By Matthew Holloway |
The U.S. Environmental Protection Agency (EPA) has given final approval to a Maricopa County air quality rule allowing fleet owners to generate emissions credits by replacing or upgrading higher-emitting vehicles, county officials announced Thursday.
Under Rule 205, qualifying reductions from on-road vehicles can generate credits used to offset emissions from new or expanding industrial facilities. The county said the approval allows its Air Quality Department to begin issuing the credits immediately.
“Rule 205 is a win-win for our residents, demonstrating that Maricopa County can prioritize both cleaner air and a strong economy,” Board of Supervisors Chair Kate Brophy McGee said. “By incentivizing rather than punishing job creators, this approach will deliver measurable improvements in air quality while creating new opportunities for businesses to invest and expand.”
The program connects voluntary fleet improvements with federal permitting requirements for industrial development. Under the Clean Air Act’s nonattainment New Source Review program, new major stationary sources and major modifications to existing major stationary sources must provide offsets for increased emissions.
Fleet owners can submit replacement or retrofit projects to the Air Quality Department for evaluation. Qualifying reductions must be real, quantifiable, surplus, permanent, and federally enforceable before the county certifies them.
Certified credits may then be traded for use as offsets. A facility relying on those credits cannot begin operating until the corresponding vehicle replacements or retrofits have occurred. The required offsets must exceed the facility’s emissions increase under the applicable offset ratio.
The guidance identifies eligibility conditions, including that fleet vehicles be based and operated within the Phoenix-Mesa ozone nonattainment area. Certain projects completed on or after January 1, 2017, may qualify, subject to the rule’s requirements.
The county’s rule history lists an initial adoption date of April 26, 2023, and a revision on May 21, 2025. The county submitted the revised version to the EPA on May 30, 2025.
Vice Chair Debbie Lesko praised EPA Administrator Lee Zeldin’s work with the county.
“I applaud EPA Administrator Lee Zeldin for working with Maricopa County to find Clean Air solutions that fit the unique needs of our region,” Lesko said. “It’s proof we can partner with the federal government to streamline regulations while still protecting the quality of the air we breathe.”
Maricopa County is also pursuing emissions credits for upgrades to railroad locomotives and construction equipment through Rule 204. The EPA proposed approving that rule on October 6, extending the county’s approach to voluntary emissions reductions from nonroad engines.
The EPA said the proposed Rule 204 approval would allow qualifying reductions in nitrogen oxides or volatile organic compounds to generate credits for facilities seeking to build or expand within the county’s ozone nonattainment area.
In its October announcement, the EPA identified portions of Maricopa County as being in moderate nonattainment for the 2015 federal ozone standard. That designation subjects covered industrial projects to additional permitting and emissions-offset requirements.
Rule 205 has received final approval. The county described Rule 204 as remaining at the proposed-approval stage.
Matthew Holloway is a senior reporter for AZ Free News. Follow him on X for his latest stories, or email tips to Matthew@azfreenews.com.
