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Support Center for Regulatory Atmospheric Modeling (SCRAM)

7th Conference on Air Quality Modeling

On May 19, 2000, the U.S. Environmental Protection Agency (EPA) announced the Seventh Conference on Air Quality Modeling.  The modeling conference, mandated by Section 320 of the Clean Air Act, was held in Washington, D.C. from June 28th through 29th, 2000. The main purpose of the Conference was to receive comments on EPA's proposal to add several new modeling techniques to Appendix W of 40 CFR Part 51.

Based on public comments from the 7th Modeling Conference, the Guideline on Air Quality Models (Appendix W to 40CFR Part 51) was substantially revised.  The public comments clearly supported many proposed changes, notably:

  • adoption of CALPUFF in appendix A, as proposed, for assessing long range transport of pollutants and their impacts on Federal Class I areas;
  • removal of Climatological Dispersion Model (CDM), Ram and the Urban Airshed  Model (UAM) from appendix A, as proposed;
  • simplification of complex terrain screening techniques in section 5;
  • revision of section 9 to reflect our October 1997 settlement with the Utility Air Regulatory Group regarding specification of emissions from background sources, as proposed;
  • transfer of appendix B and appendix C to our website, as proposed.

Regarding AERMOD, nearly every commenter urged EPA to integrate aerodynamic downwash into AERMOD (i.e., not to require ISC-PRIME for some analyses and AERMOD for others).  The only cautions were associated with the need for documentations, evaluation and review of the downwash enhancement to AERMOD. As a result of AERMIC's (the American Meteorological Society (AMS)/ EPA Regulatory Model Improvement Committee) efforts to revise AERMOD, incorporating the PRIME algorithm and making a few other incidental modifications and to respond to the public's cautions, we believe that AERMOD, as modified for downwash, merits further examination of performance results.  Also, since the April 2000 proposal, the Federal Aviation Administration decided to configure EDMS3.1 to incorporate the AERMOD dispersion model, and results of its performance with AERMOD only recently became available.  Consequently, AERMOD and EDMS4.0, as well as other conforming changes for the Guideline, will be the subject of a separate, later regulatory action.

Disclaimer: The material provided below were presented during the proceedings of the Seventh Conference on Air Quality Modeling. The information contained in some of these presentations may not reflect U.S. EPA policy and should not be considered as an official endorsement of the Agency.

Conference Information:


Conference Review Material:

Please direct any additional questions concerning the Seventh Conference on Air Quality Modeling to Mr. George Bridgers, email: