HUNTINGTON BEACH, Calif. (AP) – The nation’s largest desalination plant would be built along the coast under a controversial proposal that was narrowly approved by the City Council.

The council voted 4-3 Tuesday in favor of the $250 million plant that a Stamford, Conn.-based company called Poseidon Resources Corp. has worked for years to build.

The facility would produce up to 50 million gallons of fresh water daily by processing ocean water that’s already pumped into an adjacent power plant. It still must be approved by the California Coastal Commission, the state Regional Water Quality Control Board and the State Lands Commission.

Backers say the plant would provide an important alternative to the existing water supply, which the Metropolitan Water District estimates is adequate through 2030.

“We live in a desert, and we need all the sources of fresh water that we can develop,” said Councilwoman Cathy Green.

Opponents, including some residents and environmental groups, say it’s inappropriate to build more industrial plants along the city’s tourist-heavy beaches and worry sea life could be killed by the plant’s briny discharge.

“Frankly, it would be irresponsible of us to make our city a guinea pig for this,” said Mayor Dave Sullivan.

Huntington Beach has agreed to buy 3.2 million gallons of water a day from the plant – about 10 percent of the city’s usage. The plant would sell the remainder to as-yet-unknown buyers.

Poseidon officials said their water will cost about five times more than groundwater and double the price of imported water. They’re banking on a surge in cost of existing supplies.

A smaller plant that the company built in Tampa Bay, Fla. was plagued by technical and financial problems and was taken over by a public water agency.

Another Poseidon facility proposed for Carlsbad is expected to go before the City Council there in May.