The evolution of the field saturated hydraulic conductivity of four covers located on a reclaimed saline-sodic shale overburden from oil sands mining is presented. Three covers consisted of a surface layer of peat/glacial topsoil over a mineral, soil. and one cover was a single layer of mixed peat and mineral soil. Measurements of the field saturated hydraulic conductivity of the cover and shale materials were made with a Guelph permeameter between 2000 and 2004. The hydraulic conductivity of the cover materials in the multilayered covers increased by one to two orders of magnitude over the first few monitoring seasons. The hydraulic conductivity of the single-layer cover system, which was placed three years before the multilayered covers, marginally increased from 2000 to 2002 and then remained relatively unchanged. The hydraulic conductivity of the shale underlying all four covers increased approximately one order of magnitude. Soil temperature measurements indicated that one freeze/thaw cycle occurred each year within all cover soils and the surficial overburden. This suggests that freeze/thaw effects were the cause of the observed increases in hydraulic conductivity, as previously observed by other researchers working on compacted clays.

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Historically, final landforms for waste rock stockpiles consist of linear (in plan), planar slope surfaces with unvarying gradients and angular slope intersections. Slope drainage structures are generally oriented along contours and are highly engineered, while revegetation efforts follow artificial configurations. By contrast most natural slopes are characterized by a variety of shapes (typically concave), and drainage systems follow natural drop lines with catchment sizes defined by undulating relief on the slope. Vegetation on natural slopes grows in discrete vegetation units that are adjusted to hillside hydrogeology, incident solar radiation, and other microclimate effects. This paper reviews the key elements of natural slopes and proposes methodologies for improved design of final landforms, and in particular, methodologies for the reclaimed slopes of waste rock stockpiles. Two case studies are included to demonstrate that natural slope configurations are more stable than highly engineered landforms over the long term. The design methodologies and supporting discussions presented in this paper are also applicable to any above-ground waste storage facility with topographic relief.