Picture a streetscape, New York City at night. Even if you’ve never been you probably have a clear picture in mind. Flickering neon bar signs, the subway rattling underfoot, a solitary cop walking his midnight beat – and a backdrop of steam, pouring out of the pavements.
It’s an integral part of our perception of Manhattan. For the opening shot of Taxi Driver, Scorsese chose to show steam rising from a grill. It gives us location and mood – decrepitude, tension, and, to borrow a line from Tom Waits, a feeling “like the whole goddamn town is ready to blow”.
The plumes rising from New York’s manholes are real – but they are not the product of an ancient, broken down sewer system, or a side effect of the subway trains, as one might assume. In fact we are seeing the world’s largest steam heating networks in action.
The first city-wide heating steam networks sprang up across North America in the 1870s. In 1882, the commercial New York Steam Company completed its own network, covering Manhattan from the Battery right up to 96th Street. Its pipes delivered steam from generator plants, to paying customers the length of the city.
This steam was used in laundries, to sterilise hospital equipment, and to humidify valuable museum exhibits. Most of all, it was used to keep buildings warm during the harsh -25C winters.
At its height, the network was used by over 2,500 buildings, among them some of New York’s most famous landmarks: Grand Central Station, the Empire State Building, the Chrysler Building, Rockefeller Center. Each new skyscraper of the gilded age was a testament to the steam service’s efficiency – just plumb in and you’re set. (Some have suggested this ease of use actually contributed to the network’s decline, as lower-level customers got away with illegally tapping the main lines.)
What is really going on under the streets of New York. Image: Con Edison.
Though today it serves only 1,800 buildings the network is still going strong. It’s now owned by the power giant Con Edison, and its scale is still incredible: three thousand vents and manholes pepper a network which comprises 105 miles of piping, taking 11m tonnes of steam around the city.
But even with an army of workers maintaining the ancient pipes, things have occasionally gone wrong. Since 1987 there have been 12 steam pipe explosions in the city. Two people were killed in 1989; in 2007 an explosion at a busy intersection during rush hour injured 45. Eye witness accounts describe a boiling plume of steam rose as high as the nearby 77-story Chrysler building.
That’s not the only reason more cities haven’t built their own steam heating networks: a system like this can only ever be viable in a big, densely-populated area like Manhattan. The infrastructure of heavily insulated ceramic piping doesn’t come cheap, so must service whole blocks, rather than individual buildings. Similarly the system relies both on a huge centralised boiler system and injections of waste steam from large power plants located close by. None of this is easy to replicate in a city that already exists.
Incidentally, the stuff we see rising from manholes isn’t steam from inside the system at all. On cold, wet nights, rain and other condensation enters the ventilation system where it comes into contact with the hot pipes. The result is perfectly harmless plumes of water vapour, pouring up from the streets.