document: The calm waters of Prince William Sound have stymied efforts to disperse the largest oil spill in U.S. history , which spewed from a ship that ran aground trying to avoid chunks of ice , officials said . The spill of some 270,000 barrels _ or 11.3 million gallons _ occurred early Friday when the 987-foot tanker Exxon Valdez went hard aground on Bligh Reef , about 25 miles outside Valdez , the northermost ice-free port in the United States . Coast Guard spokesman Ed Wieliczkiewicz said the use of chemicals to disperse and sink the heavy North Slope crude oil failed because the agents depend in part on rough seas to break up the oil . He said Exxon officials plan to pump the oil remaining aboard the Exxon Valdez onto the Exxon Baton Rouge , another tanker . Early Friday the Exxon Valdez was losing 20,000 gallons of oil per hour , but the flow slowed to a trickle later . An oil slick snaked about five miles from the ship as wind and tide pushed the crude oil into the sound and away from shore . `` This is the largest oil spill in U.S. history and it unfortunately took place in an enclosed water body with numerous islands , channels , bays and fiords , '' said Richard Golob , publisher of the Golob Oil Pollution Bulletin . Gov. Steve Cowper said the ship was `` impaled on the reef . '' He said the vessel steered from its course to avoid chunks of ice and did not return to its normal traffic lane . Dan Lawn , an engineer for the state Department of Environmental Conservation , said the captain could not steer the Exxon Valdez back on course in time to avoid a collision . Lawn likened the ship 's situation to `` trying to park a Cadillac in a Volkswagen spot . '' Divers were to check the ship 's hull and their findings were to be used in making plans for the removal of crude oil still aboard the vessel . `` A spill of this size in such a complex environment promises to be a cleanup nightmare , '' said Golob , a Cambridge , Mass.-based consultant whose firm has studied oil spills and environmental disasters for 15 years . In Washington , Interior Department spokesman Steve Goldstein said efforts had begun to evacuate waterfowl , sea otters and other wildlife from the danger area . The Exxon Valdez had loaded 1.2 million barrels of oil at the Alyeska Pipeline Service Co. marine terminal at Valdez and was en route to Long Beach , Calif. , when it crunched onto the reef . The ship marks the second aniversary of its maiden voyage today . The terminal was closed early Friday to tanker traffic as officials tried to deal with the mammoth spill . The flow in the trans-Alaska oil pipeline also was reduced to 800,000 barrels daily from 1.2 million barrels . Alyeska spokesman Tom Brennan said that , at the reduced rate , the marine terminal 's capacity would allow nine days of operation before the line would have to be shut down . Valdez , a town of about 3,000 year-round residents that grows to more than 4,000 with a summer influx of fishing industry workers and travelers , is a picturesque community about 125 miles east of Anchorage . It relies on the fishing , oil and tourism industries . The sound is considered a playground for kayakers , sport fishermen and tourists . Jason Wells , executive director of the Valdez Fisheries Development Association , said he believed the oil slick would cause little damage unless wind pushes it back toward Valdez . The fishing industry is between seasons . Wells said the black cod fishery is scheduled to begin April 1 , but the region 's major herring fishery is not expected to get under way until mid-April . But the spill likely will draw increasing fire from environmentalists sensitive about the trans-Alaska pipeline and efforts to open the Arctic National Wildlife Refuge to oil development . `` It 's of concern for two reasons : one is the size of the spill and that this is such a sensitive , very productive area , '' said Lisa Speer , senior staff scientist with the Natural Resources Defense Council in New York . Valdez City Manager Doug Griffin said the 800-mile trans-Alaska pipeline which carries oil from Prudhoe Bay to Valdez and the marine terminal have an enviable environmental record . But he added : `` Living in Valdez , we 've always worried that sometime something like this could happen . '' Previously , the largest U.S. tanker spill was the Dec. 15 , 1976 , grounding of the Argo Merchant tanker off the Nantucket shoals off Massachusetts , in which 7.6 million gallons of oil spilled , Golob said . The largest tanker spill in history was in the July 19 , 1979 , collision off Tobago of the supertankers Atlantic Empress and Aegean Captain , in which 300,000 tons _ more than 80 million gallons _ of oil was lost .
extractive_keyphrases: oil spills bligh reef oil slick environmental conservation crude oil environmental disasters
abstractive_keyphrases: u.s. tanker spill 987-foot tanker exxon valdez