The Exxon Valdez oil spill occurred in Prince William Sound, Alaska, on March 24, 1989 and spilled 11 to 38 million US gallons of crude oil. The Valdez spill was the largest in US waters until the 2010 Deepwater Horizon oil spill, in terms of volume released.The region is a habitat for salmon, sea otters, seals and seabirds. The oil, originally extracted at the Prudhoe Bay oil field, eventually covered 1,300 miles of coastline. Captain Joseph Hazelwood, who was widely reported to have been drinking heavily that night, was not at the controls when the ship struck the reef. The radar was not turned on. In fact, the tanker's radar was left broken and disabled for more than a year before the disaster, and Exxon management knew it.It took more than four summers of cleanup efforts before the effort was called off .Chemical dispersant, a surfactant and solvent mixture, was applied to the slick. Because there was not enough wave action to mix the dispersant with the oil in the water, the use of the dispersant was discontinued. One trial explosion was also conducted during the early stages of the spill to burn the oil, in a region of the spill isolated from the rest by another explosion. The test was relatively successful, reducing 113,400 liters of oil to 1,134 liters of removable residue, but because of unfavorable weather no additional burning was attempted. The cleanup effort included 10,000 workers, about 1,000 boats and roughly 100 airplanes and helicopters. Exxon says it spent about $2.1 billion on the cleanup effort. Thousands of gallons of Exxon Valdez oil still pollute areas; this oil is still toxic and still hurting the ecosystem near the shore. The government considers, as of 2010, only 13 of the 32 monitored wildlife populations, habitats and resource services that were injured in the spill as fully recovered or very likely recovered. This includes a pod of orcas, which lost 15 of its 22 members after the spill with only of older female left. Persistent oil poisoning, and a cascade of ecological effects, continue.