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Second Avenue Subway
The Metropolitan Transportation Construction Tunnel Boring Cut-and-Cover Mining Removal and Reuse of Excavated Material
Authority (MTA) and MTA New York
Three main techniques will be used for tunnel and Cranes, small rail cars and conveyors will be used
City Transit have begun the final station construction depending on geological conditions to bring excavated rock and debris to the street
planning and environmental analysis and on specific facilities that could be needed at street level. At the surface, material will be transferred
for a full-length Second Avenue level, such as station entrances and vent shafts. The either directly to a barge or to trucks. Trucks will
1
three construction methods are tunnel boring, cut-and- then transport loads out of the city or bring the
Subway, from 125th Street to the cover and mining. excavated material to a barge for removal. Two
Financial District in Lower Manhattan. barge facilities are being proposed: one located
Our goal is to initiate construction by near the line’s north end, the other at the south end.
the end of 2004. 2
Most of the excavated material will be clean
2 crushed rock that can be used for such projects as
The Second Avenue Subway will 1 filling abandoned mines, building artificial reefs,
reinforcing bulkheads or paving roads.
reduce overcrowding and delays on 1
the Lexington Avenue Line and
improve access to mass transit for
commuters and residents of the far
Much of the Second Avenue Subway will be built using Most of New York City’s subway system was built using The third technique to be used to build the subway
East Side of Manhattan. tunnel boring technology, in which a powerful circular the cut-and-cover technique. With this method, a tunnels is mining. The primary method of mining in
cutting machine drills a tunnel in rock or soil with trench is cut in the street, the soil is supported by rock is drill and blast. This procedure involves drilling
minimal disruption to the street ( 1 ). The excavated vertical walls and a many small holes within a rock area and then placing
material is then taken to street level and removed by frame is built to small amounts of explosives in each hole. Under
truck ( 2 ). Tunneling will be done through bedrock support concrete or carefully controlled and monitored conditions,
wherever possible, which is quicker and more cost metal street decking explosives are then detonated sequentially for short
effective than mining or cut-and-cover. ( 1 ). The decking intervals, breaking the rock while spreading the release
allows the street to of energy from the explosives over a longer period,
There are two types of boring machines: the Tunnel remain open to traffic lessening potential ground vibration at nearby
Boring Machine (TBM), used in rock, and the Earth and pedestrians structures. When mining is done in soil, the drill and
Pressure Balance Machine (EPBM), typically used in while excavation and blast method is not required. Soil and rock will be
soil. A TBM is likely to be used between approximately construction excavated and removed by backhoes, bulldozers, and
6th Street and 92nd Street, where the bedrock is close continue in the a clamshell shovel suspended by a crane ( 1 ).
to the surface. An EPBM may be used in soil south of Cut-and-Cover at Times Square tunnel below.
6th Street, because the bedrock is relatively deep. Mining will be used on portions of the tunnel too short
Cut-and-cover is likely to be used at many station to make tunnel boring cost effective, and on curved
The actual tunnel construction will occur without many locations, at other places where access to the street is portions of the tunnel that are too constrained for a
street disruptions. However, the street will be required, and for sections of the alignment where the TBM. Some stations will be excavated from below
Tunnel Boring Machines excavated and significant street disruptions will occur tunnel will be very close to the surface, such as the street level, and the street will be penetrated to build
where the TBM is inserted into and removed from the section between the existing tunnel segments, which station entrances and venting. Additionally, an access
ground, where excavated material is removed, and were built in the 1970s. Through the “cut” in the street, shaft is needed to remove excavated materials and to
where stations and support facilities, such as vent excavated material can be removed and equipment bring in or remove equipment from the tunnel.
shafts, are located. can enter or exit the tunnel ( 2 ).
Brooklyn, NY 11201
130 Livingston Street, Third Floor
Second Avenue Subway Project
New York City Transit
Metropolitan Transportation Authority
Traffic Mitigation Building and Infrastructure Protection Construction Compliance and Green Design Second Avenue Subway
A key aspect of Structural and ground All work will Stay Involved Second Avenue Subway
construction is to improvement techniques comply with
develop a plan will be used to minimize applicable Stay informed of upcoming meetings and receive the
that will allow the ground settlements, and federal, state and latest information on the project.
city to continue to preserve the structural city codes and
to function integrity of various regulations, with MTA New York City Transit Tunnel Construction
normally during facilities, including utility the goal of Second Avenue Subway Project Techniques
construction. lines, buildings, tunnels achieving the 130 Livingston Street, Third Floor
Every effort will be made to minimize disruptions to and ramps. highest degree of Brooklyn, NY 11201
pedestrian and vehicular traffic. public safety.
Underpinning is a Web site: http://www.mta.info/planning/sas
In general, the project will not require closing of entire structural process that The Second Avenue Subway project will include design E-Mail: secondavenuesubway@nyct.com
streets. During construction, at least two lanes will includes the use of drilled elements that foster the prevention of pollution and Telephone Hotline: (718) 694-5164
remain open to traffic. Efforts will be made to maintain or jacked supporting minimization of waste. Wherever possible, the project
access to businesses and residences. piles to provide will use technologies to minimize adverse environmental
temporary support or reinforcement to protect existing impacts and incorporate sustainable design principles,
structures. Ground freezing and grouting are typical including energy efficiency, enhanced environmental
soil improvement options used to control ground quality and material conservation.
settlement and distortion.
August 2002
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