Abstract: At approximately 3:00 p.m. on July 18, 2013, Employee #1, employed by a construction company, was operating a hydraulic pile driver machine at a commercial building site. He dropped the pile sheet into the ground slot. Then, as he raised the vibro hammer to an approximate height of 30 feet, one of the retainer/fastening bolts sheared off inside the fixed jaw of the hydraulic clamp. The load now was supported by only one bolt. Due to vibration, that bolt loosened. The jaw along the bolts came out from the hydraulic clamp body, fell, bounced off the pile sheet, and struck Employee #1's left foot. This occurred as he stood approximately 15 to 20 feet away from the suspended hammer's danger zone. Employee #1 was transported to the San Leandro Hospital, where he was admitted and treated for displaced fractures of the second, third, and fourth metatarsals in his left foot. He was discharged on July 20, 2013. Based on the interviews conducted and documentation developed during the subsequent investigation, it was determined that neither the general contractor nor the subcontractor (Employee #1's employer) had violated any of the Title 8 code sections. Employee #1 and all his coworkers were well experienced and trained. At the time Employee #1 was injured, he and all his coworkers were standing away from the danger zone and not under the suspended load. The foreman performed daily inspections of the bolts in question. They had been physically checked that day with an ellen wrench, and they were not loose when checked. There definitely was no overloading of the hammer vibro jaws. This was the first time the employer had encountered a bolt failure. According to the investigation report, the bolt may have failed due to metal fatigue.