In a rule published July 2, 2002, EPA found the Arizona Department of Environmental Quality’s "Plan for Attainment of the 24-Hour PM10 Standard – Maricopa County PM10 Nonattainment Area" (May 1997), inadequate to achieve attainment of the 24-hour National Ambient Air Quality Standards for particulate matter 10 microns or fewer in aerodynamic diameter (PM10) at the Salt River monitoring site. The 1997 ADEQ SIP revision included attainment and Reasonable Further Progress demonstrations for the 24-hour NAAQS at the Salt River air quality monitoring site of the Maricopa County PM10 Serious Nonattainment Area, as well as at three other monitoring sites in the Phoenix area, - the Maryvale, Gilbert, and West Chandler sites. On August 4, 1997, EPA approved ADEQ’s attainment and RFP demonstrations for the Salt River monitoring area, which showed that the 24-hour PM10 NAAQS would reach attainment in the area by May 1998. Due to continuing violations of the 24-hour PM10 NAAQS at the Salt River air quality monitoring site since May 1998, EPA subsequently required Arizona to submit a revision to correct SIP inadequacies. This document consists of Arizona’s revisions to the state implementation plan for the Maricopa County PM10 Serious Nonattainment Area as described by EPA in its Federal Register notice of disapproval.