NEW ORLEANS - A former BP rig supervisor was scheduled for trial Tuesday on a misdemeanour charge connected to pollution from the April 2010 Deepwater Horizon offshore oil rig disaster in the Gulf of Mexico.

Robert Kaluza once faced much more serious charges: manslaughter counts connected to the deaths of 11 workers who died when the rig exploded. But federal prosecutors backed off the most serious charges late last year.

Tuesday's trial is for a single charge of violating the Clean Water Act.

Another rig supervisor, Donald Vidrine, pleaded guilty to the same charge last year after manslaughter charges were dropped.

Prosecutors say Kaluza and Vidrine, botched a "negative pressure test" and missed clear signs of trouble before the well blowout, which spewed millions of gallons of oil into the Gulf of Mexico.

After major charges were dropped against Kaluza and Vidrine, there was little in the way of individual criminal convictions resulting from a sweeping Justice Department criminal investigation into the rig explosion.

The government did secure a landmark criminal settlement and record civil penalties against the corporation, which BP said would cost the corporation billions of dollars. But in terms of individual criminal responsibility, only four mostly lower-ranking employees faced charges, and those cases unraveled before skeptical jurors and judges.

The dropping of the manslaughter charges against Kaluza and Vidrine followed the June acquittal of former BP executive David Rainey. A jury found him not guilty of manipulating calculations to match a far-too-low estimate of the amount of oil spewing into the Gulf.

Former BP engineer Kurt Mix once faced two serious felony charges for allegedly deleting text messages that prosecutors said were related to investigations of the spill. After a yearslong legal ordeal, he pleaded guilty last November to a misdemeanour charge and received no jail time. He made clear publicly that he believed he had done nothing wrong and felt vindicated.

Vidrine's guilty plea to a misdemeanour charge ended a similar ordeal. Kaluza chose to keep fighting.

"From Bob's standpoint, he's charged with a crime he didn't commit, and he's going to go to trial to clear his name," Kaluza's attorney, Shaun Clarke, said in December.


Associated Press reporter Michael Kunzelman contributed to this story.