2026-22647·ENVIRONMENTAL PROTECTION AGENCY

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

Final RuleFinal Rule

Published: Nov 5, 2026
Effective: Dec 7, 2026
Citation: 91 FR 69694
Docket: EPA-R09-OAR-2026-1684, FRL-13268-02-R9

Final rule.

Summary

The Environmental Protection Agency (EPA) has formally approved a revision to Arizona’s State Implementation Plan that creates a new, federally enforceable program for generating emission‑reduction credits (ERCs) in Maricopa County. The program lets owners of on‑road vehicles earn credits by retrofitting or replacing older, higher‑polluting cars and trucks with newer, lower‑emitting models, provided they also satisfy other Clean Air Act requirements. These credits can then be used by large, stationary pollution sources—such as factories or power plants—to offset any new emissions they would otherwise add, helping the county meet air‑quality goals while giving businesses a flexible compliance option. The rule was issued by the EPA and applies primarily to the Maricopa County Air Quality Department, vehicle owners and operators in the county, and major stationary emitters subject to the department’s Non‑attainment New Source Review (NNSR) program. By integrating vehicle‑based reductions into the existing SIP, the EPA aims to broaden the tools available for achieving and maintaining federal air‑quality standards in the region. The final rule was published in the Federal Register on November 5, 2026 (91 FR 69694) and takes effect on December 7, 2026. With the rule now in force, the Maricopa County Air Quality Department can begin issuing ERCs for qualifying vehicle retrofits, and stationary sources can start using those credits to satisfy offset requirements under the NNSR program. No further public comment period is required, but affected parties will need to follow the new procedures as they are implemented.

AI-generated summary — verify against the Federal Register text.

Official abstract

The U.S. Environmental Protection Agency (EPA) is taking final action 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 for the generation of emission reduction credits (ERCs) by retrofitting or replacing existing on-road vehicles with lower emitting vehicles while meeting other Clean Air Act (CAA or "Act") requirements. These ERCs are intended to be used as offsets for major stationary sources under the Department's Nonattainment New Source Review (NNSR) program. The EPA is approving this SIP revision because we find that it meets the applicable CAA requirements.