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Management tools for contaminated sediment

Contaminated sediments collected at the bottom of the St. Lawrence waters, distant or recent legacy from industrial activities, represent a risk for human health and ecosystems when they are resuspended. Using new scientific knowledge, the governments must update regularly their contaminated sediments management tools, in order to reduce risks associated with contamination.

Projects 2016-2021

Assess the ecotoxicological risk and health risk of contaminated sediment sites in restoration projects

The assessment of the sediment quality is performed in comparison with the criteria for assessing the quality of Quebec’s sediments. However, comprehensive assessment also requires the use of more specific tools for informing management decisions.


In the previous phases of the SLAP, our team determined the method to assess the risk related to the release of dredging sediments in free water for the St. Lawrence freshwater ecosystems. Furthermore, the analysis of actual cases allowed the development of risk assessment tools to be initiated for contaminated sediment sites. In order to assess the effects of this discharge on aquatic wildlife, the team analyzed the contaminants present in the sediments and then studied their effects by performing, among other, toxicity tests in the laboratory and studies on the invertebrate communities present in the St. Lawrence River. 

During this SLAP phase, our team pursue its work throughout the St. Lawrence River. The creation of the necessary risk assessment tools for the ecosystems is completed as the risks of contaminated sediments on human health, which was initiated at the same time as the previous phase.

Identify the main environmental issues related to the presence of contaminated sediment sites in the St. Lawrence

This project aims to locate aquatic sites where the chemical quality of the St. Lawrence River’s sediments is of concern in accordance with the Criteria for the Assessment of Sediment Quality in Quebec and Application Frameworks: Prevention, Dredging and Remediation (2007). To do so, an analysis of the existing data and data collection on-site will be performed. This work will allow the extent of the different sectors of concern to be identified, assess their degree of contamination and to perform an initial assessment of the risk that contaminated sediments can have for the aquatic environment and its use (fishing, swimming, drinking water, etc.). The documentation of these contaminated sites guide new data collection, determine the necessary environmental interventions, and set their order of priority to better guide future actions, if necessary.

Projects 2011-2016

Assess the ecotoxicological risk and health risk of sites with contaminated sediment as part of restoration projects

Sediment quality is assessed through comparison with numerical criteria. However, comprehensive assessment also requires the use of more specific tools for informing management decisions. First, the development of an assessment methodology for characterizing the ecotoxicological risk of projects in sediment management will assist in gauging the ecotoxicological risk associated with sediment management. Next, the project will enable development of a methodology for assessing the risk to human health through use of sediment exposure criteria and definition of the exposure pathways specific to the sites with contaminated sediment.

Read the backgrounder for this project. Read also the Ecological Risk Assessment of Open-Water Sediment Disposal to Support the Management of Freshwater Dredging Projects guide.

Develop a toxicity test to asses the sediments in the brackish water zone of the St.Lawrence

The project involves defining toxicity tests that can be used to assess the potential impact of sediment dredging or dumping in the brackish waters of the St. Lawrence downstream of Île d'Orléans.

Read the backgrounder for this project.

Identify the key environmental issues related to the targeted areas of contaminated sediment

 A review of the Criteria for the Assessment of Sediment Quality in Quebec allows a targeting of the sectors of the St. Lawrence where sediment quality is an issue of concern. The issues in terms of various types of exposure to contaminated sediment, both for the ecosystem and humans, will be defined. Finally, the definition and documentation of these issues could assist in prioritizing actions throughout the St. Lawrence and focusing the various restoration activities carried out within specific sectors. 

Read the backgrounder for this project.

Develop a joint decision making framework (federal-provincial) for the management of sites with contaminated sediment

This framework will serve in defining the necessary timing and conditions for sediment decontamination as well as determining the various solutions to the problems identified. This project will assist in prioritizing sectors associated with the greatest potential benefits of sediment restoration efforts for the ecosystem while also taking into account current regulations and the impact of decontamination (environmental benefits and socioeconomic factors) in terms of cost.

Read the backgrounder for this project.