An aerial view of the oil leaked from the Deepwater Horizon wellhead, May 6, 2010. (REUTERS/Daniel Beltra)

An oil soaked bird struggles against the oil slicked side of the HOS Iron Horse supply vessel at the site of the Deepwater Horizon oil spill in the Gulf of Mexico off the coast of Louisiana Sunday, May 9, 2010. (AP Photo/Gerald Herbert)

Oil washes onto the sides of a 100-ton concrete-and-steel pollution containment chamber as the mobile offshore drilling unit Q4000 lowers it into the water at the Deepwater Horizon site on May 6, 2010 in the Gulf of Mexico . The chamber was designed to cap the oil discharge that was a result of the Deepwater Horizon incident. (Patrick Kelley/U.S. Coast Guard)

Seawater covered with thick black oil splashes up in brown-stained whitecaps off the side of the supply vessel Joe Griffin at the site of the Deepwater Horizon oil spill containment efforts in the Gulf of Mexico off the coast of Louisiana Sunday, May 9, 2010. (AP Photo/Gerald Herbert)

MOBILE, ALABAMA (May 6, 2010) Aerial images of the Deepwater Horizon oil spill taken from a US Coast Guard HC-144 aircraft. The flight was conducted primarily for media support and to plot the locations of the Deepwater Horizon oil spill. US Navy Photo by Mass Communication Specialist First Class Michael B. Watkins

Dark clouds of smoke and fire emerge as oil burns during a controlled fire in the Gulf of Mexico, May 6, 2010. The U.S. Coast Guard working in partnership with BP PLC, local residents, and other federal agencies conducted the "in situ burn" to aid in preventing the spread of oil. (REUTERS/Mass Communication Specialist 2nd Class Justin Stumberg-US Navy)

Gas from the damaged Deepwater Horizon wellhead is burned by the drillship Discoverer Enterprise May 17, 2010, in a process known as flaring. Gas and oil from the wellhead are being brought to the surface via a tube that was placed inside the damaged pipe. U.S. Coast Guard photo by Petty Officer 3rd Class Patrick Kelley.

Gas from the damaged Deepwater Horizon wellhead is burned by the drillship Discoverer Enterprise May 16, 2010, in a process known as flaring. Gas and oil from the wellhead are being brought to the surface via a tube that was placed inside the damaged pipe. U.S. Coast Guard photo by Petty Officer 3rd Class Patrick Kelley.

Homeland Security (DHS) Secretary Janet Napolitano surveys the oil sheen in the Gulf of Mexico, Friday, April 30, 2010 aboard a Coast Guard HC-144A Ocean Sentry aircraft. Efforts to stop the flow of oil and minimize the impact to environmental and economic resources has been underway since the incident occurred April 20, 2010. U.S. Coast Guard photo by Petty Officer 3rd Class Cory J. Mendenhall.

Dr. Erica Miller, a member of the Louisiana State Wildlife Response Team, cleanses a pelican of oil at the Clean Gulf Associates Mobile Wildlife Rehabilitation Station on Ft. Jackson in Plaquemines Parish, La., May 15. The station has stood up to provide support for animals that may have been affected as a result of the April 20 explosion on Mobile Offshore Drilling Unit Deepwater Horizon. (U.S. Navy photo by Mass Communication Specialist 2nd Class Justin Stumberg/Released)

A pod of Bottlenose dolphins swim under the oily water Chandeleur Sound, Louisiana, Thursday, May 6, 2010 in the Gulf of Mexico. (AP Photo/Alex Brandon)

Oily water is seen off the side of the Joe Griffin supply vessel at the site of the Deepwater Horizon oil spill containment efforts in the Gulf of Mexico on Saturday, May 8, 2010. (AP Photo/Gerald Herbert)

Oil, scooped up with a bucket from the Gulf of Mexico off the side of the supply vessel Joe Griffin, coats the hands of an AP reporter at the site of the Deepwater Horizon oil spill in the Gulf of Mexico, May 10, 2010. (AP Photo/Gerald Herbert)

A U.S. Air Force chemical dispersing C-130 aircraft from the 910th Airlift Wing at Youngstown-Warren Air Reserve Station, Ohio, drops an oil dispersing chemical into the Gulf of Mexico as part of the Deepwater Horizon Response effort May 5, 2010. Members of the 910th Airlift Wing are in Mississippi to assist with response to the Deepwater Horizon oil spill. The 910th AW specializes in aerial spray and is the Department of DefenseÕs only large area fixed wing aerial spray unit. (U.S. Air Force Photo by Tech. Sgt. Adrian Cadiz)

Oil from the Deepwater Horizon oil spill makes its way to shore on Chandeleur Islands in Louisiana on May 7, 2010. (AP Photo/The Dallas Morning News, Vernon Bryant)