Manslaughter charges were dropped Wednesday against a BP supervisor responsible for safety aboard the rig where an explosion killed 11 workers in 2010, and he pleaded guilty to a misdemeanor charge of violating the federal Clean Water Act.

Donald Vidrine appeared in court in New Orleans for the change-of-plea hearing. The judge agreed to prosecutors' request to drop the manslaughter charges and accepted Vidrine's guilty plea to the only remaining charge.

In their court filing, prosecutors didn't give a reason for the request, saying only that dismissing the 11 manslaughter charges against each man is "in the interests of justice."

Kaluza did not appear Wednesday. No hearing is scheduled for him.

Vidrine will be sentenced in April. The judge has not indicated whether the recommended sentence -- including 10 months of probation, 100 hours of community service and $50,000 in restitution for a project to fix damage from the oil spill -- will be accepted.

Neither side gave immediate comment on the case Wednesday.

The Deepwater Horizon rig, which London-based BP PLC leased from Houston-based Transocean Ltd., was about 48 miles from the Louisiana coast at the time of the deadly blast in April 2010. Residents up and down the coast watched in horror as oil from the spill coated birds, fouled beaches and threatened delicate fishing areas.

This summer, the global energy giant agreed to a record settlement of nearly $20 billion to states affected by the spill in hopes of bringing an end to a legal drama that has cost the company billions. At the time, the company said the settlement would bring its full obligations to an estimated $53.8 billion.

But the settlement did not affect ongoing criminal cases such as those of Vidrine and Kaluza.

Prosecutors have said Vidrine and Kaluza botched a key safety test and disregarded abnormally high pressure readings indicating signs of trouble ahead of the blowout of BP's Macondo well.