Abstract: At approximately 8:00 a.m. on December 23, 2011, Employee #1, a 51-year-old male with Schwerman Trucking Company, arrived with a tank trailer loaded with Mameno acid. Employee #1 prepared his vehicle for off-loading by pressurizing the trailer with air from the on board air compressor of the Volvo tractor. When air from the plant became available, Employee #1 then switched to the plant air which was set and regulated to 32 p.s.i. A security camera located directly over the manhole on the trailer showed Employee #1 standing on the platform adjacent to the manhole and accessed by a ladder attached to the trailer, beating on the handles of the locking bolts with a hammer, presumably to prevent air from leaking out of the manhole. The cover of the manhole blew off the lip of the manhole and was found 62 feet from the trailer. Two of the locking bolts used to secure the manhole cover were found over 100 feet from the vehicle. Employee #1 was either struck by the cover and knocked off the platform falling eight-feet to the ground where he struck his head or fell backwards to the ground striking his head. Workers at the plant heard a loud pop and when they went to the off-loading site, they found Employee #1 on the ground. Cardiopulmonary resuscitation (CPR) was initiated and kept up until Emergency Medical Services arrived, and Employee #1 was transported to the hospital, where he died on December 26, 2011.