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 collected before it could enter the Gulf waters. In its permit to drill the well, BP estimated the worst-case flow at . Immediately after the explosion the USCG did not estimate any oil leaking from the sunken rig or from the well. On 24 April, USCG Rear Admiral Mary Landry announced that a damaged wellhead was indeed leaking. She stated that "the leak was a new discovery but could have begun when the offshore platform sank . . . two days after the initial explosion." Initial estimates by USCG and BP officials, based on remotely operated vehicles as well as