Ocean Standards - CWA §316(b) Regulation


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).

The Policy is implemented through an adaptive management strategy by which the standards can be achieved without disrupting the critical needs of the state's electrical generation and transmission system. The Statewide Advisory Committee on Cooling Water Intake Structures (SACCWIS) reviews implementation plans and schedules to ensure the schedules take into account local area energy needs and grid reliability. SACCWIS provides recommendations to the State Water Board at least annually. The State Water Board considers SACCWIS's recommendations and makes modifications to the Policy, as appropriate.

Eight plants have ceased their once-through cooling operations. In 2016, the eleven plants still operating once-through cooling systems withdrew slightly more than four billion gallons of water a day. These eleven 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.

Policy Amendments

Table of OTC Policy Amendment History - Dates and Short Summaries

Encina Power Station Compliance Date Extension Amendment

Moss Landing Power Station Compliance Date Extension Amendment

Reassignment of NPDES Permitting Responsibility to Regional Boards Amendment

LADWP Power Stations Compliance Dates Extension and Additional Entrainment Measures Amendment

Policy Adoption

Questions or Comments about Power Plant Once-Through Cooling Regulation?

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