It could take three months for crews to fully plug a well that is dumping 5,000 barrels of oil a day into the Gulf of Mexico, in one of the worst ecological disasters in U.S. history.
Executives from BP, the company at the heart of the disaster, estimate the leak could even worsen to 40,000 barrels a day if crews fail to stem the flow of oil.
Crews have already begun the work of drilling a relief well sideways into the leaking well, which they plan to plug with concrete. However, that work could take three months because it requires crews to dig 13,000 feel below the seafloor.
So far, crews have drilled 1,275 feet down.
"The challenge is unprecedented," John Curry, a spokesperson for BP, said Tuesday.
Meanwhile, company executives told members of Congress Tuesday that in a worst-case scenario, between 10,000 and 60,000 barrels of oil a day could flow into the water should efforts to cap the leak fail. The leak began April 20, when the Deepwater Horizon drilling rig exploded and sank, killing 11 workers.
During the meeting with lawmakers, executives from BP, Transocean and Halliburton repeated their earlier claims that they had been sure a backup plan for the rig's blowout preventer was unnecessary and they had been confident the rig could not sink.
As the spill threatens to overtake the Exxon Valdez incident as the worst oil spill in U.S. history, crews clamoured but failed to activate a shutout valve to stem the leak.
Among the measures being employed are nine remote-controlled underwater robots that are both spraying chemicals to disperse the oil and trying to activate a blowout preventer that failed to prevent the leak after the explosion.
The robots, which are the size of Humvee trucks and are operated by a three-person crew on land using joysticks, are capable of a wide range of jobs.
"Some of those operators can pour cups of coffee, can pick up 600 pounds or pick up an eggshell without breaking it," said Lou Dennis of Perry Slingsby Systems, the maker of the robots.
Company executives said the robots' work with chemical-dispersants appears to have been somewhat successful at keeping some of the oil from reaching the water's surface.
As the robots work, crews still hope to install a 98-ton concrete-and-steel containment dome on top of the main leak by the weekend at the earliest. The dome's pipes are designed to funnel oil into a tanker.
However, the device has never been tested at more than a kilometre below the water's surface, and BP executives are concerned that the oil may clog the pipes.
"We don't know for sure" whether it will work, said BP spokesperson Bill Salvin. "What we do know is that we have done extensive engineering and modeling and we believe this gives us the best chance to contain the oil, and that's very important to us."
Calm seas help cleanup efforts
Calmer seas helped crews gain some ground on the spill Tuesday. Workers were able to put more containment equipment out on the water, as well as repair booms damaged by poor weather over the weekend.
Crews had also been scheduled to try and burn off some of the oil from the water's surface later Tuesday.
Coast Guard officials told a news conference Tuesday that forecasts predict the oil is not expected to reach land for at least three more days.
However, a BP official at the same news conference said boats had been sent to Chandeleur Island to follow up on reports that some oil had come ashore there.
However, BP's chief operating officer, Doug Suttles, said crews have yet to find evidence of oil reaching shore at the island.
Meanwhile, satellite image taken Sunday appeared to show that the slick is smaller in size compared to late last week. The new image indicates the oil covers about 5,180 square kilometres, smaller than the 8,800 square kilometres observed last Thursday.
The new figures suggest the oil has gone underwater, said Hans Gruber of the University of Miami.
