What Lies Beneath?

The July steam pipe explosion in New York City raises questions about the city’s underground infrastructure, asbestos in pipe insulation, and how to rebuild.

September 1, 2007

New York City moves at a pace that is unmatched, so when a large underground steam pipe ruptured in the middle of rush hour on Wednesday, July 18, 2007, it was no small disruption in the city’s usual state of constant motion. The explosion took place near Grand Central Terminal at Lexington and 41st Street. Because it occurred near a water main, the result was a blast of steam, water, and debris shooting hundreds of feet into the air. The eruption left a 25-foot crater in the street, a wrecked tow truck in the middle of the hole, and the windows of a nearby (and luckily empty) school bus blown out. More than 40 people were injured, and one woman died of cardiac arrest. As serious and frightening as the explosion was, there was some comfort in the cause: Mayor Michael R. Bloomberg was able to promptly point to a steam pipe, rather than terrorism, as the root of the explosion.

The 24-inch pipe was laid in 1924 as part of the 105-mile steam system now maintained by Consolidated Edison (Con Ed) as a vital energy conduit for many commercial and residential Manhattan buildings. It has been hypothesized that heavy rainstorms may have left the pipe surrounded by cold water, causing dangerous condensation in a closed section of pipe, which led to the blast. This phenomenon, known as water hammer, occurs when cold water mixes with steam, and pressure in a pipe increases dramatically.

The New York City explosion raised many critical questions, including the following:

  • Would asbestos—which the pipe was wrapped in—be found in the air and the debris?
  • How would the clean-up be handled, and how quickly could businesses in the area be back up and running?
  • What about the underlying infrastructure for this and similar systems in other cities? What are the chances that this will occur again, and how can it be avoided?
Testing for Asbestos

The number one concern for city officials was the possibility of asbestos in the air. Like many older pipes, this one was wrapped in asbestos for insulation. Unfortunately, this was not the first time Con Ed and New Yorkers faced the fear of exposure. In 1989, a major steam pipe explosion occurred near Gramercy Park—killing three people—and the company waited 4 days before notifying area residents that they might have been exposed to the carcinogen. This time, apparently having learned from the earlier misstep, company representatives said almost immediately after the blast that they assumed asbestos had been released into the air.

Within an hour of the incident, Con Ed had shut down parts of Manhattan’s underground system and stopped the blast of steam. As repair personnel assessed the damage and dug through the rubble, testing for asbestos began and an investigation got under way. The city enforced a “frozen” zone between 40th and 43rd Streets, and between Vanderbilt and Third Avenues.

According to a press release from Con Ed, following the steam-pipe rupture, Con Ed and the New York City Department of Environmental Protection (DEP) conducted extensive air monitoring in the area, testing numerous samples of muddy debris for asbestos. It was confirmed that there was no airborne asbestos present, although several samples of debris did contain asbestos.1

The Clean-Up Begins

Clean-up efforts at the site began as soon as the steam was turned off and the workers could get started. Fire Department crews hosed down building exteriors in the frozen zone around Grand Central Terminal. According to NYTimes.com, the U.S. Environmental Protection Agency (EPA) said that special street sweepers with high-efficiency filters were set to start roaming the area vacuuming up debris.2

A New York City Office of Emergency Management (OEM) press release stated that OEM is coordinating the interagency response to the explosion. Other agencies participating in the effort include the New York Police Department (NYPD), the Fire Department, the DEP, the Department of Health and Mental Hygiene (DOH), and the Metropolitan Transit Authority. Fortunately, there are no structural defects or breaches of the subway infrastructure, and no debris from the explosion was found in the subway tunnels nearby.3

Specially trained contractors are leading the clean-up efforts, and building inspectors and forensic engineers are helping OEM. Electrical work also is necessary before the frozen zone can be opened up again fully. As of July 20, a Con Ed press release noted that all but 5 of 19 steam service customers in the area had their service restored, and work was continuing to restore the remaining customers’ service.1

Several steps must be taken before buildings near the blast can be reopened. Owners of contaminated buildings will have to hire qualified inspectors to check their ventilation systems and interior spaces for asbestos. If buildings are found to be contaminated, owners will have to hire certified contractors to clean them before occupants can return. (Con Ed will reimburse owners for these efforts.) According to NYC.gov, the following steps must be completed before New York City will clear a building for reoccupation.

  • Street entrances must be cleared for pedestrian traffic.
  • Utility services must be restored.
  • Building owners and managers must submit building inspection, clean-up, and testing results to the DOH.
  • The Fire Department must approve the building for public access.
  • The building must be inspected by the DOH and cleared for re-entry.4

A July 24, 2007, press release from the Office of the Mayor notes that Governor Eliot Spitzer and Mayor Bloomberg have announced that the State has requested a Physical and Economic Injury Disaster declaration from the federal Small Business Administration (SBA) to assist New York businesses affected by the steam pipe explosion. If approved, this will provide additional aid to business owners as they try to rebuild. More than 1,000 business suffered severe economic damage from the incident.5

Could the Blast Have Been Avoided?

Of all the questions raised by the explosion, perhaps the most important is whether the incident could have been avoided in the first place. The underground infrastructure in New York City and other U.S. cities consists of miles of steam pipes, some of which date back to the early 1900s and are wrapped in asbestos insulation. Perhaps it is time to examine whether these pipes should be replaced altogether—a topic on which there are varying opinions.

According to NYTimes.com, in March, Con Ed workers repaired a leaking steam main under 41st Street and Lexington Avenue, the site of the July 18 explosion. Con Ed says that on March 14, repair crews patched a minor leak where two segments of the pipe were joined. On June 10, Con Ed responded to complaints about another, smaller pipe that was leaking about 25 feet east of the main pipe that exploded at the Midtown intersection. The large pipe that eventually burst was visually inspected on June 8 and again on July 18, just hours before the explosion, and workers noted no cause for concern.6

Clean-up must be completed before workers can climb down into the crater and investigate the pipe, which lay about 15 feet below the street, along with wires, cables, and sewer pipes. To many, it seems that the age of the system would have to play a role in such a massive failure; but Con Ed notes that parts of the steam pipe network in the city are 100 or more years old with no history of failing, so the pipe’s age should not have been the issue. The most likely scenario is that cold water from the rain, and the resulting condensation, led to the blast.

Steam is a critical component of New York City’s power infrastructure, as well as those in other Northern cities like Boston, Chicago, and Philadelphia. It is used to power buildings like the Empire State Building and Rockefeller Center, as well as hospitals, museums, and colleges. It consumes less space than alternatives, such as boilers or other bulky and expensive machinery, and it is a greener technology than other options because in many cases it is a by-product of electricity generation. Because steam pipes are buried, they are usually less susceptible to extreme weather conditions.

Still, a massive explosion in the middle of Midtown calls the city’s infrastructure into question, just as it did after the Gramercy Park explosion in 1989. NYTimes.com reports that Con Ed replaced its cast-iron piping with stronger steel pipe and removed or replaced more than 200 vulnerable pipe joints since that event. It also replaced the asbestos insulation with woven fiberglass in all of its manholes and anywhere crews have repaired steam pipes. It has left asbestos-wrapped pipes in other places because replacing them would involve digging up most of the streets of Manhattan.6

So the question, in the end, might be whether the July 18 explosion indicates that a more expensive and disruptive “emergency” approach should be taken on a wider scale throughout the city as a preemptive measure.

Disclaimer: Whenever asbestos must be removed or cleaned up, use a licensed asbestos abatement contractor. For more information, go to www.insulation.org. Unless specifically noted at the beginning of the article, the content, calculations, and opinions expressed in any article in Insulation Outlook do not necessarily reflect the views of the National Insulation Association (NIA).


(1) www.coned.com/newsroom/news/pr20070720.asp
(2) www.nytimes.com/2007/07/20/nyregion/20asbestos.html?ex=1187236800&en=de9074df643157a3&ei=5070
(3) http://home2.nyc.gov/html/oem/html/pr/07_07_19_steam_pipe3.shtml
(4) http://home2.nyc.gov/html/doh/html/ei/20070725_asbestos.shtml
(5) www.nyc.gov/portal/site/nycgov/menuitem.c0935b9a57bb4ef3daf2f1c701c789a0/index.jsp?pageID=mayor_press_release&catID=1194&doc_name=http://www.nyc.gov/html/om/html/2007b/pr25407.html&cc=unused1978&rc=1194&ndi=1
(6) www.nytimes.com/2007/07/20/nyregion/20explode.html?ex=1187236800&en=09c32e3b293a7c00&ei=5070