Ocean Standards - CWA §316(b) Regulation

Cooling Water Intake Structures
Once-Through Cooling Water Policy - Interim Mitigation Measures

The State Water Resources Control Board (State Water Board) Statewide Water Quality Control Policy on the Use of Coastal and Estuarine Waters for Power Plant Cooling (Once-Through Cooling or OTC Policy) requires owners or operators of existing power plants to implement measures to mitigate interim impingement and entrainment impacts resulting from their cooling water intake structures. The interim mitigation period commenced on October 1, 2015, and continues up to and until owners or operators achieve final compliance with the OTC Policy.  Section 2.C.3 of the OTC Policy provides information for demonstrating compliance with the interim mitigation.  Resolution No. 2015-0057 (2015 Resolution) describes the procedures for calculating the mitigation payment. The State Water Board calculates the interim mitigation payments by summing three components: an entrainment payment, an impingement payment, and a management and monitoring payment.

The State Water Board calculates interim mitigation payments annually, based on data and information provided by the power plant owners and operators. The State Water Board provides letters with the calculated annual interim mitigation payment and instructions for the payment process. When appropriate, the State Water Board prepares draft determinations for mitigation measures on a case-by-case basis. Consistent with the 2015 Resolution, draft determinations are posted for a public comment period of 20 days and circulated to persons who have requested public notice on matters related to the OTC Policy. After considering the public comments received on a draft determination, the Executive Director shall consider whether, in light of unusual circumstances or significant controversy, the final approval of the determination should be made by the State Water Board at a public meeting.

Flow Chart on the Process for Approving Interim Mitigation Measures per Section 2.C.(3)(b) of the OTC Policy


  • Notice of Opportunity for Public Comment on the 2018-2019 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
    • 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 this webpage below each power plant name.

Determinations Approving Interim Mitigation Measures

Delegation of Authority

State Water Board-Contracted Expert Review Panel II on Intake Impacts and Mitigation

The State Water Board contracted with the Moss Landing Marine Laboratory to establish an expert panel to address issues associated with minimizing and mitigating intake impacts from power plants and desalination facilities. The panel members were Dr. Michael Foster, Dr. Greg Cailliet, Dr. Jim Callaway, Dr. Pete Raimondi, and Mr. John Steinbeck. The panel met on August 8, 2011 and on November 15, 2011.  A public meeting was held March 1, 2012 at the Moss Landing Marine where panel members presented their recommendations and took questions and comments from the public on the panel’s Draft Report.  Updates were given on the other two studies.  The panel members deliberated and made changes to their report, which was finalized on March 14, 2012.

  • Expert Review Panel II on Intake Impacts and Mitigation

Questions or Comments