State regulators are proposing to phase out using ocean water to cool California's coastal power plants, including three in San Diego County -- a move that could boost fish populations and electric rates.

The proposal is an outgrowth of environmentalists' campaign to halt the annual slaughter of millions of fish, crabs and other marine life that get swept into plants with the 16 billion gallons they use daily to cool turbines, according to the California State Lands Commission.

At the same time, it has huge implications for utility ratepayers as those plants account for close to half the electricity generated in California.

Plant operators say they would be saddled with $2 billion in costs that would be passed on to electricity customers.

The State Water Resources Control Board issued the draft policy this week. It would force the generating stations to scale back the volume of water they pipe in from the Pacific by 93 percent.

The policy is expected to be adopted by early 2010.

Plants would be given different target dates for complying with the rule. The state proposed deadlines of Dec. 31, 2012, for the South Bay Power Plant in Chula Vista; Dec. 31, 2017, for the Encina Power Plant in Carlsbad; and Dec. 31, 2022, for the San Onofre Nuclear Generating Station.

William L. Rukeyser, a spokesman for the water board in Sacramento, said it is uncertain when the policy will be adopted because the state wants to give the public and affected players plenty of time to comment on the plan. But he said it is likely a decision will come late this year or early next year.

"We're anxious for this work to be done, but we're not so anxious that it is going to be rushed," he said.

Rukeyser said plants could comply by cooling with air. Or, he said, they could build tanks to hold the large amounts of water required for cooling and reuse it instead of continuing to pipe new water in from the ocean.

In any event, they would have to curb the amount of ocean water they use by 93 percent. Plants still could draw in water from the ocean, but they would have to scale back their use substantially by storing that water in tanks and reusing it.

Plants would be asked to check to see if recycled water was available to replace the ocean water.

As for the timing of compliance, Rukeyser said officials want to gradually phase in the changes to avoid disrupting power supplies.

"No one has forgotten the lessons of 2000 and 2001 in terms of grid system reliability," he said, referring to the crisis that repeatedly sent ripples of blackouts across the state.

Joe Geever, policy coordinator for the environmental group Surfrider Foundation and a longtime champion of ending ocean-water cooling, said the proposal appears to be a sound one.

"On the surface, it looks to me like it's well balanced," Geever said. "It's something that's feasible and can be implemented within the time frame that they have set out."

But Steve Hoffmann, Western Region president for NRG Energy, operator of Carlsbad's Encina plant, said he is not so sure the time frame can be met.

Hoffmann said what is being proposed is a sweeping change. "Over 40 percent of the generation in California relies on ocean water for cooling," he said.

And he said complying would cost 19 plants $2 billion collectively, and Encina about $100 million.

Hoffmann said Princeton, N.J.-based NRG Energy intends to comply with the proposed mandate by replacing its existing 965-megawatt gas-fired plant with a modern 540-megawatt natural gas plant that would be built elsewhere on the company's site, between the railroad tracks and Interstate 5.

With an anticipated completion date of 2013, the new plant would be cooled by air, Hoffmann said.

But he said a portion of the existing plant probably will need to remain in operation well after the new facility is completed, and possibly after 2017. That's because the region and state are moving in a big way to sun and wind power, and the existing plant may need to continue generating power while that switch is being made.

Gil Alexander, a spokesman for Southern California Edison, majority owner of the San Onofre nuclear plant, warned that the proposed policy could "needlessly increase customer rates," threaten the stability of the California grid and dilute the state's ambitious efforts to curb greenhouse gas emissions scientists blame for global warming.

Alexander said Edison already has taken extensive measures to soften the environmental impacts of San Onofre's cooling process.

Hoffmann said NRG will not have difficulty meeting the state's mandate.

But, he said, "a 90 percent reduction in flow is not practical for many of these older plants."

Rukeyser said that under the policy operators would get the chance to make the case that they cannot meet the goal. If they were to convince state officials they were right, he said, operators could take other measures, such as installing screens on water intakes, to avoid harming marine life.

The draft policy may be viewed here.

Call staff writer Dave Downey at 760-745-6611, ext. 2623.