Glen Wagner, 35, of McDonald, Penna., pleaded guilty Wednesday to a charge of willfully violating an OSHA regulation that caused the death of an employee. Wagner Excavation Service, Inc., of North Fayette Township, Penna., also pleaded guilty to the same charge. Under federal law, corporations can be charged with crimes as though they were individuals.

William Partin, 39, of North Fayette, was killed and another man injured in June 2004 while they were working in a 12-foot-deep trench on a storm water drainage project in North Franklin Township, about 25 miles southwest of Pittsburgh.

Wagner faces up to six months in prison and a fine of up to $250,000 when he's sentenced Jan. 6 before U.S. District Judge Terry McVerry. Wagner Excavation faces a criminal fine of up to $500,000.

Wagner is also vice president of Wagner Development Inc., which contracted with North Franklin Township to install the drainage system. Wagner Development, which wasn't charged, subcontracted with Wagner Excavation to dig the trenches. Wagner is the president of the excavating firm.

OSHA had previously imposed the largest trench-related workplace fine ever in Pennsylvania, $382,875, against Wagner's companies. OSHA found the companies weren't using a trench box at the time of Partin's death. Prosecutors said the companies had workers in trenches without proper reinforcement although OSHA had issued previous warnings at the site, at which there had been other cave-ins that didn't injure workers.

The companies had rented a trench box, but it was lying unused nearby when Partin was killed, and the trench he was in was too deep, authorities said.