THE CREW WAS SETTING A CONVEYOR FOR THE SAND SCREW. THE TAIL END OF THE CONVEYOR WAS SETTING ON AN ABUTTMENT APPROX.5'OFF THE GROUND. THE CREW STARTED BUILDING LEGS UNDER THE HEAD END OF THE CONVEYOR, SECURED BY THE LOADER BUCKET. EE STEPPED ON THE TAIL END TO SECURE THE SAFETY CHAINS BEFORE IT WAS LIFTED TO GET MEASUREMENTS. THE CONVEYOR ROLLED & DROPPED EE FELL ON STABILIZER.