Approval and Promulgation of Implementation Plans and Designation of Areas for Air Quality Planning Purposes; Ohio; Indiana; Redesignation of the Ohio and Indiana Portions of the Cincinnati-Hamilton Area to Attainment for Ozone

EPA is approving the requests of Ohio and Indiana to redesignate the Ohio and Indiana portions of the Cincinnati-Hamilton, OH-KY-IN 8-hour ozone nonattainment area, "the Cincinnati-Hamilton area," to attainment for that standard, because these requests meet the statutory requirements for redesignation under the Clean Air Act (CAA). The Ohio Environmental Protection Agency (Ohio EPA) and the Indiana Department of Environmental Management (IDEM) submitted these requests on December 14, 2009, and January 21, 2010, respectively. (EPA will address the Kentucky portion of the Cincinnati-Hamilton area in a separate rulemaking action.) These approvals involve several related actions. EPA is making a determination under the CAA that the Cincinnati-Hamilton area has attained the 1997 8-hour ozone National Ambient Air Quality Standard (NAAQS). The Cincinnati-Hamilton area includes Butler, Clermont, Clinton, Hamilton, and Warren Counties in Ohio, Lawrenceburg Township in Dearborn County, Indiana, and Boone, Campbell, and Kenton Counties in Kentucky. This determination is based on three years of complete, quality-assured ambient air quality monitoring data for the 2007-2009 ozone seasons that demonstrate that the 8-hour ozone NAAQS has been attained in the entire Cincinnati-Hamilton area. EPA is also approving, as revisions to the Ohio and Indiana State Implementation Plans (SIPs), the States' plans for maintaining the 8-hour ozone NAAQS through 2020 in the area. EPA is approving the 2002 base year emissions inventory submitted by IDEM on June 13, 2007, as meeting the base year emissions inventory requirement of the CAA for the Indiana portion of the Cincinnati- Hamilton area. EPA is approving the 2005 base year emissions inventory submitted by Ohio EPA as part of its redesignation request as meeting the base year emissions inventory requirements of the CAA for the Ohio portion of the Cincinnati-Hamilton area. Finally, EPA finds adequate and is approving the States' 2015 and 202