One of the first cleanups I worked was a new pond created by back-flooding a ravine. As the water rose an oil sheen appeared on the surface, then an oil skim. A previous owner had worked as a metal drum recycler and instead of disposing of wastes properly he re-drummed everything and buried them in the ravine.
The cost of that cleanup was a couple million bucks. The landowner couldn't afford the legal battle and let the bank foreclose on the property.
