Environmentalists, residents and government officials peppered proponents of a proposed desalination plant with questions Wednesday about everything from the temperature of the plant's freshly-minted drinking water to where the water lines would run.

About 50 people attended a Wednesday afternoon public meeting on the $270 million, privately funded project. A second meeting, held Wednesday evening, attracted half that many people.

Both meetings kicked off research for an Environmental Impact Report on the proposed plant, which would turn 50 million gallons of salt water a day from Agua Hedionda Lagoon into drinking water. Proposed by developer Poseidon Resources of Connecticut, the plant would go on a four-acre site next Encina Power Station.

"My concern is it's co-located with the power plant," environmental lawyer Marco Gonzales, a partner with the Encinitas-based Coast Law Group, said after the meeting. "We believe in 20 years this (power) plant will be obsolete."

He said he didn't want the desalination plant to get "a free ride" by using the power plant's seawater inflow and outflow pipes. Poseidon plans take water the power plant uses as coolant, treat it and turn it into drinking water. That means the desalination plant won't have to build its own lagoon access point, a construction project that would require an additional, extensive environmental review.

Gonzales grilled Poseidon project manager Peter MacLaggan about whether there were any similar plants already operating in the United States ---- there aren't.

Other people asked how much the water would cost ---- $900 to $950 an acre foot, depending on how far it had to be transported; who would get the water ---- Carlsbad, Vista, Oceanside and San Marcos residents; and whether it would be hotter than the drinking water people now receive --- it won't be.

Carlsbad residents currently pay about $700 an acre foot for water.

Renata Breisacher Mulry, who lives in Carlsbad, brought a notebook sheet with questions to the afternoon meeting.

"I thought (MacLaggan's) answers understandably were guarded," she said afterward, adding that she believes the water will cost more than estimated. "I'm very concerned about the cost slipping and we, the residents of Carlsbad, paying a massive bill for something that isn't yet certain."

Government officials had nuts and bolts questions.

Floyd Best, manager of the McClellan-Palomar Airport, wanted to know exactly where the pipelines from the plant would go. One of the proposed pathways would go through the northern end of the airport site, he told MacLaggan after the meeting as they reviewed maps together.

Several residents at the evening session had the same question as Best. Ruth Gans, who lives near Maerkle Reservoir, wanted to know if Poseidon would use the same route that the reservoir pipeline uses. That route isn't finalized yet, MacLaggan told her.

Ocean Pointe resident Elizabeth Mullensky said she wasn't opposed to the project, though she had questions about the details.

"It seems to me the technology is very simple ... I think it's very forward thinking to be doing this now," she said.

Others called it "good insurance" in times of water shortages. Don Perkins, a representative for the Sierra Club, said his group hoped the project would be a success.

The environmental report, which is paid for by Poseidon and managed by the city of Carlsbad, will detail everything from the project's effects on wildlife to traffic congestion. Carlsbad officials have said they hope to have the document done by the end of 2004 or early 2005, about the same time they want to begin processing permits for the project.

It's the second of two environmental reports on desalination plants at the site. Poseidon originally approached the San Diego County Water Authority with plans to build the plant and sell it to the agency, which serves 23 cities and water agencies in San Diego County, including Carlsbad.

The two groups suspended negotiations in January, but the water authority is still working on its environmental report and expects to have it done by fall 2005.