Constructing a cut-and-cover tunnel in a congested Manhattan area

A cut-and-cover tunnel project in New York, involving the construction of the shell of a subway station underneath Second Avenue, between 91th and 100th streets is in ENR's list of best Airports/Tunnels projects. Two Geoengineer.org's Corporate Sponsors, Geocomp and Nicholson Construction Co, actively participated in the construction process in different key roles! 

The cut-and-cover tunnel, at an estimated cost of $370 million, is going to host a new subway station, extending all the way from 91st to 100th streets of the Upper East Side of Manhattan. Due to the location of the project, in a congested area of the Upper East side of Manhattan, construction works had to be performed with the minimum possible disturbance to traffic, general public and the adjacent buildings. 

One of the major obstacles was the extended repositioning of 3.5 miles of utility lines (sewer, water, gas, electrical and telephone) over a 0.2 mile long part on Second Avenue to within two 15ft wide corridors on either side of the street. The repositioning works of the utility lines lasted about 14 months and required the continuous collaboration of transit agencies, building owners and utility companies.

The massive excavation works and their support through slurry walls was the second largest challenge for the constriction companies. Located a few feet away from fragile buildings, 3.5ft thick reinforced slurry walls panels were constructed, having varying lengths of 60 to 120ft and extending along three city blocks, on the east and west sides of the street. Slurry walls served as the main shell of the tunnel, while underpinning of the buildings was performed with jet grouting, compaction grouting, compensation grouting and mini piles.

Two Corporate Sponsors of Geoengineer.org were actively involved in the present project. Namely, Nicholson Construction Co was responsible for the slurry wall and jet grouting works, while monitoring and instrumentation was performed by Geocomp.