Authors: Fitton, TG; Neumann, WJ

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Fitton, TG & Neumann, WJ 2015, 'Dredging of an active thickened tailings storage facility at the Ernest Henry Mine', in R Jewell & AB Fourie (eds), Proceedings of the 18th International Seminar on Paste and Thickened Tailings, Australian Centre for Geomechanics, Perth, pp. 239-246.

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Abstract:
After some 15 years of operation as a copper and gold mine, the Ernest Henry Mine installed a magnetite extraction plant to enable the recovery of magnetite concentrate as well. A study was carried out to determine the feasibility of re-mining the tailings from an active thickened tailings storage area, which proved it viable. Dredging, dry mining and hydro mining methods of extraction were examined, costed and compared. Dredging was the selected method. In the months to follow, a dredging operation was set up on the tailings storage facility, which mined magnetite-rich tailings from it whilst simultaneously enabling the storage facility to remain active for receiving the thickened barren tailings from the magnetite extraction plant. The Ernest Henry tailings storage facility is a square-shaped thickened discharge system with a perimeter embankment, and a beach that slopes from one corner to the opposite one. This slope of the beach presented one challenge to the dredging operation, which was effectively addressed with the adoption of a systematic progressive mining method. The need to minimise the sterilisation of the magnetite-rich tailings beneath a layer of new barren tailings presented another challenge, which also required some careful planning. An overview of the dredging operation is presented, as well as some relevant details of it. The management of the tailings discharge during dredging is also discussed, as is the slurry transport and pumping requirements for the dredging. A number of other technical and practical challenges are also discussed, such as the initial excavation of the starter pond, launching and retrieving the dredge, and anchoring of the dredge. Dredging can be a very effective and economical means of extracting tailings from a storage facility, even in cases where thickened tailings have been discharged to create a sloping beach.



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