Bair Island, a sprawling expanse of former marshes near Redwood City long known as a flash point for battles between developers and environmentalists, will soon be returned to conditions not seen since Harry Truman was president, Bing Crosby topped the pop charts and ``It's a Wonderful Life'' filled movie theaters.

State and federal biologists are putting the finishing touches on a $12 million plan to restore 1,400 acres at Bair Island to tidal marshes for wildlife.

The last time the area was in a similarly wild state was 1946.

Then the Leslie Salt Co. carved the teeming marshes near Whipple Avenue at Highway 101 into industrial salt evaporation ponds. Now that salt-making has ended and environmentalists have defeated efforts over the past 30 years by developers to build homes, offices and stores on the bay-front property, the U.S. Fish and Wildlife Service is working to turn back Bair Island's ecological clock.

The agency's plan is to breach old levees, restore wetlands with millions of pounds of dredged mud, and then wait for the bay waters, along with wild plants, fish and flocks of birds, to return.

The project ranks among the largest wetland restorations in the Bay Area, and is expected to serve as a practice run for wider efforts to restore 16,500 acres of other former salt ponds ringing San Francisco Bay during the next 30 years.

``When I was growing up in the South Bay, wetlands were considered bad, and you filled them in,'' said Clyde Morris, manager of the Don Edwards San Francisco Bay National Wildlife Refuge.

`It is so exciting'

``Then after a while when we learned more, and you had to get a permit to fill them in. Now we are finally restoring them. This is the last phase. It is so exciting.''

The Fish and Wildlife Service, along with the California Department of Fish and Game, released a draft environmental impact report for the project in August.

If all goes according to plan, work will begin in 2006, said Morris, and end by 2009.

The goal is to restore endangered species, such as the California clapper rail, a diminutive bird, and the salt marsh harvest mouse. Other species, including herons, egrets, harbor seals and steelhead trout, also are expected to benefit.

In a wider sense, the project seeks to atone for the environmental sins of Bay Area generations long gone.

Since 1850, San Francisco Bay has shrunk by one-third because of diking, dredging and filling for development. Although those changes ended with tough environmental laws by the 1970s, the bay had lost 80 percent of its tidal wetlands -- the key areas that serve as nurseries for young fish, filters to clean bay waters and shelter for birds, ducks and other wildlife.

``This is ecologically significant,'' said Josh Collins, an environmental scientist with the San Francisco Estuary Institute in Oakland.

``It can help restore populations of endangered species. It is large enough that these habitats should be able to sustain themselves. They are not fragments.''

Bair Island, named for a 19th-century Peninsula farm family, is a system of three islands -- Outer, Middle and Inner Bair. They are separated by sloughs, with only Inner Bair Island accessible without a boat. In all, about 3,000 acres make up the property. Most is owned by the state or the federal Don Edwards National Wildlife Refuge.

Roughly 250,000 people a year now jog, hike and walk dogs on the levees of Inner Bair. When restoration is complete, most access still will be allowed, said Morris. Some of Outer Bair Island has restored itself, as old levees have worn down over time, and bay waters have flowed in, bringing seeds, plants and eventually wildlife.

Work at Inner Bair

Inner Bair will require the most work. Because the former salt ponds sank several feet after they dried out, crews will have to pump in roughly 1 million cubic yards of mud from Redwood City Harbor dredging. That will raise the bottom by about two feet to the mean high-tide line, so that it becomes a marsh, rather than a lake, and plants like pickleweed and bulrushes can re-establish themselves.

Restoration will help reduce the risk of West Nile virus, said Morris, because moving water will flow through the property, and mosquitoes require standing water.

The area, home to a series of billboards along Highway 101, has been the center of some of Silicon Valley's roughest land-use fights.

In the 1950s, developers filled wetlands to build Foster City. Then in the 1960s, they did the same to build Redwood Shores.

``Bair Island was going to be the next domino to fall,'' said Ralph Nobles, 84, of Redwood City, a longtime advocate to preserve Bair Island. ``But it didn't fall because a number of people said `That's the wrong thing to do.' ''

In 1982, Nobles and his friends sprung into action when Mobil Oil's development arm won approval from the Redwood City Council to build ``South Shores,'' a mix of 4,700 homes, offices and a hotel on Bair Island. Opponents fought the project and collected signatures, and it was defeated by 47 votes in 1982.

When a Japanese developer came back in the 1990s with a similar plan, the non-profit Peninsula Open Space Trust bought Bair Island in 1997 for $15 million, saving it.

Even this year, Nobles, a San Mateo County planning commissioner, led a fight to block plans by another developer to build a $1 billion complex of 17 condominium towers next to the property. On Tuesday, Redwood City voters rejected it by a ratio of 55 to 45.

`A special place'

``The main reason we like to live in the Bay Area is the bay,'' said Nobles. ``That's what makes it a special place. The wetlands are at the base of the food chain. They are the lungs of the bay. Without them, the bay would become basically a cesspool.''

To see Bair Island heading back to its original state is immensely satisfying, Nobles said.

``I think this is great,'' he said. ``I've been waiting so many years for it to happen.''