Working on old trucks involves a bunch of chemicals, grease, oil, and such sludges.
For example the shop has a 5 gallon bucket of water based degreaser that I recently drain from my parts cleaner. In ancient times this would have been hucked over the fence, but we need to be conscience of where all this garbage goes these days. So I'll put a lid on it and haul it over to the chemical waste place. It's easy being green.