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Recommendations for the Management of Suspended Solids (SS) During Dredging Activities

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Ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques and Environment and Climate Change Canada
December 2016

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Abstract

The St. Lawrence River is a complex ecosystem whose properties change from its headwaters to its outlet. Opened in 1959, the St. Lawrence Seaway allows ocean-going vessels to travel from the Atlantic Ocean to the Great Lakes, a distance of more than 3200 km. To ensure safe navigation conditions, roughly 450 000 m3 of sediment are dredged annually in the St. Lawrence. One of the major concerns associated with dredging is the temporary increase in suspended solid (SS) concentrations, which can pose a threat to aquatic life.

The surface water quality criteria adopted by the MDDELCC help protect aquatic life from the harmful effects of suspended solids. These quality criteria are used, in particular, to limit SS concentrations in wastewater effluents discharged into the environment. SS management criteria specific to dredging activities have now been identified, taking into account ambient SS concentrations observed in the St. Lawrence and SS concentrations measured in dredging situations.

In clear waters (where ambient SS concentrations are generally below 25 mg/L), average SS concentrations measured 100 m from the dredge and point of discharge should not increase by more than 25 mg/L compared with ambient concentrations. At 300 m from the dredge and point of discharge, the increase should not be more than 5 mg/L compared with ambient concentrations. In turbid waters (where ambient SS concentrations are generally greater than 25 mg/L), the average SS concentrations measured 100 m from the dredge and discharge point should not increase by more than 100% compared with ambient concentrations, while at 300 m from the dredge and discharge point, they should not increase by more than 25 mg/L compared with ambient concentrations. The average SS concentration is measured over the daily dredging period or, if dredging is continuous, over a period of 6 consecutive hours. These management criteria are complemented by a series of targets associated with the protection of sensitive areas and aquatic species, as well as industrial, commercial and recreational uses.

Project Team

Ministère du Développement durable, de l’Environnement et de la lutte contre les Changements climatiques

  • Aurélie Mutz, Direction générale du suivi de l’état de l’environnement, Direction des avis et des expertises – Milieu aquatique
  • Lise Boudreau, Direction générale du suivi de l’état de l’environnement, Direction des avis et des expertises – Milieu aquatique
  • Isabelle Guay, Direction générale du suivi de l’état de l’environnement, Direction des avis et des expertises – Milieu aquatique
  • Pierre Michon, Direction de l’évaluation environnementale des projets hydriques et industriels

Environment and Climate Change Canada

  • Julien Gravière, Environmental Protection Operations Directorate
  • Serge Lepage, Environmental Protection Operations Directorate
  • Simon Blais, Environmental Protection Operations Directorate
  • François Marchand, Environmental Protection Operations Directorate
  • Magella Pelletier, Science and Technology Branch, Water Quality Monitoring and Surveillance
  • Myriam Rondeau, Science and Technology Branch

Collaboration

  • Vincent Escher, Master’s of Environment student, Université de Sherbrooke
  • Hélène Houde, Master’s of Environment student, Université de Sherbrooke
  • Dominique Robert-Dubord, Master’s of Environment student, Université de Sherbrooke
  • Philippe Thibert-Leduc, Master’s of Environment student, Université de Sherbrooke
  • Emmanuelle Vallières-Léveillé, Master’s of Environment student, Université de Sherbrooke
  • Serge Hébert, Direction générale du suivi de l’état de l’environnement, ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques

Scientific Review

  • Hélène Dufour, Direction générale du suivi de l’état de l’environnement, ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques

Correct citation for this publication :

Ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques and Environment and Climate Change Canada, 2016. Recommendations for the Management of Suspended Solids (SS) During Dredging Activities. 62 pp. + 4 appendices.

Published by Authority of the Minister of Environment and Climate Change
© Her Majesty the Queen in Right of Canada, 2016

Published by Authority of the Ministre du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques du Québec
© Government of Quebec, 2016

Cat. No.: En84-142/2016E-PDF

ISBN : 978-0-660-06668-4 (PDF)