This report provides perspectives on issues, strategies, and research requirements for disposing of potentially acid generating mine tailings and mine waste rock in a permafrost environment. It is important to distinguish between the continuous and the discontinuous permafrost environment. Within the discontinuous region the warm permafrost conditions are very susceptible to thaw degradation.
Acid generation within mine tailings has been noted at two minesites in Canada’s permafrost regions. Acidic seepage and runoff have also been documented in the natural permafrost environment. Cold temperature leach column testing shows that acid generation is slowed down but not necessarily reduced to negligible levels at temperatures approaching freezing.
Processes related to acidic drainage in cold climates have been reviewed. Important processes that require further study include the influence of sulphide minerals and process chemicals on unfrozen water content, thaw degradation due to oxidation, reaction rates at low temperatures, and frozen hydraulic conductivity of saturated and unsaturated mine waste materials.
Control strategies that take advantage of permafrost conditions include freeze control and climate control. Freeze control of tailings would appear to be a viable strategy however there is a need for more cost effective insulating cover designs and a more thorough understanding of frozen tailings thermal properties. There is potential for using the beneficial permafrost climate for achieving modest engineering control strategies in waste rock dumps using zoning of different material types.
Implementation of reliable and economic AMD control strategies are impeded by a lack of understanding of important cold weather processes and demonstrated performance. A program for researching freeze control of mine tailings is scoped out. Development of freeze control and climate control strategies for mine waste rock requires a much better understanding of mass transfer and geochemical processes acting within waste rock dumps. A fairly substantial effort will be required to achieve this level of knowledge. A general program of research in this area should be considered.
