Technicore was the tunnel and shaft subcontractor to Aecon Construction and Materials for this project. Upon encountering substantial boulder content during launch shaft excavation, at the depth of the tunnel alignment, Technicore proposed a no cost change to the owner to use a tunnel digger shield instead of a Microtunnel Boring Machine (MTBM) to reduce the risk of having to potentially sink a retrieval shaft in the travelled of the 407 due to hindrance of advancement by potential large obstructions. The single drive tunnel was successfully completed in glacial till deposits with very high boulder content without any issues.

This project involved pipe jacking of 126m of 1200mm ID reinforced 140D class microtunnelling pipe. The tunnel was constructed with a 1524mm tunnel digger shield machine equipped with a face shield and screw conveyour as to facilitate sealing of the excavation face if required. Bentonite slurry was used for pipe lubrication and contact grouting was performed upon tunnel completion to ensure no voids existed around the pipe. Furthermore, one intermediate jacking pipe/jacking station was utilized along the alignment. The tunnel was excavated into silty clayey over-consolidated glacial till with cobbles and boulders an average depth below the highway of 7m.

Additionally, this contract included the excavation and support of the jacking shaft and retrieval shaft. The jacking shaft has a diameter of 7.4m with a depth of 8m and was supported with liner plates that were grouted in place. The retrieval shaft has a diameter of 7.4m with a depth of 10m and is supported with liner plates that are grouted in place. Both shafts were excavated into silty clayey over-consolidated glacial till.