The government panel charged with determining the flow rate from BP's leaking well now estimates that between 20,000 and 40,000 barrels per day leaked from the well between April 20 and June 3, the day the riser was cut to make way for BP's latest containment approach.
Marcia McNutt, head of the U.S. Geological Service and chair of the Flow Rate Technical Group, released the numbers on a conference call Thursday afternoon. McNutt said several groups developed models for measuring flow rate and the highest estimate was 50,000 barrels per day. However, McNutt said the best current estimate was that the flow rate was somewhere between 20,000 and 40,000 barrels per day.
McNutt said a group headed by Energy Secretary Steven Chu was continuing work on another estimate based on pressure readings from inside the riser and outside the riser. She expected that group to have an estimate in the next couple of days. McNutt said the numbers would continue to be refined in the coming days and weeks, including numbers for the flow rate since June 3 when the riser pipe was cut.
An earlier estimate by the Flow Rate Technical Group put the spill rate at between 12,000 and 19,000 barrels per day, but that did not include an estimate from groups using video and other data from below sea level. That earlier estimate was a "lower bound" estimate. McNutt says the new estimates now include an upper bound.
This is at least the third time the government has increased its official flow rate estimate, first going from 1,000 to 5,000 and then from 5,000 to between 12,000 and 19,000 before releasing the latest revised estimates.
If the flow rate is indeed 40,000 barrels per day, that would put the total amount of oil spilled into the gulf between April 20 and June 3 at 1.8 million barrels of oil, which translates to 75.6 million gallons. That's six times larger than the Exxon Valdez oil spill, and it doesn't include any of the flow since June 3, after which point the flow rate has increased, though a portion of that increased flow rate is now being captured at the surface.
At a fine of $4,300 per barrel, BP could face a fine of up to $7.74 billion if the 40,000 barrel per day number ends up being accurate. (Edit/update: This would just be for the period between April 20 and June 3, and it wouldn't include other fines and things like royalties on the spilled oil.)