Abstract: At approximately 5:00 p.m. on November 12, 1999, Employee #1, a mechanic, was replacing the rear hatch door of tractor trailer tank #117, which had developed a small leak after it had returned to the yard with a load of salt water from a gas well site. After the load was dumped at the yard disposal facility, the tank trailer was backed up to the maintenance shop and Employee #1 unbolted the hatch. He could not remove the hinge pin, which was tack welded, so he retrieved an oxyacetylene torch and cut the top of the hinge pin. Flammable vapors from the residual petroleum condensates inside the tank were ignited and exploded, blowing off the top and rear hatches. The rear hatch struck and killed Employee #1.