Integrated Surface Water and Groundwater Modelling for Oil Sands Reclamation

The reclamation of oil sands tailings ponds is a challenging long-term process requiring the management of saline pore-water in the tailings sand, which is thought to be critical for successful reclamation. Returning disturbed land to a pre-disturbance equivalent requires an understanding of environmental performance of conceptual reclamation designs. Research on challenges of reclamation of tailings ponds as well as research into the hydrology of the natural boreal landscape has identified the following desirable hydrologic characteristics of reclaimed tailings ponds: (1) a water balance that maximises outflow to limit “evapoconcentration” of salts and sustain end-of-pit lakes; (2) a shallow subsurface flow system to limit transport of salts from within tailings ponds; and (3) depth to groundwater table in the uplands that limits potential for upward migration of salinity.

This study demonstrates the value of using a fully integrated hydrologic model, such as HydroGeoSphere, to assess the long-term performance of potential mine closure designs.

Presentation from Environmental Services Association of Alberta, WaterTech 2015

Integrated Surface/Subsurface Models in Support of Mine Closure Planning

Today's mine operator must consider a variety of complex, integrated systems when developing a mine closure plan that is sustainable from both an engineering and environmental perspective, thereby meeting their corporate expectations and those of regulators and the public.  Forecasting the outcome of an engineering design with independent groundwater and surface water computer programs has acknowledged limitations, as the real systems under consideration include feedback mechanisms between the two domains that can be critical in determining overall temporal behavior of the proposed closure design.  Numerical approaches which attempt to loosely couple existing surface and subsurface computer codes are often problematic due to the complex, non-linear nature of the governing equations; and (at times) the simplifications necessary to reach stable numerical solutions may compromise the understanding of the real processes involved. An alternative approach, presented at Mine Closure Solutions, 2014, is to use integrated, physically-based numerical models to solve coupled groundwater and surface water flow equations simultaneously; using real-world mine closure examples to illustrate how this approach has been used successfully to understand (and forecast) the future behavior of such systems.  Example applications include the sustainability of sensitive peat fen ecosystems and wetlands in a reconstructed environment that is subject to the pressures of a chaotically changing climate; and proof-of-concept for maintaining saturation in a co-disposed waste rock and tailings impoundment at a former pyrite mine.