Carlsbad Desalination Plant

Poseidon Resources (Channelside) LP owns and operates the Claude “Bud” Lewis Carlsbad Desalination Plant, which is located on the southern shore of Agua Hedionda Lagoon in the City of Carlsbad, California. The Carlsbad Desalination Plant is the nation’s largest seawater desalination plant, producing an average daily flow of 50 million gallons per day (MGD) of drinking water per day from seawater through a reverse osmosis process that results in a brine waste approximately twice the salinity of the ocean. The Carlsbad Desalination Plant is currently using cooling water from the Encina Power Station as the source water for the desalination facility and discharges the commingled brine waste to the to the Pacific Ocean through the Encina Power Station channel. Once the Encina Power Station is decommissioned, the Carlsbad Desalination Plant proposes to withdraw up to 299 MGD of seawater from the Agua Hedionda Lagoon and use flow augmentation to dilute the brine prior to discharge into the Pacific Ocean. The San Diego Water Board is currently working on the reissuance of the NPDES permit for the facility and is also working in consultation with the State Water Board on issuing a determination pursuant to Water Code section 13142.5(b) for the stand-alone desalination facility.

The current permit is Order No. R9-2006-0065, with amendments incorporated.

Permit Renewal

The current permit, Order No. R9-2006-0065, expired in 2011, but remains in effect under an administrative extension until such time as it is superseded by the reissued NPDES permit. The reissuance of the NPDES permit for the CDP is a high priority for the San Diego Water Board and the State Water Board.

Written public comments received on January 28, 2019 on Tentative Order No. R9-2019-0003:

Notice of Availability - Tentative Order No. R9-2019-0003. The California Regional Water Quality Control Board, San Diego Region (San Diego Water Board) is releasing, for public review and comment Tentative Order No. R9-2019-0003, NPDES No. CA0108928, Waste Discharge Requirements for the Poseidon Resources (Channelside) LP Claude "Bud" Lewis Carlsbad Desalination Plant Discharge to the Pacific Ocean. The Tentative Order and Public Notice, which contains instructions on how to submit written comments, are available using the links below. Questions and comments should be directed to Mr. Ben Neill at or 619-521-3376.

Science Advisory Panel (SAP): Chapter III.M.2.a(1) of the California Ocean Plan provides that regional water boards may require an owner or operator of a desalination facility to hire a neutral third party entity to review studies and models and make recommendations to the boards regarding a Water Code section 13142.5(b) determination for the best available site, design, technology and mitigation measures feasible to minimize the intake and mortality of all forms of marine life at new or expanded desalination facilities. At the San Diego Water Board's direction, Poseidon funded a previously convened independent SAP to provide scientifically justified assessment and recommendations to the Board on the intake technology and mitigation measures feasible to minimize the intake and mortality of all forms of marine life for the stand-alone operation of the CDP. The members of the SAP are Dr. Peter Raimondi, UC Santa Cruz; Dr. Brett Sanders, UC Irvine; and Dr. Richard Ambrose, UCLA.

Meetings with Poseidon Resources regarding NPDES permit development:

Executive Officer Reports

Reports regarding the Carlsbad Desalination Project are available in the Executive Officer's Reports for the following months:


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