EMPLOYEE WAS OPERATING A WATER WAGON WHEN THE STEERING FAILED (HYDRAULIC HOSE FAILURE). THIS CAUSED THE WATER WAGON TO LEAVE THE ROADWAY. WHEN THE WATER WAGON CAME TO A STOP, THE EMPLOYEE STRU CK THE SIDE WINDOWS, WHICH WAS RESULTED IN A HEAD LACERATION. THE EMPLOYEE ALSO INCURRED TWO MINOR RIB FRACTURES ON THE LEFT SIDE OF HIS CHEST AREA. WAS WEARING HIS SEAT BELT.