Five seawater desalination plants that combined could produce nearly 120 million gallons of drinking water a day have been proposed to the Metropolitan Water District of Southern California by cities and water agencies along the Pacific Coast between San Diego and Los Angeles.
Metropolitan, the region's largest water importer and wholesaler, hopes to increase the Southland's water supply through financial subsidies to local agencies building plants that convert the highly salty Pacific Ocean into purified drinking water.
"Desalinated seawater will be part of the portfolio of water resources that we are developing to help assure Southern California a reliable water supply for the next 20 years and beyond," said Metropolitan board Chairman Phillip J. Pace.
"We're not putting all of our eggs in one basket, and desalination is definitely one of the eggs we're hatching," Pace said. "Because the Southland's water supplies are interconnected, any water produced by any of these proposals would have a regional benefit by adding to the region's overall supply reliability."
By Thursday's 4 p.m. deadline, proposals had been submitted by the city of Los Angeles' Department of Water and Power; the San Diego County Water Authority in conjunction with the cities of Carlsbad and Oceanside; the Long Beach Water Department; the Carson-based West Basin Municipal Water District; and the Municipal Water District of Orange County.
Metropolitan is seeking to competitively add 50,000 acre-feet of desalinated seawater to the region's annual water supply, and the five submissions propose projects of more than twice that amount. (An acre-foot is about 326,000 gallons, enough water for a typical family for two years.) The proposals include plans for the pumps and pipelines needed to deliver the treated supplies to consumers.
"We're really pleased by the number of proposals we received," said Stephen N. Arakawa, Metropolitan's manager of water resource management. "These proposals will be reviewed, and those that are responsive will be invited to submit more detailed documents by June 28.
"We hope to have agreements negotiated and finalized by June 30, 2003, and we could see plants built and operating in 2007," Arakawa said.
Metropolitan hopes that new technology has increased the efficiency and lowered the cost of desalting ocean water. Due to high costs -- primarily the large amount of energy needed to operate them -- there are currently no major plants converting seawater to drinking water known to be operating in California. Brackish, or salty, groundwater can be desalted far more economically because it is far less saline than seawater.
Thirteen groundwater desalting and cleanup plants currently operate in Southern California with funding from Metropolitan, producing about 25,000 acre-feet annually, with nine more scheduled. In addition, local agencies produced another 18,000 acre-feet of recovered groundwater last year without funding from Metropolitan.
Desalination is commonly divided into two basic technologies, distillation and reverse osmosis. In the reverse osmosis process, saltwater is forced through filters, or membranes, that screen out the minerals. Four of the desalination proposals submitted to Metropolitan propose to use reverse osmosis technology.
The San Diego County Water Authority proposal seeks to locate a plant at the Encina Power Station in Carlsbad and would produce 50 million gallons per day (mgd), or 56,000 acre-feet per year, for use in Carlsbad, Oceanside and other county areas.
The Municipal Water District of Orange County's proposal would site a plant in Dana Point that would produce 27 mgd and 30,240 acre-feet annually.
West Basin Municipal Water District's proposal would be to build a plant at an unspecified coastal location that would produce 20 mgd and 22,400 acre-feet annually.
Long Beach's proposed plant would produce 8-to-10 mgd and 9,000 to 11,000 acre-feet a year. Los Angeles proposes to build its plant at one of three existing coastal generating plants. It would produce 10 mgd and 11,200 acre-feet annually.