Large scale mine cover monitoring and mine cover design for cold regions

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Following the completion of mining, one element of the final closure of mine sites is the construction of reclamation soil covers to control water, gas, and/or contaminant loadings to the environment along with monitoring of the performance of these covers. This proposed research focuses on the development of novel monitoring and cover design tools associated with these reclamation soil covers. The single most challenging element of soil cover monitoring is the development of a water balance that captures the hydrological performance of the soil cover across the entire landscape of the closed mine. This monitoring has traditionally been done using localized monitoring systems such as soil monitoring stations or runoff weirs. However, the localized measurements are difficult to integrate across large reclaimed areas. This is a particular challenge in oilsands mining where the reclaimed areas for one mine might extend over 100s of square km. This research will investigate the use of geological weighing lysimeters (GWLs) to monitor key hydrological events, such as snowmelt runoff, seasonal evaporation, or runoff associated with high intensity summer rainstorms. GWLs measure changes in surface load (such as the weight of water held within the soil profile) by detecting small changes in pore-water pressure within underlying geological formations that occur in response to these loads. A second project will investigate the feasibility of designing a seasonally frozen capillary break diversion (SFCBD) cover for northern mine sites; here, insufficient fine-grained soils exist to create low infiltration covers but frozen, near saturated soils zones can be developed as a result of the cold climate. These covers can be constructed of layered coarse soil (i.e., sand/gravel) to enhance the lateral diversion of fresh snow melt water away from the underlying mine waste into adjacent water collection structures. This novel design approach combines a known cover design method (capillary break layers) with the unique northern climatic conditions and provides another potential option for cover design for mines in northern Canada.