Hamilton Harbour: Area of Concern

Environment and Climate Change Canada and its partners have implemented many projects and studies to restore water quality and ecosystem health in the Hamilton Harbour Area of Concern (AOC). The last two major steps in the remediation process are the cleanup of contaminated sediment at the Randle Reef location and the upgrading of the Woodward Avenue Wastewater Treatment Plant in Hamilton.

Why was it listed as an Area of Concern?

Hamilton Harbour was designated as an AOC because a review of available data indicated that water quality and environmental health were severely degraded. The harbour had been subject to the impacts of intensive industrial and urban development around its shores for many years which resulted in nine of the Great Lakes Water Quality Agreement's ten beneficial use indicators of environmental quality being deemed as impaired. Historically, the economy of the area surrounding Hamilton Harbour was dominated by the steel and iron industry. Today, the harbour remains a major shipping centre and supports one of the largest concentrations of heavy industry in Canada. It also receives the discharge from three wastewater treatments plants, as well as urban runoff from the cities of Hamilton and Burlington. Some sediment in the harbour are contaminated by metals, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) which were released into the environment by past industrial practices, stretching back over more than a century.

What has been accomplished?

The Randle Reef cleanup project is a major step in the process to remediate Hamilton Harbour and remove it from the list of AOCs. Randle Reef is an area of highly contaminated sediment located in the southwest corner of Hamilton Harbour. Construction of the Randle Reef Contaminated Sediment Remediation began in 2015. This project will improve water quality, remove current restrictions on navigation and generate economic returns through the creation of valuable port lands. The project will cost $138.9 Million and take seven years to complete. Environment and Climate Change Canada, and the Ontario Ministry of the Environment and Climate Change, have each committed $46.3 Million, with the final third of funding coming from the City of Hamilton, City of Burlington, Halton Region, Hamilton Port Authority, and U.S. Steel Canada. The cleanup will remediate approximately 695,000 cubic metres of contaminated sediment which will significantly reduce harmful contaminant levels and improve water quality in Hamilton Harbour. The project is currently in Stage One, which involves the construction of the Engineered Containment Facility (ECF) into which the dredged contaminated sediment will be placed.

An upgrade to the Woodward Avenue Wastewater Treatment Plant (WWTP) and the construction of combined sewer overflow tanks have reduced the amount of raw sewage and surface debris entering the harbour and allowed for the opening of local beaches.

A project to upgrade the Skyway Wastewater Treatment Plant to tertiary treatment was completed in early 2016. The tertiary treatment upgrades to the Woodward and Skyway WWTPs were designed to achieve Hamilton Harbour Remedial Action Plan target for nutrient loading. With 50% of the flows into Hamilton Harbour coming from WWTPs, this work is important to reduce future algae blooms and improve overall water quality.

Programs have been implemented to return aquatic vegetation to Cootes Paradise Marsh. These include measures to control carp, improve water quality and water clarity. Similar programs are in place for the Grindstone Marsh ecosystem. In addition, fish habitat has been constructed along the western shoreline of the harbour, Bayfront Park, LaSalle Park and the northeastern shoreline. In total, approximately 376 hectares of fish and wildlife habitat and 12 kilometres of shoreline habitat have been restored.

A shoal has been constructed in the northeast corner of Hamilton Harbour to provide spawning habitat for walleye and smallmouth bass, and to encourage species such as lake herring and whitefish to return to Hamilton Harbour.

Islands for the nesting of colonial waterbirds have been constructed in the harbour and a 15-hectare wetland has been constructed in Windermere Basin, which includes islands for common tern nesting.

What’s left to do?

Once the Randle Reef ECF has been constructed, dredging of priority 1 and 2 contaminated sediments (the most highly contaminated sediment) will begin and the dredgate placed into the ECF. After dredging has been completed, the ECF will be capped, and in-situ capping of the lesser contaminated sediment will be undertaken.

Additional remediation of contaminated sediment at the ArcelorMittal Dofasco Boat Slip and the Strathearne boat slip is being investigated, to mitigate high levels of PCBs, PAHs and heavy metals that are a legacy of past industrial processes around the bay.

Federal, provincial and municipal funding has been secured for further upgrading of the Woodward plant to advanced tertiary treatment and project design engineering is underway with construction targeted for completion by 2021. This will significantly reduce the amount of phosphorus and sediment entering Hamilton Harbour by providing three levels of treatment to wastewater.   


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 Hamilton Harbour AOC. It is anticipated that actions will be completed beyond 2020.


Efforts in Hamilton Harbour 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 the Hamilton Harbour AOC:

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