KITTERY – Even as the fight to get Portsmouth Naval Shipyard off the Defense Department’s base closure list is just beginning, residents of the Kittery area are giving thought to ways in which the site can be redeveloped.

Those who remain focused on saving the shipyard say they can see how 278-acre Seavey Island at the mouth of the Piscataqua River could have a broader appeal.

“It’s a beautiful piece of property,” said Kittery Town Council Chairwoman Ann Grinnell.

Ideas for the site along a choice section of the New England coast range from upscale condominiums and a seaside park to an industrial zone and a transportation terminal.

But aside from the fate of the shipyard itself, one of the biggest uncertainties is the island’s environmental condition after 200 years of heavy industrial use. Since access to the shipyard is controlled, few people other than those who work there are even familiar with the existing facilities and layout.

Those closest to the yard are generally not yet ready to look at the site as prime waterfront real estate. Their No. 1 concern is the fight to keep the facility open.

But Portsmouth, N.H., Realtor Betty LaBranche says she can imagine the property becoming home to waterfront condominiums. LaBranche cites the example of nearby New Castle, a neighboring island on the New Hampshire side of the river.

The most prominent building on New Castle is the historic Wentworth by the Sea, a once-again grand 19th-century hotel that had slid into disrepair by the 1980s. During the last 20 years, New Castle has experienced a resurgence with the construction of a marina, condos, clusters of expensive homes, and the restoration of the hotel under the Marriott Corp.

The potential centerpiece of the Seavey Island project, LaBranche said, could be one of the shipyard’s most attractive buildings, an empty naval prison known as “The Castle.” The building caught the attention of a developer even before the yard’s future was in doubt.

New Hampshire developer Joseph Sawtelle secured a lease from the Navy on the old brig in 1999 with plans to transform it into office space for technology companies. The project, which would have been the first commercial complex on an active Navy base, collapsed after a slump in the high-tech economy and Sawtelle’s death in 2000.

The mammoth concrete building overlooking Portsmouth Harbor continues to occupy the thoughts of people considering alternative uses for Seavey Island, according to LaBranche.

“Waterfront is everything,” she said. “Every time we’re out on a boat and we look at the prison, everybody says, ‘Wouldn’t that be beautiful condos.'”

Even the lure of waterfront property would mean little, however, if Seavey Island turns out to be riddled with toxic contamination. Shipyards have notorious records for leaving their mark on the environment and the Portsmouth Naval Shipyard is likely no exception.

“The question is how much contamination is out there, and if there is a lot, is that going to give people the confidence to do residential?” said Portsmouth developer Michael Kane. “It’s like the ultimate in speculation.”

Grinnell says one of her goals would be to ensure the island does not become a gated community for the wealthy. Kittery has 350 residents who work at the shipyard, she says, and creating new jobs for those people has to be a priority in any redevelopment plan.

“I don’t want it to be gobbled up by the rich for McMansions,” she said. “We would not want all [residential] development. We need jobs.”

Grinnell says she thinks the island is large enough to accommodate several uses, including open space, housing and industry.