The San Diego County Water Authority’s board will consider this week whether to spend $30,000 to study the feasibility of building a seawater desalination plant in or near Rosarito.

The concept under consideration envisions a desalination plant capable of producing 25 million gallons of drinking water each day, with the potential to expand to 50 million gallons — enough for 112,000 homes and the same size as the proposed Carlsbad desalination plant.

The study and preliminary design is being done in cooperation with the Los Angeles-based Metropolitan Water District, the Southern Nevada Water Authority and the Central Arizona Water Conservation District. The Arizona district is paying for 10 percent of the study, the other agencies are each paying for 30 percent. Mexican agencies are contributing “in-kind” services, a water authority presentation says.

A Mexican desalination plant would have several potential water customers. The San Diego County Water Authority or Mexican water agencies could buy the water and use it locally. But the participation of the Arizona district, which operates the Central Arizona Project, and the Southern Nevada Water Authority, which supplies parched Las Vegas, could lead to a bi-national water swap.

Mexico is guaranteed 1.5 million acre feet of Colorado River supplies annually, per the terms of a 1944 U.S.-Mexico treaty. That’s enough water for 3 million homes each year. One of the inland agencies could agree to buy a share of Mexico’s Colorado River supply in exchange for building and guaranteeing supplies from the desalination plant. It’s a means for water agencies without access to the ocean (it’s a long way to Las Vegas from here) to tap into the Pacific Ocean without laying down hundreds of miles of pipes — an exorbitant expense.

Building the plant in Mexico could also shorten a lengthy permitting process. Poseidon Resources, the Connecticut-based developer of the Carlsbad plant, has worked for at least six years on the project here, and it isn’t yet finished. The company still needs approval from the San Diego Regional Water Quality Control Board.

This idea has been floated before by private developers. The local men behind the failed Bajagua project, which aimed to expand Tijuana’s sewage capacity, had some interest in building a desalination plant, too. They were going to call the project “Nevagua,” and potentially engineer a trade with a Nevada water agency.

When I reported that story a year ago, J.C. Davis, a spokesman for the Southern Nevada authority, told me that his water-hungry agency was definitely interested in desalination.

From that story:

The (Southern Nevada) authority’s general manager has signaled an interest in pursuing desalination projects in California or Mexico. [T]he authority will listen to any proposals, Davis said.

“Any opportunity that we can take that helps secure our water future, we are all ears,” Davis said.

The San Diego County Water Authority has already been studying other potential desalination plant sites locally. The authority has spent $825,000 studying the feasibility of building a plant on Camp Pendleton. It’s also starting a year-long study in 2009 of potential sites along the U.S.-Mexico border.

Even in the best of circumstances, though, desalination plants aren’t short-term solutions to the current water supply crunch. The authority estimates that it takes eight to 10 years to secure necessary permits and construct a plant.

ROB DAVIS

Dagny Salas

Dagny Salas was web editor at Voice of San Diego from 2010 to 2013. She was an investigative fellow at VOSD from 2009 to 2010.

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