Last month, workers completed the installation of the spire atop One World Trade Center — making it the tallest building in the western hemisphere. The event was covered by media across the globe as a monumental achievement that took over 10 years to complete.

But there’s an equally massive construction project taking place underneath New York City that many are unaware of: the building of the Second Avenue Subway.

Patrick Cashin, a staff photographer for the Metropolitan Transportation Authority of New York, has documented the construction from the very beginning.

After 90 years of planning and delays, the Second Avenue Subway is the first line to be constructed in New York City since 1932. The $4.5 billion transportation project will improve access to mass transit and reduce overcrowding and commuter delays on the east side of Manhattan.

Phase one began in 2007 and included the excavation of new tunnels eight stories (80 feet) beneath Manhattan’s Upper East Side, as well as access shafts at 69th and 72nd Streets.

Patrick began taking pictures of the site when the first hole was big enough for workers to climb into.

“When I arrived on the scene in 2009, it was just a lot of mud and dirt,” Patrick says. “But as I kept going back, this hole kept getting deeper and deeper and soon it extended several blocks.”

Construction workers brought down and assembled a 485-ton, 450-foot long tunnel boring machine to drill through the mountain of bedrock. The machine used a 22-foot diameter cutterhead to mine 7,780 feet into two tunnels.

“I think when you’re down there for all of 10 seconds, you know that this is a dangerous place to be,” Patrick says. “When the boring machine is on and cutting, it’s loud and extremely dusty. I understand there’s about 800 workers spread out all over the project. Each are drilling, paving, moving rocks – everyone’s constantly in motion.”

Patrick visits the site every few months and each time marvels at the progression. What was once walls of thick black rock suddenly became large, empty cavernous spaces.

“What’s really impressive is when you walk through where the tunnel boring machine had cut the 22-foot hole,” Patrick says, “And and then BOOM, you’re in this huge cavern. It’s this huge hole where the 72nd Street Station is going to be, and it just hits you how big, how much digging they had to do to get this cavern made. It’s just amazing.”

The intended Second Avenue station is 110-feet high and 75-feet wide. Patrick admits being down below the city streets almost feels like being on another planet.

“This thing is definitely an engineering feat,” Patrick says. “These caverns are man-made — created from scratch. It feels like you’re in the center of the Earth but really we’re right underneath the busiest city in the world. It’s incredible.”

Patrick feels that with every picture he takes, he’s documenting a piece of history.

“10 years ago there was nothing there, and now there’s this big cavern; there are these two tubes running underneath the streets. To show the progression and how it’s being built from start to finish is pretty exciting.”

Visit the MTA’s photostream to see more of their photography.

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