MARK WAS HELPING ANOTHER EMPLOYEE CARRY A 20FT. LENGTH OF 12INCH PLASTIC PIPE,(APPROX. 250LBS.) THE OTHER EMPLOYEE STEPPED ON UNEVEN SURFACE ON THE MINE FLOOR AND ROLLED HIS ANKLE. THIS CAUSED THE OTHER EMPLOYEE TO LOOSE HIS BALANCE AND DROPHIS END OF THE PIPE. WHEN THE OTHER EMPLOYEE'S END OF THE PIPE HIT THE FLOOR, THE END INJURED WAS CARRYING JARRED HIS SHOULDER.