Advisory committee finds no extensions needed yet for California once-through cooling policy, but flags grid risks

The State Water Resources Control Board received an informational presentation June 17 on the 2025 report of the Statewide Advisory Committee on Cooling Water Intake Structures (SACWIS), which monitors compliance with the OTC policy and the implications for grid reliability as coastal power plants retire or convert cooling systems.

SACWIS members told the board the committee is not recommending extensions of OTC compliance deadlines at this time. "The final SACWIS report does not recommend any compliance state extensions," said Jonathan Dolan, environmental scientist in the Ocean Standards Unit, summarizing the advisory panel’s March 21 work.

Why it matters: the OTC policy requires coastal power plants to stop using once-through cooling to protect marine life. As plants retire or retrofit, grid planners and operators have tracked reliability risk and contingency needs. SACWIS’s 2025 report found 12 of the original 19 OTC plants are now fully compliant; the other seven are on track to meet their schedules.

Key findings presented by interagency members:

- Water use and compliance: historic and projected daily water use at OTC plants has declined as units have complied or retired. SACWIS’s projection through 2031 showed fleetwide daily flows below policy-design flow rates.

- Air permitting and operational constraints: Lan Ma of the California Air Resources Board said operating OTC units must meet Title V permitting requirements; some units qualify for limited exemptions under South Coast AQMD rules but exemptions do not apply if an OTC system is removed while the fossil-fuel unit remains in operation.

- Grid reliability and procurement: Christine Root of the California Public Utilities Commission said net qualifying capacity procurement has been strong through 2024, with record additions of storage and solar. Neil Miller of the California ISO described using some OTC units sparingly during 2024 heat events as part of the Strategic Reliability Reserve. "We instructed the once-through cooling units in our footprint to start up on three separate occasions last summer," Miller said, noting in each instance units were held at minimum load and were not needed beyond that duty.

- Contingency planning: Alicia Gutierrez of the California Energy Commission summarized the joint SBA 46 reliability assessment and said the system shows surplus capacity under average peak conditions in 2025, but under extreme multi-region heat events and import reductions there could be shortfalls — in downside scenarios as large as several hundred to thousands of megawatts depending on assumptions about delayed procurement and import availability.

Los Angeles Department of Water and Power (LADWP) representatives described progress toward replacing or retrofitting their OTC units. LADWP said environmental analyses and permitting are underway at Scattergood and other sites, pipeline work is in construction, and voluntary environmental-benefit payments to the Coastal Conservancy have begun.

Board Chair Joaquin Esquivel thanked SACWIS and other agencies for interagency coordination. No board action was requested; SACWIS continues to meet at least annually and the interagency working group will track compliance, procurement and permitting developments.

The committee’s bottom-line recommendation: continue monitoring and coordination but do not seek system-wide OTC compliance deadline extensions at this time; the committee will reconvene if grid conditions or procurement delays indicate a need for contingency relief.