EMPLOYEE AND CO-WORKERS WERE WORKING ON THE JAW CRUSHER AT THE QUARRY, SHORTLY BEFORE NOON EMPLOYEE WAS WITNESSED FALLING FROM THE SUPPORT STRUCTURE TO THE GROUND. EMPLOYEE WAS TREATED AT THE HOSPITAL. DURING THE ACCIDENT INVESTIGATION IT WAS DETERMINED THAT EMPLOYEE HAD CROSSED OVER A HANDRAIL ONTO A PIECE OF UNGUARDED CATWALKING. THE STRUCTURE FAILED AND THE EMPLOYEE FELL 15'.