This 25-year, $2 billion, program consists of a number of substantial infrastructure projects that will significantly improve the water quality in the Lower Don River, Taylor-Massey Creek and along Toronto’s Inner Harbour. Thie program will be accomplished by:

  • Keeping combined sewer overflow (a mixture of sewage and rainwater) out of the Don River, Taylor-Massey Creek and Toronto’s Inner Harbour by:
    • capturing it
    • storing it, when the system is overloaded by heavy rainstorms
    • transporting it for treatment
  • Upgrading the technology and capacity to pump stormwater and sewage to treatment.
  • Upgrading the capacity for and location that effluent (treated wastewater) is discharged – especially important during heavy rainstorms.
  • Providing erosion and sediment control in Ashbridges Bay.
  • Replacing a current chlorine gas disinfection system with a new technologically advanced UV disinfection system.
  • Opportunities to upgrade local areas and infrastructure (as a result of this construction work).

In 1987, the International Joint Commission identified the 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 extreme rainstorms. This is compounded by the increased frequency of these storms.
  • 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 construction of Ashbridge’s 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 will begin 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 showing the Don River and Central Waterfront Tunnel System and the Integrated Pumping Station located at Ashbridges Bay Wastewater Treatment Plant

This map shows the Don River and Central Waterfront Tunnel System and the Integrated Pumping Station located at Ashbridges Bay Wastewater Treatment Plant.


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

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 Wastewater Treatment Plant

Construction at Coxwell Ravine Park

Ashbridges Bay Treatment Plant  Integrated Pumping Station

Site Preparation

Ashbridges Bay Park Construction and Upgrades

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