MTA Queens Tunnels – New York City, NY
The New York Metropolitan Transport Authority’s Queens East Side Access project will connect the Long Island Rail Road’s Main and Port Washington lines in Queens to a new LIRR terminal beneath Grand Central Terminal in Manhattan.
The Queens open-cut structure was created to serve as the TBM assembly and TBM launch chamber for the Queens soft ground tunnels prior to its permanent use as an interlocking and an emergency exit/ventilation facility and substation. Four tunnels were to be constructed – using specialized tunnel boring machines called Slurry TBM’s. This open-cut excavation was created by constructing slurry walls on highly fractured bedrock and groundwater inflow was an immediate problem. The main contractor Granite -Traylor - Frontier JV used several grouting, double row jet grouting, slurry grouting and low mobility grouting techniques but without a reduction in seepage.
Panel 109 was identified as the most problematic area with a recorded leak rate of 95 Gal/min. Sovereign International mobilized to site and commenced a short grouting trial – first by sealing the leaking seams in the bedrock and then the slurry wall/rock interface. The dewatering pumps were turned of and only a few drops were visible after two days on site.
The criteria as per the contract was bettered and Sovereign was invited to design a program to remedy the remainder of the leaking excavation.
