Carlsbad Desalination Plant Upgrades to Protect Marine Life

December 15, 2022

Final phase of intake-discharge modifications moves ahead after Board action

The San Diego County Water Authority’s Board of Directors today unanimously authorized an agreement with Poseidon Resources (Channelside) LP to make major upgrades to the Claude “Bud” Lewis Carlsbad Desalination Plant, as required by the state’s Ocean Plan Amendment. The new facilities ensure the plant will continue to meet California’s evolving standards for protecting marine life. 

Upgrades to the seawater intake and discharge facilities were anticipated in the 2012 Water Purchase Agreement that launched construction of the nation’s largest seawater desalination plant in Carlsbad; however, the current Ocean Plan Amendment was not in place at the time. Since the start of commercial operations in 2015, the plant has produced more than 100 billion gallons of drinking water, helping protect the San Diego region’s economy and quality of life during the worst drought in more than 1,200 years.

Today’s Board action authorized the Water Authority general manager to sign a Water Purchase Agreement Contract Administration Memorandum with plant owner Poseidon-Channelside for the final phase of intake-discharge modifications. Those upgrades will cost an estimated $274 million, financed in part through California tax exempt bonds and a low-interest loan from the Water Infrastructure Finance and Innovation Act, a federal credit program for water and wastewater infrastructure projects.

“This action by the Board moves the Carlsbad Desalination Plant one step closer meeting state marine life mandates,” said Water Authority Board Chair Mel Katz. “Staff has worked diligently to ensure that the costs are as low as possible while continuing to provide our region with a drought-proof source of water. We are thankful to have this resource when so much of the West is suffering from extreme drought, and we expect it will be increasingly valuable as climate change further disrupts California’s hydrology.”

The desal plant’s intakes were originally configured to draw seawater from the Encina Power Station’s once-through-cooling system. That system was phased out by the state, and the power station shut down in December 2018. Its closure led to temporary intake-discharge operations at the desalination plant until new fish-friendly dilution pumps came online in 2020.

Today’s action by the Board moves the project to the final phase of the intake-discharge facility construction. Completion is anticipated within two years and includes:

·      New dual-flow screen system and ancillary systems supported on a new concrete access bridge including piles, pile bents, and access ramps

·      Dual-flow spray wash system which includes pumps, piping, and nozzles

·      Screen debris removal/management system

·      Floating debris boom system

·      Large organism exclusion system

·      New electrical building to house motor controls, variable speed drives, and other controls

·      Instrumentation and controls required for the Permanent Modifications

·      Connecting piping between the existing intake tunnel and the existing intake pump station

·      Abandonment of the generation station intake and discharge tunnel portions no longer needed to support operations

The desalination plant produces an average of more than 50 million gallons of high-quality, locally controlled water every day. A 30-year Water Purchase Agreement between Poseidon (Channelside) LP and the Water Authority allows for the production of up to 56,000 acre-feet of water per year, enough to meet the needs of approximately 400,000 people.

More information about the upgrades is in the Water Authority Board memo for Dec. 15 at

  • The San Diego County Water Authority sustains a $268 billion regional economy and the quality of life for 3.3 million residents through a multi-decade water supply diversification plan, major infrastructure investments and forward-thinking policies that promote fiscal and environmental responsibility. A public agency created in 1944, the Water Authority delivers wholesale water supplies to 23 retail water providers, including cities, special districts and a military base.

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