UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION 8

Ref: 8P-AR The Honorable Dennis Daugaard Office ofthe Governor 500 East Capitol Avenue Pierre, South Dakota 57501 Dear Governor Daugaard: 1595 Wynkoop Street Denver, CO 80202-1129

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

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Thank you for your staffs recommendations dated September 16, 2015 , on air quality designations for the state of South Dakota for the 2010 revision to the primary National Ambient Air Quality Standard (NAAQS) for sulfur dioxide (S02 )

. Reducing levels of S02pollution is an important part ofthe U.S. Environmental Protection Agency's (EPA's) commitment to a clean, healthy environment. Exposure to S02can cause a range of adverse 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 designations

. On June 3, 2010 , the EPA strengthened the health-based or "primary" standard for S02 by establishing a standard for I-hour average S02 concentrations at a level of 75 parts per billion. Within one year after a new or revised standard is establisk.ed, 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 that time designate other areas. Pursuant to a March 2, 2015, courtordered schedule, 1 the EPA must complete the remaining S02designations 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 of March 2, 2015 , for retirement and that according to the EPA ' s Air Markets Database emitted in 2012 either (i) more than 16,000 tons of S02 or (ii) more than 2,600 tons of S02with an annual average emission rate of at least 0.45 pounds of SOi/mmBTU.

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

### 1Because the EPA has insufficient information to determine whether the following area is meeting or not meeting the S02NAAQS , the EPA intends to designate this area as unclassifiable: Intended Unclassifiable Area Grant County* Intended Unclassifiable Counties Grant County The asterisk(*) indicates

.the designation for this intended unclassifiable area represents a modification to the attainment designation that you have recommended. EPA will not take action on the September 16, 2015, designation recommendations for areas other than Grant County at this time. The enclosed Technical Support Document provides a detailed analysis that supports our intended designation decisions. Ifyour state has additional information that the EPA should consider prior to finalizing these designations, please submit it to us by April 19, 2016. We also will be publishing a notice in the Federal Register announcing a 30-day period for the public to provide input on the EPA ' s intended designation decisions. We will promulgate the designations for these areas by July 2, 2016

. We will designate all other previously undesignated areas in the state on a schedule consistent with the prescribed timing ofthe court order, i

.e. , by December 31 , 2017 , or December 31, 2020. We look forward to a continued dialogue with you and your staff as we work together to complete the area designations and implement the 2010 primary S02 standard. For additional information regarding designations under the S02 standard, please visit our website at www.epa.gov/so2designations. Should you have any questions , please do not hesitate to call me, or have your staffcontact Carl Daly of my staff at (303) 312-6416 or daly.carl @ epa.gov .

Enclosure

cc: Steven M. Pirner Shaun L. McGrath Regional Administrator

Secretary, Department ofEnvironment and Natural Resources Brian Gustafson Administrator, Air Quality Program Janet G. McCabe, Acting Assistant Administrator for Air and Radiation Stephen D. Page, Director, Office ofAir Quality Planning and Standards

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