The U.S. Coast Guard announced the cause of the November 2004 oil spill in the Delaware River, saying a submerged 18,000-pound anchor of unknown origin caused the gash in the hulking Greek tanker, the Athos I.
The other objects that had been suspected in the accident - a pump casing, a large concrete block, an 11-ton propeller - have been cleared of all charges.
It was a costly accident, both financially and environmentally. More than $150 million has been spent on the cleanup so far, and the effects of the oil on the ecosystem will take years to fully determine.
Initial surveys of the river bottom after the spill showed several objects in the area - including the anchor, the pump casing, and the concrete block. Citgo is responsible for maintaining the river bottom between the shipping channel and the terminal, and the last sonar survey before the spill - a month before the Athos I incident - showed no obstructions. The Athos I actually did strike the anchor, the concrete block and the pump casing, but that analysis of the paint chips
and the dimensions of the damage to the vessel ruled out all but the anchor as the source of the gash.
The source of the anchor remains unknown. It has likely been recently dislodged by another ship.