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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

News

  • A Fact Sheet and Responses to Comments on proposed revisions to the OTC Policy’s Interim Mitigation Memorandum of Understanding are now available for public feedback. Public feedback must be submitted by noon on June 21, 2025. Instructions are contained in the notice (aviso), and more project details are listed below on this webpage.

Public Meetings

Staff from the State Water Resources Control Board, the Ocean Protection Council, and the State Coastal Conservancy will present a joint information item on proposed revisions to the OTC Policy’s Interim Mitigation Memorandum of Understanding before the State Water Resources Control Board on June 3, 2025. Instructions on attending the meeting are contained in the notice (aviso).

Proposed Revisions to the Interim Mitigation Memorandum of Understanding

This section contains documents and information pertaining to proposed revisions to the OTC Policy’s Interim Mitigation Memorandum of Understanding (MOU). The MOU is a joint document between the State Water Resources Control Board, Ocean Protection Council, and State Coastal Conservancy that outlines how interim mitigation funds should be allocated and used. The original MOU was adopted in 2016, and proposed revisions to the MOU follow the State Water Board’s revisions to the interim mitigation calculations. Proposed revisions in part address comments received from the public and tribes during the process to revise the interim mitigation calculations. The proposed revisions ensure the continued effective allocation of interim mitigation funds while also identifying opportunities to engage and receive input from tribes and environmental justice groups on the use of interim mitigation funds.

Draft Determinations Approving Interim Mitigation Measures

This section contains the 2022-2023 draft determinations to approve mitigation measures for the Water Quality Control Policy on the Use of Coastal and Estuarine Waters for Power Plant Cooling (Once-Through Cooling or OTC Policy). These documents were posted on February 27, 2025, along with the notice and public comments were due by noon on March 21, 2025. The draft determinations are for the eight power plants listed below:

Final Determinations Approving Interim Mitigation Measures

Annual Reports – Use of Interim Mitigation Funds

Most owners and operators elected to comply with interim mitigation requirements via Sections 2.C(3)(b) and 2.C(3)(e) of the OTC Policy. Section 2.C(3)(b) directs interim mitigation funds to be paid to the Ocean Protection Council (“OPC”) and State Coastal Conservancy (“Conservancy”) to fund appropriate mitigation projects. Section 2.C(3)(e) of the OTC Policy states that it is the preference of the State Water Board that funding is provided to the Conservancy, working with the OPC, for mitigation projects directed toward increases in marine life associated with the State’s Marine Protected Areas (MPA) in the geographic region of the facility, including restoration of wetlands. Mitigation projects are defined in the OTC Policy as projects to restore marine life lost through impingement mortality and entrainment, and may include projects to restore and/or enhance coastal marine or estuarine habitat, and may also include protection of marine life in existing marine habitat, for example through the funding of implementation and/or management of MPAs. Projects that the OPC funds with interim mitigation payments are intended to support and protect the MPA network.

In accordance with the 2016 Memorandum of Agreement entered into by the State Water Board, the OPC, and the Conservancy (2016 MOU), the State Water Board participates in the selection process and approves of appropriate mitigation projects. Section 8 of the 2016 MOU states that the OPC and the Conservancy will each produce an annual report to the State Water Board identifying each completed mitigation project and the monitoring and maintenance activities that have occurred on each project which requires continued monitoring and maintenance.

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

Revision to Interim Mitigation Payments Calculation

On April 17, 2024, the State Water Board revised the interim mitigation payment calculation, which was established in 2015 through the adoption of Resolution No. 2015-0057. The revision updated the costing multipliers used to calculate the entrainment and impingement payments, and the annual inflation escalator approach. The revision to the interim mitigation calculation ensures that annual payments will continue to appropriately compensate for interim impacts to marine life based on current mitigation costs.

Documentos en Español

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