Adams, BM, Scully, KH, Seto, JTC & Harrison, B 2022, 'Faro Mine, Yukon Territory, Canada: a case study for optimising zinc load capture by clean water diversion and focused contact water capture', in AB Fourie, M Tibbett & G Boggs (eds), Mine Closure 2022: 15th International Conference on Mine Closure
, Australian Centre for Geomechanics, Perth, pp. 341-354, https://doi.org/10.36487/ACG_repo/2215_22
The Faro Mine, located in the central Yukon, produced lead, zinc, silver, and gold from the late 1960s until 1998, when the mine was abandoned. Seepage from sulfidic waste stored in the Faro waste rock dumps (WRDs) has variably impacted groundwater and surface water reporting to the North Fork of Rose Creek (NFRC), a fish-bearing surface water body, which passes along the toe of the Faro WRDs. Zinc is the primary parameter of concern, reaching several orders of magnitude higher than applicable water quality guidelines, and previous yearly maximum concentrations.
Interception of contact water before it reaches the NFRC has been challenging due to the complex seepage patterns within the WRDs and proximity of the creek. Despite existing collection systems intercepting high concentration seepage pathways, zinc remained elevated in the creek. The NFRC Realignment Project commenced in 2015 to ‘keep clean water clean’ by diverting the NFRC into the non-contact water diversion channel (NCWDC) and allowing focused collection of WRD seepage in the remnant NFRC channel. The first phase of the contact water collection and conveyance system (CW System) was focused on the interception of shallow groundwater and surface flow in the remnant NFRC. The NCWDC was commissioned on 24 October 2020, and the initial CW System was commissioned on 15 April 2021.
Isolating the clean water through construction of the NCWDC substantially reduced the surface water available for dilution. Both the uncertainty in capturing contact water prior to it reaching the creek and the inefficiency of capturing contact water once mixing occurred with creek flow were mitigated with this approach. A year after commissioning the NFRC Realignment Project, performance monitoring shows measured zinc concentrations in the NFRC approximately two orders of magnitude lower at the downstream monitoring station than realised by previous efforts.
Keywords: contact water, mine closure, water management, creek diversion, zinc, remediation, pumping, modelling, hydrogeology, hydrology, civil engineering, geochemistry, cold regions
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