2007 Applications of Ecotoxicity Methods and Bioassay Testing for Site Specific Risk Assessments

Gladys Stephenson, Stantec Consulting Ltd.

Why and when terrestrial toxicity tests should be used for Tier 2 assessments; Which tests and which species should, can, and must
be used for Tier 2 assessments and soil sample collection and preparation for ecotoxicity assessments.

Toxicity tests are used to determine if there are concentrations of contaminants in site soils that adversely affect survival and growth of plants and survival, growth, and reproduction of soil-dwelling organisms
• They are a persuasive line of evidence that existing contaminant concentrations are not harmful (no adverse effects)
• Data from these tests can be used to estimate risks associated with contamination and to quantify reduction of risks
• Data can be used to establish site-specific remedial objectives (SSROs) at Tiers 2 and 3
• Toxicity tests can also be used to evaluate the efficacy of remediation technologies

Site evaluations: are the soils toxic?
• Residuals (contaminant concentrations that are recalcitrant and virtually stable) are above the Tier 1 or screening level standards
• Sites with soils whose physico-chemical characteristics differ from those for which the standards were developed (e.g., CWS PHC were developed using course sandy-loam and moderately fine clay-loam soils)
• Sites with soils contaminated with well weathered and aged product (e.g., historical PHC contamination) or sparingly-soluble substances (e.g., barium sulphate)
• Sites with soils contaminated with substances that differ substantially from those for which standards were developed (e.g., heavy crude oil)
• To support site-specific ecological risk assessments

2007 Stantec_Ecotoxicity and Bioassay for SiteSpecific Risk Assessments Presentation