St. Clair River: Area of Concern

The St. Clair River was designated a binational Area of Concern (AOC) in 1987 under the Canada-U.S. Great Lakes Water Quality Agreement. Years of industrialization, urbanization and agricultural land use activities led to severely degraded water quality and ecosystem health in the river and its tributary watersheds. Nine out of 14 beneficial use impairments (BUIs) were identified, which measure the environmental, human health and economic impact of poor water quality. A further three beneficial uses were deemed as “requiring further assessment”, meaning more information was required to determine whether they were impaired.

Accomplishments

Over the past 30 years, there has been significant progress in restoring the water and environmental quality of the river. This includes:

the clean-up of 13,300 cubic meters of mercury-contaminated sediment by Dow Chemical in 2002
the placement of an erosion-resistant cover over contaminated sediments in the three remaining priority areas, completing the final remedial action for this AOC
improved spill notification, response and prevention, resulting in fewer spills and closures of drinking water intakes since the 1980s

Restoration of beneficial uses

Over the last decade, significant progress has been made to improve environmental conditions on the Canadian side. These beneficial uses are no longer considered “impaired”:

tainted fish and wildlife flavour (2011)
added costs to agriculture or industry (2012)
degradation of aesthetics (2016)
beach closings (2018)
restrictions on dredging activities (2018)
bird or animal deformities or reproductive problems (2018)
fish tumours (2020)
restrictions on drinking water (2021)

As of 2025, assessment reports recommending a “not impaired” status for the following BUIs have been completed for:

degradation of fish and wildlife populations − studies show that fish and wildlife populations are similar to or better than populations found outside the AOC
loss of fish and wildlife habitat − data confirms that the restoration criteria for this BUI have been met

Work continues on restoring the remaining beneficial uses:

restrictions on fish and wildlife consumption – data shows improvements to fish contaminants and concentrations of several contaminants in wildlife
degradation of benthos − management of contamination is complete and ongoing monitoring will be conducted

Recent actions

The overall health of the St. Clair River has improved through these recent actions:

ten shoreline projects have restored more than two kilometers of nearshore fish habitat since 2012, improving access to the river by other aquatic wildlife such as mink
over 300 hectares of coastal wetland habitat from Walpole Island to the southern end of Mitchell’s Bay have been enhanced by removing invasive plants, and adding habitat structures and native plants to provide valuable habitat for fish and wildlife
in March 2025, an erosion-resistant cover was placed over contaminated sediment in three areas downstream of Sarnia

Remaining actions

We will continue to work with local and provincial partners to support monitoring and assessment studies needed to confirm environmental quality objectives are met. Priorities are to:

complete the assessment of restrictions on fish and wildlife consumption, and engage communities on the related status report
develop and implement a strategy to assess benthos populations, prepare a status report and engage with the community for input

Outlook

The St. Clair River AOC has made significant progress, and it is anticipated that two of the four remaining BUIs will be restored by 2025. All sediment and habitat restoration actions are complete. Under the Canada-Ontario Agreement on Great Lakes Water Quality and Ecosystem Health, we will work with the province of Ontario to continue making progress towards remediation, environmental recovery and restoration of beneficial uses. As a binational AOC, Canada and the United States continue to work closely together to achieve delisting.

Our partners

On the Canadian side, we partner with other levels of government, non-government groups, Indigenous communities and members of the public. This restoration work requires a large amount of scientific and technical expertise, local knowledge, hard work and the help of:

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