Abstract
Authors: Helga Sonnenberg1, Jim Perrone1, Trevor Chandler1
1 EcoReg Solutions Inc., Guelph, Ontario, Canada
Whether the site is an abandoned gold mine or a new facility at a historical mining location, arsenic frequently exceeds the conservative 5 µg/L Canadian Water Quality Guideline for protection of freshwater aquatic life (CWQG-FAL). To further complicate environmental management decisions around arsenic, there are very large differences between federal and provincial limits, which increases regulatory ambiguity and the need for comprehensive assessment of appropriate effluent limits and ultimate receiving water quality. To complete this successfully, an assessment of current potential aquatic habitat effects in the receiving environment integrated with assimilative capacity and water quality modeling studies of the receiving environment are required. This work reduces uncertainty and provides the confidence needed to develop suitable receiving water objectives.
This presentation will review how this process unfolded during three projects involving receivers containing elevated arsenic:
- Restarting a historical gold mill tailings impoundment area (TIA)
- A new open pit gold mine development close to several historical gold mines
- A historical mining area
With respect to the current aquatic habitat effects assessment, when arsenic or other metal(loids) are elevated, it is important to understand whether the metal is in a form that is bioavailable, bioaccumulating and/or causing toxicity. To evaluate the implications of elevated arsenic concentrations, a simple comparison to water and sediment quality guidelines is not sufficient. More sophisticated field and laboratory based approaches should be used to assess whether elevated arsenic in water or sediment are causing adverse effects on resident aquatic organisms (phytoplankton, benthic invertebrates and fish), Additionally, more advanced chemical analyses can be conducted to evaluate what forms of arsenic are available and/or accumulated.
The case studies presented will provide examples of this integrated approach to site specific biological assessment and water quality modeling. Outcomes of each project and how sound environmental management decisions can be made will be discussed. Finally, multiple perspectives from the proponent, regulators and stakeholders will be integrated.