Blowout preventer will be replaced

BP and government officials said Thursday that they planned to remove the damaged existing blowout preventer on top of the company’s troubled oil well and replace it with a new, stronger one -- a move they said would allow them to safely carry out the final “kill” of the well, but would delay the ultimate fix until after Labor Day.

Earlier in the crisis, BP had estimated that it would be able to complete the final step to plug the well, called the “bottom kill,” in mid-August. But because the well has not been spewing oil since July 15 -- when crews affixed a giant cap on the blowout preventer -- federal and company experts have decided to move slowly and carefully, preparing thoroughly for possible complications.

“We’re taking a little more time than we would have otherwise to make sure we’ve got everyone on board with what we’re doing in a very systematic approach,” said BP Senior Vice President Kent Wells.

In a hearing Thursday on Capitol Hill, the National Oceanic and Atmospheric Administration took fire on a controversial oil spill “budget” released Aug. 2 that estimated that a large part of the oil released into the Gulf of Mexico by the Deepwater Horizon spill was gone.

In fact, perhaps three-fourths of the pollutants from the 4.1 million barrels spewed into the gulf are still lingering in the environment, Bill Lehr, senior scientist with NOAA’s Office of Restoration and Response, conceded under questioning.

“This is a continuing operation,” Lehr emphasized. “The spill is far from over. We’re beginning a new phase, and NOAA and all the other agencies will be involved in this.”

Lehr said booming and burning probably only managed to clean up about 10% of the spilled oil. Much of the oil has evaporated or dispersed, but remains a source of hydrocarbons in the ecosystem, he said. An unknown amount washed up on beaches and is no longer polluting the gulf, he added.

The Aug. 2 report rendered more optimistic figures because it included the 800,000 barrels of oil captured directly by ships, Lehr said under questioning by Rep. Edward J. Markey (D-Mass).

Agency scientists also have not tallied the significant quantities of methane gas and heavy metals released into the gulf as a result of the spill, Lehr said.

“We have seen some premature celebration,” said Markey, who convened the House Energy and Environment Subcommittee hearing. “What we have learned today is that the oil is not gone. The oil remaining in the gulf waters or washed up on the shore is equivalent to 10 Exxon Valdez spills, and could be much more.”

Also Thursday, a group of ocean researchers announced they had found conclusive evidence of a 22-mile-long oil plume, directly attributable to the BP blowout, deep below the surface of the Gulf of Mexico.

The 1.2-mile wide, 650-foot high plume appears to be breaking down slowly and could linger in the gulf “for some time,” the researchers reported.

The findings by scientists at the Woods Hole Oceanographic Institution, to be published Friday in the journal Science, represent the most rigorous study to date of the deepwater remnants of the BP spill.

The studies and assessments come as engineers and the federal response team focus on the bottom kill, which involves drilling a relief well into the original well deep under the seafloor and injecting it with mud and concrete. A similar injection through the top of the well earlier this month appears to have sealed off the inside of the well pipes.

But the plans for the bottom kill have been complicated by some good news arising from the first injection of concrete: Officials believe that the injection may have not just plugged up the well’s pipes, but also created a seal outside of them, at the base of the annulus, which is the space between the pipes and well bore.

Officials fear that with the bottom sealed off, the injection of mud from the bottom kill could cause a pressure spike inside the annulus that could burst seals at the top of the well, or even rupture the new base seal.

Experts decided to replace the old blowout preventer with one that can handle any pressure jolts. BP and government officials said they were confident that the well would be secure during the swap.

Thad Allen, the national spill response chief, was reluctant to give a precise timeline for the events leading up to the bottom kill, but he said that if all went well, the well could be intercepted the week after Labor Day, which is Sept. 6.

“We’re very close to putting this well away,” he said. “I think none of us wants to make a mistake at this point. And I have no problem, as national incident commander, with an overabundance of caution.”

A blowout preventer is supposed to shut down a well in the event of the kind of high-pressure geyser of oil and gas that shot through BP’s well on April 20, setting off explosions and fires that killed 11 workers.

BP’s damaged device will be placed in government custody and will likely be central to the Coast Guard’s investigation into the cause of the disaster. The Department of Justice has also launched a criminal investigation.

The federal probes and a tangled web of litigation are apparently causing friction among the major companies involved. On Thursday, drilling company Transocean, which owned the rig, released a seven-page letter accusing BP of withholding evidence necessary to fully investigate the blowout.

The letter, which was also sent to the Coast Guard and members of Congress, said BP had been asked seven times to turn over technical documents that might shed light on what caused the explosion’s cause. According to Transocean, BP has not provided any information since June 21.

BP said the letter was full of “misguided and misleading assertions, including the assertion that BP is ‘withholding evidence’

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richard.fausset@latimes.com

kim.murphy@latimes.com

Times staff writer Julie Cart in Los Angeles and Jim Tankersley in the Washington bureau contributed to this report.