Oil Sands Tailings Preliminary Ecological Risk Assessment

Golder Associates Ltd.
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This report outlines a conceptual and analytical framework for quantifying risks to terrestrial wildlife that might be exposed to solid-phase materials potentially associated with oil sands reclamation. The initial phase of the assessment involved screening the soil-tailings against published criteria to produce a short list of 10 constituents (8 organic and 2 inorganic) that pose a potential risk to terrestrial biota. After the 10 constituents were identified, a probabilistic model was developed that: (1) simulated exposure doses to three representative terrestrial wildlife receptors (deer mouse, white-tailed deer, American kestrel), (2) computed the probability of exceeding a chemical exposure limit for each of the receptors, and (3) summarized the relative contribution of the different exposure pathways (i.e., water and food ingestion, incidental soil ingestion, inhalation) to the total exposure dose. Due to the paucity of data, a number of conservative assumptions were applied to this study that precluded firm conclusions with respect to potential risks associated with each of the soil tailings mixtures. Nonetheless, the findings of this study provide useful information for directing future ecological risk assessments to assist in reclamation planning for the oil sands sites.