In this aerial photo taken in the Gulf of Mexico more than 80 kilometres southeast of Venice on Louisiana's tip, the Deepwater Horizon oil rig is seen burning on April 21, 2010. (Gerald Herbert/Gerald Herbert/AP)
This April 21 aerial photo shows oil in the Gulf of Mexico as the Deepwater Horizon oil rig burned. Eleven workers were killed. (Gerald Herbert/Gerald Herbert/AP)
This image provided by the U.S. Coast Guard Saturday April 24, shows oil leaking from the drill pipe of the Deepwater Horizon drilling rig after it sank. (US Coast Guard/The Associated Press)
In this handout from NASA, an oil slick from the sunk Deepwater Horizon drilling platform is seen April 29, off the coast of Louisiana in the Gulf of Mexico. (NASA/Getty Images)
A satellite image taken on April 26, 2010 shows cleanup vessels near the oil slick resulting from the explosion of the Transocean Deepwater Horizon oil rig, in the Gulf of Mexico. (DIGITAL GLOBE/DIGITAL GLOBE/REUTERS)
The U.S. Coast Guard cutter Southern Responder (R) is pictured April 28 during cleanup activity in the Gulf of Mexico. (SEAN GARDNER/SEAN GARDNER/REUTERS)
Two brown pelicans and a flock of seagulls rest on the shore of Ship Island as a boom line floats just offshore on April 29, in Gulfport, Miss. Several hundred yards of boom line was set up on the north side of the island to try and contain the oncoming oil spill. (WILLIAM COLGIN/WILLIAM COLGIN/AP)
An oil boom barrier lies washed up on the beach after heavy swells and winds hit the coast of Louisiana on April 30. (MARK RALSTON/AFP/Getty Images)
Dr. Erica Miller, right, and Danene Birtell with Tri-State Bird Rescue and Research work to help a Northern Gannet bird, covered in oil, normally white when full grown, at a facility in Fort Jackson, La., on April 30. (Alex Brandon/Alex Brandon/AP)