The Long Island Rail Road (LIRR) is the biggest commuter railroad system in the country, connecting commuters from Penn Station in Manhattan to Montauk, more than a hundred miles away at the eastern tip of Long Island.
But with 272,000 passengers every 24 hours, the system is straining its boundaries. Overcrowding is common on the LIRR, and nearly half of the riders who end their journey at Penn Station must walk a considerable distance or take another form of transportation to get to work.
The LIRR East Side Access project is designed to alleviate congestion and offer easier access to Manhattan by creating a railway link between Queens and Grand Central Terminal.
As tunnel consultant to the Program Management team, Mott MacDonald provides essential tunneling expertise, including design review and expert advice on tunnel design and construction:
- Tunnel lining
- Ventilation systems
- Fire/life safety issues
- Assessment of tunneling methods
The technical difficulties are daunting. New rail lines will run from the Harold Interlocking yard in Queens, already the busiest railroad interchange in the country. Tunnel portals under the Sunnyside Rail Yard will connect to the partially completed 63rd Street tunnel, which runs under the East River. The existing tunnel will be extended about one mile through glacial tills and fill, with boulders and high groundwater levels expected.
On the Manhattan side, twin tunnels are being driven under Park Avenue, through hard micaceous schist that is subject to rock bursts (popping). Abrasive conditions and very hard intrusions make the job tougher.
In all, about 7 miles (11 kilometers) of new tunnel will be driven beneath Queens and Manhattan. The diameter of each tunnel is about 22 feet (6.7 meters) with some tunnels circular and others arched. About 17,500 feet or more than three miles (5.3 kilometers) of previously constructed tunnels will also be rehabilitated as part of this enormous project.
Special tunnel boring machines are needed to handle the soft ground in Queens, with precast concrete segments installed as the machine advances. In Manhattan, two customized TBMs bore through the hard Manhattan schist, with steel rings and other rock supports installed so that mining can continue without interruption.
Finally, two caverns are being mined under Grand Central Terminal to create a second major terminal consistent with the classic architecture of Grand Central. This will be the biggest passenger terminal to be built in the US since the 1930s. Each of eight platform tracks will accommodate 12-car LIRR trains.
The East Side Access project is expected to be completed in 2019. When it is open to the public, it will ease crowding at Penn Station by diverting about half the LIRR commuters to Grand Central.
Commuters from Queens and Long Island will shorten their commutes by 30 to 40 minutes a day. Car travel will be reduced by an estimated 500,000 miles per day, reducing air pollution and the emission of greenhouse gases.
In addition to thousands of construction jobs, the project is expected to have positive and long-lasting economic benefits. An easier, more pleasant commute, coupled with easier access to midtown Manhattan, will support business growth in Manhattan and the greater New York City area.