Deep Beneath Manhattan’s Streets: The Construction of NYC’s New Subway

There are large, damp, labyrinthine caves and hulking monsters beneath the borough of Manhattan. However, they are not the kind that feature in B movies, but rather are the product of human industry. These vast caverns under one of the world’s most vibrant cities have been bored, drilled and blasted to create New York’s newest subway, the Second Avenue Subway. Inside the cavities are bright yellow “monsters,” the heavy machinery required for such a massive undertaking.


Image: Metropolitan Transportation Authority / Patrick Cashin
A shaft of light resembles a laser piercing the tunnel’s fluorescent lighting.

Down in the tunnels, it’s easy to forget that the busy streets of the metropolis are no more than 90 feet (27.4 meters) above. In contrast with that highly urban environment of concrete and petrol fumes, here it is muddy, slippery and smells of earth. New York Times photographer Richard Barnes describes the environment as “a completely different, bizarre world. I compared it to Piranesi’s etchings because of the strange spatial component and the shades of gray.”


Image: Metropolitan Transportation Authority / Patrick Cashin
Light filters through from above.

The Second Avenue Subway has been called “The Line That Time Forgot.” In the past, the project was started and then stopped several times thanks to World War Two and the financial woes of the Great Depression and later the 1970s. The subway – which will run from Harlem’s 125th Street and Lexington Avenue down Second Avenue to Hanover Square – was first proposed as far back as 1929. Yet it was only on April 12, 2007 that construction finally began in earnest. These photographs show the latest work at the site of the underground 86th Street station.

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Image: Metropolitan Transportation Authority / Patrick Cashin
The ground beneath the heavy machinery is muddy and slippery.

Commuters on the heavily-populated Upper East Side of Manhattan may be thankful for the new construction, as they currently have only one rapid transit option – the overcrowded IRT Lexington Avenue Line, which has to cater to a staggering 1.3 million riders a day. That’s more than the daily traffic of the whole Washington Metro system!


Image: Metropolitan Transportation Authority / Patrick Cashin
Currently, the floors and ceilings are made up of gray rock.

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The Second Avenue Subway will be eight-and-a-half miles (13.7 kilometers) long. As you might expect, building a subway system of any length underneath a large city full of towering high-rises and skyscrapers is not a uniform procedure. Most of the tunneling has been done with a tunnel boring machine, but other methods, such as cut and cover as well as drill and blast, have also been used where required. Two of the stations, at 72nd Street and 86th Street, have been mined – but fortunately for the buildings above, with only two shafts needed.

In the 19th century, it was up to humans alone to judge the safest and most effective places to put their explosives when tunnel blasting. However, over the years, techniques have changed considerably, and today computers undertake a range of crucial tasks, including designing blast patterns and drilling and monitoring blast holes. Everything needs to be carefully calculated, because accidents involving underground explosives can be catastrophic.

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Image: Metropolitan Transportation Authority / Patrick Cashin
The workers must have been on a coffee break when these photos were taken.

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Although there is between 85 feet (25.9 meters) and 90 feet (27.4 meters) of solid rock separating the mined stations from the city above, that doesn’t stop the vibrations being felt on the surface. Around East 72nd Street, shaking buildings jangled the nerves of those living near to the blast site while the work was in progress. And at the 86th Street site, blasting is expected to rattle the locals until November 2013.


Image: Metropolitan Transportation Authority / Patrick Cashin
The yellow tape cautions those near this section of the construction.

Another possible source of aggravation for people living above the new subway’s construction site is air pollution. After residents around the East 72nd Street site complained of dust and bad odors from the construction, air at 86th Street is being carefully monitored. Measures aimed at controlling smoke and dust have also been improved following criticism surrounding the East 72nd Street construction.

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Image: Metropolitan Transportation Authority / Patrick Cashin
Some machinery used in the construction process, inside a smaller tunnel

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Sometimes it’s more than vibrations and dust that affect the surface level above the blasting. On August 21, 2012, a tunnel blast got out of control, causing an explosion that sent lumps of rock flying up to eight stories into the air, shattering windows and startling all those in the area at the time. Fortunately, there were no reported injuries, and inspectors found that none of the surrounding buildings appeared to have been structurally damaged. Still, it’s a cautionary indication of the possible disasters such projects might cause if they are not carefully managed.


Image: Metropolitan Transportation Authority / Patrick Cashin
It’s hard to picture smooth walls and sleek trains in these surroundings.

If building the Second Avenue Subway presents a few inconveniences for those at the surface, it is dirty and potentially dangerous work for those who must go below ground to dig out these gigantic caverns. Around 475 workers, known as “sandhogs,” labor in muddy conditions under fluorescent lights to blast, drill and concrete the tunnels, with only short breaks for lunch.

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Image: Metropolitan Transportation Authority / Patrick Cashin
Machinery stands between two vast portions of rock.

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So far, no sandhog has died while working on the Second Avenue Subway tunnels, although injuries have occurred. One worker lost a finger in an accident, while in a separate incident, another became trapped up to his waist in mud – and it took over 100 emergency workers four hours to free him. Still, those who labor here know the dangers; Aaron Profit wears a pendant of St. Barbara. “St. Barbara is the patron saint of miners and airplane pilots,” Profit told The New York Times. “She’s the patron saint of instant death. If something was to happen, that you would die instantly instead of suffering.”


Image: Metropolitan Transportation Authority / Patrick Cashin
We wonder how deep this pool of groundwater is.

In times past, building a subway like this would have relied largely on manpower. Workers with pickaxes would have had to manually cut their way through the rock, unless they blasted it with dynamite. These days, there is assistance from equipment like the hard rock tunnel boring machine. Also known as a “mole,” this machine powers through rock using disc cutters mounted in its head. The cutters slice away the rock ahead by creating stress fractures.

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Image: Metropolitan Transportation Authority / Patrick Cashin
The digger looks like a toy within the giant tunnel cavern.

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Sometimes, even more sophisticated techniques are used to hollow out the tunnels. In one section, the rock was not solid enough to dig through without endangering the buildings above. In this case, the ground was frozen solid by pumping calcium chloride brine chilled to -13 degrees Fahrenheit (-25 degrees Celsius) into it for 10 weeks before drilling.


Image: Metropolitan Transportation Authority / Patrick Cashin
Cat on the prowl beneath the ground

The terrain along the subway route is by no means uniform. Some sections pass through solid rock, others through sand and silts. There are also faults and fractured rock to consider. And it all makes digging the tunnels a real feat of engineering.

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Image: Metropolitan Transportation Authority / Patrick Cashin
Workers who don’t like heights can’t enjoy using the zig-zagging stairs at the back of the shaft.

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At the moment, the Second Avenue Subway is scheduled for completion in December 2016, at a cost of over $17 billion. The project has not been without its critics and unfortunate incidents, but once it is completed, it should prove a benefit to the many who will have a new public transport option for their daily commutes – and that has to be a good thing.

Sources: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13

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