Riders on New Jersey Transit (NJ TRANSIT )trains to New York City take 46 million trips a year. That’s over four times the ridership of just twenty years ago, and vastly more than traveled a hundred years ago when the first tunnels under the Hudson River to the new Pennsylvania Station in Manhattan were opened. Those single-track tunnels—one for trains into New York, one for trains back to New Jersey—were marvels of their age. That age passed a long time ago, as today’s riders—elbow to elbow and traveling those same two tunnels—are reminded on every commute. The Trans-Hudson Express (THE) Tunnel Project will provide significant relief: two new tracks and other improvements to bring the New Jersey-New York train commute into the 21st century.
Planning for the new tunnel began in 1993, when various agencies agreed to fund a feasibility study, and was fully underway two years later. Over the next dozen years a series of exacting studies refined the tunnel’s route, design and features, and minimized the environmental impact on the river and both shores. Preliminary engineering began in 2006; construction begins this year with projections for trains to begin running in 2017. The cost is currently budgeted at $8.7 billion, with funding to be provided by the federal government, The Port Authority of NY & NJ and the State of New Jersey.
When the tunnels open, riders on eight different NJ TRANSIT lines will have direct (transfer-free) service to Manhattan; riders on five lines will have more frequent and express service. The expanded rail service is projected to induce 22,000 drivers to leave their cars at home every weekday, reducing traffic congestion and greenhouse gas emissions.
The new trans-Hudson tunnel will reach the west side of Manhattan between 28th and 29th Street and will terminate at an expanded Penn Station under 34th Street.
In addition to the New Jersey, Hudson River and Manhattan tunnels, THE Tunnel Project includes new surface railwork in New Jersey and an expansion of Penn Station in Manhattan.
For centuries the only way to cross the Hudson River was by boat. By the 1870s, railroads were transforming American travel but the lack of rail connections between New Jersey and New York City threatened to stall the rapid growth of the metropolitan area. After decades of public debate, the Pennsylvania Railroad in the first decade of the 1900s undertook the pioneering of the trans-Hudson tunnels that remain in use today. (The “Hudson Tunnels” shown on the map above were built at the same time by a different railroad company to service downtown; these are today’s PATH tunnels.)
The tunnels will be excavated through igneous, sedimentary, and metamorphic rock types and through glacial, lacustrine, and estuarine soil deposits. Beginning at the western portal, the Palisades Tunnels will traverse almost the full thickness of the Palisades diabase sill. Continuing beneath the east side of the Palisades ridge, the tunnels will penetrate a sequence of sedimentary rocks.
The Hudson River Tunnels will continue intermittently in sandstone beneath the western portion of the Hudson River,with some mixed-face zones, before encountering a full soft-ground face. The remaining length of the Hudson River Tunnels will be constructed primarily through a thick sequence of soft, gray, clay and silt with traces of fine sand and shells.
The Manhattan Tunnels and the Penn Station Expansion will be constructed through intermixed mica schist and granite with pegmatite intrusions and various other rock types.
This generalized geologic profile was developed based on an extensive subsurface investigation program. Over 240 test borings have been drilled to date, to depths up to 400 feet below
the ground surface. If all the geotechnical borings drilled were placed end-to-end in a straight line, they would stretch for approximately six miles.
The Pennsylvania Railroad began digging its way from New Jersey to mid-Manhattan in 1902, the same year it started work on its iconic Manhattan station. The tunnels and station opened in 1910.
The new tunnels will allow up to 48 trains per hour to arrive at Penn Station during rush hours, more than doubling the current capacity of 23 trains per hour.
While Madison Square Garden now sits where the above ground Pennsylvania Station once soared, the New Jersey portal looks much as it did a century ago. The tunnels are now used and will continue to be used by Amtrak and NJ TRANSIT trains.
The original tunnels were constructed the old fashioned way: drilling and blasting through a variety of subterranean material.
A century ago, cast-iron shields were pushed through silt and clay, followed by 11-ton cast iron rings bolted by hand to form the circular body of the tunnel. Teams of sandhogs worked from both sides of the Hudson, racing to meet each other—at up to 30 feet a day—at the state line under the river.
Like all the deep-rock tunnels in this exhibit and many others around the world since the 1980s, the Trans-Hudson tunnels will be excavated by tunnel boring machines (TBM). Two types TBMs will be used for these excavations: a Hard Rock TBM for the New Jersey and Manhattan sections and a Pressurized Faced TBM with hard rock cutting capabilities for the section through mixed materials under the Hudson River.
As the TBM cuts through the earth, a tunnel lining is erected inside the TBM or tunnel shield. As the tunnel shield advances forward, the tunnel lining is left in its place. Pictured above is a soft ground TBM similar to the type which will be used for the Hudson River Tunnels.
The new station expansion beneath 34th Street will feature high speed escalators, wider platforms, enhanced safety/security systems and improved connections to existing subway lines.
This rendering shows two of the six new tracks planned for the expanded Penn Station. Eight existing rail lines will finally offer direct (transfer-free) service to Manhattan.
Commuters will have access to subway concourses at 8th and 7th Avenues, as well as additional subway and PATH service at 6th Avenue and Herald Square.