BP once again has resumed its "top kill" operation, the company's latest effort to stem the flow of oil into the Gulf of Mexico in what appears to be the worst oil spill in U.S. history based on new estimates of the oil flow released today by a government task force.
BP earlier said that it halted the top kill operation late Wednesday evening. The company said it was not a sign of a problem with the procedure, but that it was pausing to assess the effectiveness of its pumping of drilling fluid into the well. It could take 24 to 48 hours to determine whether it has worked.
The process resumed at around 6 p.m. local time today, BP said this evening.
In a press conference at the White House this afternoon, President Obama took full responsibility for the government's response to the spill, defending his administration's decisions and calling the effort to contain and clean up the oil the largest of its kind in the nation's history.
"The American people should know that from the moment this disaster began, the federal government has been in charge of the response effort," he said. "BP is operating at our direction. Every key decision and action they take must be approved by us in advance."
Earlier in the day, the scientific team charged by Obama with determining the rate of oil flow estimated that the initial release following the accident was 12,000 to 19,000 barrels of oil per day, far higher than the 5,000 barrel-per-day estimate long maintained by BP and the U.S. Coast Guard.
"The original estimate was, of course, based on very limited data," said Marcia McNutt, the U.S. Geological Survey director who worked on the task force, which also included scientists from National Oceanic and Atmospheric Administration and Mineral Management Service.
The new spill estimate amounts to up to 798,000 gallons of oil per day since April 20, when the Deepwater Horizon rig blew up and later sank, larger than the volume of an entire Olympic-sized swimming pool.
Even under the most conservative estimate, nearly 17 million gallons would have leaked from the Deepwater Horizon well since the start of the disaster. On the high end of the estimate, some 29.5 million gallons may have been spilled. Either total would mean that the current crisis in the Gulf far surpasses the 1989 Exxon Valdez disaster, which spilled 11 million gallons of oil off the coast of Alaska.
Also today, Elizabeth Birnbaum, the head of the MMS, the government agency that regulates offshore drilling, resigned from her office under pressure.
Unified Area Command and BP said today that they're still waiting for a sign as to whether the "top kill" operation they started Wednesday had been effective. BP believed that the technique, which pushes a mud-like drilling fluid into the well, has a 60 to 70 percent chance of success.
Earlier today, officials had said that the top kill had been working as planned, and that oil and gas had stopped flowing temporarily because of the mud injection.
"They are pumping mud into the well and as long as the mud is going down, the hydrocarbons are not coming up," said Coast Guard Adm. Thad Allen in an afternoon press conference. "The goal is to put enough mud into the well bore to produce zero pressure so they can put a cement plug over it. They are still in the process of doing that."