Conference Proceedings Paper
ECOLOGICAL RISK ASSESSMENT: HOW MUCH EVIDENCE IS ENOUGH? APPROACHES FOR MAKING REMEDIATION RECOMMENDATIONS FOR A CONTAMINATED SEDIMENT SITE AND THE ROLE OF PROFESSIONAL JUDGMENT*
3rd Canadian Nuclear Waste Management Decommissioning and Environmental Restoration - 2016 Sept. 11-14
R. Silke (Canadian Nuclear Laboratories)
M.J. Bond (Canadian Nuclear Laboratories)
M. Stuart (Canadian Nuclear Laboratories)
J. Carr (Canadian Nuclear Laboratories)
D.J. Rowan (Canadian Nuclear Laboratories)
The resources put into ecological risk assessment at contaminated sites can vary substantially depending on several factors, including the types of contaminant(s) and their concentrations, location of the site, public perception and available funding, among many others. These factors may substantially impact remediation decisions, but fundamentally, assessment of risk associated with potential or actual (measured) impacts on the environment from the contamination in question should form the basis of a remediation decision. It is commonly understood that the detection of contaminant concentrations above generic screening levels can provide focus to investigations by identifying contaminants of potential concern; however, they should not be the sole basis of a remediation decision. The ecological risk assessment for the contaminated sediment site adjacent to Canadian Nuclear Laboratories’ Chalk River Laboratories (CRL) site considered multiple lines of evidence; (i) comparisons of recommended benchmark dose and screening levels with concentrations in water and sediment, (ii) relevant exposure pathways and biological receptors, (iii) measured and (or) modelled contaminant exposure to benthic receptors and transfer of contaminants to upper trophic level receptors, (iv) whole-sediment laboratory toxicity tests using benthic invertebrates and fish, and (v) field studies assessing possible intermediate or long-term effects on aquatic biota at the population and community levels. This paper explores how the additional information gathered in this case was used in a weight-of-evidence approach to assess the need for remediation. We also discuss the role of professional judgment in these approaches.
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