Toronto and region: Area of Concern

The contributions of federal, provincial and local agencies, local industries, and others continue to have a positive impact on restoring water quality and ecosystem health within the Toronto and Region Area of Concern (AOC).

Why was it listed as an Area of Concern?

The Toronto region was designated as an AOC in 1986 because a review of available data indicated that water quality and environmental health were severely degraded. Several centuries of agriculture and urban development have dramatically reshaped the natural environment of the Toronto and Region AOC. Contaminants from stormwater runoff and melting snow from the area’s six watersheds create serious impacts in Lake Ontario. Overflows of stormwater mixed with raw sewage are a serious problem following heavy rains in the lower portions of the Don and Humber Rivers and along the waterfront. Spills, road runoff and chemical input to sewers from industries and residences also contribute to poor water quality. In the Toronto and Region AOC’s Remedial Action Plan (RAP) report, Clean Waters, Clear Choices: Recommendations for Action (1994) eight beneficial uses were identified as impaired and three were identified as requiring further assessment.

What has been accomplished?

Since the RAP began in 1987, agencies, municipalities and non-governmental organizations have worked together to improve the environmental conditions in the Toronto AOC. Implementation of remedial and restoration actions began in 1994 and has led to significant and demonstrable improvements in the quality of water and sediment, the amount and condition of terrestrial and aquatic habitats, and the health of aquatic biota and aquatic communities. As an example: phosphorus levels along the waterfront now meet the mesotrophic target set for the RAP; there has been a substantial reduction in loadings of E. coli bacteria to the waterfront which has resulted in a steady decline in beach closings; the health of benthic communities has improved, and; the creation of hundreds of hectares of terrestrial and aquatic habitat along streams and along the waterfront have improved conditions for both fish and wildlife.

A measure of progress from thirty years ago is that four of the original 11 beneficial uses identified as “impaired” or “requires further assessment” have now been re-designated as “not impaired”. These beneficial use impairments (BUIs) are: bird or animal deformities or reproductive problems (2011); fish tumors or other deformities (2011); degradation of benthos (2016), and; restrictions on dredging activities (2016). In addition, an assessment report on the degradation of aesthetics will be completed in 2016 recommending that this beneficial use be re-designated as “not impaired” based on three years of data.

In terms of water quality, the City of Toronto has made significant progress in implementing the City's Wet Weather Flow Master Plan, which is a priority action identified in the Toronto and Region RAP. Since 2003, the City has invested $485 Million in wet weather flow management projects to improve water quality in Toronto's watercourses and the Lake Ontario shoreline, build resilience to infrastructure to reduce flooding risks associated with extreme storms, and carry out projects to restore and protect watercourses from future erosion, to support ecosystem health.

Eight of Toronto’s eleven beaches are now certified as Blue Flag beaches, up from four in 2005 and six in 2007. This reflects their high standards for water quality, along with other factors such as environmental education, environmental management, safety and services. The remaining non-Blue Flag beaches - Marie Curtis Park East Beach, Sunnyside Beach and Rouge Beach - are near the mouths of creeks and rivers, and are therefore greatly affected by stormwater and other inputs of pollution into these tributaries. Environment and Climate Change Canada has recently completed extensive surveillance and microbial source tracking analyses to identify sources of E. coli bacteria that cause beach postings at Marie Curtis East Park and Sunnyside Beaches.

In addressing the degradation of fish and wildlife habitat and populations significant progress has been made through Aquatic Habitat Toronto (AHT) a unique, collaborative organization responsible for implementing the Toronto Waterfront Aquatic Habitat Restoration Strategy (TWAHRS), in support of the Toronto and Region RAP. AHT is comprised of representatives from Environment and Climate Change Canada, Fisheries and Oceans Canada, Ontario Ministry of Natural Resources and Forestry, Toronto and Region Conservation Authority, the City of Toronto, Ports Toronto and Waterfront Toronto. Considerable efforts have been made to protect and restore habitats for fish and wildlife within the Toronto and Region AOC. The development and implementation of TWAHRS has resulted in extensive restoration work being done in Tommy Thompson Park and along the Toronto waterfront. This has included restoring and creating coastal wetlands, restoring and naturalizing shorelines, restoring habitat lost through urban development and creating new habitats to support the complex lifecycle requirements of fish and wildlife.

What is left to do?

In the Toronto and Region AOC, implementing large infrastructure projects and upgrading Toronto’s Main Sewage Treatment Plant are major priorities. These projects, as well as the City of Toronto’s Wet Weather Flow Management Plan, the Don River and Central Waterfront Trunk Interceptor Project, and the Combined Sewer Overflow Control and Treatment Strategy, will all significantly improve water quality on the Toronto waterfront.

Realigning and naturalizing the mouth of the Don River is another major restoration project. This project will reduce flooding, create a more natural river mouth, and add a significant amount of new wetland and riparian (the interface between land and a river or stream) habitat to the Toronto waterfront. 

The restoration of coastal wetland habitat for fish and wildlife is a priority for Toronto, due to the historic filling of 428 hectares of Ashbridges Bay Marsh on the Don River mouth to create Toronto’s port facilities. As such, the continued implementation of the Toronto Waterfront Aquatic Habitat Restoration Strategy is key to ensure that waterfront projects incorporate improvements to aquatic habitats and fisheries resources to create a more liveable and sustainable waterfront, with the ultimate goal of delisting Toronto as an AOC under the Great Lakes Water Quality Agreement and the Canada-Ontario Agreement on Great Lakes Water Quality and Ecosystem Health.


Under the Canada-Ontario Agreement on Great Lakes Water Quality and Ecosystem Health, Canada and Ontario will continue to make significant progress towards remedial action implementation, environmental recovery and restoration of beneficial uses in the Toronto and Region AOC. It is anticipated that actions will be completed beyond 2020.


Efforts in Toronto and Region AOC are undertaken in a partnership between the Government of Canada, other levels of government and non-government groups, including members of the public. 

Undertaking environmental restoration requires a large amount of scientific and technical expertise, local knowledge and hard work. One agency or group cannot engage in such a large task on its own without the help of others.

Listed below are participants that have contributed to efforts in Toronto and Region AOC:

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