Don River and Central Waterfront Wet Weather Flow System & Connected Projects – Project List
Don River and Central Waterfront Wet Weather Flow System (DR&CW WWF System)
The DR&CW project will keep combined sewer overflows out of Lower Don River, Taylor-Massey Creek and Inner Harbour by:
capturing it within the tunnel system.
transporting it for treatment.
storing it during heavy rain until system capacity is restored and the water can be transported for treatment.
The project will be done in stages. The first stage is the Coxwell Bypass Tunnel, a 10.5 km long, 6.3 m diameter tunnel. The complete DR&CW Tunnel System will include:
a 22 km tunnel system consisting of three integrated tunnels:
Coxwell Bypass Tunnel (stage one)
Taylor-Massey Creek Tunnel
Inner Harbour Tunnel
11 wet weather flow storage shafts along the tunnels.
27 connection points to the tunnels for stormwater and combined sewer overflow.
seven off-line storage tanks.
Real-Time Control (RTC) to regulate flows in the City’s sewer system.
Timing
Construction of phase one of the Coxwell Bypass Tunnel runs from 2018 to 2025. Timing of the future stages is dependent on funding, regulatory approvals, and other considerations.
Coxwell Bypass Tunnel: As of March 2025, the Coxwell Bypass Tunnel (stage one) is approximately 99 per cent complete. The construction of the five main shafts that are connected to this tunnel is complete: at Ashbridges Bay Treatment Plant; in the Keating Railyard (Lakeshore Ave and Don Roadway); on Bayview Avenue at Bloor Street; at the North Toronto Wastewater Treatment Plant; and at the Coxwell Ravine Park.
Inner Harbour West Tunnel: As of March 2025, this project is in the design phase. Construction is anticipated to begin in 2029.
Taylor-Massey Creek Tunnel: In the early planning stages. More details to come when work is closer to starting.
Integrated Pumping Station: Ashbridges Bay Treatment Plant
The new integrated pumping station will move raw sewage from underground sewers into the treatment plant. The plant will:
receive and pump the additional flows that come from the Don River and Central Waterfront Tunnel System.
provide additional capacity for population growth.
replace the current two pumping stations, one of which has been in operation since the 1900s and the other since the 1970s.
be constructed on the property south of Lake Shore Boulevard East (both of the old pumping stations are north of Lake Shore Boulevard East in Main Sewage Treatment Playground).
provide erosion and sediment control to improve passage for boats, eliminating the need for regular dredging in the Coatsworth Cut area of Ashbridges Bay.
be built south of the Ashbridges Bay Wastewater Treatment Plant and will be the site of the high-rate treatment facility and a stormwater treatment wetland.
The high-rate treatment facility is designed specifically to provide treatment of CSOs intercepted by the new tunnel system.
Timing
Construction of the Ashbridges Bay Treatment Plant Landform began in 2020 and is expected to be completed in 2025.
Project Update
Ashbridges Bay Treatment Plant Landform: As of March 2025, the Ashbridges Bay Treatment Plant Landform is approximately 89 per cent complete.
High Rate Treatment Facility: As of March 2025, procurement of design services is planned for 2025.
Images
UV (Ultraviolet) Disinfection Wastewater Treatment System: Ashbridges Bay Treatment Plant
The UV Disinfection Wastewater Treatment System will:
provide reliable disinfection as part of the wastewater treatment process without the use of chemicals.
replace the current chlorine disinfection system.
use next-generation UV lamp technology which is more energy-efficient and requires less space than conventional UV lamps.
include sodium hypochlorite disinfection and de-chlorination for excessive flows to the plant caused by heavy rain.
Timing
Construction began in 2019 and is expected to be completed in 2025.
As of March 2025, the Ashbridges Bay Treatment Plant UV Disinfection project is more than 94 per cent complete.
Images
Ashbridges Bay Treatment Plant Outfall (Video)
Ashbridges Bay Treatment Plant Outfall full-length video
The Ashbridges Bay Treatment Plant (ABTP) outfall is being built to improve capacity and better convey and disperse effluent (fully treated wastewater) to Lake Ontario.
The completed outfall construction includes:
a 14 metre diameter shaft, approximately 85 metre deep.
a 3.5 kilometre long, 7 metre diameter tunnel, mined through rock beneath the lakebed.
50 riser pipes connected to the tunnel to disperse treated and disinfected effluent into Lake Ontario.
tunnel cleaned.
Future work:
Effluent conduits will be constructed to connect the ABTP disinfection system to the outfall shaft. This will allow fully treated wastewater from the ABTP plant to flow by gravity to the lake.
Tunnelling operations were supported from an onshore shaft.
The riser pipes were drilled from in-water barges.
Timing and Budget
Construction began in 2019 and by end of 2025 the outfall is anticipated to be complete and operational (in-use).
As of March 2025, the Ashbridges Bay Treatment Plant Outfall project is approximately 92 per cent complete.
Images
Ashbridges Bay Treatment Plant Outfall short video
Ashbridges Bay Treatment Plant Outfall short video with project highlights
Main Sewage Treatment Playground: Park Usage and Upgrades
Usage
While building the Coxwell Bypass Tunnel and the Integrated Pumping Station over the next 10 years there will be activity at the Main Sewage Treatment Playground. This park runs south from Eastern Avenue to Lake Shore Boulevard East; west of Coxwell Avenue. The activities here will include:
Space along the west end of Main Sewage Treatment Playground at the current location of the Tubs & Gee Gage Rugby Field will be used for construction activities as well as storing construction materials, equipment, and trailers.
The eastern half of the existing parking lot located at the northwest end of the park will be used for construction administration office trailers.
Upgrades
The Tubs and Gee Gage Rugby Field will be relocated within the park, north of Ashbridges Skateboard Park.
Two new basketball courts will be built, offering an additional enhancement to the playground.
A new parking lot with 55 parking spaces, bike racks and lighting system, will be constructed on the east side of the park.
