A River-Protection Approach to Deriving Site-Specific Water-Quality Guidelines for Heavy Metals in Mitigation Planning for an Industrial Site
Rivers and lakes are often contaminated by discharges from industrial operations, as often occurs near repositories of mine tailings. Decision-support tools intended to protect receiving watercourses from heavy metals seeping from the tailings can be critically important in evaluating the effectiveness of various engineering impact-management measures. Parties finding themselves responsible for Orphan or Abandoned (O&A) minesites rarely, however, have sufficient data immediately available to guide development of a site-mitigation or management plan. Even well-run modern mines with abundant monitoring data can be challenged to determine how best to plan for site clean-up during closure planning. As well, cleanup of contaminated reaches of rivers near O&A sites is typically inhibited by a paucity of parties willing to share the (very high) remediation costs, by the fear of acknowledging legal liability, and, sometimes, by politicization of the cleanup issue. Even with operating sites nearing the end of their life, competing interest among upstream and downstream parties can complicate closure planning and and associated site-reclamation planning.
This paper outlines an ecosystem-risk-based approach to site impact-mitigation planning. Seven questions guided the development of a Site-Management Plan to protect aquatic habitats and biota:
• Which chemical loadings are of greatest environmental concern to the local receiving waters?
• Where are the loading pathways to the sensitive ecological receptors located?
• What are the ‘real’ (and ‘perceived’) aquatic impacts and what is their spatial distribution?
• What is the extent of ecological health in the receiving waters?
• Must a site-management plan meet water-quality guidelines, or are there credible risk-based alternative approaches to defining performance targets for impact-management measures?
• What tools and methods are available to design a site-specific impact-mitigation plan?
• How effective must impact-management measures be to protect aquatic habitats and biota in the receiving waters?