Cornwall Sediment Strategy

A long-term commitment to environmental protection of the St. Lawrence River (Cornwall)


Until a few decades ago, industrial waste and other pollutants discharged directly into the St. Lawrence River. These contaminants settled and built up in high concentrations in the sediment along the Cornwall waterfront. The chief contaminant in this sediment is mercury, a toxic substance that stays in the River environment for years. With the closure of several industries and stricter environmental regulations, cleaner sediment has begun to settle slowly over key areas of contamination, and a natural cap has been created. Cornwall Sediment Strategy administrative controls have been established to ensure mercury contaminated sediment deposits located in 3 zones along the Cornwall waterfront be left in place, undisturbed, to allow a natural recovery process to occur over time.

As they currently exist, historically contaminated sediments in these zones are stable and covered with a cleaner layer of sediment and therefore, do not pose a significant ecological risk.However, certain development activities requiring dredging, filling, covering, piling, or scouring have potential to disturb, expose or re-suspend these deeper more contaminated sediments. This is why a commitment to collaborate on safeguarding these sensitive zones along the Cornwall waterfront has been made.

Collaborating groups and agencies include:

  • Environment Canada and Climate Change
  • Fisheries, Oceans, and Canadian Coast Guard
  • Ontario Ministry of the Environment and Climate Change
  • Ontario Ministry of Natural Resources and Forestry
  • Mohawk Council of Akwesasne
  • Raisin Region Conservation Authority

The Strategy


The Cornwall Sediment Strategy (CSS) has been designed to address 3 zones of contaminated river sediment identified in the St. Lawrence River at Cornwall. These zones of mercury contamination result from several decades of industrial activity. In 2005 a plan for recovery was introduced to address these near-shore areas. This recovery plan combines a near shore planning control process with a commitment to long-term monitoring.

The goal of the CSS is to leave the river bottom in these near shore zones as undisturbed as possible, subsequently allowing for cleaner particles of gravel and sand to cover over deeper and more contaminated sediment .
The CSS represents a science-based course of action for dealing with contaminated sediments along the Cornwall Waterfront.

• Cornwall Sediment Strategy  • CSS Brochure  • CSS Administrative Controls Protocol  • CSS Administrative Controls Protocol Guidance Document

So You Have or Want to Put in a Dock?


To protect the environment from sediments being released, a set of controls has been developed to prevent the natural cap over contaminated sediment from being disturbed.

The key control is to ensure docks are pre-approved before being constructed. This approval is free of charge and ensures that if minor changes are required on the size or method of dock construction, design changes can be made before installation. The following information is important:

  • Pick up the Cornwall Sediment Strategy information kit from Raisin Region Conservation Authority (RRCA) or access the information at
  • Once you have reviewed the information, should you wish to discuss the work you are planning, we encourage you to call RRCA to pre-consult.
  • Complete the dock application form and return it to RRCA and wait for them to provide comments about the design prior to installation and/or shoreline work.

It is also important to submit documentation on docks that have already been installed. We require these details because it tells us where docks are located and what kind of in-water activity might be taking place. This knowledge is important as more research data continues to be gathered on these key areas of the River. For owners who have installed a dock already – please fill out the application form/dock design and provide the approximate date it was installed. Your co-operation will assist us in protecting the environment. If you have questions please contact Lissa Deslandes at 613-938-3611 (ext.237).

Looking for More Information?


Please visit the Raisin Region Conservation Authority website for more information.

Join Our Mailing List