Abstract: On July 13, 2005, Employee #1 was a regular employee of his company, working construction for his employer. The firm was part of the project of expanding the Loker Student Union building at California State University, Dominguez Hills, Carson Campus (CSUDH, Carson). The company was excavating and pouring concrete for the entire building. A concrete roof structure 120 ft wide and 13 ft tall had been poured earlier. It was provided with a guardrail or handrail at a height of 13 ft to provide fall protection. From the edge of that structure, 30-in. by 30-in. concrete beams had been poured as well. Next to those beams, 0.63-in.-thick drywall boards had been placed horizontally, flush with the top surfaces of the beams, to prevent dust in the construction area from entering the area underneath, which was not part of the construction activities. After Employee #1 and some workers had completed work on the roof structure, they were advised by a supervisor to wait on the structure, inside the peripheral handrail area. Employee #1 was holding a tube that was to be used for pouring concrete on a part on the structure attached to the other end of one of the beams. He was told by a coworker to go to the other end of the beam, where the next operation was to take place. He was told that he could walk not only on the beam, but on the drywall boards as well. Employee #1 set forth on the beam, but as soon as he stepped on one of the horizontal drywall boards, it broke through. Employee #1 landed on the floor 13 ft below. He sustained fractures to his hips on both sides. He was hospitalized at the Harbor-UCLA Medical Center for two weeks. A causal factor is that Employee #1 did not use an approved fall arrest system while working 13 feet up.