BP Resumes "Top Kill" Mud Pumping to Plug Leak

Updated at 8:05 p.m. ET

BP resumed pumping mud in an effort to plug the Gulf of Mexico oil leak. The company announced late in the day that it had suspended shooting heavy drilling mud into the blown-out well 5,000 feet underwater around midnight Wednesday so it could bring in more materials.

Special Section: Disaster in the Gulf

BP Chief Operating Officer Doug Suttles announced the stoppage during a Thursday evening news conference. He said the early morning halting was so crews could monitor their work and bring in more drilling mud.

It could be late Friday or the weekend before the company knows if it has cut off the oil that has been flowing for five weeks.

Live Shot of Gushing Underwater Leak

The company acknowledged drilling mud was escaping from a broken pipe along with the leaking crude.

"The fact that we had a bunch of mud going up the riser isn't ideal but it's not necessarily indicative of a problem," said spokesman Tom Mueller.

News that it would be at least 24 more hours before officials know if the procedure will work came as dire new government estimates showed the disaster has easily eclipsed the Exxon Valdez as the biggest oil spill in U.S. history.

BP started shooting heavy drilling mud into the blown-out well 5,000 feet underwater on Wednesday afternoon, then stopped later that night to monitor the work and bring in 630,000 more gallons of mud, said Suttles, who insisted nothing had gone wrong.

"The fact that it's taken more than 24 hours is not a big surprise," he said. "We'll stay at this until we're successful or we determine we can't be successful."

On Thursday, Suttles said less than 15,000 barrels of drilling fluid were pumped into the well Wednesday night. While 50,000 barrels of the mud were still available, Suttles said the company wanted to make sure a "sufficient volume" was on hand before the next pumping.

When the fluid was pumping into the well, BP's 30,000 horsepower engine used 65 barrels to 70 barrels per minute, which Suttles described as a high rate.

Suttles described the fluid gushing out of the blowout preventer all day Thursday as a combination of drilling mud and some oil and gas.

Suttles said crews may also shoot assorted junk such as golf balls and rubber scraps into a piece of equipment known as a blowout preventer to fill holes.

The top kill try was the latest in a string of attempts to stop the oil that has been spewing for five weeks, since the Deepwater Horizon rig exploded and sank off the coast of Louisiana. Eleven workers were killed in the accident.

The news came after a day of BP saying the risky procedure was going according to plan. Earlier Thursday, Coast Guard Adm. Thad Allen said that the mud was stopping some oil and gas but BP was still pumping it in.

"It's a work in progress," Allen said. "We need to let it play itself out."

A team of scientists trying to determine how much oil has been flowing since the offshore rig Deepwater Horizon exploded April 20 and sank two days later found the rate was more than twice and possibly up to five times as high as previously thought.

The fallout from the spill has stretched all the way to Washington, where the head of the federal agency that oversees offshore drilling resigned Thursday and President Obama insisted his administration, not BP, was calling the shots. His comments marked a change in emphasis from earlier administration assertions that the government was overseeing the operation.

More Press Conference Coverage

Obama Defends Oil Spill Response, Cites Mistakes
Obama Reacts to MMS and Reponse
Obama: There's a Reason I Never Said "Drill, Baby, Drill"
Obama on Katrina Comparison: "I'll Let You Decide"
Obama's Critics "Don't Know the Facts"
Obama: Malia Asked "Did You Plug The Hole Yet?"
Oil Spill Hits Home for Obama

As for the spill, new estimates showed the spill has already surpassed the Exxon Valdez as the worst in U.S. history.

Even using the most conservative estimate, the leak has grown to nearly 18 million gallons over the past five weeks. In the worst case scenario, if 39 million gallons has spilled, the oil would fill enough jugs to stretch from the Louisiana marshes to Prince William Sound in Alaska. That's where the Exxon Valdez ran aground in 1989, spilling nearly 11 million gallons.

"Now we know the true scale of the monster we are fighting in the Gulf," said Jeremy Symons, vice president of the National Wildlife Federation. "BP has unleashed an unstoppable force of appalling proportions."

BP and the Coast Guard estimated soon after the explosion that about 210,000 gallons a day was leaking, but scientists who watched underwater video of well had been saying for weeks it was probably more.

U.S. Geological Survey Director Marcia McNutt said two different teams of scientists calculated the well has been spewing between 504,000 and more than a million gallons a day.

BP spokesman Steve Rinehart said the previous estimate came from industry experts and scientists based on the best data available at the time. Asked for the company's response to the new numbers, he replied: "It does not and will not change the response. We are going all out on our response."

Marine scientists also said Thursday they have discovered a massive new plume of what they believe to be oil deep beneath the Gulf, stretching 22 miles from the leaking wellhead northeast toward Mobile Bay, Ala. The discovery by researchers on the University of South Florida College of Marine Science's Weatherbird II vessel is the second significant undersea plume recorded since the rig exploded.

Last week, BP inserted a mile-long tube to siphon some of the oil from the gushing well into a tanker. It sucked up 924,000 gallons, but engineers had to dismantle it so they could start the top kill Wednesday afternoon.

If that works, BP will inject cement into the well to seal it. The top kill has been used above ground but has never been tried 5,000 feet beneath the sea. BP pegged its chance of success at 60 to 70 percent, and Obama cautioned that it "offers no guarantee of success."

Lt. Commander Tony Russell, an aide to Allen, said Thursday the mud had a ways to go before it proved successful.

"As you inject your mud into it, it is going to stop some hydrocarbons," Russell said. "That doesn't mean it's successful."

In Washington, meanwhile, Minerals Management Service Director Elizabeth Birnbaum stepped down from the job she has held since July 2009. Her agency has come under withering criticism from lawmakers of both parties over lax oversight of drilling and cozy ties with industry.

An internal Interior Department report released earlier this week found that between 2000 and 2008, agency staff members accepted tickets to sports events, lunches and other gifts from oil and gas companies and used government computers to view pornography.

Polls show the public is souring on the administration's handling of the catastrophe, and Obama sought to assure Americans that the government is in control.

"I take responsibility. It is my job to make sure this thing is shut down," Obama said at a news conference.

He announced that a new moratorium on drilling permits will be extended for six months. He also said he was suspending planned exploration drilling off the coasts of Alaska and Virginia and on 33 wells currently being drilled in the Gulf of Mexico.

Amy Jaffe, an oil industry expert at Rice University, said an extended moratorium will force the U.S. to eventually rely even more on imports, though she wondered whether offshore drilling would be affected globally, too. Jaffe said the U.S. relies on oil produced in the Gulf of Mexico, and halting new exploration would guarantee that oil prices will rise.

"Of course we can" stop drilling, she said. "But how much are you really willing to pay for gasoline?"

Fishermen, hotel and restaurant owners, politicians and residents along the 100-mile stretch of Gulf coast affected by the spill are also fed up with BP's failures to stop the spill. Thick oil is coating birds and delicate wetlands along the Louisiana coast.

"I have anxiety attacks," said Sarah Rigaud, owner of Sarah's Restaurant in Grand Isle, La., where the public beach was closed because blobs of oil that looked like melted chocolate had washed up on shore. "Every day I pray that something happens, that it will be stopped and everybody can get back to normal."

Seven cleanup crew members who reported dizziness, severe headaches and nausea while working in boats off the Louisiana coast remained hospitalized Thursday. The Coast Guard pulled commercial fishing boats from cleanup efforts in Breton Sound on Wednesday after workers first reported feeling sick. Later, the Coast Guard approved about half of Louisiana's proposed 86-mile wall of sand to protect the coastline from the oil.

If the top kill fails, BP says it has several backup plans. The only permanent solution is drilling a second well, but that will take a couple of months. BP plans to go ahead with that even if the top kill works.

Though the spill is now the biggest in U.S. history, it's not the biggest ever in the Gulf. An offshore drilling rig in Mexican waters - the Ixtoc I - blew up in June 1979, releasing 140 million gallons of oil.