SOUTHPORT – Bigelow Laboratory for Ocean Sciences faces concerns from Southport Island residents as it moves ahead with a plan to build a $12 million facility to expand its biomedical work.

The 60,000-square-foot glass-and-wood facility would replace the four cramped buildings in Boothbay Harbor that Bigelow has leased from the state for the past 27 years.

Trustees for the private, nonprofit marine research center searched for years before deciding on a 24-acre site owned by Bigelow at Cameron Point. They hope to open the facility by 2007.

“This is the best site for us,” Executive Director Louis “Sandy” Sage said Tuesday. “We already own it, it’s on deep water so we can bring ships in, and it allows us to stay in the area.”

But some residents on the island, which is linked by bridge to Boothbay Harbor, worry about the project’s impact on land and sea traffic, and the local water supply.

Because the land is zoned for residential uses, Bigelow needs the town to approve a zoning change that would allow it to build a scientific facility. A public hearing on the zoning amendment is scheduled for Feb. 15.

Critics say the proposed zoning change would be tantamount to “spot zoning.”

“We don’t want any scientific facilities here,” said Alden Stickney, who has lived on Cameron Point since the 1960s. “Then you don’t have a residential district anymore.”

Sharing the island’s scarce water supply is a big issue. The local water quality is so poor that seasonal water comes from Boothbay Harbor, across Townsend Gut. Residents worry that drilled wells for such a large project, with up to 80 employees, might lower the water table enough to draw in salt water.

Sage said the facility would have composting toilets, which decrease water usage by 80 percent. “We will use the equivalent of one household’s worth of water, just 500 gallons a day,” he said.

Other concerns include the lab’s proposed 100-foot pier, its 300-foot research vessels and increased traffic on the road from people using the lab.

Bigelow is at the forefront of oceanographic research, drawing scientists to Maine from around the world. The lab has the largest collection of phytoplankton in existence, microscopic marine life that will likely play a large role in future cancer studies.

Charles “Mike” Grimes is among the island residents who support having the lab on Southport.

“Bigelow has a very positive economic impact on the whole peninsula,” he said. “I think it would be a terrible loss if we let them get away.”

But Selectman Gerald Gamage believes Bigelow will have a tough job convincing residents to allow the project.

“They’re nonprofit, pay no taxes, and have to prove they’re offering enough to make up the difference,” he said.

Residents will make the final decision on the proposed zoning change at the March 5 town meeting. If approved, Sage said, Bigelow will begin applying for permits and undertake a fund-raising campaign.

If residents reject the plan, the lab will seek a new location.