Mr. Ron Curry, Regional Administrator 

Mary Fallin 

Governor 

August 17, 2015 

U.S. Environmental Protection Agency, Region 6 

1445 Ross Avenue, Suite 1200 

Dallas, Texas 75202-2733 

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15 AUG 26 PM S: 24 

Subject: Affirmation of Designation Recommendation for 20 l 0 Sulfur Dioxide NAAQS for 

Noble, Choctaw, and Muskogee Counties in Oklahoma 

Dear Administrator Curry: 

Oklahoma has evaluated the letter from Acting Assistant Administrator McCabe dated March 20, 

2015, which gave an update on the U.S. Environmental Protection Agency's (EPA's) status on 

implementing the revised primary National Ambient Air Quality Standard (NAAQS) for sulfur 

dioxide (S02) (75 FR 35520, June 22, 2010). Accompanying the letter was the "Updated 

Guidance for Area Designations for the '2010 Primary Sulfur Dioxide National Ambient Air 

Quality Standard. '" In the letter, EPA outlined three future rounds of designation actions to 

comply with the federal consent decree and court order issued in Sierra Club, et al v. Regina 

McCarthy, Case No. 3: l 3-cv-03953-SI (N.D. Cal.), and identified areas in Noble, Choctaw, and 

Muskogee Counties as affected by the first round of designations. Each of these areas contains a 

source that meets the criteria established in the federal consent decree for inclusion in the first 

round of designation actions. The letter provided an opportunity to submit an updated 

recommendation and supporting information for EPA consideration for designation of the 

affected areas. 

As required by section 107(d)(l)(A) of the federal Clean Air Act (42 U.S.C. § 7407) and on 

behalf of the State of Oklahoma, I recommended on May 27, 20 11 , Noble and Choctaw Counties 

be designated attainment, and Muskogee County be designated unclassifiable for the revised S02 

standard. Our recommendation for these three counties/areas remains unchanged. 

Under separate cover, Oklahoma is submitting an air quality evaluation, performed by the 

Oklahoma Department of Environmental Quality (DEQ), to support our current 

recommendation. DEQ's report evaluates certified S02 monitoring data, and modeling for 

contributing S02 sources in the three identified areas. Specifically, the evaluation demonstrates 

ST.-JTE CAPITOL BUILDl.VG • 2300 N. ll.\'COL.\' BOULEVARD. SUITE 212 • OKLAHOH~ CITY. OKLAHOA4A 73105 • 1405) 521-2342 • FAX: 1405) 511-3353 
attainment for the areas associated with the two facilities in Noble and Choctaw Counties. The 

air quality analysis for Muskogee County shows no violation of the 20 10 S02 NAAQS has been 

detected at the source-oriented S02 monitoring site located approximately 4 kilometers NNW of 

the facility for the last three years of available certified data. However, modeling for the facility 

indicates there may be a potential for a NAAQS violation under certain conditions during the 

period prior to full implementation of the facility's federally-enforceable BART requirements 

and other planned changes (e.g., in response to Mercury and Air Toxics Standards). The 

evaluation identified significant uncertainties regarding the effects of available meteorological 

data on the modeling results. (Modeling did not show any potential violations at receptors 

located outside Muskogee County.) We believe this information collectively supports a 

designation of unclassifiable for Muskogee County. 

If you desire additional information or have questions concerning this matter, please contact Mr. 

Eddie Terrill, DEQ's Director of Air Quality, at (405) 702-4100. 

Sincerely, 

Mary Fallin, G 

State of Oklahoma 

cc: Michael Teague, Secretary of Energy and Environment 

Scott Thompson, Executive Director, Department of Environmental Quality 

Eddie Terrill, Director of Air Quality, Department of Environmental Quality