Ecological Risk Assessment (ERA) of Open-water Disposal of Sediment to Support the Management of Dredging Project in the St. Lawrence River

The St. Lawrence River is subject to various anthropological pressures that can entail negative consequences for the ecosystem. As a result of the third and fourth St. Lawrence Action Plans, the current vision of sustainable management of this river and its main functions emphasizes the need for sound risk-based assessment approaches to support management Manuscript received August 3, 2011; accepted for publication February 28, 2012; published online October 23, 2012. Centre d’expertise en analyse environnementale du Quebec – MDDEP, 2700 Einstein St., Quebec, QC, G1P 3W8, Canada. DSEE – MDDEP, 675 Rene-Levesque, Quebec, QC, G1R 5V7, Canada. EPOD – Environment Canada, 105 McGill, Montreal, QC, H2Y 2E7, Canada. STB – Environment Canada, 105 McGill, Montreal, QC, H2Y 2E7, Canada. Aquarium du Quebec, SEPAQ, 1675 av. des Hotels, Quebec, QC, G1W 4S3, Canada. DEE – MDDEP, 675 Rene-Levesque, Quebec, QC, G1R 5V7, Canada. IRSTEA UR MALY, 3 bis quai Chauveau, 69336 Lyon, France. Copyright VC 2012 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. 105 Contaminated Sediments: Restoration of Aquatic Environment STP 1554, 2012 Available online at www.astm.org DOI:10.1520/STP104257 Copyright by ASTM Int'l (all rights reserved); Wed Mar 6 07:59:15 EST 2013 Downloaded/printed by Univ Laval pursuant to License Agreement. No further reproductions authorized. decisions. More specifically, the sustainable navigation strategy, drawn up under St. Lawrence Action Plan III, explicitly identifies the need to develop sediment quality assessment tools, including those derived from ecotoxicological studies. The first management option addressed in this perspective was the open-water disposal of dredged sediments. In this context, an ecotoxicological risk assessment (ERA) approach using chemical characterization in Tier 1 and benthic organisms’ toxicity tests in Tier 2 was elaborated based on physicochemical, toxicity testing, and benthic community structure data acquired from sediment samples collected in 59 sites along the St. Lawrence River. Hence this ERA approach will be used to determine whether the risk posed by the exposure of benthic organisms to dredged sediments at deposit sites and downstream is acceptable and compatible with open-water disposal.