Ask a New Yorker about the Second Avenue Subway and you’ll usually get a laugh. The city first drew it up in the 1920s. It spent the next hundred years getting proposed, funded, shelved, and proposed again, and only opened its first three stations in 2017. East Harlem, the part that was promised the most, is still waiting.<\/p>\n
That changed a little on June 8, when the MTA broke ground at 120th Street and Second Avenue. The thing that’s finally supposed to finish the job isn’t another study or funding formula. It’s a machine. A 700-ton tunnel boring machine, built in Germany, designed to read the ground in front of it and swap its own tools as it digs.<\/p>\n
There’s a good coincidence buried in the dirt. The last time the city broke ground on this tunnel was 1972. At the groundbreaking, Governor Kathy Hochul pointed out that the Knicks were in the middle of what became their last title run for decades. She undersold it. Within a week, the Knicks won their first championship since 1973.<\/p>\n
Here’s what makes this borer different from the ones that dug the subway a century ago. It’s a variable-density machine, which is a real engineering category and not marketing. When it hits hard rock, it uses one kind of cutter. When it hits soft soil or sand, it switches to another, and it does that on the move without stopping the dig.<\/p>\n
That matters more than it sounds under East Harlem, where the ground flips between solid Manhattan rock and loose, wet fill. The machine’s 23-foot tungsten-carbide cutterhead, about seven meters across, grinds the face while the machine injects a slurry of clay, cement and water to hold the loose earth in place so the hole doesn’t cave. Crews working behind it never actually see raw dirt. The concrete lining goes in as fast as the tunnel opens.<\/p>\n
The whole point is not getting stuck. Kurt Egger, an MTA executive on the project, told Gothamist<\/a> the design takes away the risk of hitting a ground condition you weren’t ready for and having to stop cold. New York learned that lesson on the first phase, and Seattle’s Bertha<\/a> is the cautionary tale that still hangs over the whole industry. The largest boring machine in the world at the time, she jammed roughly 1,000 feet into a 9,270-foot dig in 2013 and sat there for two years.<\/p>\n The machine weighs more than 1.5 million pounds, comfortably north of 700 tons, and it isn’t small in any direction. Assembled, it runs 250 to 300 feet long, and it can chew 35 to 40 feet of tunnel a day. The MTA is bringing in two of them.<\/p>\n A machine this size doesn’t arrive on a flatbed and roll into a tunnel. It shows up in pieces from Herrenknecht in Germany, and the MTA figures it will take at least three months just to get it down to the launch site at 120th Street before crews can even bolt it together underground.<\/p>\n That access problem is the real headache, not the digging. “The hardest part of the job is the access points,” Magued Iskander, a geotechnical engineering professor at NYU, told Gothamist. You have to lower a machine the length of a football field into a hole in the middle of Manhattan and assemble it there.<\/p>\n Not everyone builds tunnels this way. In Nashville, Elon Musk’s Boring Company<\/a> runs machines that skip the launch pit entirely. They tilt off a truck nose-first into the dirt and dig with nobody underground. Those are 12-foot, car-sized bores, though. The MTA is threading a full two-track subway under a dense neighborhood, and that job still needs the shaft, the crane and the months.<\/p>\n If you follow New York tunnels, it’s easy to mix this one up with the other giant German borer in the news, and they are not the same job. Across the river in New Jersey, the Gateway Program is bolting together a Herrenknecht machine to dig new rail tubes under the Hudson<\/a>.<\/p>\n That one is a different animal. It weighs 1,680 tons, swings a cutterhead almost 29 feet across, and has to chew through the Palisades diabase, rock so hard and abrasive that crews expect to swap worn cutters every couple of days. About 40 people ride inside it while it works.<\/p>\n The East Harlem machine is lighter and works in softer, wetter ground. Same manufacturer, same basic idea, two completely different problems. Herrenknecht borers are grinding under a half-dozen cities right now, from Washington to London to Sydney, which tells you how standardized this once-exotic work has become.<\/p>\n The reason this keeps getting framed as a minor miracle is that the city has genuinely tried and failed for a century. The Second Avenue line was first proposed in the 1920s. Voters approved a bond to build it in 1948, and then the money went elsewhere after the Korean War started.<\/p>\n Construction actually began in East Harlem in 1972. Three years later, the fiscal crisis nearly bankrupted New York, the work stopped, and the tunnels just sat in the ground.<\/p>\n Those old tunnels are now part of the plan. According to Governor Hochul’s office<\/a>, reusing a segment built in the 1970s between 110th and 120th Streets is a big chunk of how the MTA says it’s saving more than a billion dollars against the cost of Phase 1. The machine only has to bore the new stretch, from 120th up to 125th and then west toward Lexington and Park.<\/p>\n Hochul called the whole thing “a dream nearly a century in the making,” which is the kind of line politicians reach for at groundbreakings. In this case the math backs it up.<\/p>\n The tunnel boring is Contract 2, and the MTA put it at $1.97 billion. That covers more than the dig: the shaft the machine gets lowered into, controlled blasting for the future stations, and stripping asbestos and lead out of those 1970s tunnels before anyone reuses them.<\/p>\nGetting it into the ground is the hard part<\/h2>\n
This isn’t the machine digging under the Hudson<\/h2>\n
New York has broken ground on this before<\/h2>\n
The contract pays for more than a hole<\/h2>\n