Proposed rule · 2026-07405

Air Plan Revisions; Arizona; Maricopa County Air Quality Department; New Source Review; Emission Reduction Credits

The Environmental Protection Agency (EPA) is proposing to approve a revision to the Maricopa County Air Quality Department (MCAQD or "Department") portion of the Arizona State Implementation Plan (SIP). This revision establishes a federally enforceable program allowing fleet owners/operators to generate emission reduction credits (ERCs) by either retrofitting or replacing existing fleet vehicles with lower emitting vehicles while meeting other Clean Air Act (CAA or "Act") requirements. These ERCs are intended for use as offsets for major stationary sources under the Department's Nonattainment New Source Review (NNSR) program. We are proposing to approve a local rule to allow for the generation of ERCs through voluntary on-road mobile source emission reductions under the CAA. We are taking comments on this proposal and plan to follow with a final action.