British Columbia Mine Reclamation Symposium

Adaptive risk management and lessons learned : post-closure at the "mighty" Sullivan mine Peterson, R. A.; Humphries, S. A.; Unger, M. L.


The Sullivan mine in Kimberley, British Columbia, operated for almost 100 years and was one of the world’s largest producers of lead, zinc and silver. Environmental and risk management controls were initiated in the 1960s, including construction in 1979 of the world’s first high-density sludge treatment plant for treatment of acid rock drainage (ARD) associated with large impoundments of tailings, waste rock, other process wastes and underground mine workings. Large-scale assessment of surface water and groundwater systems were initiated in the 1990s in combination with the implementation of additional mitigation measures to control ARD-related impacts. The Sullivan mine officially closed in 2001, and comprehensive site investigation and risk assessment results were used to develop an adaptive site-wide risk management plan (RMP) that outlines long-term monitoring requirements for groundwater, surface water, vegetation and aquatic biota, with triggers for incremental assessment and mitigation as necessary. Since closure, predicted improvements in groundwater and surface water quality have been realised; however, in some locations, RMP action levels have been triggered and incremental assessment and mitigation have been required. As an example, action level triggers were reached in surface water at the lower mine yard, where acidic seepage high in metals from shallow groundwater discharges was detected in the adjacent creek. This triggered additional investigation and implementation of interim measures to capture the groundwater as a longer-term solution is being developed. Triggers were also reached in deeper groundwater in the lower mine yard, and monitoring programs have been adapted to these changing conditions. Other challenges have been administrative, resulting from a closure process spanning over a decade and changes to regulatory policies and mine closure requirements during this time. For example, policy changes under the British Columbia Contaminated Sites Regulation (BC CSR) now require protection of aquifers for future drinking water use, which has affected applicable water quality criteria. Soil quality criteria have also changed for a number of exposure pathways following active closure, changing risk assessment assumptions and prompting additional site investigation activities to comply with the criteria under the BC CSR. These evolving physical and administrative conditions, combined with variations in weather and watershed land use, have reinforced the need for closure plans to include appropriate post-closure monitoring, anticipate the potential need to revisit assumptions made during closure planning and set trigger levels for investigating the need to adjust risk management processes.

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