The Preferred Solution and Design
The Preferred Solution
The Preferred Solution for the Project addresses wet weather flow controls and sanitary servicing needs in one complete system, and has been developed based on the extensive research and analysis, and consultation with the public, agencies and other stakeholders.
The Preferred Solution recommends installing a series of integrated underground tunnels, and storage shafts that will capture, store, and transport stormwater and combined sewer overflows to a new wet weather flow treatment facility. The solution also recommends a number of offline storage tanks to store peak sanitary flows and to capture combined sewer overflows from remote outfall locations.
Conceptual images of an underground vertical storage shaft and odour housing control unit (above and below).
Conceptual image of an Offline Storage Tank.
The Preferred Solution includes the following:
- Three integrated tunnels (approximately over 22 km in total)
- Lower Don River Tunnel/ Coxwell Bypass
- Taylor Massey-Creek Tunnel
- Inner Harbour Tunnel
- 15 underground vertical storage shafts (30 metres in diameter), connected to the tunnel system that will temporarily store wet weather flows.
- Four underground storage tanks for offline storage of peak sanitary flows where additional capacity is needed.
- Three underground storage tanks for offline storage of combined sewer overflows from four remote outfall locations.
- Wet weather flow connections that will link all of the parts of the system (tanks, tunnels and shafts) with the problematic outfalls.
- A new pumping station at Ashbridges Grove Park.
- A treatment facility near the Ashbridges Bay Treatment Plant that will provide high-rate treatment of stormwater and combined sewer overflows.
- Upgrades to the North Toronto Treatment Plant.
A key innovation of the preferred solution is the Lower Don River/Coxwell Bypass tunnel, which will serve the dual purpose of capturing and transporting combined sewer overflows to a new wet weather flow treatment facility, as well as providing redundancy (i.e. an alternative sewage route) to the Coxwell Sanitary Trunk Sewer.
The Preferred Design
The preferred design concept (map) identifies the recommended locations for the various project elements including underground vertical storage shafts, offline storage tanks, and a wet weather flow treatment facility.
Responding to public feedback
In June 2011, the preliminary preferred design concept for the Project was presented at a series of Public Information Centres. Based on the public feedback received and further evaluation, the preferred design has been modified as follows:
- Underground vertical storage shaft in Little Norway Park has been moved to the Keating Railyard site.
- Underground vertical storage shaft at the York off ramp parkette has been moved to the Keating Railyard site.
- Underground vertical storage shaft at the Rees Street parking lot at Queens Quay has been moved to the Keating Railyard site. Temporary use of the Rees Street site as a construction shaft is being recommended to allow for construction of the Inner Harbour tunnel.