A multiple lines of evidence approach for the ecological risk assessment of an accidental bitumen release from a steam assisted gravity drainage well in the Athabasca oil sands region

To assess ecological impacts of two independent accidental bitumen releases from two steam assisted gravity drainage (SAGD) wells in the Athabasca oil sands region, a multiple lines of evidence (LOE) approach was developed. After actions were taken to minimize ecological impact following the releases, an ecological risk assessment (ERA) was conducted based on reported concentrations of bitumen related contaminants in soil, vegetation, and water. Results of biological assessments at the site were included in the risk characterization.

The ERA predicted negligible likelihood of adverse outcomes. Small mammal collection was conducted to substantiate the conclusions of the ERA. An increase in hepatic ethoxyresorufin-O-deethylase (EROD) activity was observed in voles, but was not correlated with any observable adverse population-wide biological outcomes, and no other adverse outcomes were found, supporting the overall conclusion that the likelihood of long-term adverse health effects to ecological receptors in the area was negligible.