Montague Tube Reconstruction Work Continues Through a Cold, Hard Winter
February 28th, 2014
Deep through the heart of winter and unmindful of the repeat visits of the polar vortexes, work on the Montague Tube continues. At this point, the workers are focusing largely on the demolition of concrete walls and the removal of the debris. To date, however, an impressive amount of work has been accomplished in what is nearly a complete rebuild of the tube after the ravages of Super Storm Sandy.
Work trains continue to haul out the heavy debris of the demolished duct banks and concrete walls. A tremendous amount of damage was caused by the salt water driven into the tube by Sandy’s high winds.
With the debris removed, workers are able to inspect the tunnel for leaks and stop them through a chemical grouting injection process. During this process, over 2,000 of the original bolts holding together the 18 foot diameter cast iron tunnel rings and liner are being replaced with specially manufactured grout bolts. Grouting and bolt replacement to correct the leaks are important elements of this project. Before this project is complete, it is estimated that in excess of 6,000 high strength steel bolts will be replaced.
Installation work also continues on conduits, steel reinforcement bars and the framework necessary for construction of the new duct bank. Of course, much of the work involves the pouring of concrete, a relatively easy job at street level projects, but one that takes on another level of complexity when the worksite lies below the East River. How do we transport the concrete into the under river tube? Well, you’ve seen those big cement mixers. We actually bring one into the subway to deliver the mix. The concrete truck was tested at Brooklyn’s 38th Street Yard and then, using special wheels, placed onto the subway tracks where the mixer traveled to the tube under its own power.
The concrete truck remains on site and receives concrete from a vertical chute on the Brooklyn side of the Tube. During concrete pours, the delivery trucks from the plants queue up at the Furman Street Fan Plant, and pour the concrete down the chute. The staged truck at the bottom of the chute at track level inside the Montague Tube receives the concrete into its filling port, and then moves to the pour location.
All materials except for concrete are delivered and removed by NYC Transit work trains. To date, more than 2,300 cubic yards of concrete have been poured and nearly 30,000 feet of deteriorated duct banks removed.
The Montague Tube project has required expert coordination of varied construction activities and the assignment of multiple crews within a limited work area. The tunnel has limited access points for personnel, material, and equipment. The logistics of moving multiple work trains in and out of the tunnel, while keeping the project running on schedule, requires strict timing and no margin for error.
The scope of work for the Montague Tube is extensive. The work is being performed in two contracts. The first contract involves the repair of all right-of-way components, except for signals. The second encompasses repair of the signaling equipment. Work on both contracts will be carried out during the tube’s closure. The rehabilitation is estimated to cost $308 million in total, with $220 million invested in the right-of-way repairs.