TORONTO — The Fairbank Silverthorn Storm Trunk Sewer System project, the largest basement flooding protection project in the City of Toronto, recently reached a milestone as the tunnel boring (TBM) machine finished tunnelling the new three-kilometre storm trunk sewer.
This month, the city also hosted a community information session to provide current updates on the status of phase one construction as well as details on the upcoming phase two works.
The project aims to protect against basement flooding in the Fairbank-Silverthorn community. Once construction is complete, the new infrastructure will help to reduce sewer backups and basement flooding for more than 4,645 homes and provide flood protection to a 140-hectare area.
The TBM uses rotating disc-shaped cutting wheels that bore through soil and install pipe segments to create the tunnel walls at a depth of up to 40 metres below ground. Due to the high density and quantity of soil, sediments and materials below ground, the TBM is able to excavate approximately eight to 10 metres per day.
To lower and retrieve both the main TBM and other micro-tunnel boring machines that facilitate tunnel and sewer construction, the 20 shafts that were planned across the area have been completed as well as all necessary micro-tunnelling activity. The majority of tunnelling activity was carried out through a large shaft in Fairbank Memorial Park.
The project involves three infrastructure improvements: the installation of new local storm sewers; construction of a large storm trunk sewer (main tunnel); and installation of inlet control devices (ICDs) to manage stormwater flow to catch basins.
The project is part of the city’s Basement Flooding Protection Program. The federal government has committed $73.2 million in funding through the Disaster Mitigation and Adaptation Fund . The City of Toronto is providing the remaining estimated funding of $250 million.
For phase one of the project, which runs until October 2025, the city, contracted consultant Jacobs Engineering and subcontractor EBC-Bessac Canada JV began construction of the new storm trunk sewer. A portion of the new local storm sewers began and is anticipated to take four years to complete.
Construction activity in Fairbank Memorial Park began in 2021 and is expected to finish in 2025. A large space within the park was required to construct a shaft where the contractor carried out tunnelling work with the TBM. The work involved excavating the ground and importing precast concrete to construct the storm trunk sewer.
Once the TBM is retrieved at the Bicknell Avenue and Nashville Avenue shaft, the shaft locations will be fully restored. That is expected to occur by the end of summer 2025.
The new local storm sewers will be constructed by micro-tunnelling method along Silverthorn Avenue, Gilbert Avenue, Croham Road, Harvie Avenue and Chudleigh Road. Shallower and smaller shafts will be constructed for micro-tunnelling at various locations.
The shaft sites were restored at the end of August.
In the second phase of construction, which will run from this fall to 2027, the city will construct about 17 kilometres of new storm sewers and install additional ICDs. About 330 ICDs will be installed to restrict stormwater from entering combined sewers, reducing combined sewer overflow and the risk of basement flooding.
When construction is completed, the contractor will restore local roads and tunnel shaft locations, including parks.
To see a video on the tunnelling click here.
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