OldBaldGuy:

Water tunnels is a foreign term to me, so I assuming that is the big tube that brings lots of water into the city. But I also assume that there are smaller "pipes" bringing water into individual buildings, wouldn't those be vulnerable???

Watch "Die Hard 3". These "tunnels" are big enough to put trucks through.

Document on City Water Tunnel #3 (PDF). Under Construction since 1970. Stage 1 complete in 1998. Final Stage 4, expected completion 2020.

Probably obvious, but this transportation nightmare affected all subway lines, LIRR and Metro North.

Die Hard 3 - IMDB Trivia Page Mentioned scenes filmed in City Tunnel #3