The blown-out well in the Gulf of Mexico gushed 12 times faster than the government and BP estimated in the early weeks of the crisis and has spilled 4.9 million barrels, or 205.8 million gallons, according to a more detailed analysis announced late Monday.
BP's Macondo well spewed 62,000 barrels of oil a day initially, and as the reservoir gradually depleted itself, the flow eased to 53,000 barrels a day until the well was capped July 15, according to scientists in the Flow Rate Technical Group, supervised by the U.S. Geological Survey and the U.S. Department of Energy.
The new numbers once again have nudged upward the statistical scale of the disaster. If correct — the government allows for a margin of error of 10 percent — the flow rate would make this spill significantly larger than the Ixtoc I blowout of 1979, which polluted the southern Gulf of Mexico with 138 million gallons over the course of 10 months. That had been the largest unintentional oil spill in history, surpassed only by the intentional spills in 1991 during the Persian Gulf War.
The new flow rate figures came as engineers made final preparations for a "static kill" operation that might plug the well permanently even before a relief well intercepts Macondo at its base. BP announced late Monday that the procedure would be delayed, probably until today, because of a leak in the hydraulic control system on the well's new cap.
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 the static kill.
BP senior vice president Kent Wells said if it's successful the relief wells may not be needed, but the primary relief well, near completion, will still be finished and could be used simply to ensure the leak is plugged.
The new estimate for the amount of oil that spilled is even higher than the most recent top figure of 184 million gallons.
The amount has been a major source of controversy since the April 20 explosion on the Deepwater Horizon, killing 11 workers. Early in the crisis, the Coast Guard and BP pegged the flow at 5,000 barrels a day, sticking with that figure even as outside scientists declared that it low-balled the actual rate.
The flow rate team, assembled in May, tried to come up with a more solid figure. Scientists examining the surface slick as well as video taken by submersibles soon upped the estimate. By early June, the government declared the flow to be 35,000 to 60,000 barrels a day.
Even the high end of that estimate did not quite do justice to Macondo when it was at full throttle in the early weeks of the crisis. The new figures reflect more data, including high-definition video, sonar measurements of the oil-gas ratio, and pressure readings in the new capping stack before, and then after, the sealing of the well July 15.
"We may never know the exact answer. But as we get more data, you're able to shrink the uncertainty," said Bill Lehr, senior scientist for the National Oceanic and Atmospheric Administration and a leader of one of the teams.
The new figures indicate that the roughly 800,000 barrels of oil that BP managed to capture with its various containment strategies represented only about one-sixth of the crude that surged into the gulf over the course of nearly three months.
In all, about 1.2 million barrels of oil have been accounted for so far, either burned, captured or skimmed off the ocean's surface. That's about a quarter of the new estimate for the total spill.
Where the other three-quarters has gone is unclear. Some has evaporated; some has been consumed by microbes; but scientists remain troubled by the possibility that large amounts of oil remain underwater in cloudlike plumes.
"This further confirms that a lot of the oil is still at sea. And we just don't know the implications of it," said Ron Kendall, director of the Institute of Environmental and Human Health at Texas Tech University. Kendall will testify before Congress on Wednesday about his fears that dispersant chemicals have helped much of this oil sink into deep-sea habitats.
For government lawyers preparing a case against BP, this number could help calculate the maximum civil penalty BP might face for the spill. If BP is not found to have acted with negligence, the penalty would be $1,100 per barrel. About 4.1 million barrels escaped into the gulf, according to the new estimate, so that fine would come to $4.5 billion. If BP is found to have acted with "gross negligence" in the lead-up to the spill, the maximum penalty would be $4,300 a barrel, which would work out to $17.6 billion.
In all, the 4.1 million barrels estimated to have polluted the gulf would be enough to fill the Pentagon to a depth of 18 feet or to fill 260 Olympic swimming pools. The entire Gulf of Mexico, by comparison, would fill 880 million Pentagons, or 973 billion Olympic pools.
Information from the Associated Press was used in this report.