The official government estimate of the rate at which the BP oil spill is spewing oil has just been updated again, five days after the previous update.

On June 10, we were told that three different groups of scientists had produced revised estimates of the rate of spewage. “One group estimated a range from 12,600 to 21,500 barrels a day; another estimated a range from 25,000 to 50,000 barrels a day.” And U.S. Geological Survey Director Marcia McNutt, who used to preside over the release of official estimates from the Flow Rate Technical Group, never quite got around to telling us what the third group estimated. The two known and one unknown estimates were officially summarized as a 20,000–40,000 barrels per day rate of spewage.

Now, that was a new estimate of the old rate of spewage. That is to say, the group had gone back and revisited what the rate of spewage used to be, before BP cut the damaged riser pipe on June 3:

But that last estimate, largely based on research by government-appointed scientists known as the Flow Rate Technical Group, came with a caveat: They were looking at older data, including video taken of the damaged riser pipe when it still had multiple leaks.

Cutting the riser pipe allowed BP to put in place the containment dome that is currently capturing some of the oil spilling from the leak. It is also popularly believed to have increased the rate of spewage. A 20% increase is the figure that has been bandied about ever since the pipe was cut, though it has never been clear what that figure was actually based on.

The new government estimate released yesterday relates to the new rate of spewage, after the damaged riser pipe was cut.

Hitherto, U.S. Geological Survey Director Marcia McNutt would hold a press conference to announce the Flow Rate Technical Group’s latest official estimate. Yesterday, there was just a press release, no press conference. And Marcia McNutt now shares the billing with Steven Chu and Ken Salazar. In fact, when you read the press release, it sounds like Steven Chu has taken over center stage. It’s almost as if we are being told that finally we have a scientifically accurate estimate that a Nobel laureate is willing to own:

Based on updated information and scientific assessments, Secretary of Energy Steven Chu, Secretary of the Interior Ken Salazar, and Chair of the National Incident Command’s Flow Rate Technical Group (FRTG) Dr. Marcia McNutt (Director of the U.S. Geological Survey) today announced an improved estimate of how much oil is flowing from the leaking BP well.

Secretary Chu, Secretary Salazar, and Dr. McNutt convened a group of federal and independent scientists on Monday to discuss new analyses and data points obtained over the weekend to produce updated flow rate estimates. Working together, U.S. government and independent scientists estimate that the most likely flow rate of oil today is between 35,000 and 60,000 barrels per day. The improved estimate is based on more and better data that is now available and that helps increase the scientific confidence in the accuracy of the estimate.
[...]
Today’s improved flow rate estimate brings together the work of several scientific teams and is based on a combination of analyses of high resolution videos taken by ROVs, acoustic technologies, and measurements of oil collected by the oil production ship together with pressure measurements inside the top hat. …
[...]
… The improved estimates are informed by newly available, detailed pressure measurements from within the Top Hat taken over the past 24 hours. In addition, scientists could draw on more than a week of data about the amount of oil being collected through the top hat.

The increase in the official rate of spewage over the last week has been pretty dramatic. On June 9, the Flow Rate Technical Group was still touting 19,000 barrels a day as the high end official estimate. By June 15, this has more than tripled, to 60,000 barrels a day.

From the June 10 numbers, the low end official estimate of 20,000 barrels a day has gone up by 75%, while the high end official estimate of 40,000 barrels a day has increased 50%. It’s still not clear how much of this reflects an increased rate of spewage due to cutting the damaged riser pipe, but it may not be a whole lot, apparently:

An administration official said via e-mail on Tuesday that the larger figure was the result of better data on the flow, not necessarily a reflection of the flow increasing when the riser pipe was cut.

James Riley, a professor of mechanical engineering at the University of Washington, and a member of the flow rate group, said his team, which looked at high resolution video of the geyser after the riser cut, saw evidence of an increase in flow, “but not a dramatic increase.” He stressed, however, that it’s not an exact science.

BP is currently capturing only about 15,000 barrels a day from the spill. That no longer sounds as impressive as we were once invited to believe.

For the record, BP seems to have responded to the new estimate with a corporate yawn (when will they ever learn?):

BP had no comment on the new spill rate estimate, (Robert Wine, a BP spokesman) said. Earlier projections were “presented as just estimates with a wide margin of uncertainty,” he said.

 
Previous posts:
June 11: BP Spill Flow Rate Estimates: Fact and Fiction
June 9: BP Spill Rate: Some New (And Improved) Developments
June 7: The Spill Rate Estimate That Walks On Water Has Feet Of Clay
June 7: How Much Oil Would The Oil Spill Gush (If BP Could Gush Truth)?
June 1: The Long Arm Of The Stock Market
May 27: Quote Of The Day
May 26: Scenes From A Spill
May 24: How Retarded Can One Corporation Be?
May 18: BP’s Strategy Pays Off
May 17: On The Evolution Of The Deepwater Horizon Spill Rate Estimate