Scientists have confirmed that corroded and collapsed drums of radioactive waste litter at least 30 miles of ocean floor in the Gulf of the Farallones National Marine Sanctuary. The U.S. Geological Survey team mapping the sanctuary also has detected what may be the remains of the USS Independence, an aircraft carrier used as a target in the 1946 Bikini Atoll atomic bomb tests in the Pacific. Scientists caution that it is too early to confirm its identity. The Independence was sunk Jan. 26, 1951, because it was considered too expensive and difficult to decontaminate. The barrels filled with plutonium and other dangerous nuclear material were disposed of under the Atomic Energy Commission contracts between 1946 and 1970 at the Farallon Islands Radioactive Waste Dump, located four to 15 miles southwest of the islands.