ENV-16-37 A Mixed Approach: SO2 1-hr NAAQS Implementation in the U.S.

Description:

In an unprecedented approach to determine area designations for the 2010 1-hour sulfur dioxide (SO2) National Ambient Air Quality Standards (NAAQS), the U.S. Environmental Protection Agency (EPA) issued the ‘Data Requirements Rule’ (DRR) on August 21, 2015. The rule requires states to characterize the air quality surrounding large sources of SO2 emissions (sources that emit greater than 2,000 tons per year [tpy]) across the U.S., using either an air dispersion modeling or ambient monitoring approach. In January of this year, each state submitted a final list to the EPA identifying sources around which SO2 air quality is to be characterized. By July 1, 2016, each state agency is required to identify the approach it will use for each source on the list. This paper presents the results of each state’s selected approach, with an emphasis on those areas including large refining and petrochemical facilities, and shows how these facilities may be impacted. Additionally, a refinery case study is presented to further examine potential impacts and outline differences between air dispersion modeling used to determine SO2 designations and modeling techniques typically used during New Source Review (NSR) permitting (those guidelines outlined in Appendix W to 40 CFR Part 51). For this case study, the owner submitted an air dispersion modeling demonstration consistent with a Prevention of Significant Deterioration (PSD) full impacts modeling analysis previously conducted for an approved crude expansion project to exempt the facility from installing a nearby ambient SO2 monitor and excluding it from the January 2016 source list.