2022 – Application of Risk Analysis to evaluate Freeboard for an Extreme Consequence Category Tailings Facility

Malcolm Barker – GHD, Craig Messer – GHD, Ivonne Castellanos – QAL, Terence Jibiki – Rio Tinto, Trent Scherer – QAL, Laura Beckingham – GHD

The Global Industry Standard on Tailings Management (GISTM August 2020) and the International Council on Mining & Metals (ICMM May 2021) publication Mining With Principles place great emphasis on Risk Informed Decision making. This is in keeping with the ANCOLD Guidelines on Tailings Dams (ANCOLD July 2019) wave freeboard requirement for an extreme consequence category tailings facility requiring the use of risk analysis to determine whether the freeboard is acceptable. There is a dilemma with analysing risk for a specific set of hazard and failure modes, in this case winds and waves together with floods, without consideration of other hazards and failure modes including seismic events and piping or liquefaction. This is owing to the use of tolerable risk criteria being appropriate for all hazards and not single hazards and failure modes. This will be addressed in simple terms in the paper.

The ANCOLD Tailings guidelines do not provide guidance as to how the freeboard risk analysis is to be conducted and the paper will provide the methodology used for the QAL Red Mud Dam #2 that can be applied for any facility.