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No. 7 Subway (Flushing) Line Extension

Metropolitan Transportation Authority Capital Construction (MTACC)

Gall Zeidler Consultants developed conceptual designs of construction methods for the extension of the existing No. 7 Subway (Flushing) Line from Times Square Station to 26th Street and 11th Avenue with a Terminal Station at 34th Street and 11th Avenue. The design included access tunnels, Tunnel Boring Machine (TBM) assembly and disassembly chambers, station caverns, tunnels and shafts.

Conceptual Tunnel Designs:

The designs required approximately 1.5 miles (2.4 kilometers) of TBM-driven running tunnels and two large-span station caverns measuring 60 feet (18 meters) and 100 feet (30.5 meters) wide, respectively. Each measures approximately 1,000 feet (305 meters) long with access and egress tunnels (escalator, ventilation, etc.) designed using the Sequential Excavation Method (SEM).


New York, New York


2002 – 2003


Running Tunnels, Two Stations


Approximately 1.5 miles (2.4 kilometers)


Maximum 3,700 square feet (344 square meters)


Man-Made Fill, Alluvial and Glacial Sediments, Weathered and Hard Rock (Manhattan Schist), with Groundwater Table at Approximately 20 feet


Approximately $2.1 Billion


Parsons Brinckerhoff Quade & Douglass, Inc.


Metropolitan Transportation Authority Capital Construction (MTACC)