The once-thought concept of removing salt from seawater is new again as the search intensifies in California for drought-proof sources of water.
In Carlsbad, a large scale desalination factory is within two years of delivering 50 million gallons of drinking quality tap water from the ocean every day, according to the plant's developer.
One county to the north, the Orange County Water District is considering committing financial backing and a long-term water purchase agreement to enable a sister plant to be built in Huntington Beach, though the project is not without opposition and has yet to obtain a final permit from the California Coastal Commission.
Environmental challenges have been raised on a number of issues. But the biggest hurdles for desalination is its premium price, the expense both of building plants, and of the enormous amounts of energy required to run them.
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A desalination plant built two decades ago in Santa Barbara remains an unused white elephant -- partially dismantled -- because the city found cheaper sources of water.
Behind both the Carlsbad and Huntington Beach projects is Boston-based Poseidon Water. Both have similar designs, and would draw in ocean water through the existing intake systems for the cooling systems of nearby power plants.
That design was approved for Carlsbad. But for Huntington Beach, the Coastal Commission cited concerns for fish larvae being sucked into the plant and instructed Poseidon to submerge the inlet or find another alternative to protect the larvae.
"We want better technology," said Ray Hiemstra of Orange County Coastkeeper.
That likely would further raise the cost of a plant already projected at close to a billion dollars.
Before proceeding in Carlsbad, Poseidon reached an agreement with the San Diego County Water Authority to back a majority of the financing, and to purchase water for 30 years.
At full capacity, the Carslbad plant would provide 7 percent of San Diego County's current water needs. But its price premium compared to imported water is projected to push up the typical home's water bill by $5 to $7 a month, according to the San Diego Water Authority.
"It does cost more to desalinate water," said Peter MacLaggan, Poseidon senior vice president for project development. "But the incremental cost for that bucket of water is a tremendous insurance policy. It will always be there."
The drought has dramatically reduced the availability of surface water imported from the Colorado River and from the State Water Project that draws on snowmelt from the Sierra Nevada in Northern California.
Poseidon and the San Diego Water Authority believe the cost gap will narrow and eventually cross in the middle of the next decade.
Water from the Huntington Beach plant is projected to cost the OC Water District about 50 percent more than the current cost for state water project water, according to Shawn Dewane, president of the Orange County Water Authority board.
Taking off his Coastkeeper hat for a moment and speaking as a Huntington Beach resident, Heimstra observed: "As a rate-payer, I'm very concerned about an increase in my rates."
Dewane is hopeful technology breakthroughs will lower the amount of energy required for desalination and bring down the cost.
Importing water to Southern California from the state water project also requires enormous amounts of energy to pump the water over the Tehachapi Mountains.
But it takes less energy to raise an 8-pound gallon of water nearly 3,000 feet than it does to maintain the 1,000 pounds per square inch of pressure required to push two gallons of water through the filtration membranes used in the reverse osmosis process to desalinate a gallon of water.
"This is not the right place nor the right time to build this in Huntington Beach," said Merle Moshiri, president of Residents for Responsible Desalination (R4RD), one of several advocacy groups opposing the proposed plant.
"They haven't exhausted all the options," said Joe Geever, who oversees water policy issues for the Surfrider Foundation.
Interestingly enough, the desalination foes of the OC Water District praise its efforts to expand recycling of sewage water. It is purified using a process almost identical to that for desalination, though much less expensive because the reverse osmosis phase does not require as high a pressure.
The OC Water District currently recycles 70 million gallons a day, and plans to expand that to 100 million gallons a day, twice the capacity of the proposed Huntington Beach desalination plant.
But rather than going directly to the tap, most of the recycled water is injected into the ground to replenish the underground aquifer that supplies much of the county's drinking water. The rest of the recycled water goes to landscape irrigation, and can also be used for industrial applications.
With the next expansion, the OC Water District expects to recycle about 60 percent of the county's water. But making headway on the remaining 40 percent will be more difficult, Dewane said, because it contains contaminants that cannot be removed by the district's treatment system.
In recent decades, some two dozen desalination projects have been proposed up and down the California coast. But few are moving forward, and all are watching the course of events in Carlsbad and Huntington Beach.
When it comes to staking out a new frontier, it can be easier "to move second," observed Dewane. .