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Green Line Relocation Causeway Street

Project Highlights:

• 5800 sf. Tunnel Lagging
• 19,000 cy Excavation
• 32,000 sf Slurry wall
• 540 lf 4’ Drilled Shafts
• 165 lf 6’ Drilled Shafts.
• 5,600 cy Concrete




The MBTA Green Line Relocation project from Causeway St. to the North Station Garage project involved the construction of the new Green Line tunnel and passageway/headhouse from Causeway St. to the North Station garage, as well as the construction of a Ventilation Building and Electrical Substation. As part of this contract we had to do a partial re-support of an existing structure (Fleet Center now TD Garden) by a under-pinning system which consisted of concrete slurry walls and structural steel which was done in stages to minimize the risk associated transferring the load from the existing foundation to the new foundation. This operation required careful evaluation of the existing Fleet Center and monitoring of the Center for signs of distress which was part of our quality control program.

Another major part of the work was the support of excavation and the construction of the Green line Tunnel below Causeway St. to connect to the existing Green Line tunnel. Traffic and pedestrians had to be relocated south of the Fleet Center for the support of excavation, bracing, excavation and concrete work to be performed in a confined area which had to be monitored for any settlement to Causeway Street.