Lo, RC, Stroiazzo, J & Guilleminot, G 2009, 'Transition of a major tailings facility in a sensitive environment — from operation to decommissioning at Brenda Mine', in AB Fourie & M Tibbett (eds), Mine Closure 2009: Proceedings of the Fourth International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 229-243, https://doi.org/10.36487/ACG_repo/908_16 (https://papers.acg.uwa.edu.au/p/908_16_lo/) Abstract: The Brenda Mine closure plan had been developed in consultation with regulators and stakeholders. Reclamation work at the mine was carried out whenever practical, while the mine was still in operation prior to 1990. Additional reclamation work continues to date. The molybdenum-related geochemical issue played a dominant role in the adopted closure scheme. To mitigate the impact of mine-site molybdenum- bearing water on the quality of water in the surrounding environment, a water treatment plant, with a maximum installed treatment capacity of 313 l/s was constructed. With the plant starting operation in 1998, excess molybdenum-bearing water stored in the tailings pond and pit lake, has been treated in the plant and released on a scheduled annual basis under permit. Ongoing monitoring of surface and groundwater quality at control locations has been carried out to confirm compliance of permit conditions. This paper describes how site water management has become the key to successful decommissioning at Brenda Mine. It covers all man-made landforms within the mine proper related to water management need. Moreover, the long-term dam safety aspect of the two key tailings dams are discussed in light of their design and construction history.