Frozen cover actions limiting AMD from mine waste deposited on land in Arctic Canada

• Published in: Cold regions science and technology 2001-09, Vol.32 (2), p.133-142
• Main Authors: Kyhn, Curt, Elberling, Bo
• Format: Article
• Language: English
• Subjects: Arctic; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Frozen ground; Low temperature; Management; permafrost; Pollution, environment geology; Soils; Surficial geology; Tailings
• ISSN: 0165-232X; 1872-7441
• DOI: 10.1016/S0165-232X(00)00024-0

Mining in permafrost-affected areas presents unique characteristics and possibilities that need to be considered in order to investigate alternative actions to minimize the environmental impact of mining. Encapsulating mine waste within the permafrost zone by covering is considered one of the most promising actions to limit acid mine drainage and has been investigated near Nanisivik Mine in northern Canada. Quadrant test pads consisting of approximately 2 m of inactive (non-sulfidic) material have been constructed on top of oxidizing sulfidic mine tailings. A one-dimensional physically based soil water and heat model (WinSoil) has been calibrated and used to simulate observed subsurface temperatures within and below covers. Model input parameters include meteorological data such as air temperatures as well as thermal conductivity of cover material. The model was calibrated against ground temperatures measured in 1998 and validated against ground temperatures measured since 1995. WinSoil simulations were found to match observed ground temperatures reasonably well without calibration and almost perfect matches were obtained by varying the thickness of snow cover by a few centimetres. Observations and simulations reveal that temperatures within mine tailings have been below 0°C since covering 6 years ago. In addition to simulating observed ground temperatures, WinSoil was used to predict ground temperatures in relation to cover thickness and snow cover. The simulations question whether a 2-m cover will hinder sulfide oxidation processes within covered tailings if winter snow increases significantly due to either large-scale application of covers or global climate changes.