SAN DIEGO —— County water officials this week pushed back the date they hope to have a plant start turning seawater into drinking water from 2010 to 2011.

But the one-year delay does not mean that on-again, off-again negotiations between the San Diego County Water Authority and Connecticut-based Poseidon Inc. are once again in trouble.

"Negotiations are ongoing and productive," Bob Yamada, the Water Authority's desalination program manager, said Friday.

Yamada said the revised date simply means the Water Authority is no longer in a rush to get the proposed plant in Carlsbad up and running.

He said that's because Water Authority board members voted in January to expand the production of a $171 million treatment plant they plan to build in San Marcos by 2007 from 50 million gallons a day to 100 million gallons a day.

The result, he said, is that the agency won't need the proposed Carlsbad desalination plant to help ease looming drinking water shortages on hot summer days —— predicted because regional population growth has outgrown the capacity of existing treatment plants.

Yamada said the decision to expand the San Marcos treatment plant gives the Water Authority more time to hammer out an agreement with Poseidon.

Poseidon Senior Vice President Peter MacLaggan agreed Friday.

"The pressure is off on the water supply side," he said. "That's what they conveyed to the (Water Authority) board. Now we can take a more leisurely pace."

But both the Water Authority and Poseidon once hoped the Carlsbad plant would be up and running by 2008 —— not 2011.

And any news of potential delays —— coupled with the pair's six years of sometimes contentious negotiations —— prompts questions about whether talks could fall apart.

Poseidon started studying the idea of building a seawater desalination plant at the Encina Power Plant in Carlsbad in 2000 and secured a 60-year leasehold on the proposed site.

The regional Water Authority, meanwhile, which supplies nearly all the water San Diego County residents use annually, has repeatedly said turning seawater into drinking water is an important part of making sure county residents have enough water in the future.

After joining Poseidon's study in 2001, Water Authority board members officially identified building the Carlsbad plant as their top priority.

But the agency and Poseidon have clashed while trying to hammer out a deal, in which Poseidon would build the plant and sell it to the agency after five years.

The Water Authority actually broke off three years of talks with Poseidon in 2004 after a bitter disagreement that lasted several months. Negotiations only resumed in April.

Poseidon said the dispute was over information it considered confidential.

The Water Authority said the argument was over cash —— how much Poseidon wanted for building the plant —— and briefly raised the specter of using eminent domain to force Poseidon to knuckle under.

While the Water Authority stopped talking, Poseidon brokered a deal with the city of Carlsbad to build a 50-million-gallon-per-day plant.

MacLaggan said Friday that the Carlsbad deal is still viable, that the two sides are still studying it, and that Poseidon is working on scenarios to build the plant with the Water Authority —— and without it —— at the same time.

But many observers believe no deal to build the Encina plant can be reached without the regional Water Authority.

The Carlsbad deal is contingent upon the city and Poseidon finding other partners. Carlsbad cannot use the entire 50 million gallons a day the proposed plant would produce.

Until recently, Poseidon officials said it would be too expensive to build a plant smaller than 50 million gallons per day.

But on Friday, MacLaggan said the plant didn't necessarily have to be as large as a 50-million-gallon-per-day operation. But he also said it couldn't be as small as 25 million gallons per day —— the amount Carlsbad has agreed to use.

Meanwhile, MacLaggan said his company was still courting other cities, such as Oceanside, in the hope of creating a deal to build the plant without the Water Authority.

But that hasn't happened, buttressing the belief that Poseidon and the Water Authority are left to deal with each other.

On Friday, Yamada said the Water Authority, which had planned to finish its own environmental study on building the Carlsbad plant by December, had pushed that back to February or March of 2006.

MacLaggan, meanwhile, said the company still hopes it can reach a deal with the Water Authority by next month.

He said that would clear the way for the agency and company to start seeking certification of the plant from the state's regional water quality control board and Department of Health Services next spring.

"I would say everything is on track and moving forward," MacLaggan said.

Contact staff writer Gig Conaughton at (760) 739-6696 or gconaughton@nctimes.com.