The U.S.S. Wenonah, a vintage U.S. Navy tugboat that was retired in 1974, sank Monday afternoon, causing between 500 and 700 of oil residue to leak into the San Francisco Bay, according to the Coast Guard.
About 250 gallons of oily water has been absorbed, said Lt. Cmdr. Gus Bannan, chief of incident management for the San Francisco division.
But the 100-foot Wenonah is still resting on the bottom of the Bay near Pier 1 on Treasure Island, submerged except for the top few feet of its mast in 25 feet of water.
Bannan said the Coast Guard expects to finish a salvage plan by Wednesday, but it will take at least another 36 hours after that to recover the tugboat.
The Coast Guard still doesn't know why the Wenonah sank, and although divers have been investigating it underwater, a final determination can't be made until the boat is salvaged, Bannan said.
It's also unclear who will pay for the salvage or how much it will cost, but Bannan said the oil cleanup was paid for with funds from the federal Oil Spill Liability Trust Fund.
As of this afternoon, no adverse environmental effects of the spill had been documented or reported, said Josh Nicholas of the California Department of Fish and Game.
He said his department is monitoring local marine life and birds for any signs of distress.
The Wenonah is owned by the Historic Tugboat Education and Restoration Society, which leases the space at Pier 1 on Treasure Island.
The U.S.S. Wenonah was built in 1940 and spent 33 years in service before it was decommissioned in 1974.