WASHINGTON — BP's long and halting effort to shut down its infamous Gulf well crossed a key threshold Tuesday night when the well was packed with enough heavy drilling mud to overcome the upward thrust of oil and gas.
Officials were not ready to declare the renegade offshore well dead, but called their ability to jam the well full of mud "a very significant step."
"We have reached a static condition in the well that allows us to have high confidence that there will be no oil leaking into the environment," retired Coast Guard Adm. Thad Allen, the government's point man on the spill, said Wednesday at a White House press briefing.
Although the BP well in the Gulf of Mexico was corked with a mechanical cap in mid-July and has not leaked since then, it remained full of oil and gas pushing upward from miles beneath the seabed. Tuesday's successful mud-pumping operation shoved the oil downward, essentially wresting control of the well from nature more than three months after it unleashed one of the world's largest spills.
Allen continued to emphasize, however, that the battle to permanently seal the well would not be over until one of two relief wells have bored into it sometime in mid-August. "We have significantly improved our chances to finally kill the well with the relief wells when that does occur."
BP announced the achievement as the government released a report indicating that roughly half of the huge volume of oil released during the disaster had evaporated, dissolved or was burned, skimmed or collected.
The other half — roughly 100 million gallons — dispersed into Gulf of Mexico in the form of tiny droplets, drifted around the gulf as tar balls and surface slicks, washed ashore or is buried in sand and ocean sediment.
The report, which made no assessment of the spill's long-term impact on the gulf, noted that the oil is rapidly degrading in the warm gulf environment, which is rich in oil-munching bacteria.
"There's not much oil that is visible," Jane Lubchenco, administrator of the National Oceanic and Atmospheric Administration, said at the White House briefing.
Still, she conceded that diluted oil remains beneath the gulf surface. "Diluted and out of sight doesn't necessarily mean benign. We remain concerned about the long-term impacts."
More than 200 million gallons of oil were released by the deep-sea well 50 miles off the Louisiana coast before it was capped last month.
In trying to figure where it all went, federal scientists concluded that a quarter of it was skimmed, burned or collected and funneled to oil-processing ships. Another 25 per cent evaporated or dissolved. About 24 per cent was dispersed into droplets, either naturally or by chemical dispersants that were extensively used against the spill. The rest, 26 per cent, is "either on or just below the surface as light sheen and weathered tar balls, has washed ashore or been collected from the shore, or is buried in sand and sediments," the report concluded.
With the well stuffed with mud, the government and BP will now decide if they want to shoot cement through the top of the well to finally seal it, or do that with a relief well slated for completion in mid-August.
Even if concrete is pumped into the well from the top, Allen has repeatedly said he will not declare the BP well dead until engineers can check the bottom conditions when a relief well bores into it later this month.
As progress was being made on permanently sealing the BP well, lawmakers on Capitol Hill warned of the need to monitor for lingering effects from of the widespread use of chemical dispersants during the spill.
"We are by no means through this disaster," said Senator Sheldon Whitehouse, D-R.I.
BP has stopped applying the dispersants, which were sprayed on the ocean surface and also near the leaking well nearly a mile below to break the oil up and keep it from washing ashore.
"The subsurface application of the dispersants is why we are seeing less oil on the surface of the gulf than we expected," Whitehouse said at a Senate Environment and Public Works Committee hearing. "However, it is unclear if this will limit the damage or cause even greater harm."
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Democratic senators are considering new regulations governing dispersants as part of legislation drawn up in response to the spill. The legislation, which would impose new environmental safeguards on offshore drilling, has been postponed until the Senate returns from its summer recess in September.
Republican senators, wary of new regulation, said the use of dispersants prevented more widespread environmental damage. Senator James Inhofe, R-Okla., called dispersants "the lesser of two evils."
Paul Anastas, assistant administrator for the Environmental Protection Agency's office of research and development, told the committee that the dispersants are less toxic than oil. But he and other experts said that more study is needed on their effects.
"When considering dispersant use, we are faced with environmental tradeoffs," Anastas said. "The long-term effects on aquatic life are still significantly unknown, and BP has used over 1.8 million gallons of dispersant, a volume never before used in the United States."
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