Abstract: Employee #1 and several coworkers, who were working in a trolley storage silo area, climbed onto a trolley platform to clean up a macadam spill. A trolley containing approximately three tons of macadam had been programmed to dump the load into silo #2 and the hatch was open. Due to an apparently unknown electrical problem, the trolley went to silo #1 and discharged its load on top of the hatch cover. Employee #1 and coworkers began to clean off the track and silo hatch #1, and Employee #1 walked up to chute #4 to release the trolley's manual brake. He then walked back in the direction of silo #1, moving between trolley cables and atop closed silo hatches instead of using the catwalk. He was walking on top of silo hatch #2 when he stepped through the open hatch and fell approximately 27 ft into the empty silo. Employee #1 was rescued by firemen and transported to St. Claire's Hospital in Sussex, NJ, where he underwent surgery to repair a compound fracture to his left ankle.