Evaluation of cover systems for closure of tailings storage facilities at North American Tungsten Corporation's Cantung mine

摘要

The North American Tungsten Corporation Ltd.'s (NATCL) Cantung tungsten mine (Cantung) is located in the Nahanni area of the Northwest Territories, Canada (62° N). Intermittent mining has occurred at Cantung since 1962, resulting in five current tailings and exfiltration ponds (TPs), three planned dry stack tailings storage facilities (TSFs) and a thin deposit of historic tailings located on the floodplain of the Flat River. As part of ongoing reclamation activities at Cantung, cover systems are being evaluated for the planned TSFs to reduce the acid-generating potential of these proposed landforms. The proposed dry stack TSF cover system design will be informed by data gathered at the current TPl and TP2 tailings cover system. To understand the influence of water and gas flow dynamics on performance of cover systems at TPl and TP2, a numerical model with inputs informed by the tailings containment area monitoring plan (TCAMP) program was used to estimate water flux and diffusive oxygen flux to the tailings material. The numerical model was constructed to allow for a changing oxidation rate over time for each discrete layer of tailings material within the model, representing the consumption of pyritic materials with time. The final cover system design for the planned dry stack TSFs will depend on acceptable infiltration and oxygen ingress rates that reduce loadings to acceptable levels in the receiving environment over the long term.