Air Plan Approval; Arizona; Maricopa County Air Quality Department

The Environmental Protection Agency (EPA) is proposing to approve revisions to the Maricopa County Air Quality Department (MCAQD) portion of the Arizona State Implementation Plan (SIP). These revisions concern a rule that includes definitions for certain terms that are necessary for the implementation of local rules that regulate sources of air pollution. We are proposing to approve the rule under the Clean Air Act (CAA or the Act). We are taking comments on this proposal and plan to follow with a final action.