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UBC Theses and Dissertations

Water flow through unsaturated mine waste rock in a region of permafrost Neuner, Matthew


A field experiment was constructed at the Diavik Diamond Mine in northern Canada to investigate water flow through unsaturated piles of mine waste rock in a region of permafrost. Two test piles 15 m-high were built on collection systems 60 m by 50 m, each consisting of lysimeters and a large impermeable HDPE liner, and instrumentation was installed within the piles to measure moisture content, temperature, and tension head. Upper collection lysimeters were installed near the test piles to investigate infiltration, evaporation, and the effect of the thermal regime in the upper 2 m of the waste rock. Hydrogeological characterization was performed at a range of scales to relate hydraulic properties of the fine-grained matrix to the test piles, of which, roughly half is estimated to be boulders. After the initial 1.5 year of monitoring, under drier than average conditions, net infiltration did not reach a depth of 2 m. Applied rainfall events raised the rainfall to the annual mean at one of the test piles, where a wetting front propagated to a depth of about 7 m during the summer and autumn of 2007. Infiltration into frozen waste rock froze and was then remobilized with thaw propagation, and thermal controls on flow were significant throughout the year. Rapid flow with high spatial variability was detected in response to a high-intensity applied rainfall event. Rainfall with recurrence intervals less than 10 years produced flow with less spatial variability and lower flow rates. A calibrated numerical model was developed using VS2D to aid in the description of the flow system at the upper collection lysimeters and the test piles. Solute mass loading estimates were dictated primarily by the flow behaviour, rather than by changes in solute concentrations. Loading from one of the test piles during July 2007 was twice the average rate of approximately 0.8 g SO₄²−/d/m².

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