HGS RESEARCH HIGHLIGHT – Landscape restoration after oil sands mining: conceptual design and hydrological modelling for fen reconstruction
Price, J. S., McLaren, R. G., & Rudolph, D. L. (2010). Landscape restoration after oil sands mining: conceptual design and hydrological modelling for fen reconstruction. In International Journal of Mining, Reclamation and Environment (Vol. 24, Issue 2, pp. 109–123). Informa UK Limited. https://doi.org/10.1080/17480930902955724
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This study by researchers at the University of Waterloo investigates whether fen peatlands could be reconstructed on post-mine sites. Oil sand extraction can be very harmful to the natural land surface and can have lasting impacts on local ecosystems. This paper focuses on the fen peatlands that cover 65% of the landscape in Fort McMurray, Alberta. Our ability to reinstate these peatlands after mining operations has not truly been tested at large scales, and there are many uncertain factors that can impact reclamation plans for these sensitive wetlands. The key design consideration is to ensure that the reconstructed fens maintain a sufficient level of saturation to reduce oxidation and provide suitable growing conditions for fen plants. In this study, a 2-D numerical HydroGeoSphere model is used to optimize the geometry and configuration of reconstructed fens, including the ratio of upland to fen area and the thickness of soil layers necessary to maintain critical hydrologic conditions.
Groundwater flow is the main source of water to these fens, but surface flow and precipitation are also key dynamics in fen hydrology. HydroGeoSphere was used to model the integrated hydrology of the fen system. The models were run using daily climate forcing data from 1997 – 2001, which includes the very dry summer of 1998. Long-term average climatic conditions were used to develop the initial conditions for subsequent simulations. Based on the results of numerical modelling, it was determined that successful fen reconstruction is predicated on two major requirements: the availability of suitable building materials, and sufficient upland to fen surface area to maintain adequate seepage rates.
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Abstract:
Extraction of oil sands in the relatively dry Western Boreal Plains near Fort McMurray, Alberta, destroys the natural surface cover including fen peatlands that cover upto 65% of the landscape. Industry and environmental monitoring agencies have questioned the ability to reclaim fen peatlands in the post-mine landscape. This study proposes a conceptual model to replace fen systems with fen peat materials supported by groundwater inflow from a constructed watershed. A numerical model is used to determine the optimum system geometry, including the ratio of upland to fen area, thickness and slope of sand materials, and thickness of peat and of the liner that would result in flows that sustain peat wetness to a critical threshold soil water pressure of −100 cm of water at a peat depth of 10 cm. We also test the sensitivity of the system to variations in the value and spatial configuration of the hydraulic conductivity (K) of locally available materials. The optimal conditions were achieved using an upland area at least twice that of the fen, underlain by a sloping (3%) layer of fine-grained material with hydraulic conductivity (K) of 10−10 m/s, that maintains lateral groundwater flow in a sand layer with K of 10−4 to 10−5 m/s. Using daily climate inputs that included 1998, the driest summer on record, the model suggests that adequate wetness can be sustained in the fen for the growing season, and that the extent of water table recession was similar to undisturbed systems during that period.