Abstract: At approximately 10:00 a.m. on January 3, 2012, Employee #1, a vacuum truck driver, was on top of a 5,460 gallon tank (Frell Serial Number VT-120-2446-0) that was on a trailer. After the tank was pressurized, he had climbed onto it to attempt to tighten a 13 in. lid that he thought was leaking. The lid was held in place with a flat, 16-in.-long, 3-in.-wide bracket that extended over the center of the lid. The bracket was latched on one end with a U-bolt that was welded onto the tank and extended over the width of the bracket. The opposite end of the bracket was held in place by a 1 in. wing nut on a 1 in. bolt fastened to the tank. While standing over the lid, Employee #1 used a 4 lb sledge hammer to strike the wing nut to tighten it. When the wing nut failed, the pressure blew the lid and bracket from the tank. The lid struck Employee #1's chest causing and knocked him from the tank. As he was falling to the ground, Employee #1's arm struck an angle iron that was welded to the side of the tank. He was hospitalized at Kern Medical Center for an open fracture and degloving injury of his left forearm.