This seems to be a common dumping place. Here's an idea: buy a $100 trail camera and see if you catch anyone? Think of it as a hundred dollar creative experiment. And then if you do catch someone, make a big public deal about ENFORCEMENT. Or give up on that and admit defeat and just pick a place in the park and officially label it a place for (il)legal dumping. It's better than what we're getting now. The status quo ain't working...