Coast Guard: Abandoned Containment Dome ID'd As Source of Sheen

for the Deepwater Horizon site. Image (c) BP PLC

A thin slick of oil in the Gulf of Mexico appears to be coming from a containment dome that was abandoned on the sea floor during efforts to stop the 2010 Deepwater Horizon oil spill, not from the plugged well, according to the U.S. Coast Guard and BP PLC.

Remote-controlled submarines that were sent down to search for the source of the light slick earlier this week found a small amount of oil leaking from two places on the dome, a four-story- tall steel box that in May 2010 was lowered onto the oil leaking from BP’s well some 5,000 feet below the ocean surface.

The device was meant to collect the oil and allow it to flow to a ship, but got clogged with ice crystals. It was left on the sea floor about 500 yards from the well. The flow was finally stopped on July 15, 2010, by a series of valves that were attached to the top of the well and the well was permanently sealed in September.

Video inspections of the containment dome showed small, intermittent drops of oil coming from two openings on the device, according to a Coast Guard statement. The flow rate is estimated to be less than 100 gallons per day.

Inspections of the sealed well, two relief wells, rig wreckage and a pipe that connected the drilling rig Deepwater Horizon with the well before the accident, did not show signs of leaking.

“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.

The Coast Guard has said the thin slick, or sheen, is too dispersed to recover and does not pose a risk to the coast.

BP said the latest survey, which took place over three days, is the third time since the well was sealed that it has been visually inspected at the sea floor and found not to be leaking.

The oil sheen was first reported by BP on Sept. 16 about 50 miles off the coast of Louisiana. Last week the Coast Guard notified BP and rig owner Transocean Ltd. that a lab had matched the oil from the sheen to oil from the well.