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Landform Design

OKC’s philosophy for design of final landforms for mine waste stockpiles, outlined in the Statement of Qualifications for Landform Design, can be summarized as follows:

  • Design of a final landform should take place prior to construction of the initial landform;
  • Geotechnical stability is paramount, but aesthetics and natural appearance should be considered in the design of mine landforms;
  • Geomorphic principles must be considered in order to design landforms that will be stable over the long term; and
  • Surface water management systems must be robust.

Landform design for mine closure requires a holistic view of mining operations, where each operational stage and each component of the mine is part of a plan that considers the end-use of the site as much as the immediate need. This plan, which needs to be flexible to accommodate changes in methods and/or technology, is about optimizing post-mining land capability, minimizing the costs in achieving optimal land use, and limiting long-term maintenance liabilities.

The incorporation of natural slope features into the final landform design for stockpiles not only improves aesthetics, but also emulates slopes that are in equilibrium with local conditions of rainfall, soil type, and vegetation cover [1]. The relatively small increase in costs for engineering and construction for creating natural landforms are more than offset by improved visual appeal, decreased slope maintenance costs, and improved long-term stability. In addition, constructing mine landforms that visually blend with the surrounding landscape has considerable public relations value for operators.

A reclaimed waste rock pile in northern Canada that drains surface waters via the former pile access ramp.

The consideration of geomorphic principles is fundamental when designing a stable landform. Reclamation failure can usually be traced to violation of geomorphic principles, most fundamentally having too great a disparity between force and resistance [2]. Basic geomorphic principles dictate slope angles, drainage density, and size of drainage basins, but many different landscape designs can satisfy these criteria. OKC uses creativity to develop an aesthetically pleasing landscape that not only satisfies the criteria for physical stability, but also contributes to the land capability and satisfies quantitative and qualitative criteria specified by key stakeholders.

Surface water management systems must be robust as any failure is visible to stakeholders. Even if the failure does not result in increased contaminant loading or other critical failures, small glimpses of erosion give the impression of poor design and management. In the north, ‘icing’ of surface water channels and ditches, particularly near the outlet area of the landform, is a very common failure mechanism of reclaimed mine landforms. Reclamation of large waste storage facilities should include the construction of small catchment areas and wetlands to reduce peak flows and increase sedimentation prior to reaching receiving streams. Finally, the design and implementation of a sound revegetation plan including rapid establishment of vegetation following construction can significantly limit erosion and sediment transport.

1)  Ayres, B., Dobchuk, B., Christensen, D., O’Kane, M. and Fawcett, M. 2006. Incorporation of natural slope features into the design of final landforms for waste rock stockpiles. In Proceedings of the 7th International Conference on Acid Rock Drainage, St. Louis, MO, USA, March 26-30, pp. 59-75.

2)  Toy, T.J. and Hadley, R.F. 1987. Geomorphology and Reclamation of Disturbed Lands. Academic Press Inc., Florida.