Experts have said for some time that the oil spill in the Gulf is one of the greatest environmental disasters in history, and the government has grim new figures to confirm that fact.
The Obama administration said Monday that scientists now estimate nearly 5 million barrels of oil have leaked into the Gulf since the April 20 explosion that sunk the BP-run Deepwater Horizon offshore rig.
"Not all of this oil and gas flowed into the ocean," the administration said in its latest report on the disaster, noting that about 800,000 barrels of oil were captured before the well was capped in mid-July.
The latest figures still are enough to secure the BP spill's status as the world's worst accidental release of oil, topping Mexico's 1979 spill at Ixtoc I, which leaked 3.3 million barrels of oil.
BP still has yet to permanently plug the busted well. After insisting for months that a pair of costly relief wells were the only surefire way to kill the oil leak at the bottom of the Gulf of Mexico, BP officials said Monday they may be able to do it just with lines running from a ship to the blown-out well a mile below.
As crews planned testing to determine whether to proceed with a "static kill" to pump mud and perhaps cement down the throat of the well, BP Senior Vice President Kent Wells said if it's successful the relief wells may not be needed, after all, to do the same weeks later from the bottom.
The primary relief well, near completion, will still be finished and could be used simply to ensure the leak is plugged, Wells said.
"Even if we were to pump the cement from the top, we will still continue on with the relief well and confirm that the well is dead," he said. Either way, "we want to end up with cement in the bottom of the hole."
Government officials and company executives have long said the wells, which can cost about $100 million each, may be the only way to make certain the oil is contained to its vast undersea reservoir.
The company began drilling the primary, 18,000-foot relief well May 2, 12 days after the Deepwater Horizon rig exploded and killed 11 workers, and a second backup well May 16. The first well is now only about 100 feet from the target, and Wells said it could reach it as early as Aug. 11.
"Precisely what the relief wells will do remains to be seen given what we learn from the static kill," BP spokesman Daren Beaudo said. "Can't predict it for certain."
Retired Adm. Thad Allen, the government's point man on the spill response, said Monday that the focus now is on making sure the static kill is successful. But he cautioned that federal officials don't see it as "the end all, be all until we get the relief well done."
One of the biggest variables is whether the area called the annulus, which is between the inner piping and the outer casing, has sprung an oil leak. Engineers probably won't be able to answer that question until they drill in from the bottom, he said.
"Everyone would like to have this thing over as soon as possible," Allen said, adding: "We don't know the condition of the well until we start pushing mud into it."
The company's statements Monday might signal that it is more concerned than it has acknowledged about debris found in the relief well after it was briefly capped as Tropical Storm Bonnie passed last week, said Ed Overton, a Louisiana State University environmental sciences professor.
Plus, trying to seal the well from the top gives BP two shots at ending the disaster, Overton said.
"Frankly, if they can shut it off from the top and it's a good, permanent seal, I'll take it," Overton said. "A bird in the hand at this point is a good thing with this deal."
Before the effort can begin, engineers must probe the broken blowout preventer with an oil-like liquid to decide whether it can handle the static kill process. They had hoped to begin the hours-long test Monday but delayed it until Tuesday after a small leak was discovered in the hydraulic control system.
The static kill is meant as a bit of insurance for the crews who have spent months fighting the oil spill. The only thing keeping oil from blowing into the Gulf at the moment is the experimental cap, which has held for more than two weeks but was never meant to be permanent.
BP and federal officials have managed to contain large parts of the spill through skimmers, oil-absorbant boom and chemical dispersants meant to break up the oil.
Federal regulators have come under fire from critics who say that BP was allowed to use excessive amounts of the dispersants, but government officials counter that they have helped dramatically cut the use of the chemicals since late May.
The Environmental Protection Agency released a study Monday concluding that when mixed with oil, chemical dispersants used to break up the crude in the Gulf are no more toxic to aquatic life than oil alone.