EE WAS ISNTALLING BAG OF FLOG, WHILE PUSHING THE ROCK BAG ON THE TROLLEY THE TROLLEY HUNG UP ON A PIECE OF RUBBER AROUND THE TROLLEY WAY. THE EE SECOND EFFORT TO MOVE THE FLOC CREATED A SHARP PAIN IN HIS LOWER BACK. THE EE CONTINUED TO WORKHIS REGULAR JOB AT FULL CAPACITY UNTIL 10-2-00, AT THIS TIME THE OCCURRENCE BECAME REPORTABLE DUE TO WORK DAYS MISSED.