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This paper presents a case study of an innovative solution to a problematic mined-out pit in the Pilbara region of Western Australia. The pit presented significant closure challenges, being deep, below water table and with approximately 17% of potentially acid forming (PAF) lithology on the final pit shell. Numerous closure strategy options have been under consideration; however, a new strategy of backfilling the pit with process tailings has been identified. Modelling predicts that the tailings will cover a large proportion of the PAF lithology leading to improved water quality conditions and will also fill the pit to a level that prevents the formation of a permanent pit lake. Furthermore, the initiative will negate the need for construction of further ex-pit tailings capacity and prevent the associated environmental impacts. Significant cost savings in tailings facility construction, tailings deposition and closure implementation are anticipated. Regulatory approval of the in-pit tailings facility is required, and consultation has commenced.
Keywords: pit lake, tailings, potentially acid forming waste, acid mine drainage, closure
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