Sunnyvale, Calif. ? One of the nation’s most ambitious environmental-restoration projects got under way Monday as officials began the years-long process of turning industrial salt ponds on the edge of San Francisco Bay into marshes brimming with wildlife.

The ponds were long used to produce salt: They were filled with the bay’s brackish water, and the water was allowed to evaporate, leaving behind salt that companies could sell for use in food, medicine and other products.

Under the restoration project, water is being pumped through two 4-foot-wide pipes to flush the salt out of the ponds.

The ponds will ultimately be converted into a wetlands that will support wildlife. Officials expect to see new species of birds, fish and plants move in.

“This is one of the most dynamic, complicated restoration projects in the country and in the world,” Steve Thompson, who oversees California and Nevada for the U.S. Fish and Wildlife Service, said just before he and other officials turned the wheel that opened the tidal gates.

The project is the biggest effort to restore wetlands on the West Coast. It is part of a broader effort to restore 100,000 acres of bay wetlands that were diked to accommodate a growing population in the decades after the Gold Rush.

With the help of several foundations, California and the U.S. Fish and Wildlife Service last year purchased 16,500 acres of salt ponds from Cargill Salt for $100 million.

John Krause, an associate wildlife biologist with the California Department of Fish and Game, watches as the waters of a former industrial salt pond mix with the San Francisco Bay in Sunnyvale, Calif. The environmental project got under way Monday as government scientists began to convert 15,000 acres of industrial salt ponds into tidal marsh along the southern fringe of San Francisco Bay.