Authors: Osgerby, B; Crosbie, J; Davison, N; Vogler, HG; Rohde, TK

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Osgerby, B, Crosbie, J, Davison, N, Vogler, HG & Rohde, TK 2022, 'Six months of monitoring of a tailings storage facility barrier cover trial at Rosebery Mine, Tasmania', 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. 1103-1116,

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The rehabilitation of a potentially acid forming (PAF) tailings storage facility (TSF) to minimise potential contamination is site specific; being a function, among other factors, of TSF construction method, the tailings deposition and storage method used, and climate. Two experimental barrier cover trials have been constructed at the Bobadil TSF at Rosebery Mine in the northwest of Tasmania to inform rehabilitation of the facility at the end of its operation. The primary design objective of the Bobadil TSF barrier cover is to limit rainfall infiltration (referred hereon as seepage) and to a lesser extent limit the potential for oxygen to diffuse into the underlying PAF tailings. One of the installed barrier cover trials at Bobadil TSF incorporates a geosynthetic clay liner (GCL) at the interface between the tailings and the overlying cover comprised of glacial till (450 mm) and Moorland peat (150 mm). The Moorland peat provides a perched phreatic zone that is largely anoxic and limits the potential for deeprooted trees to establish, that may potentially damage the GCL. Further, the peat provides the preferred environmental conditions for shallowrooted native grasses that will enhance the water transpiration from the cover and create an ecological community that is sympathetic to the surrounding landscape. As an alternative the barrier cover trials include a variant in which the GCL is removed. Both cover trials have been highly instrumented to allow the assessment of their relative performance over the next 3–5 years. This paper describes the first six months of performance monitoring, specifically reporting on the volumetric water content, matric suction and oxygen diffusion at various depths within the cover and tailings profile and the rates of seepage through the cover. The monitoring to date indicates that the barrier cover variant incorporating the GCL liner achieves the design objectives and the variant without the GCL liner does not.

Keywords: cover design, geochemistry, acid rock drainage

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