Thunder Bay: Area of Concern

Thunder Bay was designated as an Area of Concern (AOC) in 1987 under the Canada-U.S. Great Lakes Water Quality Agreement. Years of contamination, primarily from the forest products industry, as well as from waste disposal, urbanization and changes to the watercourse led to the degraded water quality and environmental health. Ten out of 14 beneficial use impairments (BUIs) were identified, which measure the environmental, human health or economic impact of poor water quality. One additional beneficial use was deemed “requiring further assessment”, meaning more information was required to determine whether it was impaired.


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

  • implementing stricter regulations introduced in the mid-1990s, which resulted in mill process changes, as well as upgrades to municipal wastewater treatment
  • development and implementation of the City of Thunder Bay’s Stormwater Management Plan and several low impact design features in local waterways to address the effects of stormwater on water quality and fish habitat
  • investment of $20 million to complete the Northern Wood Preservers Alternative Remediation Concept (NOWPARC) project in 2003 to isolate 32,000 cubic meters of highly contaminated sediment and create five hectares of fish habitat
  • completion of habitat rehabilitation projects to create 1,700 square meters of fish spawning and nursery areas in the Current River estuary; aquatic habitat in five tributaries flowing into Thunder Bay; island habitat at the mouth of McVicar Creek; and 3 hectares of wetland in the nearshore of McKellar River 

Restoration of beneficial uses

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

  • beach closings (2023)
  • added costs to agriculture or industry (2004)
  • restrictions on dredging activities (2012)
  • degradation of aesthetics (2019)
  • fish tumours or other deformities (2019)
  • bird or animal deformities or reproduction problems (2019)
  • degradation of phytoplankton and zooplankton populations (2020)

Work continues on restoring the remaining beneficial uses:

  • degradation of fish and wildlife populations – an assessment of the fish populations is underway and an assessment of wildlife populations has been drafted
  • degradation of benthos – monitoring and reporting is underway for two of the three focus areas involving contaminated sediment (the NOWPARC area and Kaministiquia River delta), and a best approach consultation continues for the third area (Thunder Bay North Harbour)
  • loss of fish and wildlife habitat – studies show wetlands are healthy and improvements have been made to fish habitat due to the cleanup of contaminated sediment, reconstruction of shorelines and spawning areas, and improvements to water quality; for wildlife habitat, future work will include the creation and restoration of riparian and coastal habitat
  • restrictions on fish and wildlife consumption – wildlife consumption is not impaired and  data suggests positive improvements in fish contaminants with further assessment underway 

Recent actions

The overall health of Thunder Bay has seen measurable improvement as shown by these recent actions:

  • evaluation led by a multi-stakeholder working group on ways to manage contaminated sediment in Thunder Bay North Harbour
  • review of the working group’s recommendation to develop project design and cost estimate to support project implementation 

Remaining actions

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

  • further enhance wildlife habitat, specifically near the water’s edge, and develop a wildlife habitat strategy to outline specific restoration projects
  • select and develop an approach to manage contaminated sediment at Thunder Bay North Harbour


The Thunder Bay AOC has seen significant progress towards restoration. 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. 

Our partners

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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