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Claude "Bud" Lewis Carlsbad Desalination Plant

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Key facts: The Claude "Bud" Lewis Carlsbad Desalination Plant is a seawater desalination facility in Carlsbad, California, that produces approximately 50 million gallons of drinking water a day, supplying about 10% of San Diego County's water needs[1][4].

The plant, developed and built by Poseidon Water, began commercial operations in December 2015 and was, at the time, the largest desalination plant in the Western Hemisphere[1][3]. It is named in honor of Claude "Bud" Lewis, Carlsbad's longest-serving mayor and an early proponent of desalination[1][3].

Water from the plant is purchased by the San Diego County Water Authority under a 30-year Water Purchase Agreement approved in November 2012, and distributed to member agencies including the Carlsbad Municipal Water District[1][4]. In 2019, ownership of the plant passed to Aberdeen, a global infrastructure investment firm, which established Channelside Water Resources to manage daily operations, with all provisions of the original agreement remaining in place[4].

Overview

The Claude “Bud” Lewis Carlsbad Desalination Plant is a seawater desalination facility located in Carlsbad, California, adjacent to the former Encina Power Station site on Agua Hedionda Lagoon[3][5]. The City of Carlsbad describes it as a 50-million-gallon-a-day facility supplying the San Diego region with approximately 10% of its drinking water needs, calling it the first large-scale desalination plant on the West Coast and the largest of its kind in the Western Hemisphere[1]. The San Diego County Water Authority similarly describes it as the nation’s largest seawater desalination plant, the result of a public-private partnership in Carlsbad[4][3].

The plant uses reverse osmosis technology, forcing seawater through semipermeable membranes under high pressure to separate fresh water from salt and other impurities[4][2]. According to the City of Carlsbad, the project is located within the city but is not a city project; it was developed by a private company, Poseidon Water, with water purchased and distributed by the San Diego County Water Authority[1].

History

According to Wikipedia, the effort to build a desalination plant in San Diego County began in 1993 after five years of drought, and membrane technology used in the plant was pioneered by General Atomics in La Jolla[3]. The San Diego County Water Authority traces the idea further back, noting that General Atomics commercialized reverse-osmosis membrane technology in the 1960s and that two potential sites, including the Encina Power Station site in Carlsbad, emerged from a 1991 Water Authority study[4]. Poseidon Water arrived in San Diego County in 1998 with a model of privately developing water resources for sale to public utilities, and the Water Authority approved a term sheet for a potential Carlsbad project in 2001[4].

Negotiations were suspended in 2004 but the Water Authority continued independent studies, and in 2005 the Water Authority and the City of Carlsbad agreed on how to jointly develop a regional plant at the Encina Power Station[4]. The project cleared final regulatory hurdles between 2006 and 2007, with approval from the Carlsbad City Council, the Regional Water Quality Control Board, and the California Coastal Commission[4]. Environmentalists opposed construction over concerns including energy consumption, brine discharge, and ocean water intake effects on fish, and five lawsuits were filed by groups such as the Surfrider Foundation, San Diego Coastkeeper, and the Coastal Environmental Rights Foundation, though none succeeded[3].

Construction began in December 2012, led by Kiewit Shea Desalination, a joint venture of Kiewit Infrastructure West and J.F. Shea Construction, and was originally scheduled for completion in 2016 before being advanced to late 2015 because of the ongoing California drought[4][3]. The 10-mile conveyance pipeline began construction in March 2013 and was completed June 28, 2015[4][3]. The plant was dedicated in 2015, producing approximately 50 million gallons per day, and commercial operations began in December 2015 after six months of testing[4][3][2]. The project took nearly 14 years to permit, design, and build[3].

Capacity and output

The City of Carlsbad and the plant’s operator describe the facility as capable of producing 50 million gallons of drinking water per day, enough to serve about 400,000 people and supply roughly 10% of the San Diego region’s water needs[1][2][4]. Wikipedia cites a slightly different figure, stating the plant was expected to produce about 7% of the region’s potable water needs, while a Channelside FAQ states the plant provides up to 54 million gallons per day and more than 10% of the region’s supply[3][2].

Under the Water Purchase Agreement, the San Diego County Water Authority agreed to purchase up to 56,000 acre-feet of desalinated seawater per year, equivalent to about 10 percent of regional demand, with a minimum purchase of 48,000 acre-feet per year[4][3]. By December 2018, the plant had produced its 40-billionth gallon of water, though Wikipedia notes that output fluctuated, with the plant fulfilling 95% of water orders in 2016 but only 70% the following year[3].

Operationally, the facility takes in cooling water that historically came from the adjacent Encina Power Station, filters it through gravel and sand media, and then runs it through reverse osmosis filtration, converting about half of the intake into potable water and discharging the rest as concentrated brine blended for dilution[3]. Energy recovery devices at the plant are estimated by Channelside Water Resources to save about 116 million kilowatt-hours of energy per year, reducing carbon dioxide emissions by an estimated 42,000 metric tons annually[4].

Ownership and operation

The plant was developed and built by Poseidon Water, a private, investor-owned company, under a public-private partnership with the San Diego County Water Authority[4][1][3]. The City of Carlsbad describes Poseidon as the project’s developer, noting the project is located in Carlsbad but is not a city-owned project[1]. Wikipedia identifies the main engineering and construction firms involved as GHD Group, Butier Engineering, IDE Americas (a subsidiary of IDE Technologies), Simon Wong Engineering, and the J.F. Shea Company and Kiewit Corporation, which constructed the plant[3].

According to the San Diego County Water Authority, ownership of the plant was purchased in 2019 by Aberdeen, described as a global infrastructure investment firm, which established Channelside Water Resources to manage daily operations; all provisions of the original Water Purchase Agreement remained in place[4]. Channelside Water Resources itself states that it funded the project through capital markets and equity contributions, with private investors—not taxpayers or ratepayers—assuming the majority of risks related to permitting, design, construction, and operation[2].

Poseidon also assumed responsibility for dredging Agua Hedionda Lagoon after the demolition of Encina Power Station, taking over that duty from the power plant’s former owner, NRG Energy, with Channelside Water Resources continuing stewardship of the roughly 400-acre lagoon[3][4].

Water purchase agreement

In November 2012, the San Diego County Water Authority board of directors approved a 30-year Water Purchase Agreement with Poseidon Water for the purchase of up to 56,000 acre-feet of desalinated seawater per year[4][1]. The City of Carlsbad notes that it originally planned to buy water directly from Poseidon, but when Poseidon could not secure financing, the Water Authority instead negotiated the deal to purchase water from the project and distribute it to member agencies, including the Carlsbad Municipal Water District[1].

Under the agreement, the Water Authority purchases water from the plant at pre-defined prices and does not pay if water fails to meet specified quality requirements, while the agreement transfers design, construction, and operating risk to Poseidon and its investors[4]. The Water Authority has the right to ensure the plant is operated safely and, at the end of the 30-year term, may purchase the plant for $1[4]. Wikipedia’s account of the original Water Purchase Agreement terms states the Water Authority would have the option, but not the obligation, to buy the $537 million plant after a decade of operation using a preset price formula, in addition to the eventual $1 buyout[4].

Financing for the project closed in December 2012 with $734 million in tax-exempt bond financing, which the Water Authority says saved an estimated $200 million in financing costs over three decades compared to earlier projections, aided by a 4.78 percent interest rate[4]. Wikipedia reports the total project cost reached near $1 billion, with early cost estimates ranging from $250 million in 2004 to $690 million in 2010, and notes that in late 2012 Fitch Ratings gave the bonds their lowest investment-grade rating[3]. Estimates of the resulting water cost vary: the Water Authority states desalinated water costs typical homeowners about $5 per month, while Wikipedia cites May 2015 estimates of $1,300 to $1,400 per acre-foot to produce, compared with about $300 per acre-foot for reservoir water[4][3].

Name

The plant is named in honor of Claude “Bud” Lewis, described by the City of Carlsbad as Carlsbad’s longest-serving mayor and an early proponent of desalination[1]. Wikipedia similarly states the plant was named after Lewis, a former Carlsbad mayor who held the position for almost a quarter of a century and supported construction of the facility; Lewis died in 2014, before the plant began operations[3].

Common questions

How much water does the Carlsbad Desalination Plant produce?

The plant is designed to deliver approximately 50 million gallons of drinking water per day, enough to serve about 400,000 people[4][2].

Who owns the Carlsbad Desalination Plant?

Poseidon Water developed and built the plant, but in 2019 ownership was purchased by Aberdeen, a global infrastructure investment firm, which created Channelside Water Resources to manage daily operations[4].

Why is the plant named after Bud Lewis?

It was named for Claude "Bud" Lewis, Carlsbad's longest-serving mayor, who was an early proponent of desalination and died in 2014[1][3].

Does the plant supply all of Carlsbad's water?

No; the desalination project provides about 10% of the region's water supply, with the rest coming from imported and other local sources[1].

What was the plant built next to?

The plant was built adjacent to the former Encina Power Station on the shore of Agua Hedionda Lagoon, using the power station's existing seawater intake infrastructure[5][4].

References

All sources retrieved November 2026.

  1. ^ a b c d e f g h i j k l m n o p q r s "cc_desal". City of Carlsbad. Retrieved November 2026.
  2. ^ a b c d e f g h i "Your Questions, Answered". Channelside Water Resources. Retrieved November 2026.
  3. ^ a b c d e f g h i j k l m n o p q r s t u v w x "Claude "Bud" Lewis Carlsbad Desalination Plant (Wikipedia)". Wikipedia. Retrieved November 2026.
  4. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z "Seawater Desalination - San Diego County Water Authority". San Diego County Water Authority. Retrieved November 2026.
  5. ^ a b "Encina Power Station (Wikipedia)". Wikipedia. Retrieved November 2026.