Current Developments in Heap Leach Closure

The typical conceptual approach to heap leach closure planning assumes heaps will be rinsed to achieve water quality goals, followed by physical reclamation of the heap to meet revegetation goals. While rinsing is initially effective in reducing concentrations of some constituents, primarily cyanide, experience has shown that it may be very difficult to reach drinking water standards for all constituents. Also, the addition of fresh water to the system in order to achieve water quality goals increases the volume of heap leach drain down that must be managed. Therefore, the use of rinsing must be closely evaluated considering the ultimate management of the solution during the “tail ” of the drain down curve. Effective closure will depend upon the volume and quality of the heap solution inventory; geochemical behavior of the spent ore; climate and other site conditions such as depth to groundwater, revegetation goals, and post-closure land use. In effect, there is no single “one size fits all ” closure approach for heap leach pads; each heap requires an approach that considers site-specific factors. Depending on those site factors, there are a variety of tools that can be used to achieve closure. Revegetation measures (through direct seeding of the heap or placement of a soil cover) should be considered in light of their implications for solution management; in some cases, low-permeability covers or engineered storage/evaporation covers may be warranted. Evaporation, land application, and treatment present a range of methods to deal with heap solution drain down and residual drainage. This paper presents case studies of heap leach closure plan development and implementation using a range of approaches at various Kinross properties