I stand corrected. I just checked my references. Steam lines are all over Manhattan from the Battery up to about 96th Street. They aren't built in any regular grid system, so yeah, it would be really hard to know where they are. And they don't give any warning when they go. Many of the lines are the old, brittle cast iron pipes (insulated with asbestos no less).

IIRC, NYC is close to some significant fault lines . They aren't very active, but there is evidence of some pretty large quakes in the past. So it is just a matter of time.

Thanks for bringing this all up. Gives me something to think about on my way to work besides terrorist attacks and subway disasters.