4 The record articles

U.S. EPA’s Input on the Future of Air Quality Dispersion Modeling

Posted: November 13th, 2017

Author: All4 Staff 

On September 25th, the U.S. Environmental Protection Agency (U.S. EPA) held their 2017 Regional/State/Local Modelers’ Workshop in Raleigh, NC.  Though I had originally planned to be in my beautiful hometown of Savannah, Georgia for my mom’s tenth 39th birthday, I couldn’t miss out on the opportunity to learn more about the revisions to 40 CFR Part 51, Appendix W (also known as the Guideline on Air Quality Models), and to gain insights on the future of air quality modeling…sorry, mom!

I won’t drown you with the details of the revisions to Appendix W (which, as you know, were released in December 2016). However, if you would like more information regarding these revisions, I encourage you to read previously posted ALL4 blogs. Here, you’ll find many articles, as well as contact information for our modeling team should you have any specific needs.

So, in the spirit of getting to the point, here is the latest:

  • The significant impact level (SIL) guidance for particulate matter less than 2.5 microns in diameter (PM2.5) and Ozone (O3) is currently in Washington D.C., awaiting review by the Office of Management and Budget (OMB).  The EPA expects the guidance to be issued in December 2017.
  • The U.S. EPA is continuing to develop the Model Clearinghouse.  This will serve as a recordkeeping database for all approvals of alternate modeling techniques to ensure fairness, consistency, and transparency in the modeling community.
  • You may have heard of “unofficial” updates/guidance to the “Puzzle Book” (you know, the DRAFT New Source Review Workshop Manual that included ultra-conservative modeling guidance) .  Be wary of using anything from these unofficial documents without input from your local permitting authority, as the U.S. EPA was expressly clear that they did not participate, review, or endorse these documents.  In general, if in doubt about utilizing “unofficial” modeling approaches, techniques, or assumptions, contact your Regional Office for guidance (or call ALL4 for support).
  • U.S. EPA plans to release an AERMOD System Development Plan.  The document will be a formal statement of U.S. EPA’s planned scientific updates (i.e., does not apply to bugs, usability enhancements, etc.) to AERMOD, AERSCREEN, AERMET, and AERMAP.  The U.S. EPA’s estimated date of release is early 2018, with intentions to update the plan annually thereafter.  Let’s all keep our fingers crossed that this document is released in a timely manner, as it will be invaluable to know the goals and concerns of the U.S. EPA as we strategize our air quality modeling options.

As always, the future of air quality dispersion modeling is going to be exciting and adventurous, yet challenging to navigate.  The ALL4 modeling team is here to help!  For all your modeling needs, reach out to any of the ALL4 modeling team members.


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