When you say “Is it possible for the damage to disappear completely”? Do you mean is it possible to clear it all up?
Yes it is possible to clear it all up – but often you have to make a decision about how much clearing up you do.
Do you clear it up so it is no longer a danger to anyone?
If you want to do that, then you might just seal everything in concrete and leave it there.
Do you clear it up so the hazardous material is taken somewhere else?
Of you want to do that, you might just take out the dangerous material, and knock doen the buildings, but leave it covered in concrete.
Do you want to clear it all up and plant trees on it?
You can do this, but it will take longer and cost more money.
What will actually happen is that the clean up will be done in stages. They will take out the dangerous material (which will take time), and after they do this they will b able to decide what the next step is.