On June 30, 2016 the EPA made its second round of designations for areas as “nonattainment,” “unclassifiable/attainment,” or “unclassifiable” for the 2010 Primary 1-Hour SO2 National Ambient Air Quality Standard (SO2 NAAQS). This round of designations was required to be completed by July 2, 2016 as a result of a consent decree issued by the U.S. District Court for the Northern District of California. The consent decree settles a lawsuit filed by the Sierra Club and the Natural Resources Defense Council over the EPA’s failure to make additional attainment and nonattainment designations for the standards back in 2013 when the EPA promulgated nonattainment area designations for 29 areas in 16 states. In 2013, the EPA stated that inadequate air monitoring data in many parts of the country was the reason for delaying area designations in the rest of the United States with the SO2 NAAQS.

The second round of area designations evaluated newly monitored violations of the SO2 NAAQS based on the recent three calendar years of certified air monitoring data and areas that contain any stationary source that had not been announced, as of March 2, 2015, for retirement which emitted SO2 above significant thresholds. The significant thresholds for SO2 emissions from a stationary source was any facility that emitted in excess of 16,000 tons per year of SO2 or 2,600 tons per year of SO2 with an emission rate of at least 0.45 pounds SO2/mmBtu.

This new round of designations aligns with the SO2 Data Requirements Rule (SO2 DRR) deadlines requiring air agencies to notify the EPA on how an area (which lacks an adequate monitoring network) is choosing to demonstrate attainment with the SO2 NAAQS. Areas which lack an adequate monitoring network must characterize ambient SO2 concentrations using air dispersion modeling or constructing/operating additional air monitoring stations.

Kentucky’s Division for Air Quality (DAQ) choose to submit updated area recommendations with air dispersion modeling demonstrations (Submitted in September 2015 with revisions in March 2016 and April 2016) for Ohio and Pulaski counties to demonstrate attainment with the SO2 NAAQS. Unfortunately, the Commonwealth did not receive the favorable response from the EPA it was looking for when it recommended to EPA to reclassify Pulaski County and Ohio County as “attainment.” Instead, the EPA final area designation for both counties was “unclassifiable.” With this designation, further requirements under the SO2 DRR will ensue.

Because EPA rejected Kentucky’s recommended area designations, stationary sources which emit large quantities SO2 (coal-fired electric generating utilities) in both counties will have to accept new federally enforceable permit limits (based on revised air dispersion modeling demonstrations approved by EPA) by January 13, 2017 or begin operating a new SO2 monitoring network meeting the EPA’s specifications listed in the SO2 DRR.

While this round of area designations for the SO2 NAAQS only impacts two (2) stationary sources in Kentucky, it is a prime example that the regulatory process for sources deemed to significantly impact ambient air quality is long and complex. Sources which thought they had addressed their impacts through accepting lowered SO2 emission limits in revised Title V operating permits according to Kentucky DAQ approved air dispersion modeling demonstrations are now back at square one when the Proposed SO2 DRR was promulgated in May 2014.


Stewart McCollam, P.E. is an Environmental Engineer with the Smith Management Group. Stewart can be reached at stewartm@smithmanage.com.