Year of Publication: 2002
Abstract:
Since its beginnings thirty years ago, mine reclamation practice continues to evolve. To determine the current state of practice for closure planing, landscape design, and to observe reclaimed landscape performance, 69 mines were visited. Reclamation, though generally well done, seldom satisfied stakeholders or regulators--few sites have received reclamation certification or been returned to the original owner. Until processes for setting realistic goals, multidisciplinary landscape design, and equitable transfer of residual liability are developed, mining companies will not achieve successful reclamation--mining will remain a terminal rather than temporary land use.
While most reclaimed areas of most mines exhibit good landscape performance, several shortcomings in the state of practice are clear. The use and rigor of surface-water hydrology design is lacking. Performance of slopes with erodible substrates, the high costs of trafficking soft tailings areas, and errors in predicting end-pit lake filling are particularly troublesome. Designs and regulations that accommodate the dynamic nature of landscapes are uncommon. Poor landscape performance often relates to fluxes (of ions, water, sediment, nutrients, etc) that are unanticipated or outside expected ranges or more commonly, simply fail to achieve unrealistic objectives.
Landscape engineering is introduced to help alleviate these shortcomings. It focuses on setting and achieving more realistic goals through inclusions of traditional engineering methods. Work is multidisciplinary and involve teams of specialists.
To demonstrate the technical side of landscape engineering, two studies were performed. In the first, the effects of uncertainty in substrate hydraulic conductivity were demonstrated with a database of 800 hydraulic conductivity measurements of oil sand tailings sand. Simple geostatistical tools such as the coefficient of variation, upscaling, and quantifying spatial variability are demonstrated and several design scenarios described. The second study involves predicting erosion rates of fine-grained fills. Results from the laboratory, field, and the literature indicate erosion rate predictions, even under ideal conditions, are generally only accurate to within one order of magnitude. Both the studies highlight the need to estimate common landscape fluxes, their impact on performance, and the need to deliver robust designs and institutional mechanisms that allow for inherent limitations in predicting long term landscape performance for large or complex mining landforms and landscapes.
