Volume and extent of the Deepwater Horizon oil spill Volume and extent of the Deepwater Horizon oil spill The "Deepwater Horizon" oil spill was discovered on the afternoon of 22 April 2010 when a large oil slick began to spread at the former rig site. According to the Flow Rate Technical Group, the leak amounted to about of oil, exceeding the 1989 "Exxon Valdez" oil spill as the largest ever to originate in U.S.-controlled waters and the 1979 Ixtoc I oil spill as the largest spill in the Gulf of Mexico. BP has challenged this calculation saying that it is overestimated as it includes over of oil which was
Volume and extent of the Deepwater Horizon oil spill silts and sands onshore. On 26 May 2011, the Louisiana Department of Environmental Quality extended the state of emergency related to the spill. In April 2012, oil was found dotting of Louisiana's coast. As of December 2012, of coastline remain subject to evaluation and/or cleanup operations. On 15 May 2010, researchers from the National Institute for Undersea Science and Technology, aboard the research vessel "RV Pelican", identified oil plumes in the deep waters of the Gulf of Mexico, including one as large as long, wide and thick in spots. The shallowest oil plume the group detected was at about ,