Tailings decommissioning options at Mount Nansen, Yukon, Canada ©

Authors: Kwong, YTJ Download Paper

DOI https://doi.org/10.36487/ACG_rep/1008_09_Kwong

Cite As:
Kwong, YTJ 2010, 'Tailings decommissioning options at Mount Nansen, Yukon, Canada ©', in R Jewell & AB Fourie (eds), Mine Waste 2010: Proceedings of the First International Seminar on the Reduction of Risk in the Management of Tailings and Mine Waste, Australian Centre for Geomechanics, Perth, pp. 91-101, https://doi.org/10.36487/ACG_rep/1008_09_Kwong



Abstract:
A total of 250,000 t of tailings enriched in arsenic and cyanide impounded behind an earth dam of suspect physical integrity constitute the greatest environmental liability at an abandoned gold mine on Mount Nansen, Yukon Territory, Canada. The primary cause of dam deterioration can be traced back to improper initial tailings placement, resulting in gradual melting of frozen ground into which the dam was keyed. Field investigation and sampling revealed that permafrost still underlay most of the impoundment. Subsequent comprehensive mineralogical and geochemical characterisation of the collected samples indicated that the tailings remained relatively stable chemically with low potential for metal leaching. Given that cyanide and related compounds continued to degrade naturally, rendering the tailings increasingly benign with time, and that the containment dam is unlikely to collapse catastrophically except perhaps under extreme seismic stress, it is suggested that the impounded tailings need not be relocated for permanent site decommissioning. A viable long-term alternative could involve downstream reinforcement of the dam structure, dewatering the existing shallow pond and covering the tailings with a layer of benign waste rock to arrest erosion and prevent direct access by roaming animals.

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