MAINTENANCE DEPT. HAD JUST COMPLETED INSTALLING A 6"" CAST IRON GATE VALVE INTO THE 6"" STEEL OVERHEAD WATERLINE THAT IS USED TO FILL THE WATER TRUCK. THE WATER TURCK WAS BACKED UNDER THE SPOUT TO BE FILLED. AFTER FILLING EE CLOSED THE 6"" VALVE AND COWORKER STARTED TO DRIVE OFF WHEN EE NOTICED THAT METAL SCREEN COVERING MANHOLE HAD HUNG ON FILLER SPOUT CAUSING THE 6"" DOWN SPOUT TO BR