HOUSTON — Oil in a slick discovered in the Gulf of Mexico is seeping from a 100-ton device that BP used several weeks after the 2010 oil spill in a failed attempt to cap its runaway Macondo well, the U.S. Coast Guard said Thursday.
The oil is not coming from the Macondo itself, which was sealed in a relief well operation months after the 2010 blowout.
"The latest survey marks the third time since the Macondo well was sealed permanently in September 2010 that it has been visually inspected at the seafloor and confirmed not to be leaking," BP said in a statement.
Less than 100 gallons of oil per day are leaking from the containment device on the ocean floor, the Coast Guard said. The oil will continue to dribble out slowly for the time being. Officials are trying to figure out the best course forward.
BP said the Coast Guard has determined that it is not feasible to recover oil forming the sheen, and that it does not pose a risk to the shoreline.
Transocean, which owned the Deepwater Horizon drilling rig that exploded after the Macondo blowout, declined to comment on the Coast Guard's news release. Eleven workers died in the accident, and the government estimates that more than 200 million gallons of crude spewed from the well a mile below the surface of the water.
The Coast Guard said remotely operated vehicles deployed from the offshore construction vessel Skandi Neptune collected oil samples on Wednesday from the Macondo well site to determine the source of the surface sheen.
A camera-equipped ROV also inspected the wreckage of the Deepwater Horizon, debris, relief wells, and the riser pipe that once connected the wellhead to the rig, and observed no oil leakage from those. Oil samples collected will be used for lab analysis, the Coast Guard said in its statement.
"The Coast Guard is further evaluating what is believed to be seepage from the containment dome to determine how best to respond," said Capt. Duke Walker, federal on-scene coordinator for the Deepwater Horizon response.
The Coast Guard will release video footage of the undersea inspections, a spokesman said, but it could be a few days before the video is made public.
U.S. Rep. Edward Markey of Massachusetts, a top Democrat on the House Committee on Natural Resources, said BP should immediately release the video "so that the American people and the scientific community can see for themselves that no oil is leaking from the well itself."
"In addition, BP should seek to recover all oil trapped inside the failed containment dome or any other debris that remains on the seafloor in order to prevent even more oil from spilling into the environment," Markey said.
BP had said previously that it believed the source of the oil was likely the bent riser pipe, where oil, drilling mud and seawater were trapped after a separate failed attempt to stop the spewing oil, called a top kill.
The containment device, now identified as the source of the oil slick discovered Sept. 16, is a four-story box with a dome on top that was placed over the well in early May 2010. Officials abandoned the mission after tiny ice crystals, called hydrates, formed on the device. They moved it to the seafloor near the well and it has been there ever since.
A tighter-fitting cap placed over the well in July 2010 stopped the flow of oil to the sea. A few months later, BP sealed the well for good from below using a relief well to pump in cement.
Confirmation that the oil sheen reported last month is related to the Macondo disaster comes at a critical time, just as talks intensify about possible settlement of various penalties and fines arising from the accident.
Scientists have said that residual oil from the well and the wreckage of the Deepwater Horizon rig and other equipment on the seafloor could be dredged up for months and years to come.