Kwong, YTJ 2010, 'Tailings decommissioning options at Mount Nansen, Yukon, Canada ©', in R Jewell & AB Fourie (eds), 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
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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Tailings decommissioning options at Mount Nansen, Yukon, Canada © Y.T.J. Kwong
102 Mine Waste 2010, Perth, Australia