Strabag to build Ashbridges Bay feeder tunnels

19 November 2019

Ontario – The City of Toronto awarded Strabag a CAD 120M contract for the second section of the Ashbridges Bay project, the contractor announced November 18.

The work for the water treatment facility project's new pumping station includes shaft and feeder structures. "The pumping station is part of a larger infrastructure program aimed at increasing sewage system capacity in case of heavy rainfall, thereby improving water quality in Toronto's waterways and Lake Ontario," explains Simon Köck, project manager.

The main part of the construction work consists of two shaft structures: a shaft 68m deep and 27m in diameter, another shaft 27m deep and 32m in diameter. Including five smaller manholes, this results in a total of 153m of construction work on shaft structures. Feeder tunnels with a total length of 445m are cut into the massive shaft structures, as well as a parallel pressure pipe, which is built in an open construction close to the surface.

Another component of the Ashbridges Bay Outfall project already underway  is the 3.5km-long tunnel, 7m internal diameter; under the Lake Ontario bed at depths up to 85m. The tunnel will be constructed using a shielded rock TBM and will be lined with Precast Concrete lining. The geology consists of soft rock/shale of the Georgian Bay Formation. The project includes a starting shaft 14m diameter and 85m deep and a number of 50 raisers that will be installed from barges (marine construction). The project was awarded to SAJV (group consisting of Southland and Astaldi). The contractor mobilized on site, ordered the TBM and started the shaft construction.

Owner: City of Toronto; Anticipated completion: 2024