Abstract: At 2:00 p.m. on January 12, 2000, Employee #1 was on the roof of disinfection building "N," under construction at a wastewater treatment facility. He and a coworker were sealing roof joints near the northwest corner of the 75 ft wide by 96 ft long flat roof. As he approached a 3 ft 6 in. by 5 ft duct shaft opening covered by a 4 by 8 ft sheet of plywood, he, for some reason, lifted up the sheet of plywood. Employee #1 fell 32 ft through the opening to the floor of the building. Approximately 10 ft down, he struck a newly installed bridge crane before continuing on down to the floor. Employee #1 was transported by rescue personnel to the Fairfax Hospital Shock/Trauma unit suffering from two skull fractures, a facial fracture, a punctured lung, several fractured ribs, a fractured right wrist, a dislocated hip, and severe brain damage. He remained in Intensive Care until his death during the night of January 15, 2000. Causal factors appear to have been that the cover had not been secured against displacement and had not been marked with the word "hole" or "cover" to warn of the hazard.