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Draft Certification Procedures for Light-Duty Diesel Vehicles and Heavy-Duty Diesel Engines Using Selective Catalyst Reduction (SCR) Technologies for Public Comment

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Information about this document as published in the Federal Register.

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Environmental Protection Agency (EPA).




EPA is requesting comment on draft guidance discussing our intended approach for the certification of light-duty diesel vehicles and heavy-duty diesel engines using selective catalyst reduction (SCR) systems to meet EPA emissions standards.


Comments must be received on or before December 15, 2006.


Submit your comments, identified by Docket ID No. EPA-HQ-OAR-2006-0886, by one of the following methods:

  • Follow the on-line instructions for submitting comments.
  • E-mail:
  • Fax: (202) 566-1741, Attention Docket ID No. EPA-HQ-OAR-2006-0886.
  • Mail: Air Docket, Attention Docket ID No. EPA-HQ-OAR-2006-0886, Environmental Protection Agency, Mailcode: 6102T, 1200 Pennsylvania Ave., NW., Washington, DC 20460.
  • Hand Delivery: USEPA, Air Docket, 1301 Constitution Ave, NW., Room B102, Washington, DC 20004, Attention Docket ID No. EPA-HQ-OAR-2006-0886. 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. EPA-HQ-OAR-2006-0886. Our policy is that all comments received will be included in the public docket without change and may be made available online at, including any personal information provided, unless the comment includes information claimed to be confidential business information (CBI) or other information for which disclosure is restricted by statute. Do not submit information that you consider to be CBI or otherwise protected through

The Web site is an “anonymous access” system, which means we 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 us without going through, 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, we recommend that you include your name and other contact information in the body of your comment and with any disk or CD you submit. If we cannot read your comment due to technical difficulties and cannot contact you for clarification, we may not be able to consider your comment. Electronic files should avoid the use of special characters, should not use any form of encryption, and should be free of any defects or viruses. For additional information about our public docket visit the EPA Docket Center homepage at​epahome/​dockets.htm. For additional instructions on submitting comments, go to Section I of the SUPPLEMENTARY INFORMATION section of this document.

Docket: All documents in the docket are listed in the index. Although listed in the index, some information is not publicly available, e.g., CBI or other information for which disclosure is restricted by statute. Certain other material, such as copyrighted material, will be publicly available only in hard Start Printed Page 66524copy. Publicly available docket materials are available either electronically in or in hard copy at the Air 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 Air Docket is (202) 566-1742.

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Linc Wehrly, Environmental Protection Agency, 2565 Plymouth Road; telephone number: 734-214-4826; fax number: 734-214-4053; e-mail address:

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

1. Submitting CBI. Do not submit CBI to us through 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 that you mail to EPA, mark the outside of the disk or CD as CBI and then identify electronically within the disk or CD 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:

  • Identify the rule or notice by docket number and other identifying information (subject heading, Federal Register date and page number).
  • 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.
  • Explain why you agree or disagree; suggest alternatives and substitute language for your requested changes.
  • Describe any assumptions and provide any technical information and/or data that you used.
  • If you estimate potential costs or burdens, explain how you arrived at your estimate in sufficient detail to allow for it to be reproduced.
  • Provide specific examples to illustrate your concerns, and suggest alternatives.
  • Explain your views as clearly as possible, avoiding the use of profanity or personal threats.
  • Make sure to submit your comments by the comment period deadline identified.

3. Docket Copying Costs. You may be charged a reasonable fee for photocopying docket materials, as provided by 40 CFR part 2.

II. Manufacturer Guidance Certification Procedure for Light-Duty Diesel Vehicles Using Selective Catalyst Reduction (SCR) Technologies

A. Background

On February 10, 2000, EPA published the Tier 2 emission standards for light-duty vehicles and trucks. These standards established common, “fuel neutral” emission requirements for gasoline and diesel vehicles. They also set common standards for all passenger cars, light trucks, and medium-duty passenger vehicles. The Tier 2 standards allow emission averaging and require new vehicles to meet an average NOX emission level of 0.07 grams per mile (g/mi). On January 18, 2001, EPA published a rule setting stringent new requirements for heavy-duty highway engines and vehicles starting in 2007. Manufacturers plan to meet these requirements by optimizing engine designs for low emissions and adding high-efficiency aftertreatment. The diesel engine NOX standard, which is phased-in between model years 2007 and 2010, is 0.20 grams per brake horsepower-hour (g/bhp-hr).

Diesel engine and vehicle manufacturers have examined the use of several different types of NOX reduction technologies in order to meet these requirements. One type of NOX reducing technology, selective catalyst reduction (SCR), is of particular interest to diesel manufacturers because it can achieve as high as 90% NOX conversion efficiencies. An SCR system uses a nitrogen containing reducing agent (usually ammonia or urea) injected into the exhaust gas upstream of the catalyst. The reducing agent needs to be periodically replenished. Without the reducing agent, the efficiency of the SCR catalyst drops to zero and NOX emissions can potentially increase substantially.

EPA intends to issue guidance to vehicle and engine manufacturers to discuss our intended approach for the certification of light-duty diesel vehicles and heavy-duty engines using SCR systems. In advance of issuing this guidance, EPA is requesting comment on the various elements of this draft approach to ensure that the public can provide input to EPA regarding this issue.

EPA has place the draft guidance document in EPA Air Docket EPA-HQ-OAR-2006-0886. Interested parties should submit comments according to the guidelines described at the beginning of this notice. After fully considering comments received, we will issue a final guidance document.

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Dated: November 6, 2006.

Margo Tsirigotis Oge,

Director, Office of Transportation and Air Quality.

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[FR Doc. E6-19264 Filed 11-14-06; 8:45 am]