Northern Boulevard Crossing (NBX) is the keystone portion of the massive $8.4+ billion East Side Access (ESA) Program by the Metropolitan Transit Authority Capital Construction (MTACC) to bring Long Island Railroad trains into and out of New York City's Grand Central Terminal. NBX constitutes the link between the Queens Tunnels and Manhattan Tunnels portion of ESA. The crossing consists of 120 FT of 2,000 square FT cross sectional area tunnel through soft ground, constructed utilizing Sequential Excavation Method (SEM) under the protection of a structural frozen arch.NBX extends under an active five track wide subway box, a major six lane highway, as well as through the foundation piles of operating elevated subway line structure. All of the above presented a unique challenge to the owner and contractor. NBX is the first and only SEM tunnel project within the five Boroughs of New York and was constructed by a Joint Venture of Schiavone Construction Co., LLC and Kiewit Infrastructure Co. (SK) Construction on NBX started in February 2010 with the SEM excavation starting in April of 2012 following access chamber excavation, grouting and ground freeze. Excavation was completed in November 2012 and was followed by PVC waterproofing installation and final lining concrete. This paper describes lessons learned from the SEM excavation and support, description of the freeze operation is covered in separate papers.
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