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Conference on Air Quality Modeling

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Notice of conference.


The EPA will be hosting the Tenth Conference on Air Quality Modeling on March 13-15, 2012. Section 320 of the Clean Air Act (CAA) requires a conference to be held every 3 years. The purpose of the conference is to provide an overview of the latest features of the agency's preferred air quality models and to provide a forum for public review and comment on how the agency determines and applies air quality models in the future.


Comments: Comments on how the agency determines and applies air quality models must be received on or before April 16, 2012.

Conference: The conference will be held on March 13 through 15, 2012, from 8:30 a.m. to 5:00 p.m. Requests to speak at the conference should be submitted to the individual listed below by March 5, 2012.


Comments: Submit your comments, identified by Docket ID No. EPA-HQ-OAR-2012-0056 by one of the following methods:

  • Follow the on-line instructions for submitting comments. This is the EPA's preferred method for receiving comments.
  • Email: Comments may be sent by electronic mail (email) to, Attention Docket ID No. EPA-HQ-OAR-2012-0056.
  • Fax: Fax your comments to (202) 566-9744, Attention Docket ID No. EPA-HQ-OAR-2012-0056.
  • Mail: Send your comments to: Air and Radiation Docket and Information Center, Environmental Protection Agency, Mailcode: 2822T, 1200 Pennsylvania Ave. NW., Washington, DC 20460, Attention Docket ID No. EPA-HQ-OAR-2012-0056.
  • Hand Delivery or Courier: Deliver your comments to EPA Docket Center, 1301 Constitution Ave. NW., Room 3334, 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. EPA-HQ-OAR-2012-0056. The 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 email. The Web site is an “anonymous access” system, which means the EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an email comment directly to the EPA without going through, your email 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, the 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 the EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, the 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 the EPA's public docket, visit the EPA Docket Center homepage at

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 form. Publicly available docket materials are available either electronically in or in hard copy at the Air Docket in the EPA Docket Center, EPA West, Room 3334, 1301 Constitution Ave. NW., Washington, DC. This docket facility is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The Docket telephone number is (202) 566-1742; fax (202) 566-9744.

Background Information: Additional information and a more detailed agenda are electronically available at

Conference: The conference will be held in the EPA Auditorium, Room C111, 109 T.W. Alexander Drive, Research Triangle Park, NC 27711.


George Bridgers, U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Air Quality Assessment Division, Mail Code C439-01, Research Triangle Park, NC 27711; telephone: (919) 541-5563; fax: (919) 541-0044; email address:


I. General Information

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

1. Submitting CBI. Do not submit this information to the EPA through or email. 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 the 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. Background

The Guideline on Air Quality Models (hereafter, called the Guideline, which is found in Appendix W to 40 CFR part 51), is used by the EPA, states and industry to prepare and review new source permits, source permit modifications, and State Implementation Plan submittals and revisions. The Guideline serves as a means by which national consistency is maintained in air quality analyses. We originally published the Guideline in April 1978, and it was incorporated by reference in the regulations for the Prevention of Significant Deterioration of Air Quality in June 1978. We revised the Guideline in 1986, and updated it with supplement A in 1987, supplement B in July 1993, and supplement C in August 1995. We published the Guideline as Appendix W to 40 CFR part 51 when we issued supplement B. We republished the Guideline in August 1996 (61 FR 41838) to adopt the CFR system for labeling paragraphs.

To support the process of developing and revising the Guideline during the period 1977-1988, we held the First, Second, and Third Conferences on Air Quality Modeling as required by CAA Section 320 to help standardize modeling procedures. These modeling conferences provided us with comments on the Guideline and associated revisions, thereby helping us introduce improved modeling techniques into the regulatory process.

In October 1988, we held the Fourth Conference on Air Quality Modeling to advise the public on new modeling techniques and to solicit comments to guide our consideration of any rulemaking needed to further revise the Guideline. We held the Fifth Conference in March 1991, which served as a public hearing for the proposed revisions to the Guideline. In August 1995, we held the Sixth Conference as a forum to update our available modeling tools with state-of-the-science techniques and for the public to offer new ideas. The Seventh Conference was held in June 2000 and served as a public hearing for the proposed changes to the recommended air quality models in Appendix W including the CALPUFF modeling system, AERMOD modeling system, and ISC-PRIME model. We held the Eighth Conference on Air Quality Modeling in September 2005, which provided details on changes to these recommended air quality models, including the Notice of Data Availability published in September 2003 related to the incorporation of the PRIME downwash algorithm in the AERMOD dispersion model in response to comments received from the Seventh Conference, and details on available methods for model performance evaluation. Additionally, at the Eighth Conference, there was a panel of experts discussion on the use of state-of-the-science prognostic meteorological data for informing the dispersion models.

The most recent conference was the Ninth Conference on Air Quality Modeling held in October 2008. The conference began with an overview presentation and review of Appendix W and plans to reinstitute the Model Clearinghouse. Several presentations were made on non-guideline applications of dispersion models as well as a continuation of discussions from the Eighth Conference on the use of prognostic meteorological data with respect to informing the Appendix W models. Updates were provided on the regulatory status, recent coding changes, and future development of the AERMOD modeling system, the EPA's preferred model for near-field regulatory applications, and the CALPUFF modeling system, the EPA's preferred model for long-range transport of criteria pollutants and their impacts on Federal Class I areas. The Ninth Conference concluded with a collection of presentations reviewing the available model evaluation methods and reviewing new and emerging models and techniques for future consideration under Appendix W. The proceedings, including supporting material and public comments received, are found in Docket No. EPA-HQ-OAR-2008-0604.

III. Public Participation

The Tenth Conference on Air Quality Modeling will be open to the public; no admission fee is charged and there is no formal registration. The conference will begin the first morning with introductory remarks by the presiding EPA official. The following topics will be presented:

A. Appendix W overview;

B. Model Clearinghouse update;

C. Currently preferred air quality models (AERMOD and CALPUFF) status and updates;

D. Review of prognostic meteorological data processing tool for dispersion models, MMIF;

E. Modeling for compliance demonstration of the PM2.5 National Ambient Air Quality Standards (NAAQS) including discussion of the draft PM2.5 (primary and secondary) modeling guidance;

F. Modeling for compliance demonstration of the 1-hour NO2 and SO2 NAAQS including presentations from the AERMOD Implementation Workgroup NO2 and SO2 modeling study;

G. Review of new and emerging models/techniques for future consideration under Appendix W to address long-range transport and chemistry; and

H. Other presentations by the public.

Those wishing to speak at the conference, whether to volunteer a presentation on a special topic or to offer general comment on any of the modeling techniques scheduled for presentation, should contact the EPA at the address given in the FOR FURTHER INFORMATION CONTACT section (note the cutoff date). Such persons should identify the organization (if any) on whose behalf they are speaking and the length of the presentation. If a presentation of general comments is projected to be longer than 10 minutes, the presenter should also state why a longer period is needed. Persons failing to submit a written notice but desiring to speak at the conference should notify the presiding officer immediately before the conference, and they will be scheduled on a time-available basis.

The conference will be conducted informally and chaired by an EPA official. There will be no sworn testimony or cross examination. A verbatim transcript of the conference proceedings will be produced and placed in the docket. Speakers should bring extra copies of their presentation for inclusion in the docket and for the convenience of the recorder. Speakers will also be permitted to enter written comments into the record. Additional written statements or comments should be sent to the OAR Regulatory Docket (see ADDRESSES section). A transcript of the proceedings and a copy of all written comments will be maintained in Docket ID No. EPA-HQ-OAR-2012-0056, which will remain open until April 16, 2012, for the purpose of receiving additional comments.

Dated: January 25, 2012.

Mary E. Henigin,

Acting Director, Office of Air Quality Planning and Standards.

[FR Doc. 2012-2026 Filed 1-30-12; 8:45 am]