Transocean Deepwater Inc. pleaded guilty Thursday to a misdemeanor violation of the Clean Water Act and was sentenced to pay $400 million in criminal fines and penalties, Attorney General Eric Holder announced.
A separate proposed civil consent decree, which imposes a $1 billion civil penalty, is pending, the Justice Department said.
Transocean is the owner of the Deepwater Horizon, which caught fire and sank in 2010 over BP's Macondo oil well, killing 11 men and triggering a massive disaster in the Gulf of Mexico.
The Justice Department said the amount of fines and other criminal penalties imposed on Transocean is second only to the $4 billion criminal sentence imposed on BP in connection with the same disaster
"Transocean's guilty plea and sentencing are the latest steps in the department's ongoing efforts to seek justice on behalf of the victims of the Deepwater Horizon disaster," Holder said in a statement.
Holder said most of the money will go toward "protecting, restoring and rebuilding the Gulf Coast region."
Transocean's guilty plea was accepted Thursday by U.S. District Judge Jane Triche Milazzo of the Eastern District of Louisiana.
During the guilty plea proceeding, Transocean admitted that members of its crew onboard the Deepwater Horizon, acting at the direction of BP's well site leaders, were negligent in failing to investigate fully clear indications that the Macondo well was not secure and that oil and gas were flowing into the well, the Justice Department said.
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