Assessing the impacts of uncertain future closure costs when evaluating strategies for tailings management

Abstract

Abstract This paper reports on the economic evaluation of alternative strategies for managing a hypothetical gold tailings stream in Western Australia as a slurry, as a thickened, and as a filtered tailings. Suitable project designs were developed and the lifecycle cost was calculated for each project under two different scenarios; (i) baseline scenario in which a traditional accounting approach was adopted for assessing the options in terms of the total cost of the project, and (ii) an alternative scenario which considered higher rehabilitation costs compared to the costs envisaged in the baseline scenario, and a lower discount rate for discounting them. This was done to examine the extent to which uncertainties and potential sources of variability surrounding mine closure planning, accounting and provisioning impact the costs of tailings management. The results revealed that under the baseline scenario, managing thickened tailings is the option of lowest cost, but under the alternative scenario, managing slurry tailings resulted in the most economically feasible solution. However, the better cost performance of the slurry option should be viewed with caution given the difficulties associated with the closure of slurry tailings storage facilities and increasingly stringent regulations with regards to the rehabilitation of areas disturbed by mining operations. Although presenting the highest cost under both scenarios, filtered tailings has the lowest cost sensitivity to alternative input values and assumptions associated with mine closure. This is important information to be conveyed to decision-makers when a solution for tailings management is to be selected. Designing with closure in mind, and continued focus on developing leading practices for tailings management are essential to achieve optimal sustainability performance goals in mining.