Water Authority Is Considering Desalination : Drought: Agency studies possibility of a seawater distilling plant attached to a proposed SDG&E; power plant.


Seeking new water sources amid the drought, the San Diego County Water Authority has become the first major water provider in Southern California to explore desalting ocean water.

The authority believes it can produce as much as 50,000 acre-feet of water a year, enough "to serve the entire city of San Diego for a quarter of a year," by building a desalination plant attached to a proposed new power plant, said Byron Buck, the authority's director of planning.

The plan hinges on San Diego Gas & Electric Co. winning state approval to build a 460-megawatt power plant that water officials hope would serve the dual purpose of distilling 20-million to 40-million gallons of seawater a day.

"We're very open-minded to this," said Bruce Williams, SDG&E;'s manager of generation projects. "On the face of it, there are some very attractive points."

The authority's tentative proposal, made in a letter to SDG&E;, shows faith in a technology that has been studied and rejected by the Metropolitan Water District in Los Angeles, which concluded that water desalination is too expensive and poses both political and environmental problems.

MWD spokesman Tim Skrove said, "We have always held open the option of desalting the ocean, but the limiting factor has been the extreme cost associated with it."

But desalination is now being considered in Santa Barbara, which has been hit particularly hard by the drought. The City Council there is pondering a staff proposal to negotiate with five firms to build a seawater treatment plant to begin operating in the fall of 1991. The plant would initially provide about 2,500 acre-feet of desalted water, enough to serve about one-third of the city's population.

The Orange County Water District has been desalting waste water--not ocean water--from a sewage plant for 16 years, but not for residential use. The reclaimed water is pumped into underground aquifers to create a freshwater barrier against invading seawater.

The San Diego County Water Authority is the largest agency in Southern California looking to seawater to meet domestic water needs. The authority delivers 600,000 acre-feet of water annually and serves 97% of the county's population.

Buck said that desalting 50,000 acre-feet of seawater would help the authority achieve its goal of finding alternative water resources. The authority now buys its water from MWD.

"It would be excellent quality water, you'd get essentially distilled water" that could be consumed by humans, he said.

Officials from the authority and SDG&E; will meet in two weeks to discuss the possibility of building the desalination project at SDG&E;'s proposed 460-megawatt power plant.

The power plant would cost $388 million to $577 million, depending on whether it's built inland or on the coast, and is being reviewed by the California Energy Commission. The authority has not calculated what it would cost to add the desalination project.

SDG&E; is considering five potential sites for the power plant, including the Encina power plant in Carlsbad, the South Bay power plant in Chula Vista, West Sycamore Canyon east of Miramar Naval Air Station, Blythe in Riverside County and near Heber in Imperial County.

When Buck posed the desalination idea to SDG&E;, he suggested that developing a plant to meet both energy and water needs "would also be helpful to SDG&E; in gaining a favorable decision" from the state's energy commission.

According to Buck, the plant should be built on the coast because of the nearness to seawater. That emphasis on a coastal location is disturbing to some Carlsbad city officials, who don't want a second power plant in their community.

"I'm very suspicious of any idea by SDG&E; to sweeten the pot" and make the plant proposal more appealing to the state, Carlsbad Councilwoman Ann Kulchin said.

Although it's too soon to know where the proposal is heading, there's a long history to water desalination projects.

Desalting ocean water is routine technology in the arid Middle East, but it has enjoyed smaller-scale use in the United States, such as on Naval ships and in isolated locations.

In 1988, the Metropolitan Water District undertook a $300,000 study of two possible seawater desalting projects, but came away with gloomy conclusions.

District spokesman Skrove said linking a desalination facility to a nuclear reactor was explored but "it just kind of fell apart" because "you had the social and regulatory problems" that go with using nuclear power.

MWD also considered a desalting operation in tandem with a conventional fossil fuel power plant, but there were major concerns over air pollution caused by such a facility.

"Tremendous social and political obstacles would have to be overcome" in making a commitment to seawater desalination, said Skrove.

In addition, the MWD study found that building a desalting project would cost "probably five times as much" as developing other sources of water, Skrove said. "We made a financial analysis and came up with the basic conclusion it's not a supply alternative," he said.

The MWD study didn't evaluate to what extent desalting seawater might increase water bills to consumers.

San Diego's water agency believes it can provide desalted water at less cost. According to a letter Buck sent to SDG&E;, power plants specifically designed to generate power and distill seawater "will provide a more cost-effective source of desalted water than those evaluated in the previous studies."

Buck said that consultants at Bechtel Inc. believe the costs of producing desalted water would be "attractive to the authority when considering our current marginal cost of water and given the current and projected future water supply situation."

It now costs the San Diego County Water Authority about $450 per acre-foot of water. Desalted water would cost $700-$900 per acre-foot.

Williams of SDG&E; said engineering and financial analyses must be completed before a decision is made on the desalination plan. But, he said. "we would not be interested in something if ratepayers are disadvantaged."

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