Attorney General Eric Holder pledged to hold accountable those responsible for the Deepwater Horizon oil spill this afternoon as he announced that the Justice Department has filed its long-awaited civil lawsuit in the matter.

The lawsuit names nine defendants, including BP PLC, the owner of the well, and Transocean Ltd., which owned the oil rig. More defendants could be added at a later date, Justice Department officials said.

"We intend to hold them fully accountable for their violations of the law," Holder said at a press conference, where he was joined by U.S. EPA Administrator Lisa Jackson.

As expected, the government is seeking relief via the Oil Pollution Act and the Clean Water Act, both of which allow for the government to claim damages if it can prove certain facts, regardless of the defendants' intent (Greenwire, Dec. 15).

Under both statutes, the government can claim dramatically bigger damages if Justice Department lawyers can prove negligence or misconduct.

In the lawsuit, the government alleges that the defendants failed to take necessary precautions prior to the April 20 explosion that led to the spill, did not use the safest drilling technology to monitor the well, failed to maintain surveillance of the well, and did not effectively use or maintain equipment that would have ensured safety.

"We intend to prove that these violations caused or contributed to this massive oil spill," Holder said.

Holder declined to speculate about the amount of damages the government could win. Under the Clean Water Act penalties, based on an estimated 4.9-million-barrel spill, penalties could range from a minimum of $5.4 billion, based on a $1,100-per-barrel fine, to as much as $21.1 billion, or $4,300 per barrel if the spill is deemed the result of negligence.

The Justice Department's criminal probe into the spill continues, Holder added.

In her remarks at the press conference, Jackson said the lawsuit was an "important step" in the long-term plan to tackle environmental problems on the Gulf Coast.

"This is about getting a fair deal for the region that suffered enormous consequences from this disaster," she added. The potential damages that could be awarded via the Clean Water Act penalties would be particularly important, Jackson said.

The government's intervention means it will now formally join the multi-district litigation over the law spill that is before U.S. District Judge Carl Barbier of the Eastern District of Louisiana. He is already hearing dozens of consolidated claims filed by private plaintiffs, who are also seeking damages under the Oil Pollution Act.

Environmental groups welcomed Holder's announcement

"Repairing the damage done to people, wildlife and coastal habitats is a massive undertaking, and recovery of Clean Water Act penalties will be a key part of the solution," said John Kostyack, executive director for wildlife conservation and global warming with the National Wildlife Federation.

A BP spokesman said the company "will answer the government's allegations in a timely manner and will continue to cooperate with all government investigations and inquiries."

Click here to read the complaint.