In constructing a financial model of a project significant effort is expended on capital and operating cost estimation, commodity price forecasts, and choice of discount rates while uncertainty in the primary input, the reserve, is often completely overlooked. The aim of this paper is to highlight the impact of uncertainty in the resource/reserve estimation process on the assessment of the financial performance of a project. Four qualitative processes have an impact on resource/reserve uncertainty. These stages are: 1. Ore definition 2. Geological interpretation 3. Resource estimation 4. Ore reserve estimation and mine planning. Each stage contains a number of tasks that may be considered as key performance activities (KPAs). Optimizing the manner in which these KPAs are completed can remove a great deal of uncertainty and error from the resource/reserve process. Examination of these KPAs within a company can also provide an insight to the quality of the information underlying the project. This will allow the company to identify any shortcomings in the data and to assess the resulting risks (Gilfillan, 1998). A hypothetical financial model based on a gold operation has been used to estimate the potential effect of resource/reserve uncertainty on revenue. Monte Carlo simulation has been employed to simulate a number of hypothetical scenarios: 1. a base case scenario which assumes no major errors or biases, but contains realistic margins for uncertainty that would exist in any project where work is being completed to the limit of best endeavours 2. a poor sampling scenario which assumes poor sampling practice and lack of understanding of sample preparation 3. a poor resource estimation scenario which assumes poor modelling and inappropriate choice of interpolation technique, and 4. a i?½typicali?½ scenario which represents a project where the majority of KPAs are not performed as best as they could be. The results show that realistic uncertainty ranges can generate changes in the estimate of potential revenue of plus or minus 30%. Therefore, it is important to allow for errors in these processes in any financial analysis or feasibility study. It is recommended that, when building a financial model, a review of relevant resource/reserve KPAs be carried out and appropriate ranges for uncertainty be applied to provide a range of potential outcomes. These outcomes can then be factored into the detailed cash flow analysis in order to ensure that technical uncertainty is built into financial decisions.
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