Authors: Fernandez-Iglesias, A; Correa, A; Morton, O; Laine, J; Luiña, R; Martinez, G


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Fernandez-Iglesias, A, Correa, A, Morton, O, Laine, J, Luiña, R & Martinez, G 2015, 'Risk assessment methodology for paste and thickened tailings', in R Jewell & AB Fourie (eds), Paste 2015: Proceedings of the 18th International Seminar on Paste and Thickened Tailings, Australian Centre for Geomechanics, Perth, pp. 167-180,

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According to the database compiled by the US Commission on Large Dams (USCOLD) and completed later by the International Commission on Large Dams (ICOLD) and the US Environmental Protection Agency (EPA), there have been two or more major tailing dam failure incidents per year between 1970 and 2000, proving that these catastrophic failure events are not rare occurrences. Paste and thickened tailings (P&TT) technology has emerged in recent years as a promising technique to avoid dam incidents. Due to the low water content of the P&TT, the potential for liquefaction is reduced drastically in comparison to conventional tailing dams. This is one of the major advantages of the technology, alongside the volume reduction and the absence of bleed water. However, paste also has some drawbacks such as higher energy consumption and extra equipment requirements. Due to these advantages and drawbacks, a set of different tools is required to assess the feasibility of a paste facility at a specific mine. Among these tools, those related to risk become important since one of the major advantages of paste is related to this dimension. Thus, selecting the right tool for analysis is a key factor in the decision-making process that may lead to the selection of P&TT as an alternative to conventional tailings storage. According to the AS/NZS 4360:2004 ‘Risk Management’ (Standards Australia 2004), developing a risk assessment involves a three-stage process: identify, analyse and evaluate all the risks involved. The best tool to provide structure for these stages is a failure modes and effect analysis (FMEA) of the tailings system. In the present work, a general comparison between P&TT and conventional tailings storage has been made in terms of risk, using a FMEA based on a classification of likelihood and consequences in a semi-quantitative risk assessment. All risks for stages from the concentration plant onwards are considered for each scenario, in two different categories: environmental and public safety. Paste and thickened tailings technology has more risks classifying as low to moderate than conventional tailings and has less risks classifying as moderate to high area. These results can be used as an indication of the sustainability of P&TT disposal in terms of risks. Although the goal of the study is to make a general comparison not applied to any specific mine, it can also be used as a methodology or template for a risk assessment for any existing installation.

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