THE OPERATOR WAS WORKING ON CLEANING UP A SLURRY MESS UNDER A PRELEACH THICKNER. THE SUMP PUMP HE WAS HOSING INTO WAS OVERWHELMED WITH SOLID MATERIAL CUASING THE DISCHARGE LINE. THE CAM LOCK C AME LOOSE FROMT HE DISCHARGE LINE AFTER BEING CHRGE WITH AIR. THE OPERATOR WAS STRUCK BY THE FILING ON HIS LEFT FOREARM.