A perpetual problem with such facilities is that they need a lot of design to do them properly. So a good thought problem is to begin with a nonsensical imaginary budget, say $100m, with the idea that you have to spend all of it building the facility.
The purpose of the exercise is “over-design”, to have every “bell and whistle” you could possibly want, along with energy, water and food supply, recycling of air, water and waste, ergonomics, security, entertainment, lots of redundancy, tools and spare parts, etc.
There is a method in this madness.
Biosphere II is a superb example of what could go wrong in a sealed environment that was supposed to be self balancing. Their carbon dioxide levels wildly fluctuated, many of the vertebrates and the good insects they brought with them died, and invasive insects, like cockroaches and ants were everywhere.
It cost about $100m, yet their design was poor and they made way too many assumptions.
And this is the real problem with any bunker. You really have to consider what you need, and what you don’t need, and what your limitations are.
And starting from the imaginary fantasy budget, you have to downgrade all the way to your realistic budget, which means that a lot of the stuff you thought you needed was superfluous, and that you have a pressing need for other stuff you hadn’t previously considered.
So the quality of your design, with a realistic budget, becomes a lot better.
For $100 million I’d have tunnels everywhere with rail systems for moving stuff and peeps, laid on a sidewalk so you could run on the ssids of the tracks or in between, they’d be hundreds of yards long with two being a mile away and each hhaving two openings at the distant ends.
one to go straight out the top to ground level and another to enter a pod stocked with everything “I thought” I needed, including plenty of fuel for some sort of aircraft, to get me to another bug out and two off road vehicles to continue loitering but, enabling me to move quickly back to base, wherever that it is.
I’d also make sure each pod had 200 years worth of popcor , Reesez Cups, Peanut M&M’s, Lindt White Chocolate Truffles, beer, vodka, scotch, wine and cigarettes.
It’d also be stocked with Metamucil, cuz for sure my list didn’t have anything with fiber in it.
Almost forgot: Dogs. Can’t live without dogs. So I’ll store food for them as well.