^^ Well, you can always try chemical warfare. Ants use scent trails to direct other ants in the colony to food sources, dangers, and so on. If ants are returning to that area over and over, it's likely been marked by such a scent trail. That scent can be easily overwhelmed by any strong chemical odor (perfume, Lysol spray, etc). Treat the area several times over a week or so and see if the problem disappears.
By the way, this same tactic can be used to completely destroy an ant nest. Stir up the nest using a stick or similar. Dig deep to get as many warrior ants to the surface as possible. Once enough warrior ants are on the surface to defend the nest, spray them with Lysol spray (the ammonia stings them and the perfume masks the scent of the other ants in the colony). Those warrior ants will then go about the task of killing every single ant (a perceived enemy) in the colony. Afterwards, they'll die because there are no worker ants finding food to feed them.