# f. !!!2 Protection Agency 

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OV 17 2 015 Mr. John Mooney John R. Kasich , Governor Mary Taylor, Lt . Governor Craig W. Butler, Di rector

Chief, Air Programs Branch U.S . EPA, Region 5 77 West Jackson Blvd. Chicago, Illinois 60604 Re: Ohio EPA Response to Sierra Club Designation Recommendation for the William H. Zimmer Power Plant and General James M. Gavin Source Areas for the 2010 Sulfur Dioxide National Ambient Air Quality Standard Dear Mr. Mooney: On March 20 , 2015, U .S . EPA notified states regarding a settled consent decree with Sierra Club that affects sources in certain areas yet to be designated under the 2010 1- hour sulfur dioxide (S02 ) national ambient air quality standard (NAAQS). This affects sources with 2012 emissions greater than 16 ,000 tons, or sources with emissions greater than 2,600 tons and an emission rate of at least 0.45 lbs S02/mmbtu; unless a retirement from burning coal was announced by March 2, 2015. The letter identified the General James M . Gavin Power Plant and the William H. Zimmer Power Plant as subject to the consent decree requirements. U.S. EPA allowed states an opportunity to submit recommendations on the designations of the areas around the subject facilities by September 18, 2015 . Ohio EPA submitted recommendations on September 16, 2015 based upon a 5-factor analysis outlined in U.S . EPA's March 20, 2015 memorandum Updated Guidance for Area Designations for the 2010 Primary Sulfur Dioxide National Ambient Air Quality Standard . Based upon that analysis , Ohio EPA recommended Gallia County and a portion of Meigs County be designated as attainment for the 2010 1-hour S02 standard for the General James M . Gavin source area , which included Kyger Creek Power Plant emissions. A separate submittal recommended the portion of Clermont County, excluding Pierce Township, be designated as attainment for the 2010 1 -hour S02 standard for the William H . Zimmer source area .

**~·** . · Concurrently, Sierra Club submitted a modeling analysis for both the General James M.

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### Ga~in and William H. Zimmer source areas. Sierra Club recommended a designation of > 50 West Town Street • Suite 700 • P.O. Box 1049 • Colum bus, OH 43216-1049 www.epa .oh io .gov • (614) 644-3020 • (614) 644-3184 (fax)nonattainment for both source areas . On October 20, 2015, U .S . EPA provided Ohio EPA the opportunity to review the Sierra Club's analyses since the two analyses differed in final results. Ohio EPA analyzed Sierra Club's submittal and identified multiple shortcomings, incidents of consistent over-prediction , and the inclusion of mischaracterized sources that do not warrant further consideration under the Data Requirements Rule . Ohio EPA contends that this systemic over-prediction leads to severe inaccuracies of modeled ground-level impacts. Additionally, Ohio EPA notes that Sierra Club neglected to include receptors at the location of ambient air quality monitors and made no attempt to conduct an analysis of model accuracy based on modeled versus monitored concentrations . Omission of this critical check on model performance indicates that the Sierra Club did not place a high value on assessing model accuracy orthe quality of model inputs. Ohio EPA performed this analysis on the Sierra Club modeling and demonstrated serious over-predictions of modeled values with respect to monitored concentrations . Attached is Ohio EPA's analysis of Sierra Club's modeling for both source areas . Additionally, the Sierra Club failed to follow U .S . EPA guidance in completion of the modeling submittal. The attached documentation clearly identifies the serious technical errors and flaws in the Sierra Club modeling , and we urge U.S . EPA to not give any weight to the Sierra Club submittal. Ohio EPA reiterates the recommendation of attainment for both source areas as described in Ohio's original September 16, 2015 submittals . If you have questions , please contact Jennifer Van Vlerah in our Division of Air Pollution Control at (614) 644-3696. Sincerely,

Robert Hodanbosi , P .E. Chief, Division ofAir Pollution Control Enclosure