Actually Oak Ridge is about 140mi east and Redstone 100mi south (as the crow flies)
There are no subways or even light rail in Nashville.
There is however an underground steam system used to heat buildings
https://nashvilledistrictenergy.com/about/
light rail is proposed - its never been built
yeah, a 1 mi radius up to 3000ft. Hardly a large space. About the same as they put around football stadiums during games.