Demolition Work Hits High Gear as MTA NYC Transit’s Montague Tube Work Progresses
Dozens of feet below the East River’s silt covered bed and out of sight of subway riders, a small army of workers is busy demolishing and stripping the interior of the Manhattan-bound bore of the Montague Tubes. Equipment and components have been decaying inside the nearly century-old link between Lower Manhattan and Brooklyn Heights since last October when Superstorm Sandy sent millions of gallons of salt water rushing in.
The tubes are in the midst of a 14-month closure and the R train, which normally runs through, has been replaced by yellow work trains, hard hats and work equipment. When the start of the project was announced, MTA Chairman Thomas F. Prendergast described the work as; “the closest thing to building a new under river tube as there is.” The tubes were closed to service on August 3, and work is now well underway.
Salt Water Fills 4,000 Feet of the Tube for a Week
More than 4,000 linear feet of the tube was filled with salt water for nearly a week after the passing of the historic storm. Removal of the water was delayed because of the lack of electricity to the pumps located in lower Manhattan, which remained dark south of 39th Street for several days. The expected service life of every piece of equipment in the tube was substantially reduced due to the effects of salt water. And, though train service was restored on December 21, the number of delay-causing failures mounted and they were largely attributable to the deteriorating condition of components within the tube.
Bathed in the illumination from construction lighting, the Montague is currently a landscape of broken concrete and rubble waiting to be hauled out by work trains, which occurs twice daily. Work, so far, has involved the demolition of the rotted terra cotta and concrete duct banks, as well as the removal of thousands of feet of cable and the tunnel’s lighting system.
The project’s managers are facing major challenges, particularly a severe shortage of workspace. The envelope of an under river tube is designed for subway trains and is barely larger than the train itself, so the scheduling of particular jobs and even the ordering and placement of work trains is a study in efficiency. On this job, it also proved impossible to use the motorized equipment normally employed during demolition as the cast iron liner and limited space do not permit the use of heavy equipment.
Lack of Space for Heavy Equipment Means Applying New Work Techniques
“The first major repair job we did after Sandy was work along the outdoor Rockaway branch of the A Line, which is largely at grade. It was wide open space with plenty of room for work and machinery. This project in the Montague is the exact opposite and has required us to come up with some innovative approaches,” explained John O’Grady, Infrastructure Program Coordinator who is heading up NYC Transit’s Sandy relief efforts.
Duct Bank Demolition and Dust Protection
The heaviest task currently being performed is the demolition of the old concrete duct banks, which is now more than 40 percent complete. To combat the dust created by duct bank demolition, multiple levels of protection have been developed including the use of misting and waterfall systems that use water to keep the air clear of dust. Additionally, sturdy wooden bulkheads have been built at each end of the tube effectively blocking off the work area from the customer environment.
The Montague contains four duct banks – one on either side of both tubes and demolishing the old ones is a labor intensive job. Workers break down the old bench wall and duct bank and pull and cut up the miles of cable located inside. In many cases the cable must be pulled from the duct bank first, so the duct bank is easier to break up.
Cooperation, Coordination, and Contractors
“All of the work is done in progression and there is a high level of coordination,” said Construction Manager Piyush Patel, who explained that there are upwards of 80 workers in the tubes at any one time. “We have also had the opportunity to, along with our contractor, develop innovative ways of solving some of the problems we have encountered including creating a gantry crane system to make it easier to load the demolition debris onto the work trains.”
Once the duct bank is broken down, workers stash the pieces in one-ton concrete demolition disposal bags and then place them onboard the work trains to be hauled out. By the time demolition is complete, work trains will have rumbled out of the tubes with more than 18 million pounds of debris, including 500,000 feet of cable.
Montague Street Original Construction Nearing Century Mark
On an historical note, the tube’s original construction was begun nearly a century ago, in October 1914 and the first revenue train rolled through in August 1920. The tube was opened the same day as the 60th Street Tube, allowing a one seat, nickel ride from Queens to Brooklyn via Manhattan’s BMT Broadway Line. Constructed at a cost of less than ten million, the Montague Tubes were constructed with the use of a tunnel shield and compressed air, the common tunnel building technique during the early part of last century.
Traffic Checker Charles Corbin directs customers
during the "Bus Bridge" operation.
James Cutolo, Senior Director, Operations Support
Division of Operations Planning
Office of the Executive Vice President