[decimon]

I’ve heard rumors that there is the same type of thing under San Antonio that is military related, but never could confirm the rumor and can find nothing on the internet.

My quick search reveals that San Antonio is one of the most flood prone areas of the US. If so then it's not a great place for tunnels.

[ravingnutter]

Yes, we do have flooding, that’s for sure. Like I said they are just unconfirmed rumors told to me by several different people that have lived here all their lives. Me, I’m not a native, but I got here as quick as I could and married one ; )