On February 2, 1976, one of the worst oil spills in recent history occurred in the lower Chesapeake Bay. Approximately 250,000 gallons of No. 6 oil were discharged into the bay after a barge, the STC-101, sank in a storm near the mouth of the Potomac River. The oil contaminated extensive beach and marsh areas on both sides of the bay. Cleanup operations lasted almost a month and the cost approached $400,000. The U.S. Coast Guard estimated that 167,000 gallons of oil were recovered by cleanup crews. The remaining oil is believed to be widely dispersed over large areas of the bay—possibly tied up in fringe marsh grass, buried under sand on the beaches or carried out into the Atlantic Ocean. The heavily-contaminated fringe marsh grasses were cut, leaving the root systems intact, in order to protect the fragile marsh areas. An overall assessment of the environmental damages caused by the spill is almost complete. Estimates of the number of waterfowl killed range from 20,000 to 50,000 birds. Damage to shellfish and other aquatic resources is still under study. Preliminary reports indicate that damages to the environment may not be as severe as initially expected.