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What's Going On With the 1-Hour SO2 NAAQS Implementation Process?

September 2011 | What's Going On With the 1-Hour SO2 NAAQS Implementation Process? | Dan D.

Now that we’ve all had some time to digest the plethora of guidance memoranda and updated air quality modeling programs that were released in March and April of 2011 and summarized by ALL4 in our April 4 The Record article (“Finally! Guidance and Updated Programs Catch Up with New 1-Hour NAAQS”), what has actually been happening with the 1-hour sulfur dioxide (SO2) National Ambient Air Quality Standards (NAAQS) implementation process?  As was outlined in the preamble to the final 1-hour SO2 NAAQS, an analytic approach that used both air quality monitoring and air quality dispersion modeling was being used for the attainment designation process given the limited network of ambient SO2 monitors.  Initial attainment status designations were due to U.S. EPA by June 3, 2011, and at that time most states recommended an “unclassifiable” designation for any areas that did not have monitors (since no air quality modeling had yet been completed).  States now have until April 3, 2012 to provide updated information to U.S. EPA using air quality dispersion modeling to support their attainment designations for the 1-hour SO2 NAAQS.  ALL4 was curious regarding where individual states actually were in the attainment designation process for the 1-hour SO2 NAAQS, so we contacted 22 states and asked them the following six (6) questions:

  1. Are you currently completing any air quality dispersion modeling to support the SO2 attainment designations in your state?
  2. If so, are you using AERMOD to conduct this air quality dispersion modeling?
  3. What are the screening criteria that you are using for determining what facilities to include in this air quality dispersion modeling?
  4. Who is conducting the air quality dispersion modeling?
  5. What is your timeline for completion?
  6. Do you have any other comments on the process?

What did we find out?  Of the 15 states that responded:

  • Seven (7) have begun air quality modeling using AERMOD.
  • Six (6) are following U.S. EPA guidance for the criteria for including sources.
  • Four (4) are requiring individual facilities to complete the air quality modeling.
  • Four (4) are requiring facilities to model on a “site-specific” basis.  More than likely, “site-specific” means that the states will model the smaller, less complex facilities and will require facilities with more sources and more complicated arrangements to complete the air quality modeling themselves. 
  • None of the states had any hard timeline in place and are likely relying on the U.S. EPA deadline of April 3, 2012. 

All of the results of our conversations are summarized in a table at the end of this article.

As we can see, not a lot of air quality modeling has been completed yet.  Note that if your facility is located in a state that is conducting the air quality modeling and has a

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