Abstract: At approximately 11:34 p.m. on August 1st, 2017, an employee was working to identify a potential hydraulic leak on the side arm of the Refuge Truck Number 2401. A coworker was assisting and helped identify a potential location where leaks often occur, which was at a cap/bolt on top of the arm. The employee lifted the side arm and began to loosen the bolt, when the hydraulic pressure suddenly released, the side arm came down, crushing the employee's right arm between the side arm and the cab of the truck. The local Fire Department had to use the Jaws of Life to get the employee out, and he was eventually air lifted to a nearby hospital. There were no immediate witnesses to the incident and weather was not a factor. The employee was trained in general lockout/tagout, but was unfamiliar with the hydraulic system on this truck and was unsure how to properly control the energy.