The Environmental Protection Agency (EPA) is proposing to approve in part and to disapprove in part the state implementation plan (SIP) revision submitted by the State of Arizona to meet Clean Air Act (CAA or ``Act'') requirements for the 1987 PM<INF>10</INF> national ambient air quality standards (NAAQS or ``standard'') in the West Pinal County PM<INF>10</INF> nonattainment area. The State of Arizona's ``2015 West Pinal Moderate PM<INF>10</INF> Nonattainment Area SIP'' (``West Pinal County PM<INF>10</INF> Plan'') addresses the CAA nonattainment area requirements for the 1987 PM<INF>10</INF> NAAQS, including requirements for an emissions inventory, an attainment demonstration, reasonable further progress, reasonably available control measures, contingency measures, and motor vehicle emissions budgets. The EPA is proposing to approve the base year 2008 emissions inventory for direct PM<INF>10</INF> and to disapprove the remaining elements of the West Pinal County PM<INF>10</INF> Plan.