Cleaning up Our Waterways

Toronto is embarking on the largest and most significant stormwater management program in the city’s history. With an overall budget of more than $3 billion, this program will greatly improve the water quality in the Lower Don River, Taylor-Massey Creek and along Toronto’s Inner Harbour by keeping combined sewer overflow out of our waterways through the upgrading of technology and capacity to capture, transport and treat it. Construction is well underway. More information about each individual project can be found on the project overview page.

In 1987, the International Joint Commission identified Toronto’s waterfront as one of 43 polluted “Areas of Concern” in the Great Lakes Basin, largely because of impaired water quality and sediment conditions in the Don River and Inner Harbour.

Water quality in the Lower Don River, Central Waterfront and Taylor-Massey Creek is degraded due to:

  • Combined sewer overflows: Toronto’s original sewer system dates back more than a century and was built with combined sewers—a very common design at the time. Today, just less than 25 per cent of the city is serviced by combined sewers, where stormwater runoff and sewage travel in one pipe and can be discharged, untreated, into local waterways during heavy rain.
  • Stormwater runoff: In our urban environment with many hard surfaces, water has little or no place to be absorbed and therefore makes its way into the nearest creek, river or storm sewer, picking up what is on our roofs, roads, cars and sidewalks. This water is referred to as stormwater runoff and can include oil, grease, bird/animal droppings, pet waste, cigarette butts and other litter, bacteria and other pollutants.


  • Erosion and sediment conditions: Following the construction of Ashbridges Bay Park in the mid-1970s, sediment eroding from the Scarborough Bluffs began to be deposited at the mouth of Ashbridges Bay in the Coatsworth Cut navigation channel. Erosion and sediment conditions created the need for regular dredging to maintain safe passage for boats in the area. Currently, this is being done annually; however, the increasing dredging volumes and costs have been identified as unsustainable.

The Program is the largest and most significant water quality improvement undertaking in the City of Toronto.

After years of study and design work, construction began in 2018. Once fully implemented, the Program will virtually eliminate the release of combined sewer overflows into the Lower Don River, Taylor-Massey Creek and Toronto’s Inner Harbour. It will also provide erosion and sediment control in Ashbridges Bay.

The Program is made up of several individual projects that will work together.

When fully implemented, the project will:

  • Virtually eliminate combined sewer overflows and stormwater runoff being released into the Lower Don River, Taylor-Massey Creek and Toronto’s Inner Harbour, which will:
    • significantly improve water quality in these areas
    • enhance recreational uses, such as swimming, boating, and fishing
    • improve aquatic habitat for fish and other wildlife
    • reduce nutrient levels that cause excessive algae growth
    • support revitalization efforts along the Central Waterfront
    • help the City meet provincial requirements for controlling combined sewer overflows
    • move us closer to delisting Toronto’s waterfront as a polluted Area of Concern in the Great Lakes Basin
  • Improve capacity in the system to help service population growth.
  • Via the Coxwell Bypass Tunnel (stage one of the Don River and Central Waterfront Tunnel System), allow for the diversion of the sewage flow going to the existing Coxwell Sanitary Trunk Sewer – which carries sewage for about 75 per cent of Toronto – to enable the necessary, periodic maintenance and safe operation of this very important sewer.

The Program in place today is based on extensive research, analysis, input from the public, agencies, and other stakeholders. This includes:

  • The Ashbridges Bay Treatment Plant Environmental Assessment, approved in 1999.
  • The development of the Wet Weather Flow Master Plan (WWFMP) to help reduce the impacts of stormwater runoff and combined sewer overflows, approved by Toronto City Council in 2003.
  • The Don River and Central Waterfront Class Environmental Assessment, part of the WWFMP, approved in 2012.

Map of the Don River and Central Waterfront Project

Don River and Central Watefront. Click on map to enlarge. 
The program will greatly improve the water quality in the Lower Don River, Taylor-Massey Creek and along Toronto’s Inner Harbour.

The three tunnels capture combined sewer overflow (stormwater mixed with raw sewage), thereby keeping it out of:

  1. Lower Don River: protected by the Coxwell bypass tunnel
  2. Taylor-Massey Creek: protected by the Massey Creek tunnel
  3. Toronto’s Inner Harbour: protected by the Inner Harbour West tunnel

The tunnels capture the combined sewer overflow and transport it down to Ashbridges Bay Treatment Plant – where it will be:

  1. Pumped into the Plant via a new integrated pumping station
  2. Treated (a new UV disinfection facility and a new high rate treatment facility)
  3. Returned to the Lake through a new larger outfall

Don River and Central Waterfront short video. 

As with all construction projects, disruptions to the local community will occur. Every effort will be made to keep residents informed and disruptions to a minimum. Once construction is completed, sites will be restored and enhanced in consultation with the local community.

Construction Notices

Ashbridges Bay Treatment Plant Integrated Pumping Station

Site Preparation

Ashbridges Bay Treatment Plant Outfall Tunnel Construction

Coxwell Bypass Tunnel

Construction at Ashbridges Bay Treatment Plant

Construction at Keating Railyard

Construction at Bayview Avenue and Bloor Street East

Construction at North Toronto Treatment Plant

Construction at Coxwell Ravine Park

Construction at Riverdale Park West (at River Street and Gerrard Street East)

Construction at Bayview Avenue and Rosedale Valley Road

Construction at Mount Stephen Street

Construction of a Underground Shaft at Bloor-Bayview Off-Ramp

Construction at Lake Shore Boulevard East and Carlaw Avenue

Don River Outfall

Construction to an existing outfall into the Don River

Inner Harbour West Tunnel

Site Investigations Along Waterfront

Main Sewage Treatment Playground Construction and Upgrades

Main Sewage Treatment Playground is located at 1091 Eastern Avenue.

Tubs & Gee Gage Rugby Field Relocation and New Parking Lot Construction