NEW ORLEANS - When BP used a capping stack to seal its blown-out well in the Gulf of Mexico, the device didn't just shut the source of the nation's worst offshore oil spill. Its pressure gauge also provided scientists with crucial data about the rate that crude that was spewing from the well when engineers finally killed it in July 2010.
Experts for BP and the federal government used the pressure gauge data in calculating how much oil spilled into the Gulf during the 87 days it took to plug the well. But each side will provide a federal judge with very different estimates when the second phase of a trial resumes Monday for litigation spawned by the spill.
U.S. District Judge Carl Barbier is scheduled to hear three weeks of testimony from dueling experts to help him calculate how much oil spilled into the Gulf - a key factor in determining how much more money BP and its contractors owe for their roles in the deadly disaster.
Justice Department attorneys will try to persuade Barbier that the pressure gauge on the capping stack provided the best set of data about the flow of oil from the well.
"The pressure data, collection rates and geometry of the capping stack are by far the most accurate and reliable sources of information on flow rate, and were recognized as such by all parties at the time," they wrote in a pretrial filing.
BP, however, says the government's experts ignored other important data. Company lawyers say its experts used a "proven methodology" that doesn't require "simplistic and unverified assumptions about flow conditions."
"In contrast, the United States' experts employ unproven methods that require significant assumptions and extrapolations in lieu of, and even directly inconsistent with, the available data and other evidence," company attorneys wrote.
The Deepwater Horizon drilling rig was working at the site of BP's Macondo well off the Louisiana coast when the well blew out April 20, 2010. The explosion on the rig killed 11 workers and set off a massive fire. The rig sank less than two days later to the bottom, about a mile below the Gulf surface.
The Justice Department's experts estimate 4.2 million barrels, or 176 million gallons, spilled into the Gulf after the blowout. BP has urged Barbier to use an estimate of 2.45 million barrels, or nearly 103 million gallons, in calculating any Clean Water Act fines. Both sides agree that 810,000 barrels, or 34 million gallons, escaped the well but were captured before the crude could pollute the Gulf.
Under the Clean Water Act, a polluter can be forced to pay a maximum of either $1,100 or $4,300 per barrel of spilled oil. The higher maximum applies if the company is found grossly negligent, as the government argues BP should be. But penalties can be assessed at amounts lower than those caps.
Using the government's figures, a maximum penalty if the company is found grossly negligent could total $18 billion. Using the company's figures, that maximum penalty would be around $10.5 billion.
For the trial's first phase, Barbier heard eight weeks of testimony about the causes of the April 2010 well blowout.
Barbier divided the trial's second phase into two parts. For the first segment, he heard four days of testimony last week about BP's efforts to cap the well. He set aside 12 days of testimony for the second segment, which will consist almost exclusively of technical testimony by experts.