Efforts to stem the Deepwater Horizon oil spill were ongoing from the time that the Deepwater Horizon exploded on 4/20/2010 until the well was sealed by a cap on July 15, 2010. Various species of dolphins and other mammals (61 casualties), birds (2,095 casualties), and the endangered sea turtles (467 casualties) have been killed either directly or indirectly by the oil spill. The Deepwater Horizon spill has surpassed in volume the 1989 Exxon Valdez oil spill as the largest ever to originate in U.S.-controlled waters; it is comparable to the 1979 Ixtoc I oil spill in total volume released (Ixtoc discharged 140 million US gallons (530,000 m3) to 148 million US gallons (560,000 m3); as of mid-July 2010, Deepwater Horizon has spilled 90 million US gallons (340,000 m3) to 180 million US gallons