A tanker spilled 200,000 gallons of crude oil into the Delaware River and the Coast Guard said it was a major spill. "The total environmental impact will not be determined until morning," said Coast Guard Lt. (j.g.) Aaron Davenport of the Gloucester City (N.J.) Station. Late Wednesday, a 10-mile oil sheen was present from Bridgeport, N.J., to Philadelphia, he said. The oil was expected to reach shore by morning. The vessel, the Viking Osprey, was carrying 550,000 barrels of oil and was docking at a refinery across the river from Philadelphia when the spill was discovered, Davenport said. It was not known how the spill started, he said.