Don River and Central Waterfront Wet Weather Flow System & Connected Projects – Project List

Don River & Central Waterfront Wet Weather Flow System

The Don River and Central Waterfront 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 and will include:

• a 22 km tunnel system consisting of three integrated tunnels:
  • Coxwell Bypass Tunnel
  • Inner Harbour Tunnel
  • Taylor-Massey Creek 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 to regulate flows in the City’s sewer system

Project updates and timing

Timing of the future stages is dependent on funding, regulatory approvals and other considerations.

View construction notices for all current projects.

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
• replace two existing pumping stations, one of which has been operating since the 1900s and the other since the 1970s
• be constructed on the property south of Lake Shore Boulevard East (both old pumping stations are north of Lake Shore Boulevard East in Ashbridge’s Bay Sports Hub, formerly Main Sewage Treatment Playground)

Project updates and timing

Construction will span 2018 to 2039.

View construction notices for all current projects.

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Ashbridges Bay Treatment Plant Landform

The Ashbridges Bay Treatment Plant Landform was a joint initiative between the City and Toronto and Region Conservation Authority (TRCA). Completed in May 2025 and located south of the Ashbridges Bay Treatment Plant, it is the site of a stormwater treatment wetland and the future site of the High Rate Treatment Facility.

The landform provides erosion and sediment control to improve passage for boats, eliminating the need for regular dredging in the Coatsworth Cut area of Ashbridges Bay

The landform features include:

• armourstone headlands for shoreline protection
• cobblestone shorelines between the headlands to reduce erosion
• East and Central Breakwaters to control waves and sediment movement
• underwater habitat shoals for fish and other aquatic wildlife
• a sunken tree field and woody habitat features
• naturalized shoreline areas with aquatic plantings
• public trails and walkway connecting to Tommy Thompson Park

Learn more about the landform project from TRCA.

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High Rate Treatment Facility

The High Rate Treatment Facility is designed specifically to provide treatment of combined sewer overflows intercepted by the new tunnel system. It will be built on the Ashbridges Bay Treatment Plant Landform.

Project updates and timing

The High Rate Treatment Facility is in the design phase and is expected to be completed by the end of 2038.

Ultraviolet (UV) 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

Project updates and timing

Construction began in 2019. The treatment system is expected to be in service by the end of 2026.

View construction notification for all current projects.

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Ashbridges Bay Treatment Plant Outfall (Video)

Ashbridges Bay Treatment Plant Outfall full-length video

The Ashbridges Bay Treatment Plant Outfall is being built to improve capacity and better convey and disperse effluent (fully treated wastewater) to Lake Ontario.

The outfall includes:

• a 14 m diameter shaft, about 85 m deep
• a 3.5 km long, 7 m diameter tunnel, mined through rock beneath the lakebed
• 50 riser pipes connected to the tunnel to disperse treated and disinfected effluent into Lake Ontario

Project updates and timing

As of summer 2026, the Ashbridges Bay Treatment Plant Outfall has been completed and will be put into service upon completion of the UV disinfection wastewater treatment system.

View construction notices for all current projects.

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Ashbridges Bay Treatment Plant Outfall short video

Ashbridges Bay Treatment Plant Outfall short video with project highlights

Ashbridge’s Bay Sports Hub: Park Usage & Upgrades

Usage

While building the integrated pumping station, there will be construction activity at the Ashbridge’s Bay Sports Hub (formerly Main Sewage Treatment Playground). The park runs south from Eastern Avenue to Lake Shore Boulevard East; west of Emdaabiimok Avenue. Construction activity will include:

• using the space along the west end of Ashbridge’s Bay Sports Hub at the former location of the Tubs and Gee Gage Rugby Field for construction work and storing materials, equipment and trailers
• using the eastern half of the existing parking lot at the northwest end of the park for construction administration office trailers

Upgrades

Upgrades to the park included:

• relocating the Tubs and Gee Gage Rugby Field to north of Ashbridges Skateboard Park
• a new parking lot with 55 parking spaces, bike racks and lighting system on the east side of the park
• two new basketball courts
• 11 new pickleball courts