Ocean Standards - CWA §316(b) Regulation

Cooling Water Intake Structures
Once-Through Cooling

On May 4, 2010, the State Water Resources Control Board (State Water Board) adopted a Policy on the Use of Coastal and Estuarine Waters for Power Plant Cooling (Policy). The Policy became effective on October 1, 2010.

The Policy establishes technology-based standards to implement federal Clean Water Act section 316(b) and reduce the harmful effects associated with cooling water intake structures for power generating facilities on marine and estuarine life. The Policy applied to 19 existing power plants (including two nuclear plants) with the combined ability to withdraw almost 16 billion gallons per day from the state’s coastal and estuarine waters using a single-pass system, also known as once-through cooling (OTC). Closed-cycle wet cooling has been selected as Best Technology Available (BTA). Permittees must either reduce intake flow and velocity (Track 1) or reduce impacts to aquatic life comparably by other means (Track 2).

Nine plants have ceased their once-through cooling operations. The ten remaining plants have informed the State Water Board that they are planning to comply by retiring their existing OTC plants’ equipment. In some cases, plants will repower their locations with modern non-water-cooled systems.

Official Policy Documentation


  • Notice of Opportunity for Public Comment on the 2017-2018 Draft Determinations to Approve Mitigation Measures for the Water Quality Control Policy on the Use of Coastal and Estuarine Waters for Power Plant Cooling for the following power plants:
    • Alamitos Generating Station
    • Diablo Canyon Nuclear Power Plant
    • Encina Power Station
    • Harbor Generating Station
    • Haynes Generating Station
    • Huntington Beach Generating Station
    • Ormond Beach Generating Station
    • Redondo Beach Generating Station
    • Scattergood Generating Station

    The draft determinations are posted on Interim Mitigation Measures webpage.

  • A member of the Statewide Advisory Committee on Cooling Water Intake Structures (SACCWIS) will present a summary of the 2019 SACCWIS Report to the State Water Board at the May 21, 2019 Board meeting. Please see the Public Meetings section below for more details. The Statewide Advisory Committee on Cooling Water Intake Structures (SACCWIS) met on March 8, 2019. Presentations, draft meeting minutes, and the Final 2019 SACCWIS Report are posted on the SACCWIS webpage.

Public Meetings

Annual Report from the Statewide Advisory Committee on Cooling Water Intake Structures with Recommendations Regarding Implementation Schedules in the Use of Coastal and Estuarine Waters for Power Plant Cooling

May 21, 2019
9:30 am
Joe Serna Jr./CalEPA Headquarters Bldg.
Coastal Hearing Room
1001 I Street, Second Floor
Sacramento, CA 95814

For more information, please see the Notice posted on the Clerk’s webpage and documents posted on our SACCWIS webpage.

Other Relevant Documents


The two committees listed below, were convened by the Executive Director of the State Water board, as required by the Policy. The committees are subject to the Bagley-Keene Open Meeting Act

Statewide Advisory Committee on Cooling Water Intake Structures (SACCWIS)
SACCWIS was established to advise the State Water Board on the implementation of this Policy to ensure that implementation plans and schedules established by the Policy are realistic and will not cause disruption to the State’s electrical power supply.  SACCWIS includes representatives from the California Energy Commission, California Public Utilities Commission, California Coastal Commission, California State Lands Commission, California Air Resources Board, California Independent System Operator, and the State Water Board. 

Review Committee for Nuclear Fueled Power Plants
The Review Committee was established to oversee the special studies, which will investigate ability, alternatives, and cost for two nuclear-fueled power plants to meet the Policy requirements.  The special studies will be conducted by an independent third party with engineering experience with nuclear power plants, selected by the Executive Director of the State Water Board, and paid for by the two nuclear-fueled power plants subject to the Policy.  The Review Committee includes representatives from the SACCWIS agencies, the nuclear power companies, the environmental community, and staffs of the State Water Board and appropriate Regional Water Boards.

Permitting of Affected Power Plants

The Policy is implemented through National Pollutant Discharge Elimination System (NPDES) permits for coastal and estuarine power plants. The applicable Regional Water Boards are responsible for implementing the Policy requirements in NPDES permits for existing coastal and estuarine power plants. The water boards determine requirements to implement best technology available for cooling water intake structures to be included in the permits. State Water Board staff provides technical support to the Regional Water Boards to ensure a high level of statewide consistency in implementing the Policy.  »»   Get more information …

Questions or Comments

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  (Page last updated 5/13/19)