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7th Modeling Conference

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The 7th Conference on Air Quality Modeling was held on June 28-29, 2000 in Washington,  D.C.  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. The conference was announced in the Federal Register on May 19, 2000 (Volume 65, Number 98). The conference proceedings for June 28, 2000 (PDF) (196pp, 659k) and June 29, 2000 (PDF) (150pp, 507k) are available, as well as the Summary of Public Comments and EPA Responses (PDF) (47pp, 118k).

Based on public comments from the 7th 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.


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