In this cutaway section, a vehicular roadway is suspended between the train tunnel and street-level. As they didn’t have TBMs in those days), I can only imagine the shoring and needling it would have taken to support the excavation depicted in this old illustration. In fact the (SAS) Second Avenue Subway, NY, was conceived an awfully long time ago, as this timeline attests.
The current inception of the project, involving both TBM and cut-and cover tunnels, is presently in Phase I; the 103 Street, to 63rd Street leg of the branch, which will connect with the 63rd Street Tunnel, and ultimately continue south, eventually connecting with the Fulton Street Transit Center. Station houses, ancillary entrances, and vent houses, will also be constructed along the line, presumably by 2016-2017.
For SAS, RepOne conducted several schedule and budget reviews and reports for the agency, including mitigation strategies, schedule recovery efforts, and risk assessment reviews.
Some of the challenges or encumbrances of the Second Avenue Subway, NY, project were:
Right of way acquisitions
Complex shoring & underpinning of buildings, and complex SOE (support of excavation)
Implementation of mitigation strategies
Complex systems integration
Volatile risk assessments
Rigorous MPT requirements
A link to an annotated historical timeline of the project may be found here.