decomposition of trash causes cave-ins

as trash decomposes, it'll leave vacancies, which will eventually cave-in and collapse -- so the spatial displacement of trash should reduce over time, and cause the terrain above it to also collapse, potentially destroying buildings or disrupting the flatness of surfaces built on top of it.
it's also really hard to dump trash that it's flat :)

I really, really do not want this. This is not that kind of game.

On the other hand, I think it should be that kind of game.