NEW ORLEANS | With a tight new cap installed on its leaking well in the Gulf of Mexico, BP on Tuesday prepared to begin gradual tests to determine whether the device can stop oil from pouring into the sea for the first time in nearly three months.
The cap would be just a temporary solution, but it offers the best hope yet for cutting off the crude that has fouled the Gulf since the Deepwater Horizon rig leased by BP exploded April 20, killing 11 workers.
Engineers will slowly shut down three valves that let oil flow through the 75-ton capping device to see if it can withstand the pressure of the erupting crude and to determine whether leaks spring up elsewhere in the well.
If pressure inside the cap stays in a target range for roughly six hours after the valves are closed, there will be more confidence the cap can contain the oil, National Incident Commander Thad Allen said at a news briefing at BP's U.S. headquarters in Houston. That target range is 8,000 to 9,000 pounds per square inch, he said. Anything lower could indicate another leak in the well.
Meanwhile in Washington, the Obama administration said it sent a fourth bill to BP and other parties seeking $99.7 million for costs related to the cleanup of the Gulf oil spill. The administration said three earlier bills, totaling $122.2 million, have been paid in full.
The White House has said that BP is responsible for the disaster and must pay all costs associated with the response to the spill, including efforts to stop the leak, reduce the oil's spread and the long-term recovery of the Gulf Coast region.
Adm. Allen and BP officials repeatedly cautioned there are no guarantees about the delicate work a mile below the sea. He urged Gulf Coast residents watching the possible solution evolve to be patient.
"They ought to be interested and concerned but if they hold their breath, they'll run out of oxygen. I won't be," Adm. Allen, who last month retired from the Coast Guard, told the Associated Press after the briefing.
The tests could last anywhere from six to 48 hours, Adm. Allen and BP said.
Kent Wells, a senior vice president at the oil giant, declined to talk about BP's next steps until the test results are in hand. "It's not simple stuff. What we don't want to do is speculate around it," he said at a BP news briefing.
The cap's installation Monday after three days of undersea preparations was good news to weary people on the coast from Texas to Florida, who have waited for BP to make good on its promise to clean up the mess.
"Hopefully this is the moment when they get it cut off," said Prentiss Ming, 23, a Pizza Hut manager from Pensacola, Fla., who was on the beach there. "But you can't really believe it."
Still, even if the oil is stopped, the consequences are far from over.
"I ain't excited about it until it's closed off completely," said James Pelas, 41, a shrimper working on his boat at a marina in Venice, La. "Oil's scattered all over the place."
The cap will be tested by closing off three separate valves that fit together snugly, choking off the oil from entering the Gulf. BP expects no oil will be released into the ocean during the tests, but remained cautious about the success of the system.
Even if the cap works, the blown-out well must still be plugged. A permanent solution will have to wait until one of two relief wells being drilled reaches the broken well, which will then be plugged up with drilling mud and cement. That may not be accomplished until mid-August.
Also Tuesday, there were several anti-BP protests in London, including one outside corporate headquarters in which protesters wearing T-shirts saying "BP blows" blasted South Africa's iconic vuvuzela horns, and another at the British Museum in which protesters poured dark, sticky molasses over the base of an Easter Island statue that BP had sponsored.