Air Plan Approval; Pennsylvania; Redesignation of the Warren County Nonattainment Area to Attainment and Approval of the Area's Maintenance Plan for the 2010 1-Hour Primary Sulfur Dioxide National Ambient Air Quality Standard

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The Environmental Protection Agency (EPA) is proposing to approve a state implementation plan (SIP) revision and redesignation request submitted on September 19, 2025 by the Pennsylvania Department of Environmental Protection (PADEP). The SIP revision asks the EPA to redesignate the Warren County, Pennsylvania area from nonattainment to attainment for the 2010 1-hour primary sulfur dioxide (SO 2 ) national ambient air quality standard (NAAQS). The revision also asks the EPA to approve into the SIP the Commonwealth's maintenance plan for the 2010 1-hour primary SO 2 NAAQS for the Warren County area. Furthermore, Pennsylvania requests that the EPA correct source- specific requirements for United Refining Company within the Pennsylvania SIP that were previously included in error. This proposed action is being taken under the Clean Air Act (CAA).