EMPLOYEE WAS REMOVING DISCHARGE HOSE FROM TRASH PUMP. THE PUMP WAS OFF & THE HOSE NEEDED TO BE REMOVED SO THE PUMP COULD BE PLACED IN STORAGE. WHEN THE DISCHARGE HOSE WAS REMOVED, HOT WATER, M UD & GRAVEL SPILLED ON TO THE BOTTOM OF THE EMPLOYEE'S LEFT FOREARM. THIS RESULTED IN A MILD 2ND DEGREE BURN. PUMP MAIN CAUSE.