An employee was cleaning a water sprinkler system used to keep rock moist before use. The employee as standing on top of the material bin wall. The wall is about 2.5 to 3 feet thick. The height of the wall is about 8 to 9 feet (3-blocks high : 6ft long by 3ft high). The sprinkler system's pipes run on the top of the wall. The employee was cleaning one of the holes on the pipe with both feet on the wall. When the employee was standing up, his right foot slipped and he fell forward 9 feet into the empty bin that was next to it. The employee sustained multiple fractures including the right scapula, left pelvis, lumbar vertebrae and two left ribs.