Before I moved here I never really understood why there was always steam coming out of manholes in Manhattan in the winter. My first thought was that it was the metro, second was that New Yorkers have really warm sewage (gross), and third was that maybe all of the construction workers are really members of a huge Turkish underground spa. But no, none of those hypothesis were correct.
The steam that flows out from underneath New York streets is in fact from “The New York City steam system, a district heating system which carries steam from central power stations to heat, cool, or supply power to high rise buildings and businesses.” Thanks Wikipedia.
The New York Steam company started in 1882, it provided services for lower manhattan. The company now owned by Con Edison provides service from the Battery all the way to 96th street. It services 2,000 customers and 100,000 commercial and residential buildings.
In 1879 Wallace C. Andrews decided to take on the challenge of providing steam to New York City. Along with his Chief engineer, Charles E. Emery, The New York Steam Company acquired ten boiler plants and started laying steam mains. On March 3rd 1882 the company provided heat for its first customer, the United Bank Building.
“By 1932, the tremendous Kips Bay Station (occupying the entire block along the East River between 35th and 36th Streets) and five other stations provided steam to more than 2,500 buildings. Among them were some of New York’s most famous landmarks: Grand Central Terminal, the Empire State Building, the Chrysler Building, the Daily News Building, Tudor City, Pennsylvania Station and Hotel, and Rockefeller Center. Just about every new skyscraper was a testament to the efficiency and reliability of steam service: most were built without smokestacks or individual heating plants.” ConEd.com/history/steam.asp.
Today New York has the largest steam system in the world. There are 105 miles of mains and service pipes that provide some 30 billion tons of steam yearly for heating, hot water, and air conditioning. The steam coming up from the manholes is not caused by leaks in the steam system, but actually by outside water boiling on contact with the hot steam pipes, or other hot equipment underground.
The high pressure of the steam can cause the pipes to explode especially if they have not been replaced for centuries. In 2007 a pipe exploded in mid-town causing a 40 story high shower of flying debris and a steam cloud higher than the nearby Chrysler building. The eruption was so abrupt that people thought it was a terrorist attack, one woman died of a heart attack fleeing the scene, and another man was scalded on over 80 percent of his body.