Landers, M, Faithful, J & Scrase, A 2022, 'Pit lake water quality closure tool for Hazelwood brown coal mine, Victoria, Australia', 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. 413-428, https://doi.org/10.36487/ACG_repo/2215_28
(https://papers.acg.uwa.edu.au/p/2215_28_Landers/)
Abstract: The ENGIE Hazelwood Coal Mine (HCM) was one of the world’s most significant brown coal deposits, located near Morwell in the Latrobe Valley, Victoria, Australia. The mining and power generation operations ceased in March 2017 and the site is currently in a closure and rehabilitation work phase, after over 50 years of mining. ENGIE considers closure of the open pit as a pit lake the most feasible option for rehabilitation. It is envisaged that the pit lake and nearby surrounds would have the potential for recreational, agricultural, commercial and industrial uses following relinquishment.
The pit lake water balance and water quality (WB/WQ) was identified as a critical area requiring further study. To address this a WB/WQ model (tool) for the final void at HCM was developed using the mass balance approach with GoldSim software and the Contaminant Transport (CT) module. To provide input to the model, several supplementary hydrogeochemical assessments were undertaken, including wall washing experiments and kinetic leach testing. The key objectives of the model for the HCM pit lake includes: i) prediction of the pit lake water quality for a through-flow and terminal sink at closure and modelling of how the water quality will evolve into the future; ii) modelling the demand for water to fill and maintain the pit lake during and beyond closure; and, iii) assessment of how climate change and climate variability are likely to affect the water balance and water quality of the pit lake using deterministic and stochastic (probabilistic) climate sequences. This paper describes the detailed preliminary WB/WQ modelling undertaken to support initial closure planning for HCM.

Keywords: mine closure, mine rehabilitation, pit lake, numerical modelling, GoldSim, Hazelwood Coal Mine