would provide an incremental reduction in total chlorine emissions of approximately 22 tons per year. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the cost estimates. For these reasons and costs of $24,000 per ton of total chlorine removed, we are not proposing a beyond-the-floor standard based on wet scrubbing for new cement kilns.

Feed Control of Low Volatile Metals in the Hazardous Waste. We also evaluated a beyond-the-floor level of 62 ppmv, which represents a 20% reduction from the floor level. We believe that the expense for further reduction in total chlorine emissions Start Printed Page 21261based on further control of chlorine concentrations in the hazardous waste is not warranted given the costs, nonair quality health and environmental impacts, and energy effects.

Feed Control of Chlorine in the Raw Materials and Auxiliary Fuels. Cement kilns could achieve a reduction in total chlorine emissions by substituting a raw material containing lower levels of chlorine for a primary raw material with a higher level. For a new source at an existing cement plant, we believe that this beyond-the-floor option would not be cost-effective due to the costs of transporting large quantities of an alternate source of raw materials to the cement plant. Given that the plant site already exists and sited near the source of raw material, replacing the raw materials at the plant site with lower chlorine-containing materials would be the source's only option. For a cement kiln constructed at a new greenfield site, we are not aware of any information and data from a source that has undertaken or is currently located at a site whose raw materials are inherently lower in chlorine that would consistently achieve reduced total chlorine emissions. Further, we are uncertain as to what beyond-the-floor standard would be achievable using a lower, if it exists, chlorine-containing raw material. Although we are doubtful that selecting a new plant site based on the content of chlorine in the raw material is a realistic beyond-the-floor option considering the numerous additional factors that go into such a decision, we solicit comment on whether and what level of a beyond-the-floor standard based on controlling the level of chlorine in the raw materials is appropriate.

We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of chlorine would be an appropriate control option for sources. Given that most cement kilns burning hazardous waste also burn coal as a fuel, we considered switching to natural gas as a potential beyond-the-floor option. For the same reasons discussed for mercury, we judge a beyond-the-floor standard based on fuel switching as unwarranted.

Therefore, we are proposing a total chlorine standard of 78 ppmv for new cement kilns.

G. What Are the Standards for Hydrocarbons and Carbon Monoxide?

Hydrocarbon and carbon monoxide standards are surrogates to control emissions of organic hazardous air pollutants for existing and new cement kilns. For cement kilns without bypass or midkiln sampling systems, the standard for existing sources limit hydrocarbon or carbon monoxide concentrations to 20 ppmv or 100 ppmv, respectively. The standards for new sources limit (1) hydrocarbons to 20 ppmv; or (2) carbon monoxide to 100 ppmv. New, greenfield kilns[109] , that elect to comply with the 100 ppmv carbon monoxide standard, however, must also comply with a 50 ppmv hydrocarbon standard. New and existing sources that elect to comply with the 100 ppmv carbon monoxide standard, including new greenfield kilns that elect to comply with the carbon monoxide standard and 50 ppmv hydrocarbon standard, must also demonstrate compliance with the 20 ppmv hydrocarbon standard during the comprehensive performance test. However, continuous hydrocarbon monitoring following the performance test is not required.

For cement kilns with bypass or midkiln sampling systems, existing cement kilns are required to comply with either a carbon monoxide standard of 100 ppmv or a hydrocarbon standard of 10 ppmv. Both standards apply to combustion gas sampled in the bypass or a midkiln sampling port that samples representative kiln gas. See §§ 63.1204(a)(5) and (b)(5). The rationale for these decisions are discussed in the September 1999 final rule (64 FR at 52885). We view the standards for hydrocarbons and carbon monoxide as unaffected by the Court's vacature of the challenged regulations in its decision of July 24, 2001. We therefore are not proposing these standards for cement kilns, but rather are mentioning them here for the reader's convenience.

H. What Are the Standards for Destruction and Removal Efficiency?

The destruction and removal efficiency (DRE) standard is a surrogate to control emissions of organic hazardous air pollutants other than dioxin/furans. The standard for existing and new lightweight aggregate kilns requires 99.99% DRE for each principal organic hazardous constituent, except that 99.9999% DRE is required if specified dioxin-listed hazardous wastes are burned. See §§ 63.1204(c). The rationale for these decisions are discussed in the September 1999 final rule (64 FR at 52890). We view the standards for DRE as unaffected by the Court's vacature of the challenged regulations in its decision of July 24, 2001. We therefore are not proposing these standards for cement kilns, but rather are mentioning them here for the reader's convenience.

IX. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste Burning Lightweight Aggregate Kilns?

In this section, the basis for the proposed emission standards is discussed. See proposed § 63.1221. The proposed emission limits apply to the stack gases from lightweight aggregate kilns that burn hazardous waste and are summarized in the table below:

Proposed Standards for Existing and New Lightweight Aggregate Kilns

Hazardous air pollutant or surrogateEmission standard 1
Existing sourcesNew sources
Dioxin and furan0.40 ng TEQ/dscm0.40 ng TEQ/dscm.
Mercury 267 μg/dscm67 μg/dscm.
Particulate Matter57 mg/dscm (0.025 gr/dscf)23 mg/dscm (0.0099 gr/dscf).
Semivolatile metals 33.1 × 10−4 lb/MMBtu and 250 μg/dscm2.4 × 10−5 lb/MMBtu and 43 μg/dscm.
Low volatile metals 39.5 × 10−5 lb/MMBtu and 110 μg/dscm3.2 × 10−5 lb/MMBtu and 110 μg/dscm.
Hydrogen chloride and chlorine gas 4600 ppmv600 ppmv.
Hydrocarbons 5, 620 ppmv (or 100 ppmv carbon monoxide)20 ppmv (or 100 ppmv carbon monoxide).
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Destruction and removal efficiencyFor existing and new sources, 99.99% for each principal organic hazardous constituent (POHC). For sources burning hazardous wastes F020, F021, F022, F023, F026, or F027, however, 99.9999% for each POHC.
1 All emission standards are corrected to 7% oxygen, dry basis.
2 Mercury standard is an annual limit.
3 Standards are expressed as mass of pollutant emissions contributed by hazardous waste per million British thermal unit contributed by the hazardous waste.
4 Combined standard, reported as a chloride (Cl(−)) equivalent.
5 Sources that elect to comply with the carbon monoxide standard must demonstrate compliance with the hydrocarbon standard during the comprehensive performance test.
6 Hourly rolling average. Hydrocarbons reported as propane.

A. What Are the Proposed Standards for Dioxin and Furan?

We are proposing to establish standards for existing and new lightweight aggregate kilns that limit emissions of dioxin and furans to 0.40 ng TEQ/dscm.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Dioxin and furan emissions for existing lightweight aggregate kilns are currently limited by § 63.1205(a)(1) to 0.20 ng TEQ/dscm or rapid quench of the flue gas at the exit of the kiln to less than 400°F. This standard was promulgated in the Interim Standards Rule (See 67 FR at 6797).

Since promulgation of the September 1999 final rule, we have obtained additional dioxin/furan emissions data. We now have compliance test emissions data for all lightweight aggregate kilns that burn hazardous waste. The compliance test dioxin/furan emissions in our database range from approximately 0.9 to 58 ng TEQ/dscm.

Quenching kiln gas temperatures at the exit of the kiln so that gas temperatures at the inlet to the particulate matter control device are below the temperature range of optimum dioxin/furan formation (400-750°F) may be problematic for some of these sources. Some of these sources have extensive (long) duct-work between the kiln exit and the inlet to the control device. For these sources, quenching the gases at the kiln exit to a low enough temperature to limit dioxin/furan formation may conflict with the source's ability to avoid acid gas dew point related problems in the long duct-work and control device. As a result, some sources quench the kiln exit gases to a temperature that is in the optimum temperature range for surface-catalyzed dioxin/furan formation. Available compliance test emissions data indicate that inlet temperatures to the control device range from 435-450°F. This means that temperatures in the duct-work are higher and well within the range of optimum dioxin/furan formation.

To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the Emissions Approach described in Part Two, Section VI above. The calculated floor is 14 ng TEQ/dscm, which considers emissions variability. However, the current interim emission standard—0.20 ng TEQ/dscm or rapid quench of the flue gas at the exit of the kiln to less than 400°F—is a regulatory limit that is relevant in identifying the floor level because it fixes a level of performance for the source category. We estimate that sources achieving the “rapid quench of the flue gas at the exit of the kiln to less than 400°F” part of the current standard can emit up to 6.1 ng TEQ/dscm. Given that all sources are achieving the interim standard and that the interim standard is judged as more stringent than the calculated MACT floor, the dioxin/furan floor level can be no less stringent than the current regulatory limit.[110] We are, therefore, proposing the dioxin/furan floor level as the current emission standard of 0.20 ng TEQ/dscm or rapid quench of the flue gas at the exit of the kiln to less than 400°F. This emission level is being achieved by all sources because it is the interim standard. In addition, there are no emissions reductions for existing lightweight aggregate kilns to comply with the floor level.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We evaluated activated carbon injection as beyond-the-floor control for further reduction of dioxin/furan emissions. Activated carbon has been demonstrated for controlling dioxin/furans in various combustion applications; however, no lightweight aggregate kiln that burns hazardous waste uses activated carbon injection. We evaluated a beyond-the-floor level of 0.40 ng TEQ/dscm, which represents a level that is considered routinely achievable using activated carbon injection. In addition, we assumed for costing purposes that lightweight aggregate kilns needing activated carbon injection to achieve the beyond-the-floor level would install the activated carbon injection system after the existing particulate matter control device and add a new, smaller baghouse to remove the injected carbon with the adsorbed dioxin/furans. We chose this costing approach to address potential concerns that injected carbon may interfere with lightweight aggregate dust use practices.

The national incremental annualized compliance cost for lightweight aggregate kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $1.8 million and would provide an incremental reduction in dioxin/furan emissions beyond the MACT floor controls of 1.9 grams TEQ per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the nonair quality health and environmental impacts between activated carbon injection and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of solid waste generated by 550 tons per year and would require sources to use an additional 1 million kW-hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national compliance cost estimates.

Therefore, based on these factors and costs of approximately $0.95 million per additional gram of dioxin/furan TEQ Start Printed Page 21263removed, we are proposing a beyond-the-floor standard of 0.40 ng TEQ/dscm for existing lightweight aggregate kilns. We judge that the cost to achieve this beyond-the-floor level is warranted given our special concern about dioxin/furan. Dioxin/furan are some of the most toxic compounds known due to their bioaccumulation potential and wide range of health effects, including carcinogenesis, at exceedingly low doses. Exposure via indirect pathways is a chief reason that Congress singled our dioxin/furan for priority MACT control in CAA section 112(c)(6). See S. Rep. No. 128, 101st Cong. 1st Sess. at 154-155. In addition, we note that a beyond-the-floor standard of 0.40 ng TEQ/dscm is consistent with historically controlled levels under MACT for hazardous waste incinerators and cement kilns, and Portland cement plants. See §§ 63.1203(a)(1), 63.1204(a)(1), and 63.1343(d)(3). Also, EPA has determined previously in the 1999 Hazardous Waste Combustor MACT final rule that dioxin/furan in the range of 0.40 ng TEQ/dscm or less are necessary for the MACT standards to be considered generally protective of human health under RCRA (using the 1985 cancer slope factor), thereby eliminating the need for separate RCRA standards under the authority of RCRA section 3005(c)(3) and 40 CFR 270.10(k). Finally, we note that this decision is not inconsistent with EPA's decision not to promulgate beyond-the-floor standards for dioxin/furan for hazardous waste burning lightweight aggregate kilns, cement kilns, and incinerators at cost-effectiveness values in the range of $530,000 to $827,000 per additional gram of dioxin/furan TEQ removed. See 64 FR at 52892, 52876, and 52961. In those cases, EPA determined that controlling dioxin/furan emissions from a level of 0.40 ng TEQ/dscm to a beyond-the-floor level of 0.20 ng TEQ/dscm was not warranted because dioxin/furan levels below 0.40 ng TEQ/dscm are generally considered to be below the level of health risk concern.

We specifically request comment on whether this beyond-the-floor standard is warranted.

3. What Is the Rationale for the MACT Floor for New Sources?

Dioxin and furan emissions for new lightweight aggregate kilns are currently limited by § 63.1205(b)(1) to 0.20 ng TEQ/dscm or rapid quench of the flue gas at the exit of the kiln to less than 400°F. This standard was promulgated in the Interim Standards Rule (See 67 FR at 6797).

The calculated MACT floor for new sources would be 1.3 ng TEQ/dscm, which considers emissions variability, or rapid quench of the flue gas at the exit of the kiln to less than 400°F. This is an emission level that the single best performing source identified by the Emissions Approach. However, we are concerned that the calculated floor level of 1.3 ng TEQ/dscm is not duplicable by all sources using temperature control because we estimate that sources rapidly quenching the flue gas at the exit of the kiln to less than 400°F can emit up to 6.1 ng TEQ/dscm. Therefore, we are proposing the floor as the current emission standard of 0.20 ng TEQ/dscm or rapid quench of the flue gas at the exit of the kiln to less than 400°F.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We evaluated activated carbon injection as beyond-the-floor control for further reduction of dioxin/furan emissions, and considered a beyond-the-floor level of 0.40 ng TEQ/dscm, which represents a level that is considered routinely achievable with activated carbon injection. In addition, we assumed for costing purposes that a new lightweight aggregate kiln will install the activated carbon injection system after the existing particulate matter control device and add a new, smaller baghouse to remove the injected carbon with the adsorbed dioxin/furan. The incremental annualized compliance cost for a new source to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $0.26 million and would provide an incremental reduction in dioxin/furan emissions of 0.37 grams per year. Nonair quality health, environmental impacts, and energy effects are accounted for in the cost estimates. Therefore, based on these factors and cost of $0.71 million per gram TEQ removed, we are proposing a beyond-the-floor standard based on activated carbon injection. We believe that the cost to achieve this beyond-the-floor level is warranted given our special concern about dioxin/furan. Dioxin/furan are some of the most toxic compounds known due to their bioaccumulation potential and wide range of health effects, including carcinogenesis, at exceedingly low doses. In addition, as discussed above, we note that the beyond-the-floor emission level of 0.40 ng TEQ/dscm is consistent with historically controlled levels under MACT for hazardous waste incinerators and cement kilns, and Portland cement plants. See §§ 63.1203(a)(1), 63.1204(a)(1), and 63.1343(d)(3). EPA has determined previously in the 1999 Hazardous Waste Combustor MACT final rule that dioxin/furan in the range of 0.40 ng TEQ/dscm or less are necessary for the MACT standards to be considered generally protective of human health under RCRA, thereby eliminating the need for separate RCRA standards.

We specifically request comment on whether this beyond-the-floor standard is warranted.

B. What Are the Proposed Standards for Mercury?

We are proposing to establish standards for existing and new lightweight aggregate kilns that limit emissions of mercury to 67 μg/dscm.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Mercury emissions for existing lightweight aggregate kilns are currently limited to 120 μg/dscm by § 63.1205(a)(2). Existing lightweight aggregate kilns have the option to comply with an alternative mercury standard that limits the hazardous waste maximum theoretical emissions concentration (MTEC) of mercury to 120 μg/dscm.[111] This standard was promulgated in the Interim Standards Rule (See 67 FR at 6797). One lightweight aggregate facility with two kilns uses a venturi scrubber to remove mercury from the flue gas stream and the remaining sources limit the feed concentration of mercury in the hazardous waste to control emissions.

We have compliance test emissions data for only one source; however, we have normal emissions data for all sources. For most sources, we have normal emissions data from more than one test campaign. We used these emissions data to represent the average emissions from a source even though we do not know whether the emissions represent the high end, low end, or close to the average emissions. The normal mercury stack emissions range from less than 1 to 47 μg/dscm, while the highest compliance test emissions data is 1,050 μg/dscm. These emissions are expressed as mass of mercury (from all feedstocks) per unit volume of stack gas.

To identify the MACT floor, we evaluated all normal emissions data using the SRE/Feed Approach. We considered normal stack emissions data from all test campaigns.[112] For example, Start Printed Page 21264one source in our data base has normal emissions data for three different testing campaigns: 1992, 1995, and 1999. Under this approach we considered the emissions data from the three separate years or campaigns. As explained earlier, we believe this approach better captures the range of average emissions for a source than only considering the most recent normal emissions. In addition, for sources without control equipment to capture mercury, we assumed the sources achieved a SRE of zero. The effect of this assumption is that the sources (without control equipment for mercury) with the lower mercury concentrations in the hazardous waste were identified as the better performing sources.

The calculated floor is 67 μg/dscm, which considers emissions variability, based on a hazardous waste maximum theoretical emissions concentration (MTEC) of 42 μg/dscm. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 57% of sources and would reduce mercury emissions by 8 pounds per year. If we were to adopt such a floor level, we are proposing that sources comply with the limit on an annual basis because it is based on normal emissions data. Under this approach, compliance would not be based on the use of a total mercury continuous emissions monitoring system because these monitors have not been adequately demonstrated as a reliable compliance assurance tool at all types of incinerator sources. Instead, a source would maintain compliance with the mercury standard by establishing and complying with short-term limits on operating parameters for pollution control equipment and annual limits on maximum total mercury feedrate in all feedstreams.

In the September 1999 final rule, we acknowledged that a lightweight aggregate kiln using properly designed and operated MACT control technologies, including controlling the levels of metals in the hazardous waste, may not be capable of achieving a given emission standard because of process raw material contributions that might cause an exceedance of the emission standard. To address this concern, we promulgated a provision that allows sources to petition for alternative standards provided they submit site-specific information that shows raw material hazardous air pollutant contributions to the emissions prevent the source from complying with the emission standard even though the kiln is using MACT control. See § 63.1206(b)(9).

Today's proposed floor of 67 μg/dscm, which was based on a hazardous waste MTEC of 42 μg/dscm, may likewise necessitate such an alternative because contributions of mercury in the raw materials and fossil fuels at some sources may cause an exceedance of the emission standard. The Agency intends to retain a source's ability to comply with an alternative standard, and we request comment on two approaches to accomplish this. The first approach would be to structure the alternative standard similar to the petitioning process used under § 63.1206(b)(9). In the case of mercury for an existing lightweight aggregate kiln, MACT would be defined as a hazardous waste feedrate corresponding to an MTEC of 42 μg/dscm. If we were to adopt this approach, we would require sources, upon approval of the petition by the Administrator, to comply with this hazardous waste MTEC on an annual basis because it is based on normal emissions data. Under the second approach, we would structure the alternative standard similar to the framework used for the alternative interim standards for mercury under § 63.1206(b)(15). The operating requirement would be an annual MTEC not to exceed 42 μg/dscm. We also request comment on whether there are other approaches that would more appropriately provide relief to sources that cannot achieve a total stack gas concentration standard because of emissions attributable to raw material and nonhazardous waste fuels.

In comments submitted to EPA in 1997, Solite Corporation (Solite), owner and operator of five [113] of the seven lightweight aggregate kilns, stated that the normal emissions data in our data base are unrepresentative of average emissions of mercury because the normal range of mercury concentrations in the hazardous waste burned during the compliance and trial burn tests was not captured during the tests. In their 1997 comments, Solite provided information on actual mercury concentrations in the hazardous waste burn tanks over a year and a quarter period. The information showed that 87% of the burn tanks contained mercury at concentrations below the facility's detection limit of 2 ppm. Additional analyses of a limited number of these samples conducted at an off-site lab showed that the majority of samples were actually less than 0.2 ppm.[114]

We examined the test reports of the five best performing sources that are the basis of today's proposed floor level to determine the concentration level of mercury in the hazardous wastes. The hazardous waste burned by the best performing sources during the tests that generated the normal emissions data had mercury concentrations that ranged from 0.02 to 0.2 ppm.[115] Even though the concentrations of mercury in the hazardous waste seem low, we cannot judge how these snap shot concentrations compare to long-term normal concentrations because the majority of the burn tank concentration data submitted by Solite are nondetect measurements at a higher detection limit.

Solite informed us in July 2003 that they are in the process of upgrading the analysis equipment at their on-site laboratory. Once completed, Solite expects to be capable of detecting mercury in the hazardous waste at concentrations of 0.2 ppm. Solite also indicated that they intend to assemble and submit to EPA several months of burn tank concentration data analyzed with the new equipment. We will add these data to the docket of today's proposal once available. As we discussed for cement kilns for mercury, we are requesting comment on approaches to establish a hazardous waste feed concentration standard based on long-term feed concentrations of mercury in the hazardous waste. Likewise, we invite comments on establishing a mercury feed Start Printed Page 21265concentration standard for lightweight aggregate kilns.

We also invite comment on whether we should judge an annual limit of 67 μg/dscm as less stringent than either the current emission standard of 120 μg/dscm or the hazardous waste MTEC of mercury of 120 μg/dscm for lightweight aggregate kilns (so as to avoid any backsliding from a current level of performance achieved by all sources, and hence, the level of minimal stringency at which EPA could calculate the MACT floor). In order to comply with the current emission standard, generally a source must conduct manual stack sampling to demonstrate compliance with the mercury emission standard and then establish a maximum mercury feedrate limit based on operations during the performance test. Following the performance test, the source complies with a limit on the maximum total mercury feedrate in all feedstreams on a 12-hour rolling average (not an annual average). Alternatively, a source can elect to comply with a hazardous waste MTEC of mercury of 120 μg/dscm that would require the source to limit the mercury feedrate in the hazardous waste on a 12-hour rolling average. The floor level of 67 μg/dscm proposed today would allow a source to feed more variable mercury-containing feedstreams (e.g., a hazardous waste with a mercury MTEC greater than 120 μg/dscm) than the current 12-hour rolling average because today's proposed floor level is an annual limit. For example, the concentration of mercury in the hazardous waste exceeded a hazardous waste MTEC of 120 μg/dscm in a minimum of 13% of the burn tanks based on the data submitted by Solite in their 1997 comments (discussed above). As mentioned above, Solite intends to submit several months of burn tank concentration data using upgraded analysis equipment at their on-site laboratory that we will consider when comparing the relative stringency of an annual limit of 67 μg/dscm and a short-term limit of 120 μg/dscm.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We identified three potential beyond-the-floor techniques for control of mercury: (1) Activated carbon injection; (2) control of mercury in the hazardous waste feed; and (3) control of mercury in the raw materials and auxiliary fuels. For reasons discussed below, we are not proposing a beyond-the-floor standard for mercury.

Use of Activated Carbon Injection. We evaluated activated carbon injection as beyond-the-floor control for further reduction of mercury emissions. Activated carbon has been demonstrated for controlling mercury in several combustion applications; however, currently no lightweight aggregate kiln that burns hazardous waste uses activated carbon injection. Given this lack of experience using activated carbon injection, we made a conservative assumption that the use of activated carbon injection will provide 70% mercury control and evaluated a beyond-the-floor level of 20 μg/dscm. In addition, for costing purposes we assumed that sources needing activated carbon injection to achieve the beyond-the-floor level would install the activated carbon injection system after the existing baghouse and add a new, smaller baghouse to remove the injected carbon with the adsorbed mercury. We chose this costing approach to address potential concerns that injected carbon may interfere with lightweight aggregate kiln dust use practices.

The national incremental annualized compliance cost for lightweight aggregate kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $1.1 million and would provide an incremental reduction in mercury emissions beyond the MACT floor controls of 11 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between activated carbon injection and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of solid waste generated by 270 tons per year and would require sources to use an additional 1.2 million kW-hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $209 million per additional ton of mercury removed, we are not proposing a beyond-the-floor standard based on activated carbon injection.

Feed Control of Mercury in the Hazardous Waste. We also evaluated a beyond-the-floor level of 54 μg/dscm, which represents a 20% reduction from the floor level. We chose a 20% reduction as a level representing the practicable extent that additional feedrate control of mercury in hazardous waste (beyond feedrate control that may be necessary to achieve the floor level) can be used and still achieve modest emissions reductions.[116] The national incremental annualized compliance cost for lightweight aggregate kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $0.3 million and would provide an incremental reduction in mercury emissions beyond the MACT floor controls of 3 pounds per year. Nonair quality health and environmental impacts and energy effects were also evaluated. Therefore, based on these factors and costs of approximately $229 million per additional ton of mercury removed, we are not proposing a beyond-the-floor standard based on feed control of mercury in the hazardous waste.

Feed Control of Mercury in the Raw Materials and Auxiliary Fuels. Lightweight aggregate kilns could achieve a reduction in mercury emissions by substituting a raw material containing a lower level of mercury for a primary raw material with a higher level. We believe that this beyond-the-floor option would be even less cost-effective than either of the options discussed above, however. Given that sources are sited near the supply of the primary raw material, transporting large quantities of an alternate source of raw materials, even if available, is likely to be cost-prohibitive, especially considering the small expected emissions reductions that would result.

We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of mercury would be an appropriate control option for sources. Two facilities typically burn hazardous waste at a fuel replacement rate of 100%, while one facility has burned a combination of fuel oil and natural gas in addition to the hazardous waste. We considered switching only to natural gas as the auxiliary fuel as a potential beyond-the-floor option. We do not believe that switching to natural gas is a viable control option for the same reasons discussed above for cement kilns.

For the reasons discussed above, we propose to establish the emission standard for existing lightweight aggregate kilns at 67 μg/dscm. If we were to adopt such a standard, we are proposing that sources comply with the standard on an annual basis because it is based on normal emissions data.

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3. What Is the Rationale for the MACT Floor for New Sources?

Mercury emissions from new lightweight aggregate kilns are currently limited to 120 μg/dscm by § 63.1205(b)(2). This standard was promulgated in the Interim Standards Rule (see 67 FR at 6797).

The MACT floor for new sources for mercury would be 67 μg/dscm, which considers emissions variability. This is an emission level that the single best performing source identified with the SRE/Feed Approach could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We identified the same three potential beyond-the-floor techniques for control of mercury: (1) Use of activated carbon; (2) control of mercury in the hazardous waste feed; and (3) control of the mercury in the raw materials and auxiliary fuels.

Use of Activated Carbon Injection. We evaluated activated carbon injection as beyond-the-floor control for further reduction of mercury emissions. We made a conservative assumption that the use of activated carbon injection will provide 70% mercury control and evaluated a beyond-the-floor level of 20 μg/dscm. The incremental annualized compliance cost for a new lightweight aggregate kiln with average gas flow rate to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $0.26 million and would provide an incremental reduction in mercury emissions of approximately 42 pounds per year. Nonair quality health and environmental impacts and energy effects are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of $12 million per ton of mercury removed, we are not proposing a beyond-the-floor standard based on activated carbon injection for new sources.

Feed Control of Mercury in the Hazardous Waste. We also believe that the expense for further reduction in mercury emissions based on further control of mercury concentrations in the hazardous waste is not warranted. A beyond-the-floor level of 54 μg/dscm, which represents a 20% reduction from the floor level, would result in little additional mercury reductions. For similar reasons discussed above for existing sources, we conclude that a beyond-the-floor standard based on controlling the mercury in the hazardous waste feed would not be justified because of the costs coupled with estimated emission reductions.

Feed Control of Mercury in the Raw Materials and Auxiliary Fuels. Lightweight aggregate kilns could achieve a reduction in mercury emissions by substituting a raw material containing lower levels of mercury for a primary raw material with a higher level. For a new source at an existing lightweight aggregate plant, we believe that this beyond-the-floor option would not be cost-effective due to the costs of transporting large quantities of an alternate source of raw materials to the facility. Given that the plant site already exists and sited near the source of raw material, replacing the raw materials at the plant site with lower mercury-containing materials would be the source's only option. For a new lightweight aggregate kiln constructed at a new site—a greenfield site [117] —we are not aware of any information and data from a source that has undertaken or is currently located at a site whose raw materials are low in mercury which would consistently decrease mercury emissions. Further, we are uncertain as to what beyond-the-floor standard would be achievable using a lower, if it exists, mercury-containing raw material. Although we are doubtful that selecting a new plant site based on the content of metals in the raw material is a realistic beyond-the-floor option considering the numerous additional factors that go into such a decision, we solicit comment on whether and what level of a beyond-the-floor standard based on controlling the level of mercury in the raw materials is appropriate.

We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of mercury would be an appropriate control option for sources. We considered using natural gas in lieu of a fuel containing higher concentrations of mercury as a potential beyond-the-floor option. As discussed for existing sources, we are concerned about the availability of the natural gas infrastructure in all regions of the United States and believe that using natural gas would not be a viable control option for all new sources. Therefore, we are not proposing a beyond-the-floor standard based on limiting mercury in the raw material feed and auxiliary fuels.

Therefore, we propose a mercury standard of 67 μg/dscm for new sources. If we were to adopt such a standard, we are proposing that sources comply with the standard on an annual basis because it is based on normal emissions data.

C. What Are the Proposed Standards for Particulate Matter?

We are proposing to establish standards for existing and new lightweight aggregate kilns that limit emissions of particulate matter to 0.025 and 0.0099 gr/dscf, respectively. This standard would control unenumerated HAP metals in hazardous waste, and all non-Hg HAP metals in the raw material and fossil fuel inputs to the kiln.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Particulate matter emissions for existing lightweight aggregate kilns are currently limited to 0.025 gr/dscf (57 mg/dscm) by § 63.1205(a)(7). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6797). The particulate matter standard is a surrogate control for the non-mercury metal HAP. All lightweight aggregate kilns control particulate matter with baghouses.

We have compliance test emissions data for all lightweight aggregate kiln sources. For most sources, we have compliance test emissions data from more than one compliance test campaign. Our database of particulate matter stack emissions range from 0.001 to 0.042 gr/dscf.

To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the APCD Approach. The calculated floor is 0.029 gr/dscf, which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained. The calculated floor level of 0.029 gr/dscf is less stringent than the interim standard of 0.025 gr/dscf, which is a regulatory limit relevant in identifying the floor level (so as to avoid any backsliding from a current level of performance achieved by all lightweight aggregate kilns, and hence, the level of minimal stringency at which EPA could calculate the MACT floor). Therefore, we are proposing the floor level as the current emission standard of 0.025 gr/dscf. This emission level is currently being achieved by all sources.

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2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We evaluated improved particulate matter control to achieve a beyond-the-floor standard of 29 mg/dscm (0.013 gr/dscf). The national incremental annualized compliance cost for lightweight aggregate kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $0.32 million and would provide an incremental reduction in particulate matter emissions beyond the MACT floor controls of 8.6 tons per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between further improvements to control particulate matter and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of solid waste generated by 9 tons per year beyond the requirements to achieve the floor level. Therefore, based on these factors and costs of approximately $36,600 per additional ton of particulate matter removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control.

3. What Is the Rationale for the MACT Floor for New Sources?

Particulate matter emissions from new lightweight aggregate kilns are currently limited to 0.025 gr/dscf by § 63.1205(b)(7). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6797, February 13, 2002).

The MACT floor for new sources for particulate matter would be 23 mg/dscm (0.0099 gr/dscf), which considers emissions variability. This is an emission level that the single best performing source identified with the APCD Approach could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We evaluated improved particulate matter control to achieve a beyond-the-floor standard. We evaluated a beyond-the-floor level of 12 mg/dscm (0.005 gr/dscf). The incremental annualized compliance cost for a new lightweight aggregate kiln with an average gas flow rate to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $91,400 million and would provide an incremental reduction in particulate matter emissions of approximately 2 tons per year. Nonair quality health and environmental impacts and energy effects were also evaluated and are included in the cost estimates. Therefore, based on these factors and costs of approximately $45,600 per additional ton of particulate removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control for new lightweight aggregate kilns. Therefore, we propose a particulate matter standard of 2.3 mg/dscm (0.0099 gr/dscf) for new sources.

D. What Are the Proposed Standards for Semivolatile Metals?

We are proposing to establish standards for existing lightweight aggregate kilns that limit emissions of semivolatile metals (cadmium and lead, combined) to 3.1 × 10−4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste and 250 μg/dscm. The proposed standard for new sources is 2.4 × 10−5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste and 43 μg/dscm.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Semivolatile metals emissions from existing lightweight aggregate kilns are currently limited to 250 μg/dscm by § 63.1205(a)(3). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6797). Lightweight aggregate kilns control emissions of semivolatile metals with baghouses and/or by controlling the feed concentration of semivolatile metals in the hazardous waste.

We have compliance test emissions data for all lightweight aggregate kiln sources. For most sources, we have compliance test emissions data from more than one compliance test campaign. Semivolatile metal stack emissions range from approximately 1 to over 1,600 μg/dscm. These emissions are expressed as mass of semivolatile metals (from all feedstocks) per unit volume of stack gas. Hazardous waste thermal emissions range from 3.0 × 10−6 to 1.1 × 10−3 lbs per million Btu. Hazardous waste thermal emissions represent the mass of semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. For most lightweight aggregate kilns, lead was the major contributor to semivolatile emissions.

To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the SRE/Feed Approach. The calculated floor is 3.1 × 10−4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 71% of sources, and would reduce semivolatile metals emissions by 30 pounds per year.

To put the proposed floor level in context for a hypothetical lightweight aggregate kiln that gets 90% of its required heat input from hazardous waste, a thermal emissions level of 3.1 × 10−4 lbs semivolatile metals attributable to the hazardous waste per million Btu heat input of the hazardous waste equates approximately to a stack gas concentration of 300 μg/dscm. This estimated stack gas concentration does not include contributions to emission from other semivolatile metals-containing materials such as raw materials and fossil fuels. The additional contribution to stack emissions of semivolatile metals in an average raw material is estimated to range as high as 20 to 50 μg/dscm. Thus, for the hypothetical lightweight aggregate kiln the thermal emissions floor level of 3.1 × 10−4 lbs semivolatile metals attributable to the hazardous waste per million Btu heat input of the hazardous waste is estimated to be less than 350 μg/dscm, which is higher than the current interim standard of 250 μg/dscm. Given that comparing the proposed floor level to the interim standard requires numerous assumptions (as just illustrated) including hazardous waste fuel replacement rates, heat input requirements per ton of clinker, concentrations of semivolatile metals in the raw material and fuels, and system removal efficiency, we have included a more detailed analysis in the background document.[118] Our detailed analysis indicates the proposed floor level could be less stringent than the interim standard for some sources. In order to avoid any backsliding from the current level of performance achieved by all lightweight aggregate kilns, we propose a dual standard: the semivolatile metals standard as both the Start Printed Page 21268calculated floor level, expressed as a hazardous waste thermal emissions level, and the current interim standard. This would ensure that all sources are complying with a limit that is at least as stringent as the interim standard.

In the September 1999 final rule, we acknowledged that a lightweight aggregate kiln using properly designed and operated MACT control technologies, including controlling the levels of metals in the hazardous waste, may not be capable of achieving a given emission standard because of mineral and process raw material contributions that might cause an exceedance of the emission standard. To address this concern, we promulgated a provision that allows kilns to petition for alternative standards provided that they submit site-specific information that shows raw material hazardous air pollutant contributions to the emissions prevent the source from complying with the emission standard even though the kiln is using MACT control. See § 63.1206(b)(9). If we were to adopt the proposed dual semivolatile (and low volatile) metals standards approach, we propose to retain the alternative standard provisions under § 63.1206(b)(9) for semivolatile metals (and low volatile metals). We invite comment on this approach.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We identified three potential beyond-the-floor techniques for control of semivolatile metals: (1) Improved particulate matter control; (2) control of semivolatile metals in the hazardous waste feed; and (3) control of the semivolatile metals in the raw materials and fuels.

Improved Particulate Matter Control. Controlling particulate matter also controls emissions of semivolatile metals. Our data show that all lightweight aggregate kilns are already achieving greater than 99.7% system removal efficiency for semivolatile metals, with many attaining 99.9% removal. Thus, additional control of particulate matter are likely to result in only modest additional reductions of semivolatile metals emissions. We evaluated a beyond-the-floor level of 1.5 × 10−4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which represents a 50% reduction in emissions from MACT floor levels. The national incremental annualized compliance cost for lightweight aggregate kilns to meet this beyond-the-floor level rather than to comply with the floor controls would be approximately $84,200 and would provide an incremental reduction in semivolatile metals emissions beyond the MACT floor controls of 20 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between further improvements to control particulate matter and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of solid waste generated by less than 10 tons per year and would also require sources to use an additional 2,000 kW-hours per year beyond the requirements to achieve the floor level. The costs associated with these impacts are accounted for in the national annualized compliance cost estimates. Therefore, based on these factors and costs of approximately $7.6 million per additional ton of semivolatile metals removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control.n

Feed Control of Semivolatile Metals in the Hazardous Waste. We also evaluated a beyond-the-floor level of 2.5 × 10−4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which represents a 20% reduction from the floor level. We chose a 20% reduction as a level representing the practicable extent that additional feedrate control of semivolatile metals in hazardous waste can be used and still achieve appreciable emissions reductions. The national incremental annualized compliance cost for lightweight aggregate kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $6,000 and would provide an incremental reduction in semivolatile metals emissions beyond the MACT floor controls of less than one pound per year. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the national compliance cost estimates. Therefore, based on these factors and costs of approximately $20 million per additional ton of semivolatile metals removed, we are not proposing a beyond-the-floor standard based on feed control of semivolatile metals in the hazardous waste.

Feed Control of Semivolatile Metals in the Raw Materials and Auxiliary Fuels. Lightweight aggregate kilns could achieve a reduction in semivolatile metal emissions by substituting a raw material containing lower levels of cadmium and/or lead for a primary raw material with higher levels of these metals. We believe that this beyond-the-floor option would even be less cost-effective than either of the options discussed above, however. Given that facilities are sited near the primary raw material supply, acquiring and transporting large quantities of an alternate source of raw materials is likely to be cost-prohibitive. Therefore, we are not proposing a beyond-the-floor standard based on limiting semivolatile metals in the raw material feed.

We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of semivolatile metals would be an appropriate control option for sources. Two facilities typically burn hazardous waste at a fuel replacement rate of 100%, while one facility has burned a combination of fuel oil and natural gas in addition to the hazardous waste. We considered switching only to natural gas as the auxiliary fuel as a potential beyond-the-floor option. We do not believe that switching to natural gas is a viable control option for similar reasons discussed above for cement kilns.

For the reasons discussed above, we propose to establish the emission standard for existing lightweight aggregate kilns at 3.1 × 10−4 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste and 250 μg/dscm.

3. What Is the Rationale for the MACT Floor for New Sources?

Semivolatile metals emissions from new lightweight aggregate kilns are currently limited to 43 μg/dscm by § 63.1205(b)(3). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6797).

The MACT floor for new sources for semivolatile metals would be 2.4 × 10−5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu in the hazardous waste, which considers emissions variability. This is an emission level that the single best performing source identified with the SRE/Feed Approach could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained.

To put the proposed floor level in context for a hypothetical lightweight aggregate kiln that gets 90% of its required heat input from hazardous waste, a thermal emissions level of 2.4 × 10−5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste can equate to a stack gas concentration as high as 60 μg/dscm, including contributions from typical raw materials. Thus, for the Start Printed Page 21269hypothetical lightweight aggregate kiln the thermal emissions floor level of 2.4 × 10−5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste is estimated to be as high as 60 μg/dscm, which is higher than the current interim standard of 43 μg/dscm. In order to avoid any backsliding from the current level of performance for a new lightweight aggregate kiln source, we propose a dual standard: the semivolatile metals standard as both the calculated floor level, expressed as a hazardous waste thermal emissions level, and the current interim standard. This would ensure that all sources are complying with a limit that is at least as stringent as the interim standard. Thus, the proposed MACT floor for new lightweight aggregate kilns is 2.4 × 10−5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste and 43 μg/dscm.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We identified the same three potential beyond-the-floor techniques for control of semivolatile metals: (1) Improved control of particulate matter; (2) control of semivolatile metals in the hazardous waste feed; and (3) control of semivolatile metals in the raw materials and fuels.

Improved Particulate Matter Control. Controlling particulate matter also controls emissions of semivolatile metals. We evaluated improved control of particulate matter based on a state-of-the-art baghouse using a high quality fabric filter bag material as beyond-the-floor control for further reductions in semivolatile metals emissions. We evaluated a beyond-the-floor level of 1.2 × 10−5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. The incremental annualized compliance cost for a new lightweight aggregate kiln with average gas flowrate to meet this beyond-the-floor level, rather than to comply with the floor level, would be approximately $0.11 million and would provide an incremental reduction in semivolatile metals emissions of approximately 13 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the cost estimates. We estimate that this beyond-the-floor option would increase the amount of solid waste generated by 3 tons per year and would also require sources to use an additional 0.3 million kW-hours per year beyond the requirements to achieve the floor level. Therefore, based on these factors and costs of approximately $18 million per ton of semivolatile metals removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control for new lightweight aggregate kilns.

Feed Control of Semivolatile Metals in the Hazardous Waste. We also believe that the expense for further reduction in semivolatile metals emissions based on further control of semivolatile metals concentrations in the hazardous waste is not warranted. We considered a beyond-the-floor level of 1.9 × 10−5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which represents a 20% reduction from the floor level. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the compliance cost estimates. For similar reasons discussed above for existing sources, we conclude that a beyond-the-floor standard based on controlling the concentration of semivolatile metals levels in the hazardous waste feed would not be justified because of the costs and estimated emission reductions.

Feed Control of Semivolatile Metals in the Raw Materials and Auxiliary Fuels. Lightweight aggregate kilns could achieve a reduction in semivolatile metals emissions by substituting a raw material containing lower levels of cadmium and lead for a primary raw material with a higher level. For a new source at an existing facility, we believe that this beyond-the-floor option would not be cost-effective due to the costs of transporting large quantities of an alternate source of raw material to the facility. Given that the plant site already exists and is sited near the source of raw material, replacing the raw materials at the plant site with lower semivolatile metals-containing materials would be the source's only option. For a kiln constructed at a new greenfield site, we are not aware of any information and data from a source that has undertaken or is currently located at a site whose raw materials are inherently lower in semivolatile metals that would consistently achieve reduced semivolatile metals emissions. Further, we are uncertain as to what beyond-the-floor standard would be achievable using, if it exists, a lower semivolatile metals-containing raw material. Although we are doubtful that selecting a new plant site based on the content of metals in the raw material is a realistic beyond-the-floor option considering the numerous additional factors that go into such a decision, we solicit comment on whether and what level of a beyond-the-floor standard based on controlling the level of semivolatile metals in the raw materials is appropriate.

We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of semivolatile metals would be an appropriate control option for sources. Two facilities typically burn hazardous waste at a fuel replacement rate of 100%, while one facility has burned a combination of fuel oil and natural gas in addition to the hazardous waste. We considered switching only to natural gas as the auxiliary fuel as a potential beyond-the-floor option. We do not believe that switching to natural gas is a viable control option for the same reasons discussed above for cement kilns.

For the reasons discussed above, we propose to establish the emission standard for new lightweight aggregate kilns at 2.4 × 10−5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat content in the hazardous waste and 43 μg/dscm.

E. What Are the Proposed Standards for Low Volatile Metals?

We are proposing to establish standards for existing lightweight aggregate kilns that limit emissions of low volatile metals (arsenic, beryllium, and chromium) to 9.5 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste and 110 μg/dscm. The proposed standard for new sources is 3.2 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste and 110 μg/dscm.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Low volatile metals emissions from existing lightweight aggregate kilns are currently limited to 110 μg/dscm by § 63.1205(a)(4). This standard was promulgated in the Interim Standards Rule (see 67 FR at 6797). Lightweight aggregate kilns control emissions of low volatile metals with baghouses and/or by controlling the feed concentration of low volatile metals in the hazardous waste.

We have compliance test emissions data for all lightweight aggregate kiln sources. For most sources, we have compliance test emissions data from more than one compliance test campaign. Low volatile metal stack emissions range from approximately 16 to 200 μg/dscm. These emissions are expressed as mass of low volatile metals (from all feedstocks) per unit volume of Start Printed Page 21270stack gas. Hazardous waste thermal emissions range from 9.7 × 10−6 to 1.8 × 10−4 lbs per million Btu. Hazardous waste thermal emissions represent the mass of low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. For most lightweight aggregate kilns, chromium was the major contributor to low volatile emissions.

To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the SRE/Feed Approach. The calculated floor is 9.5 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 57% of sources and would reduce low volatile metals emissions by 30 pounds per year.

To put the proposed floor level in context for a hypothetical lightweight aggregate kiln that gets 90% of its required heat input from hazardous waste, a thermal emissions level of 9.5 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste equates approximately to a stack gas concentration of 90 μg/dscm. This estimated stack gas concentration does not include contributions to emission from other low volatile metals-containing materials such as raw materials. The additional contribution to stack emissions of low volatile metals in an average raw material is estimated to be 50 μg/dscm. Thus, for the hypothetical lightweight aggregate kiln the thermal emissions floor level of 9.5 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste is estimated to be 150 μg/dscm, which is higher than the current interim standard of 110 μg/dscm. Given that comparing the proposed floor level to the interim standard requires numerous assumptions including hazardous waste fuel replacement rates, heat input requirements per ton of clinker, concentrations of low volatile metals in the raw material and fuels, and system removal efficiency, we have included a more detailed analysis in the background document.[119] Our detailed analysis indicates the proposed floor level could be less stringent than the interim standard for some sources. In order to avoid any backsliding from the current level of performance achieved by all lightweight aggregate kilns, we propose a dual standard: the low volatile metals standard as both the calculated floor level, expressed as a hazardous waste thermal emissions level, and the current interim standard. This would ensure that all sources are complying with a limit that is at least as stringent as the interim standard.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We identified three potential beyond-the-floor techniques for control of low volatile metals: (1) Improved particulate matter control; (2) control of low volatile metals in the hazardous waste feed; and (3) control of the low volatile metals in the raw materials and fuels.

Improved Particulate Matter Control. Controlling particulate matter also controls emissions of low volatile metals. Our data show that all lightweight aggregate kilns are already achieving greater than 99.8% system removal efficiency for low volatile metals, with many attaining 99.9% or greater removal. Thus, additional control of particulate matter emissions is likely to result in only a small increment in reduction of low volatile metals emissions. We evaluated a beyond-the-floor level of 4.7 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. The national incremental annualized compliance cost for lightweight aggregate kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $0.24 million and would provide an incremental reduction in low volatile metals emissions beyond the MACT floor controls of 28 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated to estimate the impacts between further improvements to control particulate matter and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of solid waste generated by less than 30 tons per year and would also require sources to use an additional 46,000 kW-hours of energy per year. Therefore, based on these factors and costs of approximately $17 million per additional ton of low volatile metals removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control.

Feed Control of Low Volatile Metals in the Hazardous Waste. We also evaluated a beyond-the-floor level of 7.6 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which represents a 20% reduction from the floor level. We chose a 20% reduction as a level representing the practicable extent that additional feedrate control of low volatile metals in hazardous waste (beyond feedrate control that may be necessary to achieve the floor level) can be used and still achieve modest emissions reductions. The national incremental annualized compliance cost for lightweight aggregate kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $150,000 and would provide an incremental reduction in low volatile metals emissions beyond the MACT floor controls of 14 pounds per year. Nonair quality health and environmental impacts and energy effects were considered and are included in the cost estimates. Therefore, based on these factors and costs of approximately $22 million per additional ton of low volatile metals removed, we are not proposing a beyond-the-floor standard based on feed control of low volatile metals in the hazardous waste.

Feed Control of Low Volatile Metals in the Raw Materials and Auxiliary Fuels. Lightweight aggregate kilns could achieve a reduction in low volatile metal emissions by substituting a raw material containing lower levels of arsenic, beryllium, and/or chromium for a primary raw material with higher levels of these metals. We believe that this beyond-the-floor option would even be less cost-effective than either of the options discussed above, however. Given that facilities are sited near the primary raw material supply, acquiring and transporting large quantities of an alternate source of raw materials is likely to be cost-prohibitive. Therefore, we are not proposing a beyond-the-floor standard based on limiting low volatile metals in the raw material feed.

We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of low volatile metals would be an appropriate control option for sources. Two facilities typically burn hazardous waste at a fuel replacement rate of 100%, while one facility has burned a combination of fuel oil and natural gas in addition to the hazardous waste. We considered switching only to natural gas as the auxiliary fuel as a potential beyond-the-Start Printed Page 21271floor option. We do not believe that switching to natural gas is a viable control option for similar reasons discussed above for cement kilns.

For the reasons discussed above, we propose to establish the emission standard for existing lightweight aggregate kilns at 9.5 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste and 110 μg/dscm.

3. What Is the Rationale for the MACT Floor for New Sources?

Low volatile metals emissions from new lightweight aggregate kilns are currently limited to 110 μg/dscm by § 63.1205(b)(4). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6797).

The MACT floor for new sources for low volatile metals would be 3.2 × 10−5 lbs low volatile metals emissions in the hazardous waste per million Btu in the hazardous waste, which considers emissions variability. This is an emission level that the single best performing source identified with the SRE/Feed Approach could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained.

As discussed for existing sources, in order to avoid any backsliding from the current level of performance for a new lightweight aggregate kiln source, we propose a dual standard: the low volatile metals standard as both the calculated floor level, expressed as a hazardous waste thermal emissions level, and the current interim standard. This would ensure that all sources are complying with a limit that is at least as stringent as the interim standard. Thus, the proposed MACT floor for new lightweight aggregate kilns is 3.2 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste and 110 μg/dscm.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We considered three potential beyond-the-floor techniques for control of low volatile metals: (1) Improved particulate matter control; (2) control of low volatile metals in the hazardous waste feed; and (3) control of the low volatile metals in the raw materials and fuels.

Improved Particulate Matter Control. Controlling particulate matter also controls emissions of low volatile metals. We evaluated improved control of particulate matter based on a state-of-the-art baghouse using a high quality fabric filter bag material as beyond-the-floor control for further reductions in low volatile metals emissions. We evaluated a beyond-the-floor level of 1.6 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste. The incremental annualized compliance cost for a new lightweight aggregate kiln with average gas flowrate to meet this beyond-the-floor level, rather than to comply with the floor level, would be approximately $0.11 million and would provide an incremental reduction in low volatile metals emissions of approximately 16 pounds per year. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the cost estimates. We estimate that this beyond-the-floor option would increase the amount of solid waste generated by 3 tons per year and would also require sources to use an additional 0.3 million kW-hours per year beyond the requirements to achieve the floor level. Therefore, based on these factors and costs of nearly $14 million per ton of low volatile metals removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control for new lightweight aggregate kilns.

Feed Control of Low Volatile Metals in the Hazardous Waste. We also believe that the expense for further reduction in low volatile metals emissions based on further control of low volatile metals concentrations in the hazardous waste is not warranted. We considered a beyond-the-floor level of 2.6 × 10−5 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which represents a 20% reduction from the floor level. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the compliance cost estimates. For similar reasons discussed above for existing sources, we conclude that a beyond-the-floor standard based on controlling the concentration of low volatile metals levels in the hazardous waste feed would not be justified because of the costs and estimated emission reductions.

Feed Control of Low Volatile Metals in the Raw Materials and Auxiliary Fuels. Lightweight aggregate kilns could achieve a reduction in low volatile metals emissions by substituting a raw material containing lower levels of arsenic, beryllium, and/or chromium for a primary raw material with a higher level. For a new source at an existing facility, we believe that this beyond-the-floor option would not be cost-effective due to the costs of transporting large quantities of an alternate source of raw material to the facility. Given that the plant site already exists and is sited near the source of raw material, replacing the raw materials at the plant site with lower low volatile metals-containing materials would be the source's only option. For a kiln constructed at a new greenfield site, we are not aware of any information and data from a source that has undertaken or is currently located at a site whose raw materials are inherently lower in low volatile metals that would consistently achieve reduced low volatile metals emissions. Further, we are uncertain as to what beyond-the-floor standard would be achievable using, if it exists, a lower low volatile metals-containing raw material. Although we are doubtful that selecting a new plant site based on the content of metals in the raw material is a realistic beyond-the-floor option considering the numerous additional factors that go into such a decision, we solicit comment on whether and what level of a beyond-the-floor standard based on controlling the level of low volatile metals in the raw materials is appropriate.

We also considered whether fuel switching to an auxiliary fuel containing a lower concentration of low volatile metals would be an appropriate control option for sources. Two facilities typically burn hazardous waste at a fuel replacement rate of 100%, while one facility has burned a combination of fuel oil and natural gas in addition to the hazardous waste. We considered switching only to natural gas as the auxiliary fuel as a potential beyond-the-floor option. We do not believe that switching to natural gas is a viable control option for the same reasons discussed above for cement kilns.

For the reasons discussed above, we propose to establish the emission standard for new lightweight aggregate kilns at 3.2 × 105 lbs low volatile metals emissions attributable to the hazardous waste per million Btu heat content in the hazardous waste and 110 μg/dscm.

F. What Are the Proposed Standards for Hydrogen Chloride and Chlorine Gas?

We are proposing to establish standards for existing and new lightweight aggregate kilns that limit total chlorine emissions (hydrogen chloride and chlorine gas, combined, reported as a chloride equivalent) to 600 ppmv. Although we are also proposing to invoke CAA section 112(d)(4) to establish alternative risk-based standards in lieu of the MACT emission standards for total chlorine, the risk-based standards would be capped at the Start Printed Page 21272interim standards. Given that we are proposing MACT standards equivalent to the interim standards—600 ppmv, an emission level you are currently achieving—you would not be eligible for the section 112(d)(4) risk-based standards. See Part Two, Section XIII for additional details.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Total chlorine emissions from existing cement kilns are limited to 600 ppmv by § 63.1205(a)(6). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6797). One of the three lightweight aggregate facilities uses a venturi scrubber to remove total chlorine from the gas stream. The system removal efficiency (SRE) achieved by this facility during compliance testing shows removal efficiencies ranging from 96 to 99%. Sources at the other two facilities do not use air pollution control equipment to capture emissions of total chlorine, and, therefore, SREs are negligible.

The majority of the chlorine fed to the lightweight aggregate kiln during a compliance test comes from the hazardous waste. In all but a few cases the hazardous waste contribution to the total amount of chlorine fed to the kiln represented at least 80% of the total loading to the kiln. The proposed MACT floor control for total chlorine is, in part, based on controlling the concentration of chlorine in the hazardous waste. The chlorine concentration in the hazardous waste will affect emissions of total chlorine at a given SRE because emissions will increase as the chlorine loading increases.

We have compliance test emissions data for all lightweight aggregate kiln sources. For most sources, we have compliance test emissions data from more than one compliance test campaign. Total chlorine emissions range from 14 to 116 ppmv for the source using a venturi scrubber and range from 500 to 2,400 ppmv at sources without scrubbing control equipment.

To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the SRE/Feed Approach. The calculated floor is 3.0 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained.

To put the proposed floor level in context for a hypothetical lightweight aggregate kiln that gets 90% of its required heat input from hazardous waste, a thermal emissions level of 3.0 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste equates approximately to a stack gas concentration of 1,970 ppmv. This estimated stack gas concentration does not include contributions to emission from other chlorine-containing materials such as raw materials. Given that the calculated floor level is less stringent than the current interim emission standard of 600 ppmv. In order to avoid any backsliding from the current level of performance achieved by all lightweight aggregate kilns, we are proposing the floor standard as the current emission standard of 600 ppmv. This emission level is currently being achieved by all sources.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We considered a beyond-the-floor standard of 150 ppmv based on the assumption that dry lime scrubbing will provide 75% control of hydrogen chloride.[120] In addition, for costing purposes we assumed that lightweight aggregate kilns needing total chlorine reductions to achieve the beyond-the-floor level would install the dry scrubbing system after the existing particulate matter control device and add a new, smaller baghouse to remove the products of the reaction and any unreacted lime. We chose this conservative costing approach to address potential concerns that unreacted lime and collected chloride and sulfur salts may interfere with lightweight aggregate dust use practices.

The national incremental annualized compliance cost for lightweight aggregate kilns to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $1.9 million and would provide an incremental reduction in total chlorine emissions beyond the MACT floor controls of 280 tons per year, for a cost-effectiveness of $6,800 per additional ton of total chlorine removed. We evaluated nonair quality health and environmental impacts and energy effects associated with this beyond-the-floor standard and estimate that this beyond-the-floor option would increase the amount of solid waste generated by 12,700 tons per year and would also require sources to use an additional 175,000 kW-hours per year and 31 million gallons of water beyond the requirements to achieve the floor level.

We note that a cost of $6,800 per additional ton of total chlorine removed is in the “grey area” between a cost the Agency has concluded is cost-effective and a cost the Agency has concluded is not cost-effective under other MACT rules. EPA concluded that a cost of $1,100 per ton of total chlorine removed for hazardous waste burning lightweight aggregate kilns was cost-effective in the 1999 MACT final rule. See 68 FR at 52900. EPA concluded, however, that a cost of $45,000 per ton of hydrogen chloride removed was not cost-effective for industrial boilers. See 68 FR at 1677. Consequently, we are concerned that a cost of $6,800 per additional ton of total chlorine removed is not warranted. Therefore, after considering cost-effectiveness and nonair quality health and environmental impacts and energy effects, we are not proposing a beyond-the-floor standard.

We specifically request comment on whether a beyond-the-floor standard is warranted.

3. What Is the Rationale for the MACT Floor for New Sources?

Total chlorine emissions from new lightweight aggregate kilns are currently limited to 600 ppmv by § 63.1205(b)(6). This standard was promulgated in the Interim Standards Rule (See 67 FR at 6797). The MACT floor for new sources for total chlorine would be 0.93 lbs chlorine in the hazardous waste per million Btu in the hazardous waste, which considers emissions variability.

To put the proposed floor level in context for a hypothetical lightweight aggregate kiln that gets 90% of its required heat input from hazardous waste, a thermal emissions level of 0.93 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste equates approximately to a stack gas concentration of 610 ppmv. This estimated stack gas concentration does not include contributions to emission from other chlorine-containing materials such as raw materials. Given that the calculated floor level is less stringent than the current interim emission standard of 600 ppmv. In order to avoid any backsliding from the current standard for a new lightweight aggregate kilns, we are proposing the floor standard as the current emission standard of 600 ppmv.

Start Printed Page 21273

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

Similar to existing sources, we considered a beyond-the-floor standard of 150 ppmv based on the assumption that dry lime scrubbing will provide 75% control of hydrogen chloride. The incremental annualized compliance cost for a new lightweight aggregate kiln with average gas flowrate to meet this beyond-the-floor level, rather than to comply with the floor level, would be approximately $0.42 million and would provide an incremental reduction in total chlorine emissions of approximately 150 tons per year for a cost-effectiveness of approximately $2,800 per additional ton of total chlorine removed. Nonair quality health and environmental impacts and energy effects were evaluated and are included in the cost estimates. We estimate that this beyond-the-floor option would increase the amount of solid waste generated by 23 tons per year and would also require sources to use an additional 0.3 million kW-hours per year and 2 million gallons of water beyond the requirements to achieve the floor level.

A cost of $2,800 per additional ton of total chlorine removed is in the “grey area” between a cost the Agency has concluded is cost-effective and a cost the Agency has concluded is not cost-effective under other MACT rules, as discussed above. Therefore, we are concerned that a cost-effectiveness of $2,800 per additional ton of total chlorine removed may not be warranted. After considering cost-effectiveness and nonair quality health and environmental impacts and energy effects, we are not proposing a beyond-the-floor standard.

We specifically request comment on whether a beyond-the-floor standard is warranted.

G. What Are the Standards for Hydrocarbons and Carbon Monoxide?

Hydrocarbon and carbon monoxide standards are surrogates to control emissions of organic hazardous air pollutants for existing and new lightweight aggregate kilns. The standards limit hydrocarbons and carbon monoxide concentrations to 20 ppmv or 100 ppmv. See §§ 63.1205(a)(5) and (b)(5). Existing and new lightweight aggregate kilns can elect to comply with either the hydrocarbon limit or the carbon monoxide limit on a continuous basis. Sources that comply with the carbon monoxide limit on a continuous basis must also demonstrate compliance with the hydrocarbon standard during the comprehensive performance test. However, continuous hydrocarbon monitoring following the performance test is not required. The rationale for these decisions are discussed in the September 1999 final rule (64 FR at 52900). We view the standards for hydrocarbons and carbon monoxide as unaffected by the Court's vacature of the challenged regulations in its decision of July 24, 2001. We therefore are not proposing these standards for lightweight aggregate kilns, but rather are mentioning them here for the reader's convenience.

H. What Are the Standards for Destruction and Removal Efficiency?

The destruction and removal efficiency (DRE) standard is a surrogate to control emissions of organic hazardous air pollutants other than dioxin/furans. The standard for existing and new lightweight aggregate kilns requires 99.99% DRE for each principal organic hazardous constituent, except that 99.9999% DRE is required if specified dioxin-listed hazardous wastes are burned. See §§ 63.1205(c). The rationale for these decisions are discussed in the September 1999 final rule (64 FR at 52902). We view the standards for DRE as unaffected by the Court's vacature of the challenged regulations in its decision of July 24, 2001. We therefore are not proposing these standards for lightweight aggregate kilns, but rather are mentioning them here for the reader's convenience.

X. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste Burning Solid Fuel-Fired Boilers?

The proposed standards for existing and new solid fuel-fired boilers that burn hazardous waste are summarized in the table below. See proposed § 63.1216.

Proposed Standards for Existing and New Solid Fuel-Fired Boilers

Hazardous air pollutant or surrogateEmission standard 1
Existing sourcesNew sources
Dioxin and furan100 ppmv carbon monoxide or 10 ppmv hydrocarbons.100 ppmv carbon monoxide or 10 ppmv hydrocarbons.
Mercury10 μg/dscm10 μg/dscm.
Particulate matter69 mg/dscm (0.030 gr/dscf)34 mg/dscm (0.015 gr/dscf).
Semivolatile metals170 μg/dscm170 μg/dscm.
Low volatile metals210 μg/dscm190 μg/dscm.
Hydrogen chloride and chlorine gas 2440 ppmv or the alternative emission limits under § 63.121573 ppmv or the alternative emission limits under § 63.1215.
Carbon monoxide or hydrocarbons 3100 ppmv carbon monoxide or 10 ppmv hydrocarbons100 ppmv carbon monoxide or 10 ppmv hydrocarbons.
Destruction and Removal EfficiencyFor existing and new sources, 99.99% for each principal organic hazardous constituent (POHC). For sources burning hazardous wastes F020, F021, F022, F023, F026, or F027, however, 99.9999% for each POHC.
1 All emission standards are corrected to 7% oxygen, dry basis.
2 Combined standard, reported as a chloride (Cl(−)) equivalent.
3 Hourly rolling average. Hydrocarbons reported as propane.

We considered whether fuel switching could be considered a control technology to achieve MACT floor control. We investigated whether fuel switching would achieve lower HAP emissions and whether it could be technically achieved considering the existing design of solid fuel-fired boilers. We also considered the availability of various types of fuel. After considering these factors, we determined that fuel switching is not an appropriate control technology for purposes of determining the MACT floor level of control. This decision is based on the overall effect of fuel switching on HAP emissions, technical Start Printed Page 21274and design considerations, and concerns about fuel availability.

We determined that while fuel switching from coal to natural gas or oil would decrease particulate matter and some metal HAP emissions, emissions of some organic HAP would increase, resulting in uncertain benefits.[121] We believe that it is inappropriate in a MACT rulemaking to consider as MACT a control option that potentially will decrease emissions of one HAP while increasing emissions of another HAP. In order to adopt such a strategy, we would need to assess the relative risk associated with each HAP emitted, and determine whether requiring the control in question would result in overall lower risk. Such an analysis is not appropriate at this stage in the regulatory process. For example, the term “clean coal” refers to coal that is lower in sulfur content and not necessarily lower in HAP content. Data gathered by EPA also indicates that within specific coal types HAP content can vary significantly. Switching to a low sulfur coal may actually increase emissions of some HAP. Therefore, it is not appropriate for EPA to include fuel switching to a low sulfur coal as part of the MACT standards for boilers that burn hazardous waste.

We also considered the availability of alternative fuel types. Natural gas pipelines are not available in all regions of the U.S., and natural gas is simply not available as a fuel for many solid fuel-fired boilers. Moreover, even where pipelines provide access to natural gas, supplies of natural gas may not be adequate. For example, it is common practice in cities during winter months (or periods of peak demand) to prioritize natural gas usage for residential areas before industrial usage. Requiring EPA regulated combustion units to switch to natural gas would place an even greater strain on natural gas resources. Consequently, even where pipelines exist, some units would not be able to run at normal or full capacity during these times if shortages were to occur. Therefore, under any circumstances, there would be some units that could not comply with a requirement to switch to natural gas.

In addition, we have significant concern that switching fuels would be infeasible for sources designed and operated to burn specific fuel types. Changes in the type of fuel burned by a boiler may require extensive changes to the fuel handling and feeding system (e.g., a stoker-fired boiler using coal as primary fuel would need to be redesigned to handle fuel oil or gaseous fuel as the primary fuel). Additionally, burners and combustion chamber designs are generally not capable of handling different fuel types, and generally cannot accommodate increases or decreases in the fuel volume and shape. Design changes to allow different fuel use, in some cases, may reduce the capacity and efficiency of the boiler. Reduced efficiency may result in less complete combustion and, thus, an increase in organic HAP emissions. For the reasons discussed above, we conclude that fuel switching to cleaner solid fuels or to liquid or gaseous fuels is not an appropriate criteria for identifying the MACT floor level of control for solid fuel-fired boilers.

A. What Is the Rationale for the Proposed Standards for Dioxin and Furan?

The proposed standard for dioxin/furan for existing and new sources is compliance with the proposed carbon monoxide or hydrocarbon (CO/HC) emission standard and compliance with the proposed destruction and removal efficiency (DRE) standard. The CO/HC and DRE standards control emissions of organic HAPs in general, and are discussed in Sections G and H below. This standard ensures that boilers operate under good combustion practices as a surrogate for dioxin/furan control. Operating under good combustion practices minimizes levels of products of incomplete combustion, including potentially dioxin/furan, and organic compounds that could be precursors for post-combustion formation of dioxin/furan. The rationale for the dioxin/furan standard is discussed below.

1. What Is the Rationale for the MACT Floor for Existing Sources?

The proposed MACT floor control for existing sources is compliance with the proposed CO/HC emission standard and compliance with the proposed DRE standard.

Solid fuel-fired boilers that burn hazardous waste cofire the hazardous waste with coal at firing rates of 6-33% of total heat input. We have dioxin/furan emission data for one source, and those emissions are 0.07 ng TEQ/dscm.

Although dioxin/furan can be formed post-combustion in an electrostatic precipitator or baghouse that is operated at temperatures within the range of 400° to 750°F, the boiler for which we have dioxin/furan emissions data is equipped with an electrostatic precipitator that operated at 500°F during the emissions test. Although this is well within the optimum temperature range for formation of dioxin/furan, dioxin/furan emissions were low. In addition, this boiler fed chlorine at levels four times greater than any other solid fuel boiler.[122] We also have emissions data from 16 nonhazardous waste coal-fired boilers equipped with electrostatic precipitators and baghouses operated at temperatures up to 480°F, all of which have dioxin/furan emissions below 0.3 ng TEQ/dscm.[123] We conclude from these data and the information discussed below that rapid quench of post-combustion gas temperatures to below 400°F—the control technique that is the basis for the MACT standards for hazardous waste burning incinerators, and cement and lightweight aggregate kilns—is not the dominant dioxin/furan control mechanism for coal-fired boilers.

We believe that sulfur contributed by the coal fuel is a dominant control mechanism by inhibiting formation of dioxin/furan. Coal generally contributes from 65% to 95% percent of the boiler's heat input with the remainder provided by hazardous waste fuel. The presence of sulfur in combustor feedstocks has been shown to dramatically inhibit the catalytic formation of dioxin/furan in downstream temperature zones from 400°F to 750°F. High sulfur coals tend to inhibit dioxin/furan formation better than low sulfur coals. Id.

Adsorption of any dioxin/furan that may be formed on coal fly ash, and subsequent capture in the electrostatic precipitator or baghouse, also may contribute to the low dioxin/furan emissions despite some boilers operating at relatively high back-end gas temperatures. This effect is similar to that of using activated carbon injection to control dioxin/furan emissions. Adsorption of dioxin/furan on fly ash is related to the carbon content of the fly ash, and, thus, the type of coal burned. Id.

Operating under good combustion conditions to minimize emissions of organic compounds such as polychlorinated biphenols, benzene, and phenol that can be precursors to dioxin/furan formation is an important requisite to control dioxin/furan emissions. Although sulfur-induced inhibition may be the dominant mechanism to control dioxin/furan Start Printed Page 21275emissions from coal-fired boilers, minimizing dioxin/furan precursors by operating under good combustion practices certainly plays a part in controlling dioxin/furan emissions.

We propose to use the CO/HC and DRE standards as surrogates to ensure that boilers operate under good combustion conditions because quantified levels of control provided by sulfur in the coal and adsorption onto collected fly ash may not be replicable by the best performing sources nor duplicable by other sources. Although coal sulfur content may be a dominant factor affecting dioxin/furan emissions, we do not know what minimum level of sulfur provides significant control. Moreover, sulfur in coal causes emissions of sulfur oxides, a major criteria pollutant, and particulate sulfates. Similarly, we cannot quantify a minimum carbon content of coal that would form carbonaceous fly ash with superior dioxin/furan adsorptive properties. In addition, restricting coal types that may be burned based on carbon content may have an adverse impact on energy production at sources burning hazardous waste as fuel. (These considerations raise the question of whether boilers operating under these conditions would still be “best” performers when these adverse impacts are taken into account.) For these reasons, and because we have emissions data from only one source, we cannot establish a numerical dioxin/furan emission standard.

Operating under good combustion practices is floor control because all hazardous waste burning boilers are required by existing RCRA regulations to operate under good combustion conditions to minimize emissions of toxic organic compounds. See § 266.104 requiring compliance with DRE and CO/HC emission standards.[124] We also find, as required by CAA section 112(h)(1), that these proposed standards are consistent with section 112(d)'s objective of reducing emissions of these HAPs to the extent achievable.

We request comment on an alternative floor that would be established as the highest dioxin/furan emission level in our data base. Because we have dioxin/furan emission data from only one coal-fired boiler that burns hazardous waste, we would combine that data point with emissions data from coal-fired boilers that do not burn hazardous waste since the factors that affect dioxin/furan emissions from these boilers are not significantly influenced by hazardous waste. These additional data would better represent the range of emissions from coal-fired boilers. Under this approach, the dioxin/furan floor would be an emission level of 0.30 ng TEQ/dscm. We would also use this approach to establish the same floor for new sources.

Finally, we note that we propose to require a one-time dioxin/furan emission test for sources that would not be subject to a numerical dioxin/furan emission standard, such as solid fuel-fired boilers. As discussed in Part Two, Section XIV.B below, the testing would assist in developing both section 112(d)(6) standards and section 112(f) residual risk standards.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

As discussed above, we propose to use the CO/HC and DRE standards as surrogates to ensure good combustion conditions, and thus, control of dioxin/furan emissions. We are not proposing beyond-the-floor standards for CO/HC and DRE, as discussion in Sections G and H below.

We investigated use of activated carbon injection or, for sources equipped with baghouses, catalytically impregnated fabric felt/membrane filter materials to achieve a beyond-the-floor standard of 0.10 ng TEQ/dscm.[125] To estimate the cost-effectiveness of these beyond-the-floor control techniques, we imputed dioxin/furan emissions levels for the six sources for which we don't have measured emissions data. To impute the missing emissions levels, we used the emissions data from the hazardous waste burning boiler as well as the emissions data from nonhazardous waste coal-fired boilers. It may be appropriate to meld these emissions data because hazardous waste burning should not affect dioxin/furan emissions from coal-fired boilers. In fact, the nonhazardous waste coal-fired boilers had somewhat higher emissions than the hazardous waste coal-fired boiler. (The emissions from the nonhazardous waste coal-fired boilers may simply represent the range of emissions that could be expected from hazardous waste coal-fired boilers, as well, given that we have emissions data from only one hazardous waste boiler.)

The national incremental annualized compliance cost for solid fuel-fired boilers to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $3.4 million and would provide an incremental reduction in dioxin/furan emissions beyond the MACT floor controls of 0.26 grams TEQ tons per year. We also evaluated the nonair quality health and environmental impacts and energy effects between activated carbon injection and controls likely to be used to meet the floor level. We estimate that this beyond-the-floor option would increase the amount of hazardous waste [126] generated by 3,300 tons per year and would also require sources to use an additional 1.2 million kW-hours per year. Based on these impacts and costs of approximately $13 million per additional grams of dioxin/furan removed, we are not proposing a beyond-the-floor standard based on activated carbon injection.

For these reasons, we propose a floor standard for dioxin/furan for existing sources of compliance with the proposed CO/HC emission standard and compliance with the proposed DRE standard.[127]

3. What Is the Rationale for the MACT Floor for New Sources?

As discussed above, we propose to use the CO/HC and DRE standards as surrogates to ensure good combustion conditions, and thus, control of dioxin/furan emissions. Because we are proposing the same DRE and CO/HC standards for existing sources and new sources as discussion in Sections G and H below, we are proposing the same dioxin/furan floor for new and existing sources.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We are not proposing beyond-the-floor standards for CO/HC for dioxin/furan for new solid fuel-fired boilers because we are not proposing beyond-the-floor standards for CO/HC and DRE Start Printed Page 21276for new sources. See discussion in Sections G and H below.

In addition, we evaluated activated carbon injection or, for sources equipped with baghouses, use of catalytically impregnated fabric felt/membrane filter materials as beyond-the-floor control for further reduction of dioxin/furan emissions to achieve a beyond-the-floor level of 0.15 ng TEQ/dscm. The incremental annualized compliance cost for a new solid fuel-fired boiler with average gas flowrate to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $0.28 million and would provide an incremental reduction in dioxin/furan emissions of approximately 0.21 grams TEQ per year, for a cost-effectiveness of $1.3 million per gram of dioxin/furan removed. We estimate that this beyond-the-floor option would increase the amount of hazardous waste (or solid waste if the source retains the Bevill exclusion under 40 CFR 266.112) generated for a new solid fuel-fired boiler with average gas flowrate by 270 tons per year and would require a source to use an additional 0.1 million kW-hours per year beyond the requirements to achieve the floor level. After considering these impacts and a cost of $1.3 million per gram of dioxin/furan removed, we conclude that a beyond-the-floor standard based on activated carbon injection or catalytically impregnated fabric felt/membrane filter is not warranted for new sources. Consequently, we propose a floor standard for dioxin/furan for new sources: Compliance with the proposed CO/HC and DRE emissions standards.

B. What Is the Rationale for the Proposed Standards for Mercury?

The proposed standard for mercury for solid fuel-fired boilers is 10 μg/dscm for both existing sources and new sources.[128]

1. What Is the Rationale for the MACT Floor for Existing Sources?

The MACT floor for existing sources is 10 μg/dscm based on adsorption of mercury onto coal fly ash and removal of fly ash by the electrostatic precipitator or baghouse.

All solid fuel-fired boilers are equipped with electrostatic precipitators or baghouses. We have compliance test emissions data for three sources equipped with electrostatic precipitators which document maximum mercury emissions ranging from 3 ug/dscm to 11 μg/dscm and system removal efficiencies of 83% to 96%. These three sources represent seven of the 12 solid fuel-fired boilers.[129] The Agency has also determined that coal-fired utility boilers can achieve significant control of mercury by adsorption on fly ash and particulate matter control.[130]

To identify the MACT floor, we evaluated the compliance test emissions data using the SRE/Feed Approach. The calculated floor is 10 μg/dscm, which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 67% of sources and would provide a reduction in mercury emissions of 0.015 tons per year.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We identified two potential beyond-the-floor techniques for control of mercury: (1) Activated carbon injection; and (2) control of mercury in the hazardous waste feed. For reasons discussed below, we are not proposing a beyond-the-floor standard for mercury.

a. Use of Activated Carbon Injection. We evaluated activated carbon injection as beyond-the-floor control for further reduction of mercury emissions. Activated carbon has been demonstrated for controlling mercury from waste combustion systems and has achieved efficiencies ranging from 80% to greater than 90% depending on factors such as: Activated carbon type/impregnation; injection rate; mercury speciation in the flue gas; and flue gas temperature. We made a conservative assumption that the use of activated carbon will provide 70% mercury control for coal-fired boilers given the low mercury levels at the floor. Applying this activated carbon removal efficiency to the mercury floor level of 10 μg/dscm would provide a beyond-the-floor level of 3.0 μg/dscm.

The national incremental annualized compliance cost for solid fuel boilers to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $1.1 million and would provide an incremental reduction in mercury emissions beyond the MACT floor controls of 0.03 tons per year. We evaluated nonair quality health and environmental impacts and energy effects and estimate that this beyond-the-floor option would increase the amount of hazardous waste (or solid waste if the source retains the Bevill exclusion under 40 CFR 266.112) generated by 1,000 tons per year and would require sources to use an additional 0.35 million kW-hours per year beyond the requirements to achieve the floor level. Based on these factors and costs of approximately $35 million per additional ton of mercury removed, we are not proposing a beyond-the-floor standard based on activated carbon injection.

b. Feed Control of Mercury in the Hazardous Waste. We also evaluated a beyond-the-floor level of 8 μg/dscm, which represents a 20% reduction from the floor level. The national incremental annualized compliance cost for solid fuel boilers to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $0.11 million and would provide an incremental reduction in mercury emissions beyond the MACT floor controls of 0.005 tons per year. Nonair quality health and environmental impacts and energy effects are not significant factors for feedrate control.

We are not proposing a beyond-the-floor standard based on feed control of mercury in the hazardous waste because it would not be cost-effective at approximately $23 million per additional ton of mercury removed. Consequently, we propose a floor standard for mercury for existing sources of 10 μg/dscm.

3. What Is the Rationale for MACT Floor for New Sources?

MACT floor for new sources would be 10 μg/dscm, the same as the floor for existing sources. This is an emission level that the single best performing source identified by the SRE/Feed Approach could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We identified the same two potential beyond-the-floor techniques for control Start Printed Page 21277of mercury: (1) Use of activated carbon injection; and (2) control of mercury in the hazardous waste feed.

We evaluated use of carbon injection for new sources to achieve a beyond-the-floor emission level of 5.0 μg/dscm. The incremental annualized compliance cost for a new solid fuel boiler with average gas flowrate to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $0.28 million and would provide an incremental reduction in mercury emissions of approximately 0.008 tons per year, for a cost-effectiveness of $37 million per ton of mercury removed. We estimate that this beyond-the-floor option would increase the amount of hazardous waste (or solid waste if the source retains the Bevill exclusion under 40 CFR 266.112) generated for a new solid fuel-fired boiler with average gas flowrate by 270 tons per year and would require a source to use an additional 0.1 million kW-hours per year beyond the requirements to achieve the floor level. After considering these impacts and, primarily, cost-effectiveness, we are not proposing a beyond-the-floor standard based on activated carbon injection for new sources. Consequently, we propose a floor standard for mercury of 10 μg/dscm for new sources.

C. What Is the Rationale for the Proposed Standards for Particulate Matter?

The proposed standards for particulate matter for solid fuel-fired boilers are 69 mg/dscm (0.030 gr/dscf) for existing sources and 34 mg/dscm (0.015 gr/dscf) for new sources.[131] The particulate matter standard serves as a surrogate for nonmercury HAP metals in emissions from the coal burned in the boiler, and for nonenumerated HAP metal emissions attributable to the hazardous waste fuel burned in the boiler.

1. What Is the Rationale for the MACT Floor for Existing Sources?

All solid fuel-fired boilers are equipped with electrostatic precipitators or baghouses. We have compliance test emissions data for seven boilers. Emissions from these seven boilers represent emissions from all 12 solid fuel-fired boilers.[132] Particulate emissions range from 0.021 gr/dscf to 0.037 gr/dscf.[133]

To identify the floor level, we evaluated the compliance test emissions data associated with the most recent test campaign using the air pollution control device approach. See discussion in Part Two, Section VI.A.2.a. The calculated floor is 140 mg/dscm (0.063 gr/dscf), which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 75% of sources. Compliance with the floor level would reduce particulate matter emissions by 33 tons per year.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We evaluated improved design, operation, and maintenance of the existing electrostatic precipitators (e.g., humidification to improve gas conditioning) and baghouses (e.g., improved bags) for these boilers to achieve a beyond-the-floor emission level of 69 mg/dscm (0.030 gr/dscf). We also evaluated a more stringent standard based on adding a polishing fabric filter to achieve a beyond-the-floor emission level of 0.015 gr/dscf. The national incremental annualized compliance cost for solid fuel boilers to meet a beyond-the-floor level of 69 mg/dscm rather than comply with the floor controls would be approximately $1.3 million and would provide an incremental reduction in particulate matter emissions beyond the MACT floor controls of 400 tons per year and an incremental reduction in metal HAP of 6.8 tons per year. We evaluated nonair quality health and environmental impacts and energy effects and estimate that this beyond-the-floor option would increase the amount of hazardous waste (or solid waste if the source retains its Bevill exclusion under 40 CFR 266.112) generated by 380 tons per year and would require sources to use an additional 3.3 million kW-hours per year and to use an additional 160 million gallons of water beyond the requirements to achieve the floor level.

Notwithstanding these nonair quality health and environmental impacts and energy effects, a beyond-the-floor standard of 69 mg/dscm (0.030 gr/dscf) based on improved particulate matter control is warranted because it is cost-effective at a cost of approximately $3,200 per additional ton of particulate matter removed and a cost of approximately $190,000 per additional ton of metal HAP removed.[134] In addition, the average incremental annualized cost would be only $120,000 per facility. We also note that, although section 112(d) only authorizes control of HAPs, and particulate matter is not itself a HAP but a surrogate for HAP metals, Congress expected the MACT program to result in significant emissions reductions of criteria air pollutants (of which particulate matter is one), and viewed this as an important benefit of the MACT (and residual risk) provisions. See 5 Legislative History at 8512 (Senate Committee Report). Finally, we note that this beyond-the-floor standard of 0.030 gr/dscf would be comparable to the floor-based standard the Agency recently promulgated for solid fuel-fired boilers that do not burn hazardous waste: 0.07 lb/MM Btu (approximately 0.034 gr/dscf). See NESHAP for Industrial/Commercial/Institutional Boilers and Process Heaters, signed Feb. 26, 2004. Because hazardous waste does not contribute substantially to particulate matter emissions from coal-fired boilers, MACT standards for solid fuel boilers should be similar irrespective of whether they burn hazardous waste.

A 34 mg/dscm beyond-the-floor standard for existing sources based on use of a polishing fabric filter would remove an additional 570 tons per year of particulate matter beyond the floor level at a cost-effectiveness of $9,800 per ton removed. We conclude that this standard would not be as cost-effective as a 69 mg/dscm standard and would result in greater nonair quality health and environmental impacts and energy effects. For these reasons, we propose a beyond-the-floor particulate matter standard of 0.030 gr/dscf (69 mg/dscm) for existing sources. We specifically request comment on whether this beyond-the-floor standard is warranted.

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3. What Is the Rationale for the MACT Floor for New Sources?

MACT floor for new sources would be 90 mg/dscm (0.040 gr/dscf), considering emissions variability. This is an emission level that the single best performing source identified by the APCD Approach (i.e., the source using a fabric filter with the lowest emissions) could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We evaluated use of a fabric filter to achieve a beyond-the-floor emission level of 34 mg/dscm (0.015 gr/dscf). The incremental annualized cost for a new solid fuel-fired boiler with average gas flowrate to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $280,000 and would provide an incremental reduction in particulate emissions of approximately 44 tons per year, for a cost-effectiveness of $6,400 per ton of particulate matter removed. We estimate that this beyond-the-floor option would increase the amount of hazardous waste (or solid waste if the source retains the Bevill exclusion under 40 CFR 266.112) generated for a new solid fuel-fired boiler with average gas flowrate by 44 tons per year and would require a source to use an additional 1.1 million kW-hours per year beyond the requirements to achieve the floor level. Notwithstanding these impacts, a standard of 34 mg/dscm (0.015 gr/dscf) is warranted because it would be cost-effective and it would remove additional nonenumerated metal HAP. We also note that this beyond-the-floor standard of 0.015 gr/dscf for new sources would be comparable to the floor-based standard the Agency recently promulgated for new solid fuel-fired boilers that do not burn hazardous waste: 0.025 lb/MM Btu (approximately 0.012 gr/dscf). See NESHAP for Industrial/Commercial/Institutional Boilers and Process Heaters, signed Feb. 26, 2004.

For these reasons, we propose a beyond-the-floor particulate matter standard of 34 mg/dscm (0.015 gr/dscf) for new sources. We specifically request comment on whether this beyond-the-floor standard is warranted.

D. What Is the Rationale for the Proposed Standards for Semivolatile Metals?

The proposed standard for semivolatile metals (lead and cadmium, combined) for solid fuel-fired boilers is 170 μg/dscm for both existing and new sources.[135]

1. What Is the Rationale for the MACT Floor for Existing Sources?

We have compliance test emissions data for four boilers. Emissions from these four boilers represent emissions from nine of the 12 solid fuel-fired boilers.[136] Semivolatile metal emissions range from 62 μg/dscm to 170 μg/dscm. These emissions are expressed as mass of semivolatile metals (from all feedstocks) per unit of stack gas.

To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the SRE/Feed Approach. The calculated floor is 170 μg/dscm, which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this floor level is being achieved by 42% of sources and would reduce semivolatile metals emissions by 0.22 tons per year.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We evaluated three beyond-the-floor approaches for semivolatile metals for existing sources: (1) Improved control of particulate matter; (2) control of semivolatile metals in the hazardous waste feed; and (3) a no-cost standard derived from the beyond-the-floor particulate matter standard. For reasons discussed below, we are not proposing a beyond-the-floor standard for semivolatile metals.

a. Improved Particulate Matter Control. Controlling particulate matter also controls emissions of semivolatile metals. Consequently, we evaluated a beyond-the-floor level of 85 μg/dscm, a 50 percent reduction in semivolatile metal emissions, that would be achieved by reducing particulate matter emissions. The national incremental annualized compliance cost for solid fuel boilers to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $0.29 million and would provide an incremental reduction in semivolatile metals emissions beyond the MACT floor controls of 0.29 tons per year. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond-the-floor standard and estimate that the amount of hazardous waste generated would increase by approximately 133 tons per year, an additional 61 million gallons per year of water would be used, and an additional 1.3 million kW-hours per year of electricity would be used. Therefore, based on these factors and costs of approximately $1 million per additional ton of semivolatile metals removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control.

b. Feed Control of Semivolatile Metals in the Hazardous Waste. We also evaluated a beyond-the-floor level of 140 μg/dscm based on additional control of semivolatile metals in the hazardous waste feed. This represents a 20% reduction from the floor level. The national incremental annualized compliance cost for solid fuel boilers to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $36,000 and would provide an incremental reduction in semivolatile metals emissions beyond the MACT floor controls of 0.046 tons per year. Although nonair quality health and environmental impacts and energy effects are not significant factors, we are not proposing a beyond-the-floor standard based on feed control of semivolatile metals in the hazardous waste because it is not cost-effective at approximately $0.78 million per additional ton of semivolatile metals removed.

c. No-cost Standard Derived from the Beyond-the-Floor Particulate Matter Standard. The beyond-the-floor standard for particulate matter would also provide beyond-the-floor control for semivolatile metals if sources were to comply with the beyond-the-floor particulate matter standard using improved particulate matter control Start Printed Page 21279rather than by reducing the feedrate of ash. To identify a beyond-the-floor emission level for semivolatile metals that would derive from the beyond-the-floor particulate matter standard, we assumed that emissions of semivolatile metals would be reduced by the same percentage that sources would need to reduce particulate matter emissions. We then developed a revised semivolatile metal emission data base considering these particulate matter standard-derived reductions and reductions needed to meet the semivolatile metal floor level. We analyzed these revised emissions to identify the best performing sources and an emission level that the average of the best performers could achieve 99 out of 100 future tests. This emission level—82 μg/dscm—is a beyond-the-floor semivolatile metal standard that can be achieved at no cost because the costs have been allocated to the particulate matter beyond-the-floor standard.

We are concerned, however, that sources may choose to comply with the beyond-the-floor particulate matter standard by controlling the feedrate of ash in the hazardous waste feed, which may or may not reduce the feedrate and emissions of metal HAP. If so, it would be inappropriate to consider the beyond-the-floor standard for semivolatile metals discussed above as a no-cost standard. We specifically request comment on whether sources may comply with beyond-the-floor particulate matter standard by controlling the feedrate of ash.

For these reasons, we propose a floor standard for semivolatile metals of 170 μg/dscm for existing sources.

3. What Is the Rationale for the MACT Floor for New Sources?

MACT floor for new sources would be 170 μg/dscm, considering emissions variability. This is the same as the floor for existing sources. This is an emission level that the single best performing source identified by the SRE/Feed Approach could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We evaluated three beyond-the-floor approaches for semivolatile metals for new sources: (1) Improved particulate matter controls; (2) control of semivolatile metals in the hazardous waste feed; and (3) a no-cost standard derived from the beyond-the-floor particulate matter standard.

a. Improved Particulate Matter Controls. We evaluated improved control of particulate matter using a fabric filter as beyond-the-floor control for further reductions in semivolatile metals emissions. We evaluated a beyond-the-floor level of 71 μg/dscm. The incremental annualized compliance cost for a new solid fuel boiler with average gas flowrate to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $0.28 million and would provide an incremental reduction in semivolatile metals emissions of approximately 0.15 tons per year, for a cost-effectiveness of $1.8 million per ton of semivolatile metals removed. We estimate that this beyond-the-floor option would increase the amount of hazardous waste (or solid waste if the source retains the Bevill exclusion under 40 CFR 266.112) generated for a new solid fuel-fired boiler with average gas flowrate by 44 tons per year and would require the source to use an additional 1.2 million kW-hours per year beyond the requirements to achieve the floor level. After considering these impacts and cost-effectiveness, we conclude that a beyond-the-floor standard for new sources based on use of a fabric filter to improve control of particulate matter is not warranted.

b. Feedrate Control. For similar reasons discussed above for existing sources, we conclude that a beyond-the-floor standard based on controlling the semivolatile metals in the hazardous waste feed would not be cost-effective.

c. No-cost Standard Derived from the Beyond-the-Floor Particulate Matter Standard. As discussed above in the context of existing sources, the beyond-the-floor standard for particulate matter would also provide beyond-the-floor control for semivolatile metals if sources were to comply with the beyond-the-floor particulate matter standard using improved particulate matter control rather than by reducing the feedrate of ash. Under this approach, the no-cost beyond-the-floor standard for semivolatile metals for new sources would be 44 μg/dscm. As discussed above, however, we are concerned that sources may choose to comply with the beyond-the-floor particulate matter standard by controlling the feedrate of ash in the hazardous waste feed, which may or may not reduce the feedrate and emissions of metal HAP. If so, it would be inappropriate to consider this beyond-the-floor standard as a no-cost standard. We specifically request comment on whether sources may comply with beyond-the-floor particulate matter standard by controlling the feedrate of ash.

For these reasons, we propose a semivolatile metals standard of 170 μg/dscm for new sources.

E. What Is the Rationale for the Proposed Standards for Low Volatile Metals?

The proposed standards for low volatile metals (arsenic, beryllium, and chromium) for solid fuel-fired boilers is 210 μg/dscm for existing sources and 190 μg/dscm for new sources.

1. What Is the Rationale for the MACT Floor for Existing Sources?

We have compliance test emissions data for four boilers. Emissions from these four boilers represent emissions from 10 of the 12 solid fuel-fired boilers.[137] Low volatile metal emissions range from 41 μg/dscm to 230 μg/dscm. These emissions are expressed as mass of low volatile metals (from all feedstocks) per unit of stack gas.

To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the SRE/Feed Approach. The calculated floor is 210 μg/dscm, which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 67% of sources and that it would reduce low volatile metals emissions by 0.45 tons per year.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We evaluated three beyond-the-floor approaches for low volatile metals for existing sources: (1) Improved control of particulate matter; (2) control of low volatile metals in the hazardous waste feed; and (3) a no-cost standard derived from the beyond-the-floor particulate matter standard. For reasons discussed below, we are not proposing a beyond-the-floor standard for low volatile metals.

a. Improved Particulate Matter Control. Controlling particulate matter also controls emissions of low volatile metals. We evaluated a beyond-the-floor level of 105 μg/dscm. The national incremental annualized compliance cost for solid fuel boilers to meet this Start Printed Page 21280beyond-the-floor level rather than comply with the floor controls would be approximately $0.32 million and would provide an incremental reduction in low volatile metals emissions beyond the MACT floor controls of 0.37 tons per year. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond-the-floor standard and estimate that the amount of hazardous waste generated would increase by approximately 83 tons per year, an additional 54 million gallons of water per year would be used, and electricity consumption would increase by 1.2 million kW-hours per year. Considering these impacts and a cost of approximately $0.87 million per additional ton of low volatile metals removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control.

b. Feed Control of Low Volatile Metals in the Hazardous Waste. We also evaluated a beyond-the-floor level of 170 μg/dscm, which represents a 20% reduction from the floor level. The national incremental annualized compliance cost for solid fuel boilers to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $98,000 and would provide an incremental reduction in low volatile metals emissions beyond the MACT floor controls of 0.13 tons per year. Although nonair quality health and environmental impacts and energy effects are not significant factors, we are not proposing a beyond-the-floor standard based on feedrate control of low volatile metals in the hazardous waste because it would not be cost-effective at approximately $0.78 million per additional ton of low volatile metals removed.

c. No-cost Standard Derived from the Beyond-the-Floor Particulate Matter Standard. As discussed above in the context of semivolatile metals, the beyond-the-floor standard for particulate matter would also provide beyond-the-floor control for low volatile metals if sources were to comply with the beyond-the-floor particulate matter standard using improved particulate matter control rather than by reducing the feedrate of ash. To identify a beyond-the-floor emission level for low volatile metals that would derive from the beyond-the-floor particulate matter standard, we assumed that emissions of low volatile metals would be reduced by the same percentage that sources would need to reduce particulate matter emissions. We then developed a revised low volatile metal emission data base considering these particulate matter standard-derived reductions and reductions needed to meet the low volatile metal floor level. We analyzed these revised emissions to identify the best performing sources and an emission level that the average of the best performers could achieve 99 out of 100 future tests. This emission level—110 μg/dscm—is a beyond-the-floor low volatile metal standard that can be achieved at no cost because the costs have been allocated to the particulate matter beyond-the-floor standard.

We are concerned, however, that sources may choose to comply with the beyond-the-floor particulate matter standard by controlling the feedrate of ash in the hazardous waste feed, which may or may not reduce the feedrate and emissions of metal HAP. If so, it would be inappropriate to consider the beyond-the-floor standard for low volatile metals discussed above as a no-cost standard. We specifically request comment on whether sources may comply with beyond-the-floor particulate matter standard by controlling the feedrate of ash.

For these reasons, we propose a floor standard for low volatile metals of 210 μg/dscm for existing sources.

3. What Is the Rationale for the MACT Floor for New Sources?

MACT floor for low volatile metals for new sources would be 190 μg/dscm, considering emissions variability. This is an emission level that the single best performing source identified by the SRE/Feed Approach could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We evaluated three beyond-the-floor approaches for low volatile metals for new sources: (1) Improved particulate matter control; (2) control of low volatile metals in the hazardous waste feed; and (3) a no-cost standard derived from the beyond-the-floor particulate matter standard.

a. Improved Particulate Matter Control. We evaluated improved control of particulate matter using a fabric filter to achieve an emission level of 79 μg/dscm as beyond-the-floor control for low volatile metals emissions. The incremental annualized compliance cost for a new solid fuel boiler to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $0.28 million and would provide an incremental reduction in low volatile metals emissions of approximately 0.17 tons per year, for a cost-effectiveness of $1.7 million per ton of low volatile metals removed. We estimate that this beyond-the-floor option would increase the amount of hazardous waste (or solid waste if the source retains the Bevill exclusion under 40 CFR 266.112) generated for a new solid fuel-fired boiler with average gas flowrate by 44 tons per year and would require the source to use an additional 1.2 million kW-hours per year beyond the requirements to achieve the floor level. After considering these impacts and cost-effectiveness, we conclude that a beyond-the-floor standard based on improved particulate matter control using a fabric filter for new sources is not warranted.

b. Feedrate Control. For similar reasons discussed above for existing sources, we conclude that a beyond-the-floor standard based on controlling the low volatile metals in the hazardous waste feed would not be cost-effective.

c. No-cost Standard Derived from the Beyond-the-Floor Particulate Matter Standard. As discussed above in the context of existing sources, the beyond-the-floor standard for particulate matter would also provide beyond-the-floor control for low volatile metals if sources were to comply with the beyond-the-floor particulate matter standard using improved particulate matter control rather than by reducing the feedrate of ash. Under this approach, the no-cost beyond-the-floor standard for low volatile metals for new sources would be 34 μg/dscm. As discussed above, however, we are concerned that sources may choose to comply with the beyond-the-floor particulate matter standard by controlling the feedrate of ash in the hazardous waste feed, which may or may not reduce the feedrate and emissions of metal HAP. If so, it would be inappropriate to consider this beyond-the-floor standard as a no-cost standard. We specifically request comment on whether sources may comply with beyond-the-floor particulate matter standard by controlling the feedrate of ash.

For these reasons, we propose a low volatile metals standard of 190 μg/dscm for new sources.

F. What Is the Rationale for the Proposed Standards for Total Chlorine?

The proposed standards for hydrogen chloride and chlorine gas (i.e., total chlorine, reported as a hydrogen chloride equivalents) for solid fuel-fired boilers are 440 ppmv for existing sources and 73 ppmv for new sources.[138]

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1. What Is the Rationale for the MACT Floor for Existing Sources?

Solid fuel-fired boilers that burn hazardous waste are equipped with electrostatic precipitators or baghouses and do not have back-end controls for total chlorine. Total chlorine emissions are controlled by controlling the feedrate of chlorine in the hazardous waste feed. We have compliance test emissions data for five boilers. Emissions from these five boilers represent emissions from 10 of the 12 solid fuel-fired boilers.[139] Total chlorine emissions range from 60 ppmv to 700 ppmv.

To identify the MACT floor, we evaluated the compliance test emissions data associated with the most recent test campaign using the SRE/Feed Approach. The calculated floor is 440 ppmv, which considers emissions variability. This is an emission level that the best performing feed control sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this emission level is being achieved by 83% of sources and that it would reduce total chlorine emissions by 420 tons per year.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We evaluated dry scrubbing to achieve a beyond-the-floor emission level of 110 ppmv for total chlorine for existing sources, assuming conservatively a 75% removal efficiency. The national annualized incremental compliance cost for solid fuel-fired boilers to comply with this beyond-the-floor level rather than the floor level would be $3.7 million, and emissions of total chlorine would be reduced by an additional 790 tons per year, for a cost-effectiveness of $4,700 per ton of total chlorine removed. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond-the-floor level and estimate that the amount of hazardous waste generated would increase by 18,000 tons per year, an additional 27 million gallons of water per year would be used, and electricity consumption would increase by 0.11 million kW-hours per year.

We note that a cost of $4,700 per additional ton of total chlorine removed is in the “grey area” between a cost the Agency has concluded is cost-effective and a cost the Agency has concluded is not cost-effective under other MACT rules. EPA concluded that a cost of $1,100 per ton of total chlorine removed for hazardous waste burning lightweight aggregate kilns was cost-effective in the 1999 MACT final rule. See 68 FR at 52900. EPA concluded, however, that a cost of $45,000 per ton of hydrogen chloride removed was not cost-effective for industrial boilers. See 68 FR at 1677.

Although a beyond-the-floor standard of 110 ppmv for solid fuel boilers under today's rule would provide health benefits from collateral reductions in SO2 emissions,[140] we are concerned that a cost of $4,700 per additional ton of total chlorine removed is not warranted. Therefore, after considering cost-effectiveness and nonair quality health and environmental impacts and energy effects, we are not proposing a beyond-the-floor standard based on dry scrubbing. We specifically request comment on whether a beyond-the-floor standard is warranted.

We also evaluated use of feedrate control of chlorine in hazardous waste to achieve a beyond-the-floor level of 350 ppmv, which represents a 20% reduction from the floor level. The national annualized incremental compliance cost for solid fuel-fired boilers to comply with this beyond-the-floor level rather than the floor level would be $0.08 million, and emissions of total chlorine would be reduced by an additional 40 tons per year, for a cost-effectiveness of $2,000 per ton of total chlorine removed. Although nonair quality health and environmental impacts and energy effects are not significant factors for feedrate control, we are not proposing a beyond-the-floor standard based on hazardous waste feedrate control because we are concerned about the practicability of achieving these emissions reductions, and our estimate of the associated cost, using feedrate control. We specifically request comment on use of feedrate control of chlorine in hazardous waste as a beyond-the-floor control technique, the emission reductions that could be achieved, and the costs of achieving those reductions.

3. What Is the Rationale for the MACT Floor for New Sources?

MACT floor for new sources would be 73 ppmv. This is an emission level that the single best performing source identified by the Emissions Approach (i.e., the source with the lowest emissions) could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We evaluated dry lime scrubbing to achieve a beyond-the-floor emission level of 37 ppmv for total chlorine for new sources, assuming conservatively a 50% removal efficiency.[141] The incremental annualized compliance cost for a new solid fuel boiler with average gas flowrate to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $610,000 and would provide an incremental reduction in total chlorine emissions of approximately 42 tons per year. Although nonair quality health and environmental impacts and energy effects are not significant factors, we conclude that a beyond-the-floor standard of 37 ppmv is not warranted because it would not be cost-effective at approximately $14,000 per additional ton of total chlorine removed.

For these reasons, we propose a floor standard for total chlorine of 73 ppmv for new sources.

G. What Is the Rationale for the Proposed Standards for Carbon Monoxide or Hydrocarbons?

To control emissions of organic HAP, existing and new sources would be required to comply with either a carbon monoxide standard of 100 ppmv or a hydrocarbon standard of 10 ppmv.[142]

1. What Is the Rationale for the MACT Floor for Existing Sources?

Solid fuel-fired boilers that burn hazardous waste are currently subject to RCRA standards that require Start Printed Page 21282compliance with either a carbon monoxide standard of 100 ppmv, or a hydrocarbon standard of 20 ppmv. Compliance is based on an hourly rolling average as measured with a CEMS. See § 266.104(a). We are proposing today floor standards of 100 ppmv for carbon monoxide or 10 ppmv for hydrocarbons.

Floor control for existing sources is operating under good combustion practices including: (1) Providing adequate excess air with use of oxygen CEMS and feedback air input control; (2) providing adequate fuel/air mixing; (3) homogenizing hazardous waste fuels (such as by blending or size reduction) to control combustion upsets due to very high or very low volatile content wastes; (4) regulating waste and air feedrates to ensure proper combustion temperature and residence time; (5) characterizing waste prior to burning for combustion-related composition (including parameters such as heating value, volatile content, liquid waste viscosity, etc.); (6) ensuring the source is operated by qualified, experienced operators; and (7) periodic inspection and maintenance of combustion system components such as burners, fuel and air supply lines, injection nozzles, etc. Given that there are many interdependent parameters that affect combustion efficiency and thus carbon monoxide and hydrocarbon emissions, we are not able to quantify “good combustion practices.”

Ten of 12 solid fuel-fired boilers are currently complying with the RCRA carbon monoxide limit of 100 ppmv on an hourly rolling average. The remaining two boilers are complying with the RCRA hydrocarbon limit of 20 ppmv on an hourly rolling average. Those boilers have hydrocarbon levels below 5 ppmv, however, indicative of operating under good combustion practices.

We propose a floor level for carbon monoxide level of 100 ppmv because it is a currently enforceable Federal standard. Although the best performing sources are achieving carbon monoxide levels below 100 ppmv, it is not appropriate to establish a lower floor level because carbon monoxide is a surrogate for nondioxin/furan organic HAP. As such, lowering the carbon monoxide floor may not significantly reduce organic HAP emissions. In addition, it would be inappropriate to apply a MACT methodology to the carbon monoxide emissions from the best performing sources because those sources may not be able to replicate their emission levels. This is because there are myriad factors that affect combustion efficiency and, subsequently, carbon monoxide emissions. Extremely low carbon monoxide emissions cannot be assured by controlling only one or two operating parameters We note also that we used this rationale to establish a carbon monoxide standard of 100 ppmv for Phase I sources in the September 1999 Final Rule.

We propose a floor level for hydrocarbons of 10 ppmv even though the currently enforceable standard is 20 ppmv because: (1) The two sources that comply with the RCRA hydrocarbon standard can readily achieve 10 ppmv; and (2) reducing hydrocarbon emissions within the range of 20 ppmv to 10 ppmv should reduce emissions of nondioxin/furan organic HAP. We do not apply a prescriptive MACT methodology to establish a hydrocarbon floor below 10 ppmv, however, because we have data from only two sources. In addition, we note that the hydrocarbon emission standard for Phase I sources established in the September 1999 Final Rule is 10 ppmv also.

There would be no incremental emission reductions associated with these floors because all sources are currently achieving the floor levels.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We considered beyond-the-floor levels for carbon monoxide and hydrocarbons based on use of better combustion practices but conclude that they may not be replicable by the best performing sources nor duplicable by other sources given that we cannot quantify good combustion practices. Moreover, we cannot ensure that carbon monoxide or hydrocarbon levels lower than the floors would significantly reduce emissions of nondioxin/furan organic HAP. This is because the portion of hydrocarbons that is comprised of nondioxin/furan organic HAP is likely to become lower as combustion efficiency improves and hydrocarbon levels decrease. Thus, at beyond-the-floor hydrocarbon levels, we would expect a larger portion of residual hydrocarbons to be compounds that are not organic HAP.

Nonair quality health and environmental impacts and energy requirements are not significant factors for use of better combustion practices as beyond-the-floor control.

For these reasons, we conclude that beyond-the-floor standards for carbon monoxide and hydrocarbons are not warranted for existing sources.

3. What Is the Rationale for the MACT Floor for New Sources?

MACT floor for new sources would be the same as the floor for existing sources—100 ppmv for carbon monoxide and 10 ppmv for hydrocarbons—and based on the same rationale.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

As discussed in the context of beyond-the-floor considerations for existing sources, we considered beyond-the-floor standards for carbon monoxide and hydrocarbons for new sources based on use of better combustion practices. But, we conclude that beyond the floor standards may not be replicable by the best performing sources nor duplicable by other sources given that we cannot quantify good combustion practices. Moreover, we cannot ensure that carbon monoxide or hydrocarbon levels lower than the floors would significantly reduce emissions of nondioxin/furan organic HAP.

Nonair quality health and environmental impacts and energy requirements are not significant factors for use of better combustion practices as beyond-the-floor control.

For these reasons, we conclude that beyond-the-floor standards for carbon monoxide and hydrocarbons are not warranted for new sources.

H. What Is the Rationale for the Proposed Standard for Destruction and Removal Efficiency?

To control emissions of organic HAP, existing and new sources would be required to comply with a destruction and removal efficiency (DRE) of 99.99% for organic HAP. For sources burning hazardous wastes F020, F021, F022, F023, F026, or F027, however, the DRE standard is 99.9999% for organic HAP.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Solid fuel-fired boilers that burn hazardous waste are currently subject to RCRA DRE standards that require 99.99% destruction of designated principal organic hazardous constituents (POHCs). For sources that burn hazardous wastes F020, F021, F022, F023, F026, or F027, however, the DRE standard is 99.9999% destruction of designated POHCs. See § 266.104(a).

The DRE standard helps ensure that a combustor is operating under good combustion practices and thus minimizing emissions of organic HAP. Under the MACT compliance regime, sources would designate POHCs that are organic HAP or that are surrogates for organic HAP.

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We propose to establish the RCRA DRE standard as the floor for existing sources because it is a currently enforceable Federal standard. There would be no incremental emission reductions associated with this floor because sources are currently complying with the standard.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We considered a beyond-the-floor level for DRE based on use of better combustion practices but conclude that it may not be replicable by the best performing sources nor duplicable by other sources given that we cannot quantify better combustion practices. Moreover, we cannot ensure that a higher DRE standard would significantly reduce emissions of organic HAP given that DRE measures the destruction of organic HAP present in the boiler feed rather than gross emissions of organic HAP. Although a source's combustion practices may be adequate to destroy particular organic HAP in the feed, other organic HAP that may be emitted as products of incomplete combustion may not be controlled by the DRE standard.[143]

For these reasons, and after considering non-air quality health and environmental impacts and energy requirements, we are not proposing a beyond-the-floor DRE standard for existing sources.

3. What Is the Rationale for the MACT Floor for New Sources?

We propose to establish the RCRA DRE standard as the floor for new sources because it is a currently enforceable Federal standard.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

Using the same rationale as we used to consider a beyond-the-floor DRE standard for existing sources, we conclude that a beyond-the-floor DRE standard for new sources is not warranted. Consequently, after considering non-air quality health and environmental impacts and energy requirements, we are proposing the floor DRE standard for new sources.

XI. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste Burning Liquid Fuel-Fired Boilers?

The proposed standards for existing and new liquid fuel-fired boilers that burn hazardous waste are summarized in the table below. See proposed § 63.1217.

Proposed Standards for Existing and New Liquid Fuel-Fired Boilers

Hazardous air pollutant or surrogateEmission standard 1
Existing sourcesNew sources
Dioxin and furan: sources equipped with dry air pollution control system 20.40 ng TEQ/dscm0.015 ng TEQ/dscm or control of flue gas temperature not to exceed 400°F at the inlet to the particulate matter control device.
Dioxin and furan: sources equipped with wet or with no air pollution control systems 2100 ppmv carbon monoxide or 10 ppmv hydrocarbons100 ppmv carbon monoxide or 10 ppmv hydrocarbons
Mercury 33.7E-6 lbs/MM Btu3.8E-7 lbs/MM BTU
Particulate matter72 mg/dscm (0.032 gr/dscf)17 mg/dscm (0.0076 gr/dscf)
Semivolatile metals 31.1E-5 lbs/MM BTU4.3E-6 lbs/MM BTU
Low volatile metals: chromium only 3, 41.1E-4 lbs/MM BTU3.6E-5 lbs/MM BTU
Hydrogen chloride and chlorine gas3, 52.5E-2 lbs/MM BTU or the alternative emission limits under § 63.12157.2E-4 lbs/MM BTU or the chlorine alternative emission limits under § 63.1215
Carbon monoxide or hydrocarbons 6100 ppmv carbon monoxide or 10 ppmv hydrocarbons.100 ppmv carbon monoxide or 10 ppmv hydrocarbons.
Destruction and Removal EfficiencyFor existing and new sources, 99.99% for each principal organic hazardous constituent (POHC). For sources burning hazardous wastes F020, F021, F022, F023, F026, or F027, however, 99.9999% for each POHC.
1 All emission standards are corrected to 7% oxygen, dry basis.
2 A wet air pollution system followed by a dry air pollution control system is not considered to be a dry air pollution control system for purposes of this standard. A dry air pollution systems followed a wet air pollution control system is considered to be a dry air pollution control system for purposes of this standard.
3 Standards are expressed as mass of pollutant emissions contributed by hazardous waste per million Btu contributed by the hazardous waste.
4 Standard is for chromium only and does not include arsenic and beryllium.
5 Combined standard, reported as a chloride (Cl(-)) equivalent.
6 Hourly rolling average. Hydrocarbons reported as propane.

We considered whether fuel switching could be considered a MACT floor control technology for liquid fuel-fired boilers to achieve lower HAP emissions. We conclude that HAP emissions from liquid fuel-fired boilers are attributable primarily to the hazardous waste fuels rather than the natural gas or fuel oil that these boilers burn. Consequently, we conclude that fuel switching is not an effective MACT floor control technology to reduce HAP emissions for liquid fuel-fired boilers.

A. What Are the Proposed Standards for Dioxin and Furan?

We propose to establish a dioxin/furan standard for existing liquid fuel-fired boilers equipped with dry air pollution control devices of 0.40 ng TEQ/dscm. The standard for new sources would be 0.015 ng TEQ/dscm or control of flue gas temperature not to exceed 400 °F at the inlet to the particulate matter control device. For liquid fuel-fired boilers equipped either with wet air pollution control systems or with no air pollution systems, we propose a standard for both existing and new sources as compliance with the proposed standards for carbon monoxide/hydrocarbon and destruction and removal efficiency. In addition, we note that we propose to require a one-time dioxin/furan emission test for Start Printed Page 21284sources that would not be subject to a numerical dioxin/furan emission standard, including liquid fuel-fired boilers with wet or no emission control device, and new liquid fuel-fired boilers equipped with a dry air pollution control device. As discussed in Part Two, Section XIV.B below, the testing would assist in developing both section 112(d)(6) standards and section 112(f) residual risk standards.

1. What Is the Rationale for the MACT Floor for Existing Sources?

As discussed in Part Two, Section I.B.5, we used a statistical analysis to conclude that liquid boilers equipped with dry air pollution control devices have different dioxin/furan emission characteristics compared to sources with either wet air pollution control or no air pollution control devices.[144] Note that we consider the type of emission control device as a basis for subcategorization because the type of control device affects formation of dioxin/furan: dioxin/furan can form in dry particulate matter control devices while it cannot form in wet (or no) control devices. We therefore believe subcategorization is warranted and we propose to identify separate floor levels for sources equipped with dry particulate matter control devices versus sources with wet or no emission control device.

a. MACT Floor for Boilers Equipped with Dry Control Systems. To identify the floor level for liquid fuel boilers equipped with dry air pollution control systems, we considered whether dioxin/furan can be controlled by controlling the temperature at the inlet to the particulate matter control device. We conclude that this control mechanism may not be the predominant factor that affects dioxin/furan emissions from these sources. We have emissions data for three boilers equipped with electrostatic precipitators or fabric filters. Emissions from two of the boilers are below 0.03 ng TEQ/dscm. We do not have data on the gas temperature at the inlet to the emission control device for these sources. The third boiler, however, has dioxin/furan emissions of 2.4 ng TEQ/dscm when the flue gas temperature at the inlet to the fabric filter is 410 °F. We conclude from this information that this boiler is not likely to be able to achieve dioxin/furan emissions below 0.40 ng TEQ/dscm if the gas temperature is reduced to below 400 °F. This is contrary to the finding we made for cement kilns and incinerators without heat recovery boilers and equipped with dry particulate matter control devices. In those cases, we conclude that gas temperature control at the dry particulate matter control device is the predominant factor affecting dioxin/furan emissions. See discussions in Sections VII and VIII above. Consequently, other factors are likely contributing to high dioxin/furan emissions from the liquid fuel-fired boiler equipped with a fabric filter operated at a gas temperature of 410 °F, such as metals in the waste feed or soot on boiler tubes that may catalyze dioxin/furan formation reactions.

We evaluated the compliance test emissions data using the Emissions Approach and calculated a numerical dioxin/furan floor level of 3.0 ng TEQ/dscm, which considers emissions variability. As discussed above, however, one of the three sources for which we have emissions data is not likely to be able to achieve this emission level using gas temperature control at the inlet to the dry particulate matter control device. Consequently, we propose to identify the floor level as 3.0 ng TEQ/dscm or control of flue gas temperature not to exceed 400 °F at the inlet to the particulate matter control device. This floor level is duplicable by all sources, and would minimize dioxin/furan emissions for sources where flue gas temperature at the control device substantially affects dioxin/furan emissions. We estimate that this emission level is being achieved by all sources and, thus, would not reduce dioxin/furan emissions.

b. MACT Floor for Boilers Equipped with Wet or No Control Systems. We have dioxin/furan emissions data for 33 liquid fuel-fired boilers equipped with a wet or no particulate matter control device. Emissions levels are below 0.1 ng TEQ/dscm for 30 of the sources. Emission levels for the other three sources are 0.19, 0.36, and 0.44 ng TEQ/dscm.

As previously discussed in Part Two, Section VII.A, we believe that it would be inappropriate to establish a numerical dioxin/furan emission floor level for sources using wet or no air pollution control systems based on the emissions achieved by the best performing sources because a numerical floor level would not be replicable by the best performing sources nor duplicable by other sources. As a result, we propose to define the MACT floor for sources with wet or no emission control devices as operating under good combustion practices by complying with the destruction and removal efficiency and carbon monoxide/hydrocarbon standards.[145] There would be no emissions reductions for these existing boilers to comply with the floor level because they are currently complying with the carbon monoxide/hydrocarbon standard and destruction and removal efficiency standard pursuant to RCRA requirements.

We also request comment on an alternative MACT floor expressed as a dioxin/furan emission concentration for liquid fuel boilers with wet or no emission control devices.[146] Although it would be inappropriate to identify a floor concentration based on the average emissions of the best performing sources as discussed above, we possibly could identify the floor as the highest emission concentration from any source in our data base, after considering emissions variability.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We evaluated use of activated carbon injection systems or carbon beds as beyond-the-floor control for further reduction of dioxin/furan emissions. Activated carbon has been demonstrated for controlling dioxin/furans in various combustion applications.

a. Beyond-the-Floor Considerations for Boilers Equipped with Dry Control Systems. For liquid fuel-fired boilers using dry air pollution control equipment, we evaluated a beyond-the-floor level of 0.40 ng TEQ/dscm based on activated carbon injection or control of flue gas temperature not to exceed 400 °F at the inlet to the particulate matter control device. The national incremental annualized compliance cost for sources to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $80,000 and would provide an incremental reduction in dioxin/furan emissions beyond the MACT floor Start Printed Page 21285controls of 0.06 grams TEQ per year for a cost-effectiveness of $1.3 million per additional gram of dioxin/furan removed. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond-the-floor standard and estimate that the amount of hazardous waste generated would increase by 100 tons per year, an additional 25 trillion Btu per year of natural gas would be consumed, and electricity consumption would increase by 0.50 million kW-hours per year.

We judge that the cost to achieve this beyond-the-floor level is warranted given our special concern about dioxin/furan. Dioxin/furan are some of the most toxic compounds known due to their bioaccumulation potential and wide range of health effects, including carcinogenesis, at exceedingly low doses. Exposure via indirect pathways is a chief reason that Congress singled our dioxin/furan for priority MACT control in CAA section 112(c)(6). See S. Rep. No. 128, 101st Cong. 1st Sess. at 154-155. In addition, we note that the beyond-the-floor emission level of 0.40 ng TEQ/dscm is consistent with historically controlled levels under MACT for hazardous waste incinerators and cement kilns, and Portland cement plants. See §§ 63.1203(a)(1), 63.1204(a)(1), and 63.1343(d)(3). Also, EPA has determined previously in the 1999 Hazardous Waste Combustor MACT final rule that dioxin/furan in the range of 0.40 ng TEQ/dscm or less are necessary for the MACT standards to be considered generally protective of human health under RCRA (using the 1985 cancer slope factor), thereby eliminating the need for separate RCRA standards under the authority of RCRA section 3005(c)(3) and 40 CFR 270.10(k). Finally, we note that this decision is not inconsistent with EPA's decision not to promulgate beyond-the-floor standards for dioxin/furan for hazardous waste burning lightweight aggregate kilns, cement kilns, and incinerators at cost-effectiveness values in the range of $530,000 to $827,000 per additional gram of dioxin/furan TEQ removed. See 64 FR at 52892, 52876, and 52961. In those cases, EPA determined that controlling dioxin/furan emissions from a level of 0.40 ng TEQ/dscm to a beyond-the-floor level of 0.20 ng TEQ/dscm was not warranted because dioxin/furan levels below 0.40 ng TEQ/dscm are generally considered to be below the level of health risk concern.

For these reasons, we believe that proposing a beyond-the-floor standard of 0.40 ng TEQ/dscm is warranted notwithstanding the nonair quality health and environmental impacts and energy effects identified above and costs of approximately $1.3 million per additional gram of dioxin/furan TEQ removed. We specifically request comment on our decision to propose this beyond-the-floor standard.

b. Beyond-the-Floor Considerations for Boilers Equipped with Wet or No Control Systems. For liquid fuel-fired boilers equipped with wet or no air pollution control systems, we evaluated a beyond-the-floor level of 0.20 ng TEQ/dscm based on activated carbon. The national incremental annualized compliance cost for these sources to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $550,000 and would provide an incremental reduction in dioxin/furan emissions beyond the MACT floor controls of 0.12 grams TEQ per year. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond-the-floor standard and estimate that the amount of hazardous waste generated would increase by 100 tons per year, an additional 25 trillion Btu per year of natural gas would be consumed, an additional 4 million gallons per year of water would be used, and electricity consumption would increase by 0.50 million kW-hours per year. We are not proposing a beyond-the-floor standard of 0.20 ng TEQ/dscm for liquid boilers that use a wet or no air pollution control system because it would not be cost-effective at $4.6 million per gram of TEQ removed.

We are also considering an alternative beyond-the-floor standard for existing liquid fuel boilers with wet or no particulate matter control devices of 0.40 ng TEQ/dscm. Although all but one source for which we have data are currently achieving this emission level, boilers for which we do not have dioxin/furan emissions data may have emissions higher than 0.40 ng TEQ/dscm. In addition, dioxin/furan emissions from a given boiler may vary over time. Other factors that may contribute substantially to dioxin/furan formation, such as the level and type of soot on boiler tubes, or feeding metals that catalyze dioxin/furan formation reactions, differ across boilers and may change over time at a given boiler. Thus, dioxin/furan levels for these sources may be higher than 0.40 ng TEQ/dscm. For example, we recently obtained dioxin/furan emissions data for a liquid fuel-fired boiler equipped with a wet emission control system documenting emissions of 1.4 ng TEQ/dscm.[147] To control dioxin/furan emissions to a beyond-the-floor standard of 0.40 ng TEQ/dscm, you would use activated carbon. We specifically request comment on this beyond-the-floor option, including how we should estimate compliance costs and emissions reductions.

3. What Is the Rationale for the MACT Floor for New Sources?

The calculated floor level for new liquid fuel boilers equipped with dry air pollution control systems is 0.015 ng TEQ/dscm, which we identified using the Emissions Approach. If dioxin/furan emissions could be controlled predominantly by controlling the gas temperature at the inlet to the dry particulate matter control device, this would be the emission level that the single best performing source could be expected to achieve in 99 out of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. This emission level may not be replicable by this source and duplicable by other (new) sources, however, because factors other than flue gas temperature control at the control device may affect dioxin/furan emissions. See discussion of this issue in the context of the floor level for existing sources. Therefore, we propose to establish the floor level as 0.015 ng TEQ/dscm or control of flue gas temperature not to exceed 400 °F at the inlet to the particulate matter control device.

As previously discussed, we believe that it would be inappropriate to establish a numerical dioxin/furan emission floor level for liquid boilers with wet or with no air pollution control systems. Therefore, we propose floor control for these units as good combustion practices provided by complying with the proposed destruction and removal efficiency and carbon monoxide/hydrocarbon standards.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We evaluated use of activated carbon as beyond-the-floor control for further reduction of dioxin/furan emissions. Activated carbon has been demonstrated for controlling dioxin/furan in various combustion applications.

a. Beyond-the-Floor Considerations for Boilers Equipped with Dry Control Systems. For liquid fuel-fired boilers using dry air pollution control equipment, we evaluated a beyond-the-floor level of 0.01 ng TEQ/dscm using activated carbon injection. The national incremental annualized compliance cost Start Printed Page 21286for a source with an average gas flowrate to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $0.15 million and would provide an incremental reduction in dioxin/furan emissions beyond the MACT floor controls of 0.005 grams TEQ per year. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond-the-floor standard and estimate that, for a new liquid fuel-fired boiler with average gas flowrate, the amount of hazardous waste generated would increase by 120 tons per year and electricity consumption would increase by 0.1 million kW-hours per year. After considering these impacts and costs of approximately $32 million per additional gram of dioxin/furan removed, we are not proposing a beyond-the-floor standard of 0.01 ng TEQ/dscm for liquid fuel-fired boilers using dry air pollution control systems.

We are also considering an alternative beyond-the-floor standard of 0.40 ng TEQ/dscm for new liquid fuel boilers equipped with a dry particulate matter control device. A new source that achieves the floor level by controlling the gas temperature at the inlet to the dry particulate matter control device to 400 °F may have dioxin/furan emissions at levels far exceeding 0.40 ng TEQ/dscm. See discussion above regarding factors other than gas temperature at the control device that can affect dioxin/furan emissions from liquid fuel-fired boilers (and discussion of emissions of 2.4 ng TEQ/dscm for a boiler operating a fabric filter at 410 °F). Therefore, it may be appropriate to establish a beyond-the-floor standard to limit emissions to 0.40 ng TEQ/dscm based on use of activated carbon injection. We also note that this beyond-the-floor standard may be appropriate to ensure that emission levels from new sources do not exceed the proposed 0.40 ng TEQ/dscm beyond-the-floor standard for existing sources. Because standards for new sources are based on the single best performing source while standards for existing sources are based on the average of the best 12% (or best 5) performing sources, standards for new sources should not be less stringent than standards for existing sources. We specifically request comment on this beyond-the-floor option, including how we should estimate compliance costs and emissions reductions.

b. Beyond-the-Floor Considerations for Boilers Equipped with Wet or No Control Systems. We evaluated a beyond-the-floor level of 0.20 ng TEQ/dscm for liquid fuel-fired boilers equipped with wet or with no air pollution control systems based on use of activated carbon. The national incremental annualized compliance cost for a source with average gas flowrate to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $0.15 million and would provide an incremental reduction in dioxin/furan emissions beyond the MACT floor controls of 0.06 grams TEQ per year. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond-the-floor standard and estimate that, for a source with average gas flowrate, the amount of hazardous waste generated would increase by 120 tons per year and electricity consumption would increase by 0.1 million kW-hours per year. After considering these impacts and costs of approximately $2.4 million per additional gram of dioxin/furan removed, we are not proposing a beyond-the-floor standard for liquid fuel-fired boilers using a wet or no air pollution control system.

We are also considering an alternative beyond-the-floor standard of 0.40 ng TEQ/dscm for new liquid fuel boilers equipped with wet or with no air pollution control systems. A new source that achieves the floor level—compliance with the standards for carbon monoxide/hydrocarbon and destruction and removal efficiency—may have high dioxin/furan emissions at levels far exceeding 0.40 ng TEQ/dscm. See discussion above regarding factors other than gas temperature at the control device that can affect dioxin/furan emissions from liquid fuel-fired boilers. Therefore, it may be appropriate to establish a beyond-the-floor standard to limit emissions to 0.40 ng TEQ/dscm based on use of activated carbon. We specifically request comment on this beyond-the-floor option, including how we should estimate compliance costs and emissions reductions.

B. What Is the Rationale for the Proposed Standards for Mercury?

We propose to establish standards for existing liquid fuel-fired boilers that limit emissions of mercury to 3.7E-6 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The proposed standards for new sources would be 3.8E-7 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste.[148] These standards are expressed as hazardous waste thermal emission concentrations because liquid fuel-fired boilers burn hazardous waste for energy recovery. See discussion in Part Two, Section IV.B of the preamble.

1. What Is the Rationale for the MACT Floor for Existing Sources?

MACT floor for existing sources is 3.7E-6 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste, which is based primarily by controlling the feed concentration of mercury in the hazardous waste. Approximately 11% of liquid boilers also use wet scrubbers that can control emissions of mercury.

We have normal emissions data within the range of normal emissions for 32% of the sources.[149] The normal mercury stack emissions in our data base are all less than 7 μg/dscm. These emissions are expressed as mass of mercury (from all feedstocks) per unit of stack gas. Hazardous waste thermal emissions, available for 12% of sources, range from 1.0E-7 to 1.0E-5 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. Hazardous waste thermal emissions represent the mass of mercury contributed by the hazardous waste per million Btu contributed by the hazardous waste.

To identify the MACT floor, we evaluated all normal emissions data using the Emissions Approach. The calculated floor is 3.7E-6 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this floor level is being achieved by 40% of sources and would reduce mercury emissions by 0.68 tons per year.

Because the floor level is based on normal emissions data, compliance would be documented by complying with a hazardous waste mercury thermal feed concentration on an annual rolling average. See discussion in Part Two, Section XIV.F below.

We did not use the SRE/Feed Approach to identify the floor level because the vast majority of mercury feed levels in the hazardous waste and Start Printed Page 21287the emissions measurements did not have detectable concentrations of mercury. Given that a system removal efficiency, or SRE, is the percentage of mercury emitted compared to the amount fed, we concluded that it would be inappropriate to base this analysis on SREs that were derived from measurements below detectable levels.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We identified two potential beyond-the-floor techniques for control of mercury: (1) Activated carbon injection; and (2) control of mercury in the hazardous waste feed. For reasons discussed below, we are not proposing a beyond-the-floor standard for mercury.

a. Use of Activated Carbon Injection. We evaluated activated carbon injection as beyond-the-floor control for further reduction of mercury emissions. Activated carbon has been demonstrated for controlling mercury in several combustion applications; however, currently no liquid fuel boilers burning hazardous waste uses activated carbon injection. We evaluated a beyond-the-floor level of 1.1E-6 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The national incremental annualized compliance cost for liquid fuel-fired boilers to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $12 million and would provide an incremental reduction in mercury emissions beyond the MACT floor controls of 0.097 tons per year. We evaluated nonair quality health and environmental impacts and energy effects of using activated carbon injection to meet this beyond-the-floor emission level and estimate that the amount of hazardous waste generated would increase by 4,800 tons per year and that sources would consume an additional 44 trillion Btu per year of natural gas and use an additional 9.6 million kW-hours per year beyond the requirements to achieve the floor level. Therefore, based on these factors and costs of approximately $124 million per additional ton of mercury removed, we are not proposing a beyond-the-floor standard based on activated carbon injection.[150]

b. Feed Control of Mercury in the Hazardous Waste. We also evaluated a beyond-the-floor level of 3.0E-6 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste, which represents a 20% reduction from the floor level. The national incremental annualized compliance cost for liquid fuel-fired boilers to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $4.2 million and would provide an incremental reduction in mercury emissions beyond the MACT floor controls of 0.036 tons per year. Nonair quality health and environmental impacts and energy effects are not significant factors for feedrate control. Therefore, based on these factors and costs of approximately $115 million per additional ton of mercury removed, we are not proposing a beyond-the-floor standard based on feed control of mercury in the hazardous waste.

For the reasons discussed above, we do not propose a beyond-the-floor standard for mercury for existing sources. We propose a standard based on the floor level: 3.7E-6 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste.

3. What Is the Rationale for the MACT Floor for New Sources?

The MACT floor for new sources for mercury would be 3.8E-7 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste and would be implemented as an annual average because it is based on normal emissions data. This is an emission level that the single best performing source identified with the Emissions Approach could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We evaluated activated carbon injection as beyond-the-floor control to achieve an emission level of 2.0E-7 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The incremental annualized compliance cost for a new liquid fuel-fired boiler with average gas flowrate to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $0.15 million and would provide an incremental reduction in mercury emissions of less than 0.0002 tons per year, for a cost-effectiveness of $1 billion per ton of mercury removed. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond-the-floor standard and estimate that, for a new liquid fuel-fired boiler with average gas flowrate, the amount of hazardous waste generated would increase by 120 tons per year and electricity consumption would increase by 0.1 million kW-hours per year. Although nonair quality health and environmental impacts and energy effects are not significant factors, we are not proposing a beyond-the-floor standard based on activated carbon injection for new sources because it would not be cost-effective. Therefore, we propose a mercury standard based on the floor level: 3.8E-7 lbs mercury emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste.

C. What Is the Rationale for the Proposed Standards for Particulate Matter?

The proposed standards for particulate matter for liquid fuel-fired boilers are 59 mg/dscm (0.026 gr/dscf) for existing sources and 17 mg/dscm (0.0076 gr/dscf) for new sources.[151] The particulate matter standard serves as a surrogate for nonenumerated HAP metal emissions attributable to the hazardous waste fuel burned in the boiler. Although the particulate matter standard would also control nonmercury HAP metal from nonhazardous waste fuels, the natural gas or fuel oil these boilers burn as primary or auxiliary fuel do not contain significant levels of metal HAP.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Few liquid fuel-fired boilers are equipped particulate matter control equipment such as electrostatic precipitators and baghouses, and, therefore, many sources control particulate matter emissions by limiting the ash content of the hazardous waste. We have compliance test emissions data from nearly all liquid boilers representing maximum allowable emissions. Particulate emissions range from 0.0008 to 0.078 gr/dscf.

To identify the floor level, we evaluated the compliance test emissions Start Printed Page 21288data associated with the most recent test campaign using the APCD Approach. The calculated floor is 72 mg/dscm (0.032 gr/dscf), which considers emissions variability. This is an emission level that the average of the performing sources could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this floor level is being achieved by 44% of sources and would reduce particulate matter emissions by 1,200 tons per year.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We evaluated use of fabric filters to improve particulate matter control to achieve a beyond-the-floor standard of 36 mg/dscm (0.016 gr/dscf). The national incremental annualized compliance cost for liquid fuel-fired boilers to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $16 million and would provide an incremental reduction in particulate matter emissions beyond the MACT floor controls of 520 tons per year. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond-the-floor standard and estimate that the amount of hazardous waste generated would increase by 520 tons per year and electricity consumption would increase by 13 million kW-hours per year. After considering these factors and costs of approximately $30,000 per additional ton of particulate matter removed, we are not proposing a beyond-the-floor standard.

For the reasons discussed above, we propose a standard for particulate matter for existing liquid fuel-fired boilers based on the floor level: 72 mg/dscm (0.032 gr/dscf).

3. What Is the Rational for the MACT Floor for New Sources?

MACT floor for new sources would be 17 mg/dscm (0.0076 gr/dscf), considering emissions variability. This is an emission level that the single best performing source identified by the APCD Approach (i.e., the source using a fabric filter [152] with the lowest emissions) could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We evaluated use of an advanced fabric filter using high efficiency membrane bag material and a low air to cloth ratio to achieve a beyond-the-floor emission level of 9 mg/dscm (0.0040 gr/dscf). The incremental annualized cost for a new liquid fuel-fired boiler with average gas flowrate to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $0.15 million and would provide an incremental reduction in particulate emissions of approximately 2.9 tons per year, for a cost-effectiveness of $53,000 per ton of particulate matter removed. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond-the-floor standard and estimate that, for a new liquid fuel-fired boiler with average gas flowrate, the amount of hazardous waste generated would increase by 3 tons per year and electricity consumption would increase by 0.54 million kW-hours per year. Considering these factors and cost-effectiveness, we conclude that a beyond-the-floor standard of 9 mg/dscm is not warranted.

For the reasons discussed above, we propose a floor-based standard for particulate matter for new liquid fuel-fired boilers: 9.8 mg/dscm (0.0043 gr/dscf)

D. What Is the Rationale for the Proposed Standards for Semivolatile Metals?

We propose a standard for existing liquid fuel-fired boilers that limits emissions of semivolatile metals (cadmium and lead, combined) to 1.1E-5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The proposed standard for new sources is 4.3E-6 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste.

1. What Is the Rationale for the MACT Floor for Existing Sources?

MACT floor for existing sources is 1.1E-5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste, which is based on particulate matter control (for those few sources using a control device) and controlling the feedrate of semivolatile metals in the hazardous waste.

We have emissions data within the range of normal emissions for nearly 40% of the sources.[153] The normal semivolatile stack emissions in our database range from less than 1 to 46 ug/dscm. These emissions are expressed conventionally as mass of semivolatile metals (from all feedstocks) per unit of stack gas. Hazardous waste thermal emissions, available for 25% of sources, range from 1.2E-6 to 4.8E-5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input of the hazardous waste.

We identified a MACT floor of 1.1E-5 expressed as a hazardous waste thermal emission by applying the Emissions Approach to the normal hazardous waste thermal emissions data.[154] This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this floor level is being achieved by 33% of sources and would reduce semivolatile metals emissions by 1.7 tons per year.

Because the floor level is based on normal emissions data, compliance would be documented by complying with a hazardous waste mercury thermal feed concentration on an annual rolling average. See discussion in Part Two, Section XIV.F below.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We identified two potential beyond-the-floor techniques for control of semivolatile metals: (1) Improved particulate matter control; and (2) control of mercury in the hazardous waste feed. For reasons discussed below, we are not proposing a beyond-the-floor standard for semivolatile metals.

a. Improved Particulate Matter Control. We evaluated installation of a new fabric filter or improved design, operation, and maintenance of the existing electrostatic precipitator and fabric filter as beyond-the-floor control Start Printed Page 21289for further reduction of semivolatile metals emissions. We evaluated a beyond-the-floor level of 5.5E-6 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The national incremental annualized compliance cost for liquid fuel-fired boilers to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $6.5 million and would provide an incremental reduction in semivolatile metals emissions beyond the MACT floor controls of 0.06 tons per year. We evaluated nonair quality health and environmental impacts and energy effects and determined that this beyond-the-floor option would increase the amount of hazardous waste generated by approximately 45 tons per year and would increase electricity usage by 0.8 million kW-hours per year. After considering these factors and costs of approximately $100 million per additional ton of semivolatile metals removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control.

b. Feed Control of Semivolatile Metals in the Hazardous Waste. We also evaluated a beyond-the-floor level of 8.8E-6 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste, which represents a 20% reduction from the floor level. The national incremental annualized compliance cost for liquid fuel-fired boilers to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $4.8 million and would provide an incremental reduction in semivolatile metals emissions beyond the MACT floor controls of 0.06 tons per year. Nonair quality health and environmental impacts and energy effects are not significant factors for feedrate control. Therefore, considering these factors and costs of approximately $81 million per additional ton of semivolatile metals removed, we are not proposing a beyond-the-floor standard based on feed control of semivolatile metals in the hazardous waste.

For the reasons discussed above, we propose a floor standard for semivolatile metals for existing liquid fuel-fired boilers of 1.1E-5 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste.

3. What Is the Rationale for the MACT Floor for New Sources?

The MACT floor for new sources for semivolatile metals would be 4.3E-6 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. This is an emission level that the single best performing source identified with the Emissions Approach [155] could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained.

Because the floor level is based on normal emissions data, compliance would be documented by complying with a hazardous waste mercury thermal feed concentration on an annual rolling average. See discussion in Part Two, Section XIV.F below.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We evaluated a beyond-the-floor level of 2.1E-6 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste based on an advanced fabric filter using high efficiency membrane bag material and a low air to cloth ratio. The incremental annualized compliance cost for a new liquid fuel-fired boiler with average gas flowrate to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $0.15 million and would provide an incremental reduction in semivolatile metals emissions of less than 0.002 tons per year, for a cost-effectiveness of $87 million per ton of semivolatile metals removed. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond-the-floor standard and estimate that, for a new liquid fuel-fired boiler with average gas flowrate, the amount of hazardous waste generated would increase by 2 tons per year and electricity consumption would increase by 0.54 million kW-hours per year. Considering these factors and cost-effectiveness, we conclude that a beyond-the-floor standard is not warranted. Therefore, we propose a semivolatile metals standard based on the floor level: 4.3E-6 lbs semivolatile metals emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste for new sources.

E. What Is the Rationale for the Proposed Standards for Chromium?

We propose to establish standards for existing and new liquid fuel-fired boilers that limit emissions of chromium to 1.1E-4 lbs and 3.6E-5 lbs chromium emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste, respectively.

We propose to establish emission standards on chromium-only because our data base has very limited compliance test data on emissions of total low volatile metals: arsenic, beryllium, and chromium. We have compliance test data on only two sources for total low volatile metals emissions while we have compliance test data for 12 sources for chromium-only. Although we have total low volatile metals emissions for 12 sources when operating under normal operations, we prefer to use compliance test data to establish the floor because they better address emissions variability.

By establishing a low volatile metal floor based on chromium emissions only we are relying on the particulate matter standard to control the other enumerated low volatile metals—arsenic and beryllium—as well as nonenumerated metal HAP. We request comment on this approach and note that, as discussed below, an alternative approach would be to establish a MACT floor based on normal emissions data for all three enumerated low volatile metals.

We request comment on whether the compliance test data for chromium-only are appropriate for establishing a MACT floor for chromium. We are concerned that some sources in our data base may have used chromium as a surrogate for arsenic and beryllium during RCRA compliance testing such that their chromium emissions may be more representative of their total low volatile metals emissions than only chromium. If we determine this to be the case, we could apply the floor we calculate using chromium emissions to total low volatile metal emissions. Alternatively, we could use the normal emissions data we have on 12 sources and our MACT methodology to establish a total low volatile metals floor.

1. What Is the Rationale for the MACT Floor for Existing Sources?

MACT floor for existing sources is 1.1E-4 lbs chromium emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste, which is based on particulate matter control (for those few sources using a control device) and controlling the feed concentration of chromium in the hazardous waste.

We have compliance test emissions data for approximately 17% of the Start Printed Page 21290sources.[156] The compliance test chromium stack emissions in our database range from 2 to 900 ug/dscm. These emissions are expressed as mass of chromium (from all feedstocks) per unit of stack gas. Hazardous waste thermal emissions, available for 13% of sources, range from 3.2E-6 to 8.8E-4 lbs chromium emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste.

To identify the floor level, we evaluated all compliance test thermal emissions data using the SRE/Feed Approach (see discussion in Section VI.C above). The calculated floor is 1.1E-4 lbs chromium emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste feed, which considers emissions variability. This is an emission level that the average of the best performing sources could be expected to achieve in 99 of 100 future tests when operating under conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this floor level is being achieved by 36% of sources and would reduce chromium emissions by 9.4 tons per year.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We identified two potential beyond-the-floor techniques for control of chromium emissions: (1) Use of a fabric filter to improve particulate matter control; and (2) control of chromium in the hazardous waste feed. For reasons discussed below, we are not proposing a beyond-the-floor standard for chromium.

a. Use of a Fabric Filter to Improve Particulate Matter Control. We evaluated use of a fabric filter as beyond-the-floor control for further reduction of chromium emissions. We evaluated a beyond-the-floor level of 5.5E-5 lbs chromium emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The national incremental annualized compliance cost for liquid fuel-fired boilers to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $5.9 million and would provide an incremental reduction in chromium emissions beyond the MACT floor controls of 0.50 tons per year. We evaluated nonair quality health and environmental impacts and energy effects and determined that this beyond-the-floor option would increase the amount of hazardous waste generated by approximately 160 tons per year and would increase electricity usage by 3.0 million kW-hours per year. Based on these impacts and a cost of approximately $12 million per additional ton of chromium removed, we are not proposing a beyond-the-floor standard based on improved particulate matter control.

b. Feed Control of Chromium in the Hazardous Waste. We evaluated additional feed control of chromium in the hazardous waste as a beyond-the-floor control technique to reduce floor emission levels by 25% to achieve a standard of 8.8E-5 lbs chromium emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. This beyond-the-floor level of control would reduce chromium by an additional 0.20 tons per year at a cost-effectiveness of $22 million per ton of chromium removed. Nonair quality health and environmental impacts and energy effects are not significant factors for feedrate control. We conclude that use of additional hazardous waste chromium feedrate control would not be cost-effective and are not proposing a beyond-the-floor standard based on this control technique.

For the reasons discussed above, we do not propose a beyond-the-floor standard for chromium. Consequently, we propose to establish the emission standard for existing liquid fuel-fired boilers at the floor level: a hazardous waste thermal emission standard of 1.1E-4 lbs chromium emissions attributable to hazardous waste per million Btu of hazardous waste feed.

3. What Is the Rationale for the MACT Floor for New Sources?

The MACT floor for new sources for chromium would be 3.6E-5 lbs chromium emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste feed. This is an emission level that the single best performing source identified with the SRE/Feed Approach could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We evaluated use of an advanced fabric filter using high efficiency membrane bag material and a low air to cloth ratio as beyond-the-floor control to reduce chromium emissions to a beyond-the-floor level of 1.8E-5 lbs chromium emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The incremental annualized compliance cost for a new liquid fuel-fired boiler with average gas flowrate to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $0.15 million and would provide an incremental reduction in chromium emissions of 0.014 tons per year, for a cost-effectiveness of $11 million per ton of chromium removed. We evaluated the nonair quality health and environmental impacts and energy effects of this beyond-the-floor standard and estimate that, for a new liquid fuel-fired boiler with average gas flowrate, the amount of hazardous waste generated would increase by 2 tons per year and electricity consumption would increase by 0.54 million kW-hours per year. Considering these factors and cost-effectiveness, we conclude that a beyond-the-floor standard is not warranted. Therefore, we propose a chromium emission standard for new sources based on the floor level: 3.6E-5 lbs chromium emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste feed.

F. What Is the Rationale for the Proposed Standards for Total Chlorine?

We are proposing to establish a standard for existing liquid fuel-fired boilers that limit emissions of hydrogen chloride and chlorine gas (i.e., total chlorine) to 2.5E-2 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The proposed standard for new sources would be 7.2E-4 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Most liquid fuel-fired boilers that burn hazardous waste do not have back-end controls such as wet scrubbers for total chlorine control. For these sources, total chlorine emissions are controlled by most sources by controlling the feedrate of chlorine in the hazardous waste feed. Approximately 15% of sources use wet scrubbing systems to control total chlorine emissions.

We have compliance test data representing maximum emissions for 40% of the boilers. Total chlorine emissions range from less than 1 to 900 ppmv. Hazardous waste thermal emissions, available for 27% of boilers, range from 1.00E-4 to 1.4 lbs total Start Printed Page 21291chlorine emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste.

The calculated floor is 2.5E-2 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste using the SRE/Feed Approach to identify the best performing sources (see discussion in section VI.C above). This is an emission level that the average of the performing sources could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained. We estimate that this floor level is being achieved by 70% of sources and would reduce total chlorine emissions by 660 tons per year.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We identified two potential beyond-the-floor techniques for control of total chlorine emissions: (1) Use of a wet scrubber; and (2) control of chlorine in the hazardous waste feed. For reasons discussed below, we are not proposing a beyond-the-floor standard for total chlorine.

a. Use of Wet Scrubbing. We considered a beyond-the-floor standard of 1.3E-2 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste based on wet scrubbing to reduce emissions beyond the floor level by 50 percent. The national incremental annualized compliance cost for liquid fuel-fired boilers to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $7.8 million and would provide an incremental reduction in total chlorine emissions beyond the MACT floor controls of 430 tons per year. We evaluated nonair quality health and environmental impacts and energy effects and determined that this beyond-the-floor option would increase both the amount of hazardous wastewater generated and water usage by approximately 3.2 billion gallons per year and would increase electricity usage by 30 million kW-hours per year. Considering these impacts and a cost-effectiveness of approximately $18,000 per additional ton of total chlorine removed, we are not proposing a beyond-the-floor standard based on wet scrubbing.

b. Feed Control of Chlorine in the Hazardous Waste. We evaluated additional feed control of chlorine in the hazardous waste as a beyond-the-floor control technique to reduce floor emission levels by 20% to achieve a standard of 2.0E-2 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The national incremental annualized compliance cost for liquid fuel-fired boilers to meet this beyond-the-floor level rather than comply with the floor controls would be approximately $3.9 million and would provide an incremental reduction in total chlorine emissions beyond the MACT floor controls of 170 tons per year. Nonair quality health and environmental impacts and energy effects are not significant factors for feedrate control. We conclude that use of additional hazardous waste chlorine feedrate control would not be cost-effective at $23,000 per ton of total chlorine removed and are not proposing a beyond-the-floor standard based on this control technique.

For the reasons discussed above, we propose a total chlorine standard for existing liquid fuel-fired boilers based on the floor level: 2.5E-2 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste.

3. What Is the Rationale for the MACT Floor for New Sources?

The MACT floor for new sources for total chlorine would be 7.2E-4 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. This is an emission level that the single best performing source identified with the SRE/Feed Approach could be expected to achieve in 99 of 100 future tests when operating under operating conditions identical to the compliance test conditions during which the emissions data were obtained.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

We evaluated wet scrubbing as beyond-the-floor control for further reductions in total chlorine emissions to achieve a beyond-the-floor level of 3.6E-4 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste. The incremental annualized compliance cost for a new liquid fuel-fired boiler with an average gas flowrate to meet this beyond-the-floor level, rather than comply with the floor level, would be approximately $0.44 million and would provide an incremental reduction in total chlorine emissions of approximately 0.13 tons per year, for a cost-effectiveness of $3.3 million per ton of total chlorine removed. We evaluated nonair quality health and environmental impacts and energy effects and determined that, for a new source with average an average gas flowrate, this beyond-the-floor option would increase both the amount of hazardous wastewater generated and water usage by approximately 140 million gallons per year and would increase electricity usage by 1.3 million kW-hours per year. After considering these impacts and cost-effectiveness, we conclude that a beyond-the-floor standard based on wet scrubbing for new liquid fuel-fired boilers is not warranted.

For the reasons discussed above, we propose a total chlorine standard for new sources based on the floor level: 7.2E-4 lbs total chlorine emissions attributable to the hazardous waste per million Btu heat input from the hazardous waste.

G. What Is the Rationale for the Proposed Standards for Carbon Monoxide or Hydrocarbons?

To control emissions of organic HAP, existing and new sources would be required to comply with either a carbon monoxide standard of 100 ppmv or a hydrocarbon standard of 10 ppmv.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Liquid fuel-fired boilers that burn hazardous waste are currently subject to RCRA standards that require compliance with either a carbon monoxide standard of 100 ppmv, or a hydrocarbon standard of 20 ppmv. Compliance is based on an hourly rolling average as measured with a CEMS. See § 266.104(a). We are proposing today floor standards of 100 ppmv for carbon monoxide or 10 ppmv for hydrocarbons.

Floor control for existing sources is operating under good combustion practices including: (1) Providing adequate excess air with use of oxygen CEMS and feedback air input control; (2) providing adequate fuel/air mixing; (3) homogenizing hazardous waste fuels (such as by blending or size reduction) to control combustion upsets due to very high or very low volatile content wastes; (4) regulating waste and air feedrates to ensure proper combustion temperature and residence time; (5) characterizing waste prior to burning for combustion-related composition (including parameters such as heating value, volatile content, liquid waste viscosity, etc.); (6) ensuring the source is operated by qualified, experienced operators; and (7) periodic inspection and maintenance of combustion system components such as burners, fuel and air supply lines, injection nozzles, etc. Given that there are many interdependent parameters that affect combustion efficiency and thus carbon Start Printed Page 21292monoxide and hydrocarbon emissions, we are not able to quantify “good combustion practices.”

All liquid fuel-fired boilers are currently complying with the RCRA carbon monoxide limit of 100 ppmv on an hourly rolling average. No boilers are complying with the RCRA hydrocarbon limit of 20 ppmv on an hourly rolling average.

We propose a floor level for carbon monoxide level of 100 ppmv because it is a currently enforceable Federal standard. Although the best performing sources are achieving carbon monoxide levels below 100 ppmv, it is not appropriate to establish a lower floor level because carbon monoxide is a surrogate for nondioxin/furan organic HAP. As such, lowering the carbon monoxide floor may not significantly reduce organic HAP emissions. In addition, it would be inappropriate to apply a MACT methodology to the carbon monoxide emissions from the best performing sources because those sources may not be able to replicate their emission levels. This is because there are myriad factors that affect combustion efficiency and, subsequently, carbon monoxide emissions. Extremely low carbon monoxide emissions cannot be assured by controlling only one or two operating parameters We note also that we used this rationale to establish a carbon monoxide standard of 100 ppmv for Phase I sources in the September 1999 Final Rule.

We propose a floor level for hydrocarbons of 10 ppmv even though the currently enforceable standard is 20 ppmv because: (1) The two sources that comply with the RCRA hydrocarbon standard can readily achieve 10 ppmv; and (2) reducing hydrocarbon emissions within the range of 20 ppmv to 10 ppmv should reduce emissions of nondioxin/furan organic HAP. We do not apply a prescriptive MACT methodology to establish a hydrocarbon floor below 10 ppmv, however, because we have data from only two sources. In addition, we note that the hydrocarbon emission standard for Phase I sources established in the September 1999 Final Rule is 10 ppmv also.

There would be no incremental emission reductions associated with these floors because all sources are currently achieving the floor levels.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We considered beyond-the-floor levels for carbon monoxide and hydrocarbons based on use of better combustion practices but conclude that they may not be replicable by the best performing sources nor duplicable by other sources given that we cannot quantify good combustion practices. Moreover, as discussed above, we cannot ensure that lower carbon monoxide or hydrocarbon levels would significantly reduce emissions of nondioxin/furan organic HAP.

Nonair quality health and environmental impacts and energy requirements are not significant factors for use of better combustion practices as beyond-the-floor control.

For these reasons, we conclude that beyond-the-floor standards for carbon monoxide and hydrocarbons are not warranted for existing sources.

3. What Is the Rationale for the MACT Floor for New Sources?

MACT floor for new sources would be the same as the floor for existing sources—100 ppmv for carbon monoxide and 10 ppmv for hydrocarbons—and based on the same rationale.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

As discussed in the context of beyond-the-floor considerations for existing sources, we considered beyond-the-floor standards for carbon monoxide and hydrocarbons for new sources based on use of better combustion practices. But we conclude that beyond the floor standards may not be replicable by the best performing sources nor duplicable by other sources given that we cannot quantify good combustion practices. Moreover, we cannot ensure that lower carbon monoxide or hydrocarbon levels would significantly reduce emissions of nondioxin/furan organic HAP.

Nonair quality health and environmental impacts and energy requirements are not significant factors for use of better combustion practices as beyond-the-floor control.

For these reasons, we are not proposing a beyond-the-floor standard for carbon monoxide and hydrocarbons.

H. What Is the Rationale for the Proposed Standard for Destruction and Removal Efficiency?

To control emissions of organic HAP, existing and new sources would be required to comply with a destruction and removal efficiency (DRE) of 99.99% for organic HAP. For sources burning hazardous wastes F020, F021, F022, F023, F026, or F027, however, the DRE standard is 99.9999% for organic HAP.

1. What Is the Rationale for the MACT Floor for Existing Sources?

Liquid fuel-fired boilers that burn hazardous waste are currently subject to RCRA DRE standards that require 99.99% destruction of designated principal organic hazardous constituents (POHCs). For sources that burn hazardous wastes F020, F021, F022, F023, F026, or F027, however, the DRE standard is 99.9999% destruction of designated POHCs. See § 266.104(a).

The DRE standard helps ensure that a combustor is operating under good combustion practices and thus minimizing emissions of organic HAP. Under the MACT compliance regime, sources would designate POHCs that are organic HAP or that are surrogates for organic HAP.

We propose to establish the RCRA DRE standard as the floor for existing sources because it is a currently enforceable Federal standard. There would be no incremental costs or emission reductions associated with this floor because sources are currently complying with the standard.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We considered a beyond-the-floor level for DRE based on use of better combustion practices but conclude that it may not be replicable by the best performing sources nor duplicable by other sources given that we cannot quantify better combustion practices. Moreover, we cannot ensure that a higher DRE standard would significantly reduce emissions of organic HAP given that DRE measures the destruction of organic HAP present in the boiler feed rather than gross emissions of organic HAP. Although a source's combustion practices may be adequate to destroy particular organic HAP in the feed, other organic HAP that may be emitted as products of incomplete combustion may not be controlled by the DRE standard.[157]

For these reasons, and after considering nonair quality health and environmental impacts and energy requirements, we are not proposing a beyond-the-floor DRE standard for existing sources.

3. What Is the Rationale for the MACT Floor for New Sources?

We propose to establish the RCRA DRE standard as the floor for new sources because it is a currently enforceable Federal standard.

4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources

Using the same rationale as we used to consider a beyond-the-floor DRE Start Printed Page 21293standard for existing sources, we conclude that a beyond-the-floor DRE standard for new sources is not warranted. Consequently, after considering nonair quality health and environmental impacts and energy requirements, we are proposing the floor DRE standard for new sources.

XII. How Did EPA Determine the Proposed Emission Standards for Hazardous Waste Burning Hydrochloric Acid Production Furnaces?

The proposed standards for existing and new hydrochloric acid production furnaces that burn hazardous waste are summarized in the table below. See proposed § 63.1218.

Proposed Standards for Existing and New Hydrochloric Acid Production Furnaces

Hazardous air pollutant or surrogateEmission standard1
Existing sourcesNew sources
Dioxin and furan0.40 ng TEQ/dscm0.40 ng TEQ/dscm.
Hydrochloric acid and chlorine gas 214 ppmv or 99.9927% System Removal Efficiency1.2 ppmv or 99.99937% System Removal Efficiency.
Carbon monoxide or hydrocarbons 3100 ppmv carbon monoxide or 10 ppmv hydrocarbons100 ppmv carbon monoxide or 10 ppmv hydrocarbons.
Destruction and Removal EfficiencyFor existing and new sources, 99.99% for each principal organic hazardous constituent (POHC). For sources burning hazardous wastes F020, F021, F022, F023, F026, or F027, however, 99.9999% for each POHC.
1 All emission standards are corrected to 7% oxygen, dry basis.
2 Combined standard, reported as a chloride (Cl(−)) equivalent.
3 Hourly rolling average. Hydrocarbons reported as propane.

A. What Is the Rationale for the Proposed Standards for Dioxin and Furan?

The proposed standard for dioxin/furan for existing and new sources is 0.40 ng TEQ/dscm.

1. What Is the Rationale for the MACT Floor for Existing Sources?

The proposed MACT floor for existing sources is compliance with the proposed CO/HC emission standard and compliance with the proposed DRE standard.

Hydrochloric acid production furnaces use wet scrubbers to remove hydrochloric acid from combustion gases to produce the hydrochloric acid product and to minimize residual emissions of hydrochloric acid and chlorine gas. Thus, dioxin/furan cannot be formed on particulate surfaces in the emission control device as can happen with electrostatic precipitators and fabric filters. Nonetheless, dioxin/furan emissions from hydrochloric acid production furnaces can be very high. We have dioxin/furan emissions data for 18 test conditions representing 14 of the 17 sources. Dioxin/furan emissions range from 0.02 ng TEQ/dscm to 6.8 ng TEQ/dscm.

We investigated whether it would be appropriate to establish separate dioxin/furan standards for furnaces equipped with waste heat recovery boilers versus those without boilers. Ten of the 17 hydrochloric acid production furnaces are equipped with boilers. We considered whether waste heat recovery boilers may be causing the elevated dioxin/furan emissions, as appeared to be the case for incinerators equipped with boilers. See 62 FR at 24220 (May 2, 1997) where we explain that heat recovery boilers preclude rapid temperature quench of combustion gases, thus allowing particle-catalyzed formation of dioxin/furan. The dioxin/furan data for hydrochloric acid production furnaces indicate, however, that furnaces with boilers have dioxin/furan emissions ranging from 0.05 to 6.8 ng TEQ/dscm, while furnaces without boilers have dioxin/furan emissions ranging from 0.02 to 1.7 ng TEQ/dscm. Based on a statistical analysis of the data sets (see discussion in Part Two, Section II.E), we conclude that the dioxin/furan emissions for furnaces equipped with boilers are not significantly different from dioxin/furan emissions for furnaces without boilers. Thus, we conclude that separate dioxin/furan emission standards are not warranted.

We cannot identify or quantify a dioxin/furan control mechanism for these furnaces. Consequently, we conclude that establishing a floor emission level based on emissions from the best performing sources would not be appropriate because the best performing sources may not be able to replicate their emission levels, and other sources may not be able to duplicate those emission levels.

We note, however, that dioxin/furan emissions can be affected by the furnace's combustion efficiency. Operating under poor combustion conditions can generate dioxin/furan and organic precursors that may contribute to post-combustion dioxin/furan formation. Because we cannot quantify a dioxin/furan floor level and because hydrochloric acid production furnaces are currently required to operate under good combustion practices by RCRA standards for carbon monoxide/hydrocarbons and destruction and removal efficiency, we identify those RCRA standards as the proposed MACT floor. See § 266.104 requiring compliance with destruction and removal efficiency and carbon monoxide/hydrocarbon emission standards.[158] We also find, as required by CAA section 112(h)(1), that these proposed standards are consistent with section 112(d)'s objective of reducing emissions of these HAP to the extent achievable.

We also request comment on an alternative MACT floor expressed as a dioxin/furan emission concentration. Although it would be inappropriate to identify a floor concentration based on the average emissions of the best performing sources as discussed above, we could identify the floor as the highest emission concentration from any source in our data base, after considering emissions variability. Under this approach, the highest emitting source could be expected to achieve the floor 99 out of 100 future tests when Start Printed Page 21294operating under the same conditions as it did when the emissions data were obtained. A floor that is expressed as a dioxin/furan emission level would prevent sources from emitting at levels higher than the (currently) worst-case source (actually, the worst-case performance test result) currently emits. We specifically request comment on this alternative MACT floor.

2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources

We evaluated use of an activated carbon bed (preceded by gas reheating to above the dewpoint) as beyond-the-floor control for dioxin/furan. Carbon beds can achieve greater than 99% reduction in dioxin/furan emissions.[159