Abstract: At approximately 8:25 a.m. on May 4, 2000, Employee #1 was working as a laborer at a sewage treatment plant. He was standing atop a 6 ft by 6 ft by 15 ft high scaffold, hydroblasting the defective concrete from the walls of clarifier #20, a 180 ft long by 42 ft wide by 18 ft deep concrete pit. Employee #1 was using a Tapt pressure gun with a rotating head and a tumble box from Autoclave Engineers, value serial # 60VM6072-015, with a working air pressure of 60,000 psi. As he was working, the pressure gun stopped while in the operating mode. Unable to attract the attention of coworkers, Employee #1 set the pressure gun on the deck of the scaffold and kneeled down to begin descending the scaffold. As he did this, the pressure gun began to operate, even though it was in the non-operating mode. The gun did not go off at full pressure, but was powerful enough to sever the tendon between this left thumb and forefinger, and to gouge a bone-deep 18 in. laceration on the inside of his left leg. Employee #1 was transported to Harbor General Hospital for treatment. The accident was caused by a defective pressure gun and insufficient training regarding the possible malfunction of a high-pressure device. Employee #1 had worked as a laborer for14 years; at the time of the accident, he had been working for Rampart Construction for about a month.