>>892834>soundproofSecure thick carpets or foam pads on the walls and ceiling. It won't look pretty, but it'll work.
>GPR proofShape your bunker with lots of steep angles, then coat the outer layer in lightly magnetized ferrous dust
>IR proofHeat rises, and the top of your bunker is closest to the surface. Maybe coat some mylar in fiberglass or PVC and layer it between the top of your bunker and the surface? Otherwise, I suppose you could rig a cooling system that uses cool water and copper piping to collect unwanted heat from your structure.
Unfortunately, OP - unless you have a shit ton of money and resources you're probably not going to be able to get this done without anyone knowing. What IS reasonable is to get it built, stock it like a storm shelter and play it off as such. In 40-50 years when everyone forgot about it and your grandkids inherit it, they'll be able to use it secretly for sex crimes and drug smuggling.
