Hamilton Harbour would be a good place to start. There are lots of sites all around the Great Lakes. The Great Lakes basin has been North America's industrial home base for probably a couple of hundred years. It's waning now, but the legacy of pollution is all around the shores.
I'd have to give some further thought to exactly where I would recommend you go. It's a big geography in the basin, but certainly the areas of concern identified by the international joint commission would be a good place to start.