METAIRIE, La. —BP used underwater robots a mile beneath the ocean Thursday to try to put a lid on the Gulf oil gusher.
Live video showed that an inverted funnel-like cap slightly wider than a severed pipe was being maneuvered into place over the oil spewing from the well. However, the gushing oil made it difficult to tell if the cap was fitting well. BP spokesman Toby Odone said he had no immediate information on whether the cap was successfully attached.
A rubber seal on the inside will attempt to keep oil from escaping, though engineers acknowledge some crude will still come out.
BP sliced off the main pipe on the leaking oil well with giant shears in the latest bid to curtail the worst oil spill in U.S. history, but the cut was jagged, and a looser fitting cap will be needed.
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"We'll have to see when we get the containment cap on it just how effective it is," said Coast Guard Adm. Thad Allen, the government's point man for the disaster.
BP turned to the giant shears after a diamond-tipped saw became stuck in the pipe halfway through the job, yet another frustrating delay in the six-week-old spill.
If the cap is successful, BP will siphon the oil and gas to a tanker on the surface.
"It's an important milestone, and in some sense, it's just the beginning," BP chief executive Tony Hayward said.
This latest attempt is risky because slicing away the section of the 20-inch-wide riser removed a kink in the pipe, and could temporarily increase the flow of oil by as much as 20 percent.
Live video footage showed oil spewing unimpeded from the top of the blowout preventer, but Allen said it was unclear whether the flow had increased.
"I don't think we'll know until the containment cap is seated on there," he said. "We'll have to wait and see."
Crews will also use methanol to try to prevent icy crystals from forming on the inside of the cap. At this depth a mile underwater, the near-freezing temperatures can cause a buildup up of hydrates, which foiled the company's attempt to place a 100-ton, four-story dome over the leak about a month ago.
Meanwhile, newly disclosed internal Coast Guard documents from the day after the explosion aboard the Deepwater Horizon rig about 50 miles off the Louisiana coast indicated that U.S. officials were warning of a leak of 336,000 gallons per day of crude from the well in the event of a complete blowout.
The well didn't have such a failure. But the volume turned out to be much closer to that figure than the 42,000 gallons per day that BP first estimated. Weeks later that was revised to 210,000 gallons. Now, an estimated 500,000 to 1 million gallons of crude is believed to be leaking daily.
The Center for Public Integrity, which initially reported the Coast Guard logs, said it obtained them from Rep. Darrell Issa, R-Calif., ranking Republican on the House Oversight and Government Reform Committee.