A hundred years from now, it is likely that tunnelers will look back at the current era of building in New York City as the Golden Age of Tunneling. The East Side Access project, Second Avenue Subway and No. 7 Line extension, as well as the construction of the Fulton Street Transit Center downtown, represent the first major works in the New York City transit system in more than a half century. Collectively, these projects represent $17 billion in construction value.
The projects bring with them a host of long-anticipated benefits that include shorter commutes, easier access, real estate development and economic opportunities that will re-define entire neighborhoods. They are also not without challenges.
Yet despite the challenges associated with building multi-billion dollar projects in the heart of one of the densest cities on the planet, work is forging ahead. By the end of the decade, New Yorkers will be realizing the fruits of the labor and looking ahead to the next wave of transit projects to meet the demands of the growing, evolving city.
In January, TBM editor Jim Rush visited several project sites in New York City and sat down for an interview with Dr. Michael Horodniceanu (p. 50), the President of MTA Capital Construction, which is overseeing the construction of these projects. MTA Capital Construction was created in 2003 to oversee system expansion projects for MTA agencies, which include New York City Transit, Long Island Rail Road, Metro-North Railroad, Bridges and Tunnels, and MTA Bus. Below is a report of the MTA mega-projects currently under construction.
Second Avenue Subway
Tunneling for the first phase of the Second Avenue Subway is nearing completion as crews are winding down blasting activities associated with the connection between the 72nd Street station and the Lexington Ave./63rd Street Tunnel. This marks a major milestone for the project. Station excavation and construction, systems work and finishes remain with the opening of the line for revenue service anticipated for December 2016.
The construction of the Second Avenue line was planned in the 1920s as part of major subway system expansion intended to allow for the dismantling of elevated trains. But while construction moved forward on lines under Sixth and Eighth avenues, the second phase of construction — the Second Avenue line — was never built.
Up through the 1940s, the East Side of Manhattan was served by three commuter lines – the Lexington Avenue subway line and elevated lines (known locally as “els”)above Second and Third avenues. But as New Yorkers tired of the commotion and ungainliness of the elevated lines, those lines were slated for dismantling – in part due to the promise of the coming Second Avenue subway.
By 1942, the Second Avenue el was discontinued, followed by the closing of the Third Avenue el in 1955. Since that time, however, the demand for commuter service on the East Side has continued to increase, with only the Lexington Avenue subway left to shoulder the burden.
Today, the Lexington Avenue line alone carries a weekday average of 1.5 million passengers. To put that into perspective, the line carries about the same number of passengers as the entire heavy rail rapid transit systems in Washington, D.C., and Chicago – combined.
Construction of the Second Avenue Subway actually began in earnest in 1972. Three portions of the line were constructed – but never put into service — before the city’s financial woes put the project on hold again. The current plan is to incorporate the previously constructed portions of the line — between 99th and 105th streets, between 110th and 120th streets and one section downtown between Chatham Square and Grand Street — as part of the full build.
The project is divided into four phases. The first phase of the project involves the construction of twin tunnels under Second Avenue from 96th Street to 63rd Street, with new stations at 96th Street, 86th Street and 72nd Street. The new lines and stations will tie in to the existing 63rd Street station.
When Phase 1 of the new Second Avenue Subway opens, it will provide immediate benefits as passengers can connect to the Broadway line to reach downtown destinations. It is anticipated that the new line will initially serve more than 200,000 passengers daily.
|Dewatering on Second AvenueBy Paul C. SchmallBefore the tunneling can begin there is the considerable matter of getting the TBM assembled in place. For the first phase tunneling of the Second Avenue Subway project between 63rd and 92nd streets, this meant excavation of a launch box 800 ft long, 100 ft wide long and 65 ft deep to assemble the 485-ton machine and associated railcar-mounted backup equipment.With rock present at approximately 25 ft below street level on the south side of the launch box site but dipping to more than 200 ft on the north side, excavation support to create the desired “bathtub” was designed as a combination of secant pile walls and deep diaphragm walls, which extended to a depth of approximately 100 ft.Site soils consisted of varved silts and clays, with groundwater present at 10 to 15 ft below street level. At excavation subgrade, up to 50 ft of hydrostatic pressure would be imposed on the excavation support. Given the low hydraulic conductivity of the soils, correspondingly low anticipated groundwater flow was anticipated. But while the deep diaphragm walls would force an extended groundwater flow path, groundwater beneath the excavation could nevertheless result in instability of the launch box floor. Dewatering of the soils below final excavation level was therefore necessary.
Specialty geotechnical contractor Moretrench was subcontracted to S3 Tunnel Constructors, a joint venture of Skanska USA Civil, Schiavone Construction and JF Shea Construction, to design, install and operate the dewatering system. The varved silts and clays, which behave similar to the notorious Manhattan “bull’s liver” soils when disturbed, had proved particularly troublesome during the previous attempt to construct the Second Avenue Subway in the 1970s, which was eventually abandoned due to the City’s financial crisis. Given that experience, this time around the dewatering operation was of critical concern to the project.
Given the low anticipated groundwater flow and depth of excavation, Moretrench elected to install an ejector system. Ejectors are typically the dewatering tool of choice where the groundwater must be lowered to appreciable depths and the hydraulic conductivity of the soil is such that vacuum application is warranted to improve soil drainage. Protecting buildings adjacent to the excavation also factored into the dewatering program. To prevent compromising the soils beneath the typically shallow foundations, specified groundwater drawdown external to the excavation was limited to 2 ft.
The dewatering system was installed within, and concurrent with construction of, the secant pile and slurry wall excavation support. Moretrench used rotary and duplex drilling techniques to install the 50, 4-in. diameter wells required for the project to as much as 100 ft below street level. Several of the wells were constructed to function as pumping wells and monitoring wells to ensure compliance with specified rate-of-drawdown and monitoring requirements. The wells were connected to a central pumping station via dedicated supply and return piping. The system piping was suspended from the internal supports beneath the decking on Second Avenue. Over 25 months of operation, the total system typically produced approximately 50 gallons per minute.
Paul C. Schmall is Vice President and Chief Engineer of Moretrench.
Final plans for construction of the subsequent phases have yet to be determined. Phase 2 consists of extending the line north to 125th Street, including new stations at 106th, 116th and 125th streets. Phase 3 will extend service from 63rd Street to 4th Street, with new stations at 55th, 42nd, 34th, 23rd, 14th and Houston streets. Phase 4 completes the alignment to Hanover Square and includes new stations at Grand Street, Chatham Square, Seaport and Hanover Square.
Major contracts related to underground construction include: Contract C-26002: Tunneling from 92nd Street to 63rd Street. Contract awarded to S3 Tunnel Contractors (a joint venture of Skanska/Schiavone/Shea) for $337 million; Contract C-26005: 96th Street Station heavy civil work. Awarded to E.E. Cruz/Tully Construction for $303 million; Contract C-26006: 63rd Street Station reconstruction. Awarded to Judlau for $176 million; Contract C-26007: 72nd Street Station, station cavern mining, G3/G4 tunnels, heavy civil structural work. Awarded to Schiavone/Shea/Kiewit for $447 million; Contract C-26008: 86th Street Station cavern mining. Awarded to Skanska/Traylor for $301 million; Contract C-81188: Engineering Services for the SAS Project, awarded to AECOM-Arup JV; and Contract C-81338: Consultant Construction Management Services, awarded to PB Americas.
One of the major challenges associated with the Second Avenue Subway project has been working with the public, which has mounted some reistance to the project because of the disruption associated with construction. The project is being built in Manhattan’s Upper East Side, which is one of the most densely populated areas in the United States with more than 100,000 residents per square mile. Construction-related disruption such as road and sidewalk closures, dust, noise and vibration are exacerbated in this sort of environment with close-in construction.
MTA Capital Construction is working with residents and businesses to help create a better environment during construction, including hosting community site tours to facilitate open, two-way dialogue and foster better understanding of the underground construction. As a result of the collaborative effort, MTACC has implemented changes including wider sidewalks, improved signage and way-finding aids for businesses that are hidden from street view. “We had to engage the public and had to become better neighbors,” MTACC’s Horodniceanu said.
TBM tunneling, using one Herrenknecht designed 6.6 m OD gripper, is complete with final hole-through occurring Sept. 22, 2011. Crews are now in the process of water proofing and installing a cast-in-place concrete liner. Excavation of the cavern that will be the 72nd Street Station is ongoing with nearly 75 percent of material excavated as of the end of March.
The contract to build the TBM launch box from 92nd to 95th Streets involved utility relocations and the installation of support of excavation (SOE) walls, roadway deck beams and concrete roadway panels. This work was followed by excavation of the launch box to invert level and the excavation and concrete lining of the two TBM tunnels. The launch box will also function as the southern half of the permanent 96th Street Station.
The SOE walls for the launch box are a combination of secant piles in the blocks between 91st and 93rd Streets and slurry walls in the remaining two blocks from 93rd to 95th Streets. The underlying rock is approximately 15 ft below the surface at the south end of the launch box and slopes down to the north where it disappears below invert around 93rd Street.
Both the 86th and 72nd Street Station caverns will be mined in rock using drill-and-blast sequential mining methods. Both caverns will contain two-track center platform structures approximately 70 ft wide. The 72nd Street cavern is approximately 1,200 ft long and 50 ft high with minimum rock cover of about 30 ft. It has an initial support of rock bolts and shotcrete and a cast-in-place concrete liner with waterproofing layer. The 86th Street cavern is approximately 950 ft long and 50 ft high. Initial support is rock bolts and shotcrete with a CIP concrete lining.
No. 7 Line Extension
Unlike the Second Avenue Subway in the densely populated Upper East Side, project leaders for the No. 7 Line extension are bringing new development to the West Side of Manhattan. The project is in the underdeveloped area near the Javits Center, Hudson Yards and industrial zones near the banks of the Hudson River. The project extends the 7 Line from the existing station at Times Square west and south to a new station at 34th Street and 11th Avenue. The new station is being built with future access to new development in mind.
The No. 7 Line extension includes several unique features for MTA projects. Chiefly, the project is being paid for by New York City, which sold bonds with the expectation that they would be repaid by property tax revenues generated by the development of the area. The project was also the first rock tunnel to be built in Manhattan using precast concrete segments, and included one of the first uses of a horizontal freeze for TBM construction.
The freeze was installed in the first 300 ft of the TBM drive and was implemented as per the original design to facilitate TBM mining in the low overburden area. Two Herrenknecht 22.5-ft diameter double-shield TBMs were used to mine approximately 6,360 ft of tunnel connecting the new station to the 7 Line terminus at 42nd Street. The project included a concrete box structure built by precision drill-blast under the Port Authority Bus Terminal that served as the receiving pit for the TBMs. Tail tracks for the No. 7 also had to be lowered to accommodate the alignment for the extension. The TBMs were launched from a shaft at 25th Street and 11th Avenue, drove to the station at 34th Street, were walked through the cavern, and re-launched for their final drives. The 12th Avenue station cavern and interlocking are more than 1,660 lf. The tunnel between the 25th Street shaft and 34th Street station will be used for tail tracks and could potentially be used in the event that the line is further extended to the south in the future.
The major underground contract, valued at $1.15 billion, was awarded to a joint venture of Shea/Skanska/Schiavone in December 2007 and was completed in October 2011, 10 months ahead of schedule. Punch list work was completed and a final acceptance inspection was conducted on Dec. 20, 2011. The remaining work involving the lining of Shaft A, added by a change order, was scheduled to be complete by spring.
Part of the project includes incorporating building foundations designed to support skyscrapers that are being constructed at several sites. Mayor Michael Bloomberg has compared Hudson Yards’ redevelopment to recent transit-oriented development in London. During a speech at Crain’s New York Business conference, he said: “On the Far West Side of Manhattan, we’re building an extension to the No. 7 subway line – the first city-funded subway track in 25 years and it will be built on time – something that you don’t hear too often about subway construction. It will do for the Far West Side what the Jubilee Tube line did for Canary Wharf in London: transform an old industrial area into one of the most dynamic neighborhoods in the world.”
In September 2011, work began on the project’s last major contract. This systems contract includes rail track, all mechanical, electrical and related systems throughout the tunnels, station, ventilation buildings and the main subway entrance at 34th Street. Completion of this contract is the last piece needed to initiate service on the No. 7 Line extension. The $513.7 million project was awarded to a joint venture of Skanska USA and the RailWorks Corp. The entire $2.4 billion No. 7 Line extension is expected to be ready for revenue service by June 2014.
The project designer is Parsons Brinckerhoff with support from Dattmer Architects for the station design. Construction management is being provided by the tri-venture team of Hill International/LiRo Group/HDR.
East Side Access
Underground caverns and tunneling work are well under way for the massive East Side Access project being built by MTA Capital Construction for the Long Island Rail Road. The project will bring the Long Island Rail Road (LIRR) directly from Long Island and eastern Queens into a new station being constructed 120 ft beneath Grand Central Terminal in the heart of Manhattan. It is the largest project ever undertaken by the Metropolitan Transportation Authority (MTA) and at a cost of $7.3 billion, one of the largest infrastructure projects currently under way in the United States. Project completion is scheduled for September 2016.
|Clearing the MuckSSK Constructors Joint Venture (Schiavone/Shea/Kiewit) is engaged in the mining of the new 72nd Street Station Cavern, G3/G4 tunnels and complete final concrete lining as part of Contract C-26007 for the Second Avenue Subway. The entire project duration is 37 months, during which all excavation, waterproofing, concrete lining, utility and street restoration at the construction shaft locations must be completed.Due to the tight timetable, it is critical that SSK maintains production of its drill-blast and mucking operations. The project involves the removal of more than 375,000 cu yd of rock, all of which needs to be removed through two 28-ft diameter shafts located at Second Avenue and 69th and 72nd Streets. The tight confines on the surface meant that typical muckpile and loading operations were not feasible, so as a result, the JV designed and built a specialty muck handling and conveyance system that is helping the project proceed on schedule.
The end product is a high-capacity muck removal system, which is enclosed in a steel-framed structure with insulated panels that serve to mitigate noise, dust and an overall impact to the neighborhood. Two identical systems were constructed, one at each shaft. The approximate dimensions are 160 ft long by 45 ft high by 32 ft wide.The system is comprised of a gantry hoist and 12 dump stations oriented in two parallel rows of six located above street level. Each dump station accommodates a 25 cubic yard muck bucket that is hydraulically dumped into a waiting tri-axle truck immediately below. The crane operating independently can lower empty buckets then raise full buckets for placement into the mezzanine storage area. The base of each shaft can accommodate up to two buckets at a time.
The key benefit of the system is that it allows the contractor to store up to 300 cu yd of material at the surface without the benefit of a muck bin. That storage allows SSK to maintain the production needed to meet project schedule. The project is on pace for completion by the end of 2013.
Anthony Del Vescovo, vice president of tunnel operations for Schiavone Construction, said the JV looked at existing mucking systems before coming up with the custom design. “We had looked at another system that used the concept of storing muck in boxes, but realized that it wouldn’t work for us. So, we came up with this new system that is less complicated with fewer moving parts and less chance of downtime. Everything except the hoists were designed and built from scratch.”
Del Vescovo added that the JV is able to remove an average of 2,000 to 2,200 cu yd of muck per day. “The muck removal system has allowed us to maximize excavation and store material at the surface where we would not have been able to do conventionally with a crane,” he said.
The steel-framed structures will continue to provide benefits when excavation is complete, as the muck box level can be decked over to provide storage space for concreting operations. The project is expected to be completed by the end of 2013.
The project involves a new route alignment connecting the LIRR’s Port Washington (Queens) Branch/Main Line tracks to Manhattan’s Grand Central Terminal via the existing 63rd Street Tunnel under the East River and a new LIRR station at Grand Central Terminal. The entire project involves the construction of approximately 50,000 lf of tunnels, as well as caverns, shafts and other structures.
The 63rd Street tunnel was built in the 1960s via the immersed tube method and included two levels, the upper level of which is being used by the New York City Transit’s F Line. LIRR will use the lower level for the East Side Access project.
The East Side Access project is broken into two section: Manhattan, which consists of tunnels and station excavation at Grand Central Terminal; and Queens, which consists of tunnels and site redevelopment.
Major construction contracts include:
- Contract CM009: Manhattan Tunnels. Awarded to Dragados/Judlau for $427.9 million.
- Contract CM019: Manhattan Structures. Awarded to Dragados/Judlau for $734 milllion.
- Contract CQ031: Queens Bored Structures. Awarded to Granite/Traylor Brothers/Frontier-Kemper for $648.9 million.
- Contract CQ039: Northern Boulevard Crossing. Awarded to Schiavone/Kiewit for $84.9 million.
- Consultant Construction Management Services are being provided by a joint venture of Jacobs/Edwards & Kelcey/LiRo.
On the Queens side, Granite/Traylor/Frontier is excavating four short tunnels, totaling about 10,000 ft, in soft ground using slurry TBMs from Herrenknecht. These tunnels will be used to carry East Side Access trains under Amtrack’s Sunnyside Yard and LIRR’s Harold Interlocking and connect to Mainline and Port Washington Branch tracks.
As of January, one tunnel bore had been completed with the second well under way. The project includes a state-of-the-art, completely redundant slurry plant to separate the cuttings from the slurry and re-circulate it to the face. To connect these tunnels to the main tunnel to Manhattan, MTA awarded a contract to Schiavone/Kiewit to construct a crossing under Northern Boulevard. This 120-ft long, 60-ft wide and 40-ft tall tunnel crosses Northern Boulevard, an elevated train and an active subway line. The contractor is using sequential excavation techniques to mine the tunnel.
On the Manhattan side, the contractor excavated eight 22-ft diameter drifts for a total 25,200 lf of tunnel using rock TBMs — one from Robbins and one from SELI. These drifts will be used to form the new station platforms beneath the existing tracks at Grand Central Terminal. The concourse level for the new LIRR station will be on the Madison Yard storage area for Metro-North, which is adjacent to active tracks at the terminal. The project includes the construction of escalator facilities to connect the concourse to the track levels. As of January, crews were in the process of water-proofing and concrete lining the caverns using 50-ft forms.
When complete, the new line will reduce travel times for Queens passengers traveling to the East Side of Manhattan by 40 minutes. Currently, those commuters must travel to Penn Station on the West Side and transfer back to the East Side.
Fulton Street Transit Center
The new Fulton Street Transit Center under construction in Lower Manhattan is beginning to take shape as the iconic oculus has been constructed, giving pedestrians on Broadway a preview of the Transit Center’s final form. In addition to the new building, the Transit Center includes the renovation of the historic Corbin Building, an eight-story brick building completed in 1889 that abuts the sleek, modern Transit Center. Coincidently, the Corbin Building is named for Austin Corbin, a former president of the Long Island Rail Road, now an MTA agency.
The Fulton Street Transit Center will connect 10 existing subway lines in the area of Fulton Street – the A,C,E,J,Z,R,2,3,4 and 5 lines. Currently, subway entrances in the area are spread out across the area – the result of independently constructed lines and stations built by competing railway owners that eventually unified under the MTA umbrella. The project also includes the construction of a pedestrian walkway beneath Dey Street to link the Transit Center to the World Trade Center site and the PATH commuter lines to New Jersey.
The $1.4 billion project is on schedule for a June 2014 completion and, alongside the new One World Trade Center building rising in the skyline, will reshape the landscape of Lower Manhattan for future generations of New Yorkers. Included in the plans for the project is 70,000 sq ft of leasable space, including shopping and dining, that will help revitalize the neighborhood.
All major heavy civil work is complete, with the majority of work remaining involving construction of the Transit Center building itself and staging of station work to keep commuter traffic flowing uninterrupted. The construction of the new transit center building, Contract 4F, was awarded to a joint venture of Plaza/Schiavone for $175.9 million. Lead design consultant for the Fulton Street Transit Center is Arup. Construction management services are being provided by a PB Americas/Lend Lease JV.
“It is going to be very exciting for downtown, particularly now when Lower Manhattan is turning to be not only a place for business, but a residential community,” Horodniceanu said. “That is a big change from what it was.”
South Ferry Terminal
While all of the above projects are still under construction, it also is worth noting that MTA recently completed the construction of the South Ferry Terminal in Lower Manhattan, located adjacent to Battery Park and Staten Island Ferry Terminal. The previous station was built in 1905 and contained a tight loop that restricted the number of train cars that could load at a given time. The new station is ADA accessible and accommodates 10 train cars (compared to five) to enhance the system’s operational efficiency. Additional entrances were added as well as a free connection to the nearby R Line. This station was completed in 2009 with a construction value of $530 million. Major underground works were completed by a joint venture of Schiavone/Granite/Halmar using cut-and-cover methods. The project was the first new station to open in two decades.
EDITOR’S NOTE: TBM would like to thank the following individuals for their time and effort in making this article possible: Rosanna Alcala, Patrick Cashin, Angela Cho, Vince Denina, Aaron Donovan, Jeff Eustace, Brian Fulcher, Bill Goodrich, Michael Horodniceanu, Shawn Kildare, Tom Peyton, Mark Rhodes, Barrie Roberts, Justin Schultz and Michael Vigna.