WHILE HYDROBLASTING INTERIOR OF TANK RAILCAR DIRECT WATER PRESSURE FROM WAND EXTENSIVELY LACERATED LEFT FOOT; DUE TO EMPLOYEE CARELESSNESS IN OPERATION OF WAND & FAILURE TO RE-POSITION AS NEEDED FOOT SHIELD OF LEG/FOOT PPE TO ENSURE PROPER COVERAGE WHERE MOVEMENT WITHIN TANK CAR CAUSED SHIELD ""FLIP UP"" TO MORE VERTICAL POSITION & LEFT TOP OF FOOT/RUBBER BOOT IMPROPERLY EXPOSED.