Abstract: On April 2, 2003, Employee #1 and other workers were doing sand blasting operations in a construction job site, inside a large water storage tank, owned by California Water Service Company. The tank was about 100 ft in diameter and 40 ft high and had two entrance doors on the ground level and one door at the top. The employees, including Employee #1 and a coworker used a rolling scaffold, which was assembled by the employees inside the tank. The rolling scaffold base area was 14 ft by 10 ft and the height was 30 ft. The rolling scaffold had six swivel casters which helped the employees to position the scaffold at different locations inside the tank. There was no manufacturer's name for the scaffold. At one point of the sand blasting operations, when the scaffold was pushed for repositioning purposes, one of the six swivel casters became disengaged from the scaffold, resulting in tipping and falling of the scaffold on the floor. Employee #1 and the coworker who were working on the top scaffold platform, fell and were injured. The coworker sustained head, chest, rib, and right ankle injury. Employee #1 sustained injuries to the head, neck and hip, together with a right hand fracture. Employee #1 was hospitalized at the Harbor General Hospital.