4 The record articles

April Showers Bring…Proposed Modeling Updates for 2015!

Posted: November 24th, 2014

Author: All4 Staff 

If there’s one (1) thing that the regulated community can agree on, it’s their concern over the challenges related to air quality modeling.  Industry is all too familiar with the conservative modeling results for their proposed projects, which can trigger stricter emissions controls required for sources or otherwise limit, postpone, or cancel expansion plans.

U.S. EPA plans to update its air quality modeling requirements in spring 2015, which will include revisions to Appendix W, U.S. EPA’s air quality modeling guidelines.  As presented in an October 28, 2014 presentation to U.S. EPA’s Clean Air Act Advisory Committee (CAAAC), the proposed revisions include:

  • Incorporating new analytical techniques to address ozone and secondary PM2.5;
  • Updating how to conduct individual source and cumulative impact analysis for the new 1-hour NAAQS; and
  • Updating current U.S. EPA-preferred models to address input and science issues.

U.S. EPA has established working groups to tackle these revisions and consider both near-field impacts and long range transport.  The proposed revisions will be discussed at the 11th Conference on Air Quality Modeling in Raleigh, NC this spring, and U.S. EPA plans to issue the final rule in spring 2016.

In addition to updates to Appendix W, U.S. EPA plans to establish two (2) new rules addressing PM2.5 significant impact levels (SILs) and ozone prevention of significant deterioration (PSD) and nonattainment new source review (NNSR) requirements.  The PM2.5 SIL reconsideration rule will re-establish PM2.5 SILs for both the 24-hour and annual standards, as well as establish revised significant emission rates (SERs) for those PM2.5 precursors that trigger the requirement for air quality analysis.  The ozone PSD and NNSR requirements rule will address screening criteria associated with the measurement of ozone impacts, and will establish SILs for the ozone standard.  In addition, the SERs for VOC and NOX (ozone precursors) that trigger the requirement for air quality analysis will be revised.

ALL4 will be keeping an eye on the proposed air quality modeling revisions and rules presented by the U.S. EPA, so check back for updates that could impact you!


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