This project was notable for its scale, urban location and complex ground conditions. It included the construction of a 765m long, 3400mm ID / 4065 OD reinforced concrete microtunnel, the largest diameter microtunnel completed to date in North America.
A 13m ID launch shaft was sunk 21.45m deep, and the tunnel incorporated two horizontal curves with radii of 300m and 500m, traversing beneath a transit railway and major highway in a dense urban area. The tunnel alignment passed through bedrock and overburden soil with water pressures up to 5.2 bar, requiring specialised equipment including a Herrenknecht AVN 2500 TBM with a mixed face cutting head and an upskin kit.
The Project used specially designed 3.3m long ASTM C76 Class V microtunnel pipes manufactured for the works, with a hydraulic jacking system capable of 2520 metric tonnes to accommodate the tunnel curves and pressures.
