Rehabilitation Sites in the
Thunder Bay Area of Concern

How to use the map viewer

This map has been grouped into several categories integral to the environmental health of Thunder Bay on Lake Superior. These categories are water quality, sediment quality, habitat, and fish and wildlife health.

Water Quality

Water quality is important to the health of an ecosystem. One of the primary reasons Thunder Bay was listed as an Area of Concern was due to industrial effluents from pulp mills and other industries that had degraded the quality of the water. Chemical contaminants such as dioxins, furans, polycyclic aromatic hydrocarbons (PAHs), creosote, polychlorinated biphenyls (PCBs) and mercury all became chemicals of concern in the Thunder Bay harbour from these various industrial operations.

In addition to these chemical contaminants, increases in water temperature and/or increased organic nutrient loads result in unsightly algal blooms. Algal blooms were a concern because when large masses of algae die decomposition of this organic material requires high levels of oxygen, called the biochemical oxygen demand (BOD). With a high BOD level any oxygen present in the water is used to decompose algal blooms and it therefore unavailable to fish and other aquatic organisms that require oxygen to survive.

By implementing new industrial processes that do not require such harsh chemicals or adding a secondary stage to the treatment of the wastewater helps to lower the BOD and reduce potential chemical contaminants entering our waterways. This map highlights some of the projects around the Thunder Bay Area of Concern that helped to remediate or cleanup the water.

Sediment Quality

Sediment quality and health are important in an aquatic environment because sediment-dwelling organisms, or benthos, live above or within the first few feet of a lake or streambed and comprise an important part of the food web for larger aquatic species.

The importance of sediment quality can be seen when looking at fish. For example, virtually all fish species and many birds will consume aquatic invertebrates at some point in their life cycle. Similarly, aquatic invertebrates also represent important food sources for both amphibians (e.g., frogs and salamanders) and reptiles (e.g., snakes and turtles). Sediments also provide an important habitat for many wildlife species during their life cycle. For example, many fish species will use the sediments for spawning or to incubate their eggs. Juvenile fish will also find refuge from larger predator fish within the sediments and aquatic vegetation the sediment supports.

Furthermore, some amphibian species will burrow into the sediments and overwinter there. Therefore the overall health of the sediment is an important ecological factor and one that various remediation projects sought to address.


In addition to improving aquatic environments through water quality and sediment remediation projects, land-based organisms require habitat to breed, forage for food, and seek shelter. Urban landscapes often fracture wildlife habitats by restricting the mobility and space wildlife has to accomplish breeding, foraging, and seeking safety and shelter. Through the Remedial Action Plan, a number of remediation projects were completed that helped create larger areas for wildlife to utilize, increased the connectivity between various habitat areas, and ensure threatened species were able to find a home.

Fish and Wildlife Health

The overall health of fish and wildlife populations is another important factor for the RAP. Improving water and sediment quality along with projects that create habitat are important factors contributing to the health of fish and wildlife. In order to have a healthy and sustainable fish or wildlife community there needs to be a well-distributed age structure with adequate number of juvenile, breeding age, and older individuals within the population.

Scroll to Top