c.2013 New York Times News Service

c.2013 New York Times News Service

HOUSTON — With billions of dollars in penalties at stake, the civil trial of the British oil company BP begins its second phase Monday, which will set the amount of oil that spilled into the Gulf of Mexico from the 2010 Deepwater Horizon rig explosion that killed 11 workers and soiled hundreds of miles of beaches.

The government will argue that a total 4.2 million barrels of oil was discharged into the sea over 87 days, the equivalent of nearly one-quarter of all the oil that is consumed in the United States in a day. BP will counter that the number was closer to 2.45 million barrels. This phase of the trial will also determine if BP prepared adequately for a blowout and if it responded properly once the oil started flowing.

Both sides will present their case in U.S. District Court in New Orleans using competing technical calculations over the next four weeks. Hanging in the balance are Clean Water Act fines that range from $1,100 for every barrel spilled through simple negligence to as much as $4,300 a barrel if a company is found to have been grossly negligent.

The first phase of the trial, which took place over two months this year, centered on whether BP and its contractors were guilty of gross negligence — tantamount to wanton and reckless behavior — in causing the blowout of the Macondo well.

Judge Carl J. Barbier has not ruled yet on the question in the bench trial. But if he agrees with the government’s position that there was gross negligence and that 4.2 million barrels was spilled, the fines could amount to more than $18 billion.

But if BP’s position is upheld that there was simple negligence and only 2.45 million barrels was spilled, then the total fines would amount to roughly $2.7 billion. In all likelihood, a decision or settlement will reach a dollar figure in between, legal experts say.

The second phase of the trial will determine not only how much oil spilled, but also whether BP was negligent or grossly negligent for not being prepared for a spill and during its efforts to stem the flow of the well between April and July 2010.

Under the Clean Water Act, only BP, and perhaps to a lesser extent Anadarko Petroleum, BP’s well partner, would be responsible for paying the fines for the spilled oil.