UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION 8

Ref: 8P-AR The Honorable Matthew H. Mead Office ofthe Governor State Capitol Cheyenne, Wyoming 82002 Dear Governor Mead: 1595Wynkoop Street Denver, CO 80202-1129

Phone 800-227-8917 www.epa.gov/region08


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Thank you for your recommendation dated October 27, 2015, on air quality designations for the state of Wyoming for the 2010 revisionto the primaryNational AmbientAir Quality Standard (NAAQS) for sulfur dioxide (S02). Reducing levels ofS02pollution is an importantpart ofthe U.S. Environmental Protection Agency's (EPA's) commitmentto a clean, healthy environment. Exposure to S02 can cause a range ofadverse health effects, including narrowing ofthe airways which can cause difficulty breathing and increased asthma symptoms. This letter is to notify you ofthe EPA's preliminary intentions regarding your recommended designation. On June 3, 2010, the EPA strengthened the health-based or "primary" standard for S02 by establishing a standard for 1-hour average S02 concentrations at a level of75 parts per billion. Within one year after a new or revised standard is established, the Clean Air Act requires the Governor ofeach state to submit to the EPA a list ofall areas in the state, with recommendations for whether each area meets the standard. Through an interactive process, the EPA considers the recommendations and then promulgates designations for all areas across the country
. On July 25, 2013, the EPA designated 29 areas in 16 states as nonattainment, but did not at thattime designate other areas. Pursuant to a March 2, 2015, courtordered schedule, 1the EPA must complete the remaining S02 designations by three specific deadlines: July 2, 2016, December 31, 2017, and December 31, 2020. This current round ofdesignations, to be completed by July 2, 2016, addresses two groups ofareas: (1) areas that have newly monitored violations ofthe 2010 S02NAAQS based on the most recent three calendar years ofcertified monitored ambient air quality data, and (2) areas that contain any stationary source that had not been announced as ofMarch 2, 2015, for retirement and that according to the EPA's Air Markets Database emitted in 2012 either (i) more than 16,000 tons ofS02 or (ii) more than 2,600 tons ofS02 with an annual average emission rate ofat least 0.45 pounds ofS02/mmBTU. Based on ambient air quality data collected between 2012 and 2014 indicating a violation ofthe 2010 S02 NAAQS, the EPA initially identified the area around the Sinclair Oil Corp Refinery in Sinclair, Wyoming, as one that would potentially create the obligation for us to designate by July 2, 2016.

1Sierra Club v. McCarthy, No. 3-13-cv-3953 (SI) (N.D. Cal. Mar. 2, 2015). 

### 1However, the EPA has since discovered thatthe monitorreading violations nearthe Sinclair Refinery had been located withinthe company's fence line, and thus was not in the ambient air. Since the monitor was not inthe ambient air it is considered a non-regulatory monitor and the air monitor data cannot be used for designation purposes. Therefore, the EPA has determined that the air monitor was nonregulatory during the 2012-2014 period in which the design value was above the 2010 S02NAAQS, and continued to be non-regulatory for the 2013-2015 period. Forthis reason, the area around the Sinclair Refinery is not subject to the July 2, 2016, deadline for designation underthe court order. We intend to designate the area by December 31, 2020, based onregulatory ambient monitoring nearthe Sinclair Refinery. We look forward to a continued dialogue with you and your staffas we work togetherto complete the 2017 and 2020 area designations and implementthe 2010 primary S02 standard. For additional information regarding designations underthe S02 standard, please visit our website at www.epa.gov/so2designations. Should you have any questions, please do not hesitate to call me, orhave your staffcontact Carl Daly ofmy staffat (303) 312-6416 or daly.carl@epa.gov.

Regional Administrator

cc: Todd Parfitt Director, Wyoming Department ofEnvironmental Quality Nancy Vehr Administrator, Air Quality Division Janet G. McCabe, Acting Assistant Administrator for Air and Radiation Stephen D. Page, Director, Office ofAir Quality Planning and Standards

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