British Columbia Mine Reclamation Symposium

Effect of soil cover system design on cover system performance and early tree establishment Barber, L. A.; Bockstette, J.; Christensen, D. O.; Tallon, L. K.; Landhäusser, S. M.


Syncrude completed construction of a field-scale soil cover system trial at the Aurora North mine operations in Fort McMurray, Alberta, Canada in 2012. Syncrude, university researchers, and consultants developed the study design with an overall objective of determining appropriate soil cover system designs and capping depth(s) for overburden reclamation at the Aurora North mine operation. Specifically, the study was designed to address the uncertainty of reclaiming upland areas using coarse textured surficial soil materials that contain embedded naturally occurring oil sand that is comprised of petroleum hydrocarbons over lean oil sand overburden that also contains petroleum hydrocarbons. The trial consisted of 36 one hectare cells, made up of 12 treatment options varying in capping material thicknesses and types. All treatments were constructed in triplicate. The research cells were instrumented and planted with three native boreal forest tree species in varying densities. Key mechanisms and processes that influence cover system performance and tree growth include freeze/thaw cycles and water retention characteristics. Instrumentation was installed to monitor water balance parameters and groundwater, and to collect pore-water. Initial results indicate that peat surface cover system materials had the lowest net percolation due to higher water storage capacity, and exhibited delayed soil warming and freezing. Tree mortality was 3% on salvaged forest floor soil capping treatments and 4% on peat capping treatments. Tree seedling growth after three growing seasons was up to 48% higher on treatments capped with mineral dominated forest floor material compared with treatments capped with organic peat material. The influence of lower subsoil material types and their arrangements on tree seedling performance is still unclear. This is a long-term study and results will serve to identify appropriate cover system configurations and guide future reclamation operations in oil sands mining.

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