Proposed rule · 2026-20612

Air Quality Plan; Arizona; Maricopa County Air Quality Department; New Source Review; Emission Reduction Credits-Rule 204

The U.S. 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 nonroad engine fleet owners/operators to generate emission reduction credits (ERCs) by either retrofitting their nonroad engines or replacing their nonroad engines with lower-emitting nonroad engines 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 nonroad engine emission reductions under the CAA.