> If society is collapsing who will cover up the hole? You pre-wire the site for demolition and set a countdown timer: if the counter is not resent regularly i

> If society is collapsing who will cover up the hole? You pre-wire the site for demolition and set a countdown timer: if the counter is not resent regularly it goes down to zero and the charges go off sealing things off. Society is needed to prevent closing things off, so if it's gone then it happens without intervention. If they accidentally go off, then things are fail-safed closed, and you have to expend resources to re-open things. If you don't want (or have) the resource to re-open then you don't have to worry about it.