An agricultural company has agreed to sell 16,500 acres of salt ponds around the San Francisco Bay, paving the way for what could be the nation’s biggest wetlands restoration project outside of the Florida Everglades. Cargill Inc., an international agriculture and food company, signed a preliminary agreement yesterday with state and federal governments and private foundations to accept $100 million over five years in exchange for turning the land over later this year. The deal was brokered by Sen. Dianne Feinstein (D-Ca.) and has been welcomed by environmentalists as the culmination of a 10-year campaign to restore tidal marsh in the San Francisco Bay, which has lost 80 percent of such marshes to development. Taken together, the salt ponds are twice the size of the city of San Francisco, and restoring them would vastly increase the amount of public shoreline in the Bay Area and provide habitat for millions of waterfowl and shorebirds.