Understanding Waste Rock Dump Hydrology is Essential for Effective Closure Planning and ARD Management

Authors: Wright, A Download Paper

DOI https://doi.org/10.36487/ACG_repo/605_34

Cite As:
Wright, A 2006, 'Understanding Waste Rock Dump Hydrology is Essential for Effective Closure Planning and ARD Management', in AB Fourie & M Tibbett (eds), Mine Closure 2006: Proceedings of the First International Seminar on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 417-426, https://doi.org/10.36487/ACG_repo/605_34



Abstract:
The creation of large unsightly waste rock dumps is synonymous with mining in much of Western Australia (WA). In many cases development of the dumps has involved only limited consideration of future closure requirements and at best has been based on known technologies of the day. The key design focus has generally been haulage cost. Now, many years later, we are faced with far more stringent decommissioning requirements and ever increasing public interest in environmental sustainability. To complicate matters, what in many cases were “ugly, but harmless mountains of mine rubble”, now appear to be “contaminant time bombs”. Seepage and runoff from the dumps are often found to have raised concentrations of salts and metals resulting in potential contamination of what might be considered pristine surface and ground water environments. The true magnitude of the problem remains unknown, but there is little doubt that at many mines it represents a potential nightmare for mine closure planners who need to minimise long term corporate liability. Too often little, if any, consideration is given to waste rock dump hydrology during mine planning stages with the result that there is limited knowledge regarding possible seepage/runoff pathways once acid rock drainage (ARD) occurs. There is little doubt that an adequate understanding of waste rock dump hydrology is essential in the development of any Source-Pathway-Receptor model. Formulating effective long term solutions is extremely risky if the pathway component is not fully understood – in this case the inner waste rock dump hydrological processes. This paper describes how gaining an insight into waste rock dump hydrology at a mine in northern WA has greatly enhanced closure planning by highlighting some of the impracticalities of earlier closure strategies. The paper discusses internal dump structure, hydrological flow paths, discharge hydrographs and water quality implications.

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