Abstract: On January 29, 2014, Employee #1, a crew foreman, and Coworkers #1, #2, and #3, all pipefitters employed by Southland Industries, were installing two 6-inch diameter pipes inside a commercial building. These were black iron steel L pipes measuring 16 feet long by 3 to 4 feet from the elbow and weighing approximately 450 pounds each. The pipes were being installed with the long end vertical against the East wall of the building's interior, located on the East-line Corridor 2, and the short end passing through an opening in the wall and onto the other side. This task proved to be difficult and time consuming, because the holes in the wall were the exact dimension of the pipe diameter. Coworker #1 operated a Gradall, using its jib and sling to lift the pipe. Coworker #2, working from the basket of a knuckle boom (articulated boom) lift, was aligning the top of the pipe. Employee #1, who was in charge of this operation, was at the bottom of the pipe and guiding/aligning it to the flange. It took approximately 2 hours to install the first pipe on the right side. After 1.5 hours attempting to install the second pipe on the left side, Employee #1 asked Coworker #3, who was passing by, to help with the installation. Now there were four workers trying to install this 450-pound pipe: Coworker #1 operated the Gradall to lift the pipe. Coworker #1, working from the basket of the lift, positioned/aligned the top part of the pipe. Coworker #3, who had come over to help, was at the bottom of the pipe, guiding and aligning it to the connection. Employee #1, the foreman, stood next to Coworker #3 and directed the operation. Coworker #3 and Employee #1 were standing on a concrete slab that measured 31 inches wide by approximately 20 feet long and rose 3 feet 6 inches above the ground. The two pipes were in the middle of this slab platform. Both Employee #1 and Coworker #3 were on the left side of the slab. Twenty minutes after Coworker #3 had begun to help with the installation, Employee #1 missed his step and fell from the concrete slab down to a wooden plank measuring 22 inches wide by 10 feet long, a fall height of approximately 3 feet 6 inches. This wooden plank acted as a bridge to connect the flooring over a trench measuring 6 feet wide. Employee #1 landed on his right foot, but the momentum of the fall caused him to lose balance and fall from the plank down to the trench below, an additional fall height of approximately 1 foot. There were pipes laid down horizontally on the trench floor. Employee #1 landed left hip first and struck these pipes. Emergency services were called, and Employee #1 was transported to the hospital, where he was admitted and treated for a fractured hip. The employer reported this event to Cal/OSHA within the required timeframe. The subsequent investigation found no employer violation related to Employee #1's fall.