The project took place in a very busy urban area in Mississauga, Ontario. The work was complete in areas with very limited footprint and located at the intersection of two arterial roads and immediately adjacent to an environmentally sensitive creek under the Credit Valley Conservation Authority’s jurisdiction. The tunnel was mined majority in shale ranging from 15 to 40 meters dep with approximately 750 meters in soil conditions that included water bearing sand and silty sand, clayey silt, silty clay, all of which had a very high content of cobbles and boulders. The project included the construction of approximately 3800 meters of 3.0 meters internal diameter sanitary trunk sewer installed in a single-pass using precast concrete tunnel liners (PCTL). Toxic hydrogen sulfide gases were encountered during tunneling operations and shaft construction, therefore a high-density polyethylene (HDPE) protective layer was installed to protect the concrete from corrosive gases.

Technicore utilized two 3.6 meter EPB TBM, designed and built by TUC to complete the project. Multiple drive lengths were completed at 2028 meters, 1120 meter and 688 meters in length in a single-pass using PCTL installed behind the machine and grouted in place. The project also involved completing an alignment curve that was a 123m radius. Since the tunnel was mined mostly in the Georgian Bay shale formation, the project involved the use of a unique, proprietary compressible grout to fill the annual space of the outside tunnel lining to deal with the time dependent deformation (TDD) after excavation. The compressible grout not only eliminated the deterioration and damage to the tunnel liners, it also secured the assembly in place and allowed for continuous EPB TBM thrust and advancement. The soft ground sections of the tunnel was completed in EPB mode. The project also encountered HS gases which required the use of a corrosion resistant lining HDPE liners installed for 250 meters of the tunnel. Five sanitary manholes were construction utilizing a combination of cast-in-place and C300 water-tight structures that were able to withstand 50psi and prevent infiltration and exfiltration into the tunnel.

Additional scope was added to include the construction of two additional tunnels approximately 805 meters in length utilizing a 1.5 meter single-pass MTBM and pipe jacking and provided a cross connection of the West Trunk Sewer to another existing trunk sewer on Mississauga Road.

On this project and as part of the original contract scope, Technicore also constructed approximately 450 meters of 300 mm diameter watermain utilizing trenchless (HDD) and open cut subcontractors. Work was completed within very environmentally sensitive area and crossing Loyalist Creek without any major issues.