Regulatory Update   |   Apr 15th, 2015 SO2 Data Requirements Update: EPA Targets 69 Sources That Should be Modeling Now


Last month, a US District Court ruling established firm deadlines for the US Environmental Protection Agency (USEPA) to complete the required designation of all areas of the country for the new 1-hour SO2 National Ambient Air Quality Standards (NAAQS).

A follow up memo from the USEPA provided updated guidance and details about how it will perform the designations in compliance with the established deadlines.

Round 1 designations must be completed by July 2, 2016 and includes areas containing 69 specified sources that exceed the emission thresholds established in the Court Order. USEPA will accept updated recommendations and additional information that will be considered in the designation process until September 18, 2015.

This fast-approaching deadline means that affected States or others who want to supply information must do so via source modeling, as specifically noted in the USEPA memo:

“We recognize that the timeline for designations by July 2, 2016, does not provide for establishment and use of data from new ambient monitors. Therefore, we anticipate that in many areas the most reliable information for informing these designations will be based on source modeling...”

Action You Should Take Now

If you are one of the 69 listed sources, or if your facility is located in the same or bordering county as one of the 69 sources, it is important to be aware of the impact and contribution of your facility’s emissions. Knowing this information now, will help you develop a strategy to address potential adverse impacts and also ensure that your facility is properly characterized in the designation recommendation.

In anticipation of expected data and information requests from your state agency, TRC recommends that your facilities’ emissions data, including past actual emissions, and modeling parameters be carefully evaluated for accuracy. These data should be incorporated in a dispersion modeling analysis to determine their impact. Modeling guidance issued by USEPA specific to the SO2 area designation process provides opportunities to model your source such that predicted impacts are more closely representative of expected monitoring results and should be considered in the modeling analysis.

TRC’s air modeling staff and engineers are currently helping clients with modeling sensitivity analyses, providing data review, verification and air dispersion modeling assistance. Our experts ensure that the air modeling analysis and information needed to best represent your facility is made available to applicable state agencies and USEPA in a timely manner. Now is the time to contact us to develop the appropriate data and modeling plan for your facility.

For more information, please contact me at 860 298-6248 or

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