Garbage Demolish Trick?

If you have a garbage dump and you demolish a dump zone dose the trash go somewhere else in your city or does the garbage in it disapear.  Beacuse the dump zone is free, if the garbage in it dose disaperar when you demolish it (and it seems to) then you don't need incererators at all.  Every once and a while you simply demolish the old dump zone and build a new one.  This is a problem if it works, and breaks the game.  Can you people at EA fix it.  I don't know if this works or not, but it seems to.