They Shoot Steam, Don’t They?

The Times explains Manhattan’s good old steam heat and what to look for to avoid trouble:

The gray mist that rises from manholes when water touches the steam pipes below seems as much a part of the New York landscape as hot dog vendors.

But five days after a steam pipe exploded in Midtown, leaving one person dead and injuring dozens of others, New Yorkers had reason to be apprehensive about the vapor, particularly after heavy rains yesterday produced fresh trails of steam from manholes around the city.

Bob Flanagan, a 29-year veteran of Con Edison’s steam division, was particularly careful yesterday as he circled the city in search of vapor plumes, which might indicate a problem with the steam pipes below.

Because water collecting inside a steam pipe or seeping into one has been a cause of previous pipe ruptures, the company routinely checks manholes for vapor after rainstorms and pumps out water that reaches the height of the pipes.

There are several possible causes of vapor streams. One is rainwater, which vaporizes when it hits the hot pipes. Sometimes water mains leak onto steam pipes. And Con Edison sometimes intentionally lets off steam during underground construction.

“I’m looking for something over one foot high but with a little force behind it,” Mr. Flanagan said, before driving his minivan past a swirl of steam at the intersection of East Broadway and Pike Street in Lower Manhattan. Without a map, he drove over the steam mains beneath South Street, Water Street, Broadway and smaller roads, pointing to buildings that buy steam from Con Edison.

Every few minutes, he spotted a “whispering” vapor stream too thin to worry about. But about five times during his one-hour loop, he found a manhole that “gushed” steam strong enough that he radioed a dispatcher, who then sent a crew to pump out the water accumulating below.

Mr. Flanagan is one of 10 Con Edison supervisors who travel the city streets after rainstorms. There are also 12 two-person crews around Manhattan that pump out rainwater.