Yard used as Trash Dump

[Tiger Lilly]

Our neighbors have apparently used their back yard as a trash dump for many years. This was never a problem in the summer with the leaves up, but as some of our family have started to visit the house in the fall, they have seen a real eye sore...an old, old washing machine, tires, and heaven knows what else...It can not be seen from the street, but only by us in our back yard. We hate to make waves, but is this legal??