2013 – Risk-based management of two water bodies at a Queensland coal mine

Rob Campbell, Christopher Dann and Mark Foster

Queensland contains some of Australia’s most significant reserves of mineable metallurgical coal, which is an essential raw material used in the production of steel. The area also has large deposits of thermal coal, used for electricity generation.
For the many active open cut and underground coal mines in Queensland, the enduring operational focus is to maximise returns and productivity, while still meeting key safety and environmental responsibilities.
Maintaining open cut pits in a dewatered state is often a key factor in achieving optimal productivity of an open cut mine. In Queensland, for many mines it is not always practical to maintain all pits in a dewatered state, given the subtropical climate and significant rainfall that can occur during the wet season, between the months of November and March. In effectively managing mine water while maintaining production, it is not unusual for excess mine water to be temporarily stored in a designated open cut pit.
The typical scale and arrangement of open cut pits at mine sites in Queensland is such that relatively deep and high volume pits can be separated by relatively narrow “landbridges”, consisting of in-situ material or mine spoil. The situation can therefore arise where a significant volume and head of mine water is stored in one pit, with mining operations continuing in an adjacent pit, and the landbridge is required to perform as a water retaining structure. This is a scenario that might not have been considered when the landbridge was originally constructed. This paper presents a study of two such landbridges at either end of a mine pit in Queensland, over a 5 year period from 2008 to 2013, with mining activities in the pit ranging from dragline pre-stripping to open cut mining, to large scale construction works and underground mining. By employing a long term interactive approach with mine operations personnel and utilising quantitative risk management techniques, risks were effectively managed, helping the mine to maintain operations while meeting safety and environmental requirements.

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