EPA is approving a Tribal implementation plan (TIP) submitted by the Gila River Indian Community (GRIC or Tribe) on February 21, 2007, as supplemented and amended on July 11, 2007, June 22, 2009, and July 17, 2010, and as described in our August 12, 2010 proposal. The TIP includes general and emergency authorities, ambient air quality standards, permitting requirements for minor sources of air pollution, enforcement authorities, procedures for administrative appeals and judicial review in Tribal court, requirements for area sources of fugitive dust and fugitive particulate matter, general prohibitory rules, and source category-specific emission limitations and standards. These provisions establish a base TIP that is suitable for the GRIC's reservation and regulatory capacities and that meets all applicable minimum requirements of the Clean Air Act (CAA or Act) and EPA regulations. The effect of this action is to make the approved portions of the GRIC TIP federally enforceable under the CAA and to further protect air quality within the exterior boundaries of the GRIC reservation.