EPA Greenlights Cleaner Air Rules for California Turbines
Published Date: 11/20/2025
Rule
Summary
The EPA just gave a thumbs-up to new rules in Eastern Kern, California, that cut pollution from stationary gas turbines. This means cleaner air by limiting harmful nitrogen oxide emissions starting December 22, 2025. Local businesses running these turbines will need to follow the updated rules, helping the community breathe easier without big costs or delays.
Analyzed Economic Effects
4 provisions identified: 1 benefits, 3 costs, 0 mixed.
Rule 425 Becomes Federally Enforceable
On December 22, 2025, the EPA approved Eastern Kern Air Pollution Control District Rule 425 into the California SIP, making the rule federally enforceable under the Clean Air Act. If you operate stationary gas turbines in the Eastern Kern district, you must follow the updated NOX requirements in Rule 425 as of that date.
Prior Deficiency Fixed; Sanctions Clocks End
By approving the November 13, 2024 version of Rule 425, the EPA concluded the prior deficiency for the rule has been addressed and permanently terminated all sanctions clocks and Federal Implementation Plan (FIP) clocks triggered by the June 15, 2023 limited disapproval. This ends the timeline toward federal sanctions that had been running.
Stricter NOX Limit for One Turbine
For the Westinghouse W251B10 combustion turbine in Eastern Kern, the NOX limit when burning gaseous fuel was lowered from 25 parts per million by volume (ppmv) to 20 ppmv, and the previous liquid-fuel limit of 65 ppmv was removed. These specific limit changes are part of the November 13, 2024 version of Rule 425 that the EPA approved into the SIP.
Reporting Requirements Incorporated into SIP
The revised Rule 425 includes updated reporting requirements, and those reporting provisions were approved into the SIP. Facilities subject to Rule 425 must submit the reports required by the rule to the Eastern Kern Air Pollution Control District.
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