Cissé, M-K, Guittonny, M & Bussiere, B 2022, 'Natural analogue of a cover with capillary barrier effects to improve the long-term performance evaluation and the design of the cover', in AB Fourie, M Tibbett & G Boggs (eds), Mine Closure 2022: Proceedings of the 15th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 949-960, https://doi.org/10.36487/ACG_repo/2215_69
(https://papers.acg.uwa.edu.au/p/2215_69_Cisse/)
Abstract: To manage acid mine drainage, some mine sites in Québec, Canada, have been reclaimed using a cover with capillary barrier effects (CCBE). The performance of this oxygen barrier cover system relies on maintaining a fine-grained material layer with a high degree of water saturation. However, after mine closure, CCBEs can be colonised by the surrounding ecosystem (plants, animals, and microorganisms) that can influence its hydraulic properties. Plant roots, for instance, can pump water and decrease the degree of saturation in fine-grained materials. Since CCBEs are expected to perform for hundreds of years, their designs must anticipate long-term environmental changes. Projections of how a changing environment could influence CCBE performance are crucial. Current numerical models to predict water balance can integrate vegetation effects but long-term environmental changes, such as climate change, soil development, and ecological succession, are usually not considered. Model input data associated with future environmental scenarios at reclaimed sites are required. Natural analogues are natural ecosystems that provide clues for more effective cover designs or indicate long-term changes in cover environment. A natural analogue (NA) of a CCBE can help to obtain data representative of long-term environmental changes that may influence the CCBE performance. In this paper, the methodology used to obtain an NA of a CCBE, including the influence of mature vegetation, is presented. The criteria developed to check the analogy between a constructed CCBE, and a natural equivalent are explained (for example, the water table level, hydrogeological properties of materials, and the required contrast between these properties). An example of vegetation data obtained from the natural CCBE analogue is described. Finally, the benefits of using NAs information for the design of engineered cover systems are discussed.

Keywords: mine reclamation, cover with capillary barrier effects, natural analogue, mature jack pine, boreal ecosystem, root development, cover performance.