Introduction to Soil Bioengineering Applications for Mining Reclamation of Re-Constructed Waterways within Alberta Oil Sands Overburden Mine Dumps

English Abstract:

In 2003 a waterway swale was retrofitted into an Alberta oil sands overburden dump. The swale has an average gradient of 4 degrees and is approximately 600 m long and 30 m wide from ridge to ridge with a depth ranging from 2 to 4 m. It is composed of two lateral swales connecting onto the main swale and has a catchment basin of approximately 32 ha. The substrate consists of muskeg placed over clay capping and oil sands tailings.

In spring 2004 an erosion control prescription using a soil bioengineering approach was implemented. It consisted of the following: brush sills installed across the swale, smaller diameter cuttings installed in the middle of each sill to improve water dispersion and the planting of live stakes. Contour fascines were also installed across the swale, in two locations above the brush sills, as a trial. After 5 years the findings of this trial site were reviewed and the soil bioengineering design was adjusted and applied to the implementation of two additional swales in 2010.

Lessons Learned

Brush sills result in channel erosion. When combined with accumulated organic debris this results in falling water or a hydraulic jump and the creation of splash erosion. The use of contour fascines, without brush sills, appears to be diffusing water instead of creating channels and splash erosion. Wetland species were established as a result of seeds germinating from within the seed bank of the applied muskeg and a wetland was created. This approach allowed for the establishment of riparian herbaceous, shrub and tree species, recreating habitat on disturbed land.

Based on these findings, trial sites using large diameter (30 cm) contour fascines were established in the spring of 2010 over two newly constructed swales within an overburden mine dump. These trial sites were monitored until the fall of 2014 and assessed as excellent. This approach is now being considered for use as a template for mine closure on reconstructed waterways of mine dumps.