Edraki, M, Baumgartl, T & Haymont, R 2006, 'Investigating the Linkage Between Water Fluxes, Geochemistry and Water Quality in the Post-Closure Landscape of the Mt Leyshon Mine, Queensland', in AB Fourie & M Tibbett (eds), Proceedings of the First International Seminar on Mine Closure
, Australian Centre for Geomechanics, Perth, pp. 647-656.
Since the closure of Mt Leyshon Gold Mine in Queensland, the quality of surface receiving waters in the
mine area has significantly improved. However, uncovered stockpiles of mill rejects (scats), partially
covered heap leach material, and covered waste rocks and tailings remain as potential sources of low pH
waters with high concentration of sulfate ions, high metals (cadmium, copper, zinc, manganese), and arsenic.
This study reviews the site geochemistry and water quality data and presents a recent assessment of the cover
performance with the aim of a better understanding of the post-closure system. The linkage between water
quality and geochemistry is established by mine water fingerprinting which shows that seepage sumps at the
base of tailings, waste rock dumps and scats stockpile have distinctive chemical characteristics that can be
related to the source. A re-assessment of the dry cover systems on the tailings and waste rocks shows greater
infiltration rates compared to the previously predicted figures. Discharge of poor quality waters is related to
water flux through the covers and interaction of infiltrating waters with geochemically reactive waste
materials. Based on the Mt Leyshon experience, it is suggested here that revisiting of rehabilitation measures
and monitoring systems in a post-mining landscape are necessary for prioritizing and improving management
strategies. It is also shown that empirical models based on historic water quality data can be useful to post-
closure monitoring. This paper is a first attempt to bring together major elements of the post-closure system
and their correlations. However, more accurate linkages would require further information, most importantly,
on flow rates and a better understanding of the hydrogeology of the site.
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Contaminant Risks and Off-Site Impacts
Mine Closure 2006, Perth, Australia 655
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Investigating the Linkage Between Water Fluxes, Geochemistry and Water Quality
in the Post-Closure Landscape of the Mt Leyshon Mine, Queensland
M. Edraki, et al.
656 Mine Closure 2006, Perth, Australia