EMPLOYEE WAS REMOVING A COVER OFF THE SUCTION LINE ON THE DREDGE, TO REMOVE SOME ROCKS THAT HAD PICKED UP DURING DREDGING OPERATIONS. THE COVER TO BE REMOVED IS UNDER THE OPERATOR'S CAB. EMPLO YEE HAD TO BEND OVER, LIFT WITH ARMS EXTENDED AND TWIST BODY. COVER WEIGHS APPROX 70 LBS.