Peninsula Harbour: Area of Concern

As of August 2012, all actions required to restore water quality and ecosystem health were completed in this Area of Concern (AOC). Environmental monitoring and assessments are being completed in order to determine environmental restoration criteria have been met. 

Why was it listed as an Area of Concern?

Peninsula Harbour was designated an AOC because a review of available data indicated that water quality and environmental health were severely degraded. Further monitoring showed high levels of contaminants in fish and sediment, loss of fish habitat, and degraded fish and benthic communities (worms and insects that live on the lake floor). These problems were caused by discharge of wastewater from the municipal sewage treatment plant, a former pulp mill, and associated chemical plant, and log booming. The situation resulted in six of the Great Lakes Water Quality Agreement’s 14 beneficial use indicators (BUIs) of ecosystem health being deemed as impaired.

What has been accomplished?

Through the combined efforts of Environment and Climate Change Canada, the Ontario Ministry of the Environment and Climate Change, local industry, concerned citizens and other partners, there has been significant improvements to water quality and ecosystem health in Peninsula Harbour. Of the original six BUIs, two have been re-designated to “not impaired” status, namely fish tumours and other deformities and restrictions on dredging activities leaving four impaired beneficial uses: restrictions on fish and wildlife consumption, degradation of fish and wildlife populations, degradation of benthos, and loss of fish and wildlife habitat.

All actions have been completed for municipal and industrial wastewater treatment. The implementation of federal pulp and paper regulations, and the provincial Municipal Industrial Strategy for Abatement regulations in the mid-1990s, led to process changes and upgrades to the Town of Marathon sewage treatment plant and the local pulp mill which closed permanently in 2009. These actions significantly improved water quality and aesthetics in the area and resolved problems with bacterial contamination, foam and odour.

In 2012, a $7 Million project placed 15 to 20 centimetres of clean sand on top of the most contaminated sediment in Jellicoe Cove - a process known as thin-layer capping. This was the first project of its kind to be undertaken in the Canadian Great Lakes. Thin-layer capping creates a clean fish habitat, stops the spread of contaminated sediment, and reduces risk to fish, fish-eating birds, mammals and people. 

In 2013, a follow-up examination concluded there was no mobilization of the cap, suggesting a successful installation. Engineering studies predict the cap will accelerate the natural recovery process by 75 years.

What’s left to do?

The capping project represents the last major restoration action to be completed in the AOC. A long-term monitoring plan is in place to evaluate the performance and effectiveness of the cap, and to monitor ecological recovery. A follow-up assessment of the cap’s integrity and re-colonization of the benthic community is planned for 2017, which will mark five years since the cap was put in place.

Environmental monitoring and assessments remain to be completed in order to determine the status of the remaining four BUIs and whether their respective delisting criteria have been met. Once monitoring and the BUI assessments confirm restoration of water quality and ecosystem health, the Government of Canada and Ontario will consult with the local and Indigenous community, and stakeholders on removing Peninsula Harbour from the list of Great Lakes AOCs.


Results of ecological and post cap construction monitoring will inform decision-making as to whether Peninsula Harbour will be delisted. A decision is expected by 2019.


Efforts in Peninsula Harbour were undertaken in partnership between the Government of Canada, other levels of government and non-government groups, including members of the public. 

One agency or group cannot engage in such a large task on its own, without the help of others.

Listed below are participants that contribute to efforts in the Peninsula Habour AOC:

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