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Proposed Rule

Availability of Additional Information for the Proposed Rulemaking for Colorado's Attainment Demonstration for the 1997 8-Hour Ozone Standard and Related Revisions

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Information about this document as published in the Federal Register.

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This document has been published in the Federal Register. Use the PDF linked in the document sidebar for the official electronic format.

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Environmental Protection Agency (EPA).

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Notice of data availability.


This document announces the availability of revised modeling that relates to EPA's notice of proposed rulemaking for Colorado's Attainment Demonstration for the 1997 8-hour Ozone Standard for the Denver Metro Area/North Front Range (DMA/NFR) nonattainment area and Related Revisions. The results of the modeling and the modeling files have been placed in the docket for this rulemaking. EPA is providing an opportunity to comment on the revised modeling.


Comments must be received on or before January 18, 2011.


Submit your comments identified by Docket ID Regulation Number EPA-R08-OAR-2010-0285 by one of the following methods:

  • Mail: Callie Videtich, Director, Air Program, Environmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 Wynkoop Street, Denver, Colorado 80202-1129.
  • Hand Delivery: Callie Videtich, Director, Air Program, Environmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 Wynkoop Street, Denver, Colorado 80202-1129. Such deliveries are only accepted Monday through Friday, 8 a.m. to 4:30 p.m., excluding Federal holidays. Special arrangements should be made for deliveries of boxed information.
  • E-mail:
  • Fax: (303) 312-6064 (please alert the individual listed in the FOR FURTHER INFORMATION CONTACT if you are faxing comments).

Instructions: Direct your comments to Docket ID No. EPA-R08-OAR-2010-0285. EPA's 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 whose disclosure is restricted by statute. Do not submit information that you consider to be CBI or otherwise protected through or e-mail. The Web site is an “anonymous access” system, 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 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 instructions on submitting comments, go to Section I. General Information 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 whose disclosure is restricted by statute. Certain other material, such as copyrighted material, will be publicly available only in hard copy. Publicly available docket materials are available either electronically in or in hard copy at the Air Program, Environmental Protection Agency (EPA), Region 8, 1595 Wynkoop Street, Denver, Colorado 80202-1129. EPA requests that if at all possible, you contact the individual listed in the FOR FURTHER INFORMATION CONTACT section to view the hard copy of the docket. You may view the hard copy of the docket Monday through Friday, 8 a.m. to 4 p.m., excluding Federal holidays.

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Mark Komp, Air Program, 1595 Wynkoop Street, Mailcode: 8P-AR, Denver, Colorado 80202-1129, (303) 312-6022,

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Table of Contents

I. General Information

II. Notice of Data Availability


For the purpose of this document, the following definitions apply:

(i) Act or CAA means or refers to the Clean Air Act, unless the context indicates otherwise.

(ii) EPA, we, us or our means or refers to the United States Environmental Protection Agency.

(iii) SIP means or refers to State Implementation Plan.

(iv) ppb means parts per billion of ozone in air.

(v) State or Colorado means the State of Colorado, unless the context indicates otherwise.

(vi) NAAQS means or refers to National Ambient Air Quality Standards.

(vii) NODA means or refers to Notice of Data Availability.

I. General Information

A. What should I consider as I prepare my comments for EPA?

1. Submitting CBI. Do not submit this information to EPA 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-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:

  • Identify the rulemaking 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.

II. Notice of Data Availability

On June 18, 2009, Colorado submitted revisions to the Colorado SIP for the 1997 8-hour ozone NAAQS for the DMA/NFR nonattainment area. The revisions included a modeled attainment demonstration using Start Printed Page 78952photochemical grid modeling that the State conducted in 2008. (Photochemical grid modeling is used to project future 8-hour ozone Design Values for comparison to the 85.0 ppb ozone NAAQS.) On July 21, 2010, we proposed to act on the State's revisions and as part of that action, proposed to approve Colorado's attainment demonstration and certain other aspects of the revisions, and proposed to disapprove other aspects of the revisions. For further information on Colorado's submittal and our proposed action, please consult the Federal Register (July 21, 2010; 75 FR 42346).

On October 7, 2010, Colorado submitted revised photochemical modeling results to us for the DMA/NFR ozone SIP. Colorado re-ran the photochemical model because in September 2010 the State discovered that errors had been made in specifying the location of certain point sources in the 2008 modeling. Latitude/longitude locations for some point sources in the original modeling effort were mistakenly derived using the degree-minute-second coordinate system rather than the correct decimal degree coordinate system. As a result, some point source locations were displaced in the grid-coordinate system used by the model. Thus, Colorado re-ran the model with the correct coordinates to determine whether the errors made in locating some point sources affected the reliability of the model results.

The projected Design Values for 2010 resulting from the revised modeling remain below the 85.0 ppb ozone NAAQS. For the SIP's 2010 base case, the revised modeling's maximum projected 8-hour ozone Design Values are found at the Rocky Flats North and Fort Collins West monitoring sites—84.7 ppb ozone at both locations in 2010. This is 0.2 ppb lower than the State's 2008 modeling projected using incorrect point source locations. Because it produced slightly lower values at the monitoring sites with maximum Design Values, the revised modeling supports the conclusions that EPA proposed regarding the 2008 modeling.

With this Notice of Data Availability, we are providing an opportunity for the public to comment on Colorado's October 2010 revised modeling, including comments on how it may affect EPA's proposed determinations as reflected in our July 21, 2010 proposal. We are not re-opening the comment period on the material that was before the Agency at the time of the July 21, 2010 proposal.

Colorado's October 2010 revised modeling is reflected in the following two documents, which we have added to the rulemaking docket:

1. Final 2010 Ozone Attainment Demonstration Modeling for the Denver 8-Hour Ozone State Implementation Plan. Docket Number: EPA-R08-OAR-2010-0285-0025.

2. MEMORANDUM, October 7, 2010: ENVIRON: Denver Final 2010 Ozone Attainment Demonstration Modeling using Correct Point Source Locations. Docket Number: EPA-R08-OAR-2010-0285-0043.

We will take final action based on our notice of proposed rulemaking that was published in the Federal Register on July 21, 2010 (75 FR 42346), the comments we received on that proposal, Colorado's October 2010 revised modeling, and any comments we receive in response to this NODA.

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List of Subjects in 40 CFR Part 52

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Dated: December 10, 2010.

Carol Rushin,

Deputy Regional Administrator, Region 8.

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[FR Doc. 2010-31738 Filed 12-16-10; 8:45 am]