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PROJECTS
C-26510 34th St. Hudson Yards Station Entrance at Site J (Yonkers Construction), MTACC, March thru June 2016
Scope – Curtain grouting of E1 and E2 incline tunnels, vent shaft and concourse-level entrance structure.

One of MTA Capital Construction’s major programs is the No. 7 line extension. This expansion of New York City Transit’s IRT line into Midtown Manhattan West, which includes 1.3 miles of twin bored tunnel and the new 34th St. – Hudson Yards Station, began in October 2007 and was opened for revenue service in September 2015. After a few months of operation, commuters expressed concerns about water dripping through ceiling panels over the entrance escalators. At the time, only one of the two station entrances (Site J) was operational. This entrance features two reinforced concrete arches which are inclined to span from Mezzanine to Concourse level (roughly 60-ft change in elevation). The south tunnel incline (E1) features one escalator and two inclined elevators. The north tunnel incline (E2) features four escalators. Unable to shut down either incline, MTA chose to address these drips at night during off-peak hours.

Sovereign-Thyssen L.P. was brought in to address ongoing leaks throughout the entrance at Site J. Of primary importance was to stop the water dripping through the crown of the E1 and E2 inclined tunnels. Additional leaks in non-public areas on the concourse level and in personnel staircases were also specified for treatment. Polymer-based emulsion was requested and NOH2O grout was selected for production grouting.

Primary grouting operations started in late March 2016. Initial treatment began with the installation of a grout curtain barrier at the vertical endwall at the top of both incline tunnels, so as to prevent displacing water up the incline and into the station entrance. Once complete, a series of holes were drilled through the reinforced concrete arch along the incline tunnels and grouted sequentially – starting with the north tunnel (E2) and finishing with the south tunnel (E1). This first effort to seal leaks along the inclined tunnels above the escalators required four six-day weeks, with grouting work taking place at night and periodic monitoring during the daytime for possible reports of water leakage. Altogether 68 holes were drilled (24 in the endwall, 22 each in both inclined tunnels) and 23,250 liters (6,142 gallons) of NOH2O were pumped in order to seal leaks along these two tunnels and endwall – treating a total of 21,450 square feet.

An interesting observation was made during the grouting of tunnel E2; prior to the selection of PBE, attempts were made by the general contractor to grout using several hydrophobic polyurethanes and a multi-component methacrylic resin. While injecting NOH2O positively into the tunnel annulus, a report was observed to a nearby construction joint. The material communicating from the joint was a murky white liquid which was later identified as the B-component of the methacrylic resin, which had been injected unreacted and remained dormant in voids adjacent to the tunnel annulus until it was pushed out due to grouting pressures.

Once the inclines were finished the remaining non-public areas for station personnel were addressed. In the aftermath of grouting the inclines, some of the water had migrated to the landing of E1 tunnel. Ceiling panels were removed and holes were drilled through the liner. It was here that several holes drilled struck a void behind the liner which was channeling much of the groundwater to this area. These holes were allowed to drain overnight and were grouted soon after. In total, 225 holes were drilled throughout the course of production grouting and 28,964 liters (7,651 gallons) of NOH2O were pumped in three months from end of March to mid-June 2016, treating 27,780 square feet. The leaks above both escalator inclines were eliminated, while station service continued uninterrupted throughout the duration of treatment.


Incline Endwall Before – 03/25/2016

Incline Endwall After – 06/20/2016

Incline Endwall Before – 03/23/2016

Incline Endwall After – 04/12/2016

Incline Arch Before – 03/31/2016

Incline Arch After – 06/20/2016