2016 – The Reliance on Engineering Judgement to Inform Tailings Dam Failure Impact Assessments

Kate Brand, Matthew Ind

Failure impact assessments of tailings dams are largely pre-determined by the input assumptions and, due to lack of supporting data, the results can be highly subjective. Despite numerous guidelines available for undertaking failure impact assessments of water dams, there are very few technical guidelines on how to form the above assumptions and how to undertake dam breach modelling of a tailings storage facility (TSF).

Tailings dam failure databases are limited, with the available information generally not analogous with the TSF under assessment, especially given the rising volume and height of modern tailings dams. ‘Rule of thumb’ methods are often referred to, with a percentage of tailings and water assumed to be discharged along with assumptions of the breach height and width made.

Using a case study, this paper compares a range of potential failure impact assessments generated using typical methods of analysis and runout modelling to demonstrate the reliance on engineering judgement in failure impact assessments. Given the subjectivity observed within the results, consideration should to be given to the level of reliance on tailings dam failure impact assessments in formulating emergency action plans. It is recommended that regulators take an active role in formulating tailings dam impact assessment guidelines.