Approval and Promulgation of Implementation Plans; Attainment Redesignation for Missouri Portion of the St. Louis MO-IL Area; 1997 8-Hour Ozone Standard and Associated Maintenance Plan

The Environmental Protection Agency (EPA) is taking final action to approve the State of Missouri's request to redesignate the Missouri portion of the St. Louis MO-IL nonattainment area, the "St. Louis area" or "area" to attainment for the 1997 8-hour National Ambient Air Quality Standards (NAAQS or Standard) for ozone (O<INF>3</INF>). The Missouri counties comprising the St. Louis area are Franklin, Jefferson, St. Charles, and St. Louis along with the City of St. Louis. EPA's approval of the redesignation request is based on the determination that the St. Louis area has met the criteria for redesignation to attainment set forth in the Clean Air Act (CAA), including the determination that the St. Louis area has attained the 1997 8-hour O<INF>3</INF> standard. Additionally, EPA is approving the state's plan for maintaining the 1997 O<INF>3</INF> standard in the St. Louis area for 10 years beyond redesignation. In a separate action the state of Illinois submitted a similar redesignation request for the Illinois portion of the St. Louis MO-IL 1997 8-hour O<INF>3</INF> area. On June 12, 2012, the EPA published a document in the Federal Register taking final action to address the Illinois portion of the St. Louis area.