Reclamation and remediation of the Tom Property, Macmillan Pass, Canada

Authors: Woloshyn, K; Hartmaier, H; Bruce, I; West, S Download Paper

DOI https://doi.org/10.36487/ACG_rep/1152_51_Woloshyn

Cite As:
Woloshyn, K, Hartmaier, H, Bruce, I & West, S 2011, 'Reclamation and remediation of the Tom Property, Macmillan Pass, Canada', in AB Fourie, M Tibbett & A Beersing (eds), Mine Closure 2011: Proceedings of the Sixth International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 485-494, https://doi.org/10.36487/ACG_rep/1152_51_Woloshyn



Abstract:
The Tom Property, owned by Hudson Bay Exploration and Development Company Limited, a subsidiary of Hudson Bay Mining and Smelting Co. Limited (HBMS), is located in the Macmillan Pass area, near the Yukon-Northwest Territories border, about 400 km northeast of Whitehorse, Yukon, Canada. The property was discovered in 1951 and between 1951 and 1991 various exploration campaigns were carried out on the property, including extensive diamond drilling from surface and underground. Underground development on the property was done via an adit located at elevation 1,440 masl. Approximately 52,000 m3 of waste rock and ore from the underground development was stockpiled on the slopes adjacent to the adit. In the early 1980s, the underground workings were extended to explore the West Zone via a decline which encountered significant inflows of water eventually forcing the decline excavation to be shut down in 1982. Between 1992 and 1994 the property was closed and decommissioned. The adit was closed with granular fill and drainage pipes were installed to permit the water from the underground workings to drain out to surface. In the spring of 1999, a routine inspection by government inspectors found that the portal backfill had been breached by a torrent of water from the adit. It was hypothesised that the drainage pipes through the backfill in the portal had frozen and the hydraulic head developed behind the frozen face eventually overcame the resistance of the backfill and washed out. The mine water discharge had degraded since decommissioning and did not meet regulatory standards as it was acidic and contained elevated concentrations of metals. To mitigate the environmental impacts associated with this situation, HBMS embarked on a multi-faceted programme of surface and underground reclamation between 2006 and 2010. This paper will describe the various components of the reclamation programme, which included the following major activities: baseline environmental studies, project alternatives assessment, environmental assessment and permitting, covering the waste rock with a high density polyethylene (HDPE) liner to reduce infiltration of runoff and precipitation, relocation of the ore stockpile into a lined disposal area, construction of a concrete water retention plug within the underground workings to flood the exposed rock surfaces and reduce acid rock drainage and metal leaching, and adaptive management plan and monitoring.

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