EE WAS OPERATING A SCOOP TO KNOCK OUT A STOPPING BETWEEN ENTRIES & CLEAN UP BLOCKS & OTHER MATERIAL. WHILE SCOOPING, THE BUCKET PICKED UP A 20' SECTION OF 4"" DIAMETER HARD PLASTIC PIPE WITH A METAL COUPLING ON ONE END. THE END OF THE PIPE OPPOSITE THE OPERATOR HIT THE RIB & THE COUPLING END CAUGHT THE INNER CORNER OF THE BUCKET ON THEOPERATOR'S SIDE, BOWED & STRUCK HIM ON THE HEAD.