The Underground Booty Squad
These tunnels may be storm drains, or they may be sanitary sewers, we don't know yet because we haven't been there. Pretty much just a simple system of two parallel tunnels under Maria Ave and Mounds Blvd, and several connecting tunnels. About a mile of total tunnels. This system probably would extend more to the east but the level of the surface goes uphill meaning that it would require more digging through the limestone bedrock to get down to the sandstone which would be too costly.
-Tunnelcity, 2004