It's not a prison. It's a cage. Faraday cage. Built to protect people who are sensitive to electromagnetic radiation. But you know what happens when you have such a closed society for a long time. Things get weird. There's no conspiracy, but this almost amish-like community now holds more power than most towns - they are not dependant on electricity and use mostly steam-powered machinery. So they are the only ones with running water and medicine and order in a world gone to hell after an EMP bomb.