What goes into creating a new tunnel under the Hudson River

If you’ve ever taken an Amtrak train on the Northeast Passage to New York City from NJ or north, then you’ve passed a tunnel under the Hudson River. There is also a chance that while traveling through this tunnel, your train encountered delays or even derailment.

For diehard New York commuters, this dysfunction has long been a part of everyday life, but a landmark request by the US Department of Transportation could help change that. In late March, the US Department of Transportation launched a call for $100 million in 2023 for a rail project for the New Jersey and New York area. Specifically, it proposes to help fund the construction of a new passenger tunnel under the Hudson River while at the same time repairing the old tunnel damaged by seawater during Storm Sandy. In total, the project cost is estimated at $12.3 billion.

First introduced by Amtrak, NY, and NJ Transit in 2011, the Hudson Tunnel project, which was formed to address this new construction, was over a decade ago. If the last funding request is signed into the 2023 appropriations bill, it would mark the first time it has received federal funding. To date, the project has received $800 million since 2012 from Amtrak, the states of New York and New Jersey, and has begun building two sections of the tunnel from Penn Station to 10th Street; It has also purchased space in Manhattan for a new ventilator and fan plant.

This tunnel project is part of a larger effort to improve Amtrak’s service across the country. It’s part of a broader initiative called the Gateway Program that aims to boost rail infrastructure across the Northeast Corridor from Washington, D.C., to Boston. Currently, delays going through the Hudson Tunnels affect 800,000 passengers going up and down that railroad.

The Hudson Tunnel Project will allow both pipelines to be closed and comprehensively rehabilitated [in the existing tunnel] “Without interrupting existing Northeast Corridor service,” Gateway’s lead spokesperson, Stephen Sigmund, said in an email.

He added that the project will create 72,000 new jobs and $19 billion in economic activity. “[It will] Reducing emissions and, most importantly, delivering a faster, more reliable, and resilient railroad for the 21st century in and out of New York and modernizing the busiest section of the Northeast Corridor. “

Despite the benefits of this project, its price has come under close scrutiny in recent years. Sigmund says former New Jersey Governor Chris Christie canceled a previous project of the project in 2010, and the Trump administration reviewed budgets related to the project.

For now, it looks like the project is ready to move forward in full force. This means that civil engineers will prepare in the coming years to dig into the muddy bottom of the Hudson River, which is rumored to contain the consistency of toothpaste, Chris Barkan, professor of railroad engineering at the University of Illinois at Urbana-Champaign, said in an email.

Barkan adds that while underwater rail tunnels are not a new engineering feat, they differ in some important ways from above-ground tunnels. “Big tunnels in mountainous areas are always dug through rocks,” Barkan says. While he says the Hudson Tunnel will have “large boulders on either side of the river,” it will be suspended in “sticky river bed” mud under the Hudson River.

“This is not unique but poses different engineering challenges in its construction and design compared to drilling in rock,” Barkan says.

To build underwater tunnels, engineers have three main construction options. They can take a tunnel-shielding approach, and use a wooden and iron frame to hold the tunnel shape in place while miners pull away from the ground to deepen the tunnel. They can alternatively use a tunneling machine to dig into rocks and earth to remove them mechanically. Or they can pre-make sections of the tunnel on land and then sink these tubes to the river bed, where they can be manually attached by divers.

Regardless of the technology, underwater tunnels must be built of concrete and steel to withstand the pressure from the water above. Such engineering feats are not without potential risks, but for a city like New York, Barkan says tunnels are a much better option than any above-ground solutions.

“An important benefit of railroad tunnels in urban areas like New York City is the ability to reach central urban areas without depreciating valuable real estate that can be better used for commercial, residential, industrial, or other purposes,” Barkan says. “This access allows railway stations to be placed in the most convenient locations for passengers, close to accommodation, employment and retail.”

Even if approved, newly proposed federal funds for this project will not become available until 2023 at the earliest. Sigmund says construction on the tunnel is already underway: Two sections of the tunnel’s concrete casings were completed in 2015. Achieving all the goals set in this project will be a long way to go, but ultimately it will hopefully lead to infrastructure that will last for centuries to come.

“All regulatory approvals and funding commitments have been obtained from our states and Amtrak is in progress,” adds Sigmund via email. “Our 2021 financial plan has a date of August 2023 to begin construction, and we are looking at some potential projects, such as the Tonnelle Ave bridge over the gateway to the new tunnel, for potential early work.”

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