UBC Theses and Dissertations
Investigations of water and tracer movement in covered and uncovered unsaturated waste rock Marcoline, Joseph R.
A better understanding of the hydrogeology of mine waste rock and cover systems is essential for the quantification, prediction and reduction of metals loading to the receiving environment. A series of experiments were conducted on an instrumented intermediate-scale waste rock pile at the Cluff Lake Mine in Saskatchewan to investigate the changes in flow and solute transport within coarse waste rock under three different surface conditions. Following these studies, the waste rock pile was deconstructed, structures were mapped, and samples were collected for physical characterization and pore water extraction. The internal structure of the waste rock pile was more important than the texture and topography under the free-dumped and ripped/leveled surface, while the surface condition was found to be the dominant control on spatial and temporal variability of outflow from the waste rock with the covered surface. Data from a deuterium tracer test, lysimeter outflow, and from TDR probes were used to derive estimates of the maximum and an average pore water velocity through the uncovered and the covered waste rock. An average pore water velocity through the matrix materials of the uncovered waste rock was approximately 1.5 m/yr and maximum preferential flow velocities were as high as 5 m/day. The post-cover pressure wave velocity of 0.1 to 1 m/day is inferred from outflow and TDR data, and average pore water velocities (0.39 m/y and 0.73 m/y) are calculated by the water flux and tracer methods, respectively. The distribution of the tracers in pore water and the internal structure were mapped during a detailed deconstruction of the waste rock pile and attempts were made to link the data to the spatial and temporal patterns of lysimeter outflow. The pore water chloride concentrations and the deuterium values did not provide conclusive data necessary to link the spatial and temporal patterns observed in the lysimeter hydrographs to internal structure; however, it provided insight into the internal flow mechanisms and water residence times.
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