Well, here I find again that Wikipedia has beaten me to the punch: At some airports, underground fuel pipes allow refuelling without the need for tank trucks. Trucks (or just a cart) just carry the necessary hoses and pressure apparatus, but no fuel.
Next time you fly into a commercial terminal, look for the covers that designate where the large underground fuel tanks. You can also see similar covers at your local gas station. Of course you know that all the fuel coming out of the pump isn't stored right in the box with the pump handle, it has to be stored underground. It's a pretty good idea, huh? No trucks maneuvering around taxiing aircraft, and no need for the trucks to have to continuously refill themselves. The pumps on the carts are portable, to allow for the different configurations of the airplanes.