Paula Wallis, Tunneltalk
- As the TBMs push forward on the soft ground running tunnels on the Queens contract, the scope of major works by the contractor on the Manhattan side of the $7.4 billion East Side Access (ESA) project has been cut back in an effort to minimize delays (Fig 1).
Fig 1. East Side Access alignment
- Last week (January 25, 2011) the Metropolitan Transportation Authority (MTA) approved a renegotiated contract with the Dragados/Judlau JV, cutting some of the contactor's workload.
- "They are well behind schedule and the MTA has adjusted their scope of work to get them finished so we can get follow-on contractors in," said Andy Thompson of Hatch Mott MacDonald (HMM) and Senior Program Manager for the project's construction management team.
- Thompson said all the Manhattan underground works are impacted. Dragados announced last Fall that it did not expect substantial completion of work until 2015, a two year slip in the schedule that at one time had all excavation complete by this Summer.
- "It is a complex project with multiple locations which are logistically difficult, and the management of it has been more challenging than the contractor anticipated," said Thompson of the construction JV's performance.
- Speaking to reporters last week, Michael Horodniceanu, President of MTA Capital Construction said the delays had placed "incredible pressure" on the project causing backups of subsequent work that cannot begin until Dragados/Judlau wraps up its work.
- The contractor is currently mining the massive station caverns under Grand Central Terminal using roadheaders and drill+blast. The top headings in both the East and West caverns were complete last Summer. The final lining in the arch of the 1,200ft (366m) Westbound cavern is complete along with about a third of the arch in the Eastbound cavern. The contractor has also excavated about 20% of the bench in the West cavern.
- Progress on the contract was shaken in November last year when a construction Sandhogs' crew suffered a fatality in the shotcreting works under Manhattan.
Madison Yard elevator shaft 4 from Westbound cavern
- Under the terms of the renegotiated contract Dragados/Judlau JV will finish excavating the caverns, but the remainder of the final lining works has been removed and has been placed in a separate contract soon to go out to bid.
- "Changing the terms of the contract will not erase the delays, but we are fairly confident we can get some overlapping work going, where we can pull back some of that time," said Thompson.
- The restructured contract also includes new incentives and penalties for Dragados/Judlau. The contractor can be hit with up to $49.5 million for future delays and earn as much as $16 million if finished before the new completion date of August next year (2013).
- Added to the Dragados/Judlau contract was the planned ventilation tunnel under 55th Street. Instead of a top-down excavation the muck will be removed through the East Side Access tunnels to Queens, to lessen impacts at street level. The JV also holds the contract for the running tunnels in Manhattan, awarded in 2006. Excavation by two rock TBMS was complete in May 2011.
- While the new contract aims to mitigate delays, there are other construction delays to Manhattan's side of the project including the repair of the tracks in the East River tunnels, which are owned by Amtrak. The repair work associated with the East River tunnels is being staged from Sunnyside Yard in Queens.
Extending the slurry lines for TBM in A tunnel
Soft ground slurry progress
In Queens, the project's other major tunneling contract is well under way. This contract will complete the soft ground tunnels that will link tracks on Long Island to the 63rd Street Tunnel under the East River, and to the Manhattan tunnels and new station platforms under Grand Central Terminal. A three-way joint venture comprising Granite Northeast, Traylor Bros, and Frontier-Kemper (GTF) holds that contract, which has the most challenging conditions of the project's program. Though short, the drives are mostly in soft ground, with mixed faces, boulders, and manmade obstacles, a high water table, low overburden, and the nation's busiest railroad interlocking junction overhead.
- Two Herrenknecht slurry TBMs are mobilized to complete two drives each. TBM T.E.S.S. started mining the 1,950ft (594m) A tunnel on August 10, 2011 and holed through some 96 working days later on December 22 (Fig 2).
- The TBM mined straight into a mixed face followed by a full face of glacial till which remained for virtually all of the drive, said Thompson.
- Thompson said one hiccup that was encountered was the need for a scheduled intervention in compressed air after a ground freezing operation did not completely take where the four slurry TBM drives for A tunnel, Yard Lead and the B/C tunnels all meet and where maintenance was scheduled in free air. Despite all, the TMB holed through 10 days ahead of its scheduled duration.
Fig 2. Schematic of Queens tunnel drives
- TBM Molina is driving the Yard Lead tunnel, which will take trains to and from the mid-day storage yard. It has completed 3,100ft (945m) and has about 912ft (278m) to go for an expected breakthrough in February (2012).
- "GTF has had a couple of 75ft plus days and in this challenging ground, anything over 75ft is an extremely good day of production," said Thompson.
- TBM T.E.S.S. is currently being retrieved from the A tunnel and its cutterhead is in the shop being redressed. It will be back in the launch shaft to begin excavating the D tunnel in mid-March. TBM Molina will follow to excavate the B/C tunnel.
- Thompson said settlement has been negligible. The Yard Lead machine excavated under the tracks with minimal impact to the railroad operations above, he said.
- "When you consider all the talk before the start of the job about this being the first use of slurry technology in New York and the inexperience of the Sandhogs, it says a lot about the GTF management and the way it is planning, training and selecting the right people for the job. There are also some very experienced people on the Construction Management side." URS is the Program Management Consultant (PMC), HMM is a sub-consultant to URS and supplies the Construction Management and other staff to the 31-member team.
- With work progressing on the Queens tunnels, and a renegotiated contract in Manhattan, the MTA is hoping the construction schedule will improve as time goes on.
Slurry TBMs ready to tackle New York ground - TunnelTalk, March 2011
East Side Access optimization - TunnelTalk, October 2009
Tunnel worker loses his life in New York - TunnelTalk, November 2011
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