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

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 potential to emit (PTE) for SO2 that is greater than 100 tons per year, it is still in your best interest to complete a parallel air quality modeling analysis.

Many states were waiting on additional air quality modeling guidance that U.S. EPA promised to provide by mid-summer.  Their patience was rewarded on September 22, 2011 when U.S. EPA released its “Guidance for 1-Hour SO2 NAAQS SIP Submissions.”  Some highlights of the guidance document are as follows:

• For implementation of the 1-hour SO2 NAAQS, U.S. EPA states that refined dispersion modeling should be used to determine if areas with sources that have the potential to cause or contribute to a violation of the new SO2 NAAQS can attain the standard.
• U.S. EPA still intends to complete SO2 attainment designations by June 2012.
• U.S. EPA anticipates initially designating areas with 2008-2010 monitoring data or refined dispersion modeling results showing a violation of the NAAQS as nonattainment.  Areas that have both monitoring data and refined modeling results showing no violations will be designated as attainment.  All other areas, including those with SO2 monitors showing no violations but without refined modeling showing no violations, will be designated as unclassifiable.  Areas with no SO2 monitors will be also be designated as unclassifiable.
• U.S. EPA will require states with areas designated as nonattainment in 2012 to submit plans to U.S. EPA outlining actions they will take to meet the SO2 standards 18 months from the effective date of the designations or by February 2014.  SO2 nonattainment areas will need to attain the standard by August 2017.
• U.S. EPA will require states with areas designated as unclassifiable to submit plans to U.S. EPA by June 2013 (three years following the promulgation of the new SO2NAAQS). These state plans must:
  • Demonstrate, through refined air quality modeling, that all sources contributing to monitored and modeled violations of the new standard, or that have the potential to cause or contribute to a violation, will be sufficiently controlled to ensure timely attainment and maintenance of the new SO2 NAAQS.
  • Include enforceable emissions limitations, timetables for compliance, and appropriate testing or reporting to assure compliance.
• While these plans do not include a deadline by which states are required to meet the standard, U.S. EPA believes that unclassifiable areas should show that they have attained the standard and are going to be able to maintain SO2 levels in the outdoor air below the standard by August 2017, the same deadline that would be required for areas designated nonattainment.

U.S. EPA has allotted 30 days for the public to review and provide comment on the draft guidance.  Following the comment period, U.S. EPA will revise the document as appropriate and finalize it for release

Before the release of the draft implementation guidance, it seemed that more was happening with the 1-hour SO2 NAAQS in the courts than anywhere else.  In the most recent legal action, Texas, North Dakota, Louisiana, the Utility Regulatory Group, and others are challenging the science behind the proposed 75 parts per billion (ppb) standard recommended by the Clean Air Scientific Advisory Committee (CASAC).  In another court battle, the Montana Sulfur and Chemical Company argued that U.S. EPA did not include the proposed mix of monitoring and modeling in the proposed version of the 1-hour SO2 NAAQS revision and that, therefore, the final rule is invalid because it violates the notice-and-comment rulemaking requirements of the Clean Air Act.  U.S. EPA has argued that it will address the attainment designation approach in “future actions” and noted that the preamble of the 1-hour SO2 NAAQS rule (where the modeling requirement is located) makes clear that U.S. EPA has taken no final action on attainment designation or its approach to making those designations.  This essentially pushes off any challenges to the rule until U.S. EPA finalizes the attainment designations (that could include air quality modeling) in June 2012.  This stance is puzzling since, based on the language in the preamble and given the limited network of SO2 monitors, air quality modeling will have to be performed in order to complete the designation process.

Questions and Answers Posed to State Agencies

Question 1: Are you currently completing any air quality dispersion modeling to support the SO2 attainment designations in your state?

Question 2: If so, are you using AERMOD to conduct the air quality dispersion modeling?

Question 3: What are the screening criteria that you are using for determining what facilities to include in this air quality dispersion modeling?

Question 4: Who is conducting the air quality dispersion modeling?

Question 5: What is your timeline for completion?

Question 6: Do you have any other comments on the process?

Question 1: Are you currently completing any air quality dispersion modeling to support the SO2 attainment designations in your state?

Question 2: If so, are you using AERMOD to conduct the air quality dispersion modeling?

Question 3: What are the screening criteria that you are using for determining what facilities to include in this air quality dispersion modeling?

Question 4: Who is conducting the air quality dispersion modeling?

Question 5: What is your timeline for completion?

Question 6: Do you have any other comments on the process?