Maintenance Plan and Redesignation Request for the Ajo PM10 Planning Area; Arizona

The Environmental Protection Agency (EPA) is taking final action to approve the "Ajo PM<INF>10</INF> Redesignation Request and Maintenance Plan (May 3, 2019)" ("Ajo PM<INF>10</INF> Maintenance Plan" or "Plan") as a revision to the state implementation plan (SIP) for the State of Arizona. The Ajo PM<INF>10</INF> Maintenance Plan includes, among other elements, an emissions inventory consistent with attainment, a maintenance demonstration, contingency provisions, and a demonstration that contributions from motor vehicle emissions to PM<INF>10</INF> in the Ajo planning area are insignificant. The EPA is also approving the State of Arizona's request to redesignate the Ajo planning area from nonattainment to attainment for the national ambient air quality standards (NAAQS or "standards") for particulate matter of ten microns or less (PM<INF>10</INF>). Lastly, the EPA is taking final action to delete the area designation for Ajo for the revoked NAAQS for total suspended particulate (TSP) because the designation is no longer necessary. The EPA is finalizing these actions because the SIP revision meets the applicable requirements under the Clean Air Act (CAA or "Act") for maintenance plans and because the State has met the requirements under the Act for redesignation of a nonattainment area to attainment with respect to the Ajo planning area.