Following the tailings dam failures at Mount Polley and Fundão, major mining companies have conducted systematic reviews of their tailings facilities worldwide. KCB has approached several of these assignments using systematic dam safety assessments. The objective of these dam safety assessments was to strike a balance between sufficient depth of review to provide positive confirmation on the presence of catastrophic hazards, and the need to prioritize a large number of dams with varying risk profiles. This paper discusses the general approach, the protocols, the level of detail, and the rationale for each. Although these assessments do not replace a dam safety review, they contain many of the same elements and could be thought of as in-between an audit and a comprehensive dam safety review.
Key elements include: a comprehensive checklist review of dam safety and governance systems, a review of consequence classification informed by a semi-quantitative dam break calculation, a review of the design criteria, and simplified calculations to check if the facilities meet the design criteria for stability and water management.
One of the benefits of approaching a large portfolio of dams in a systematic way, is that it provides the owners with a baseline to compare and prioritize across multiple sites, and to better put into context the multiple dam safety inspections and reviews which are typically prepared by a multitude of different consultants.
A suggestion for improvement of the general tailings facility engineering practice is the development of design record reports for dams which have a consequence classification equal to or greater than “High”. The design record report should document the basis for the dam consequence, design criteria, strength parameters, seismicity, flood parameters, and geochemistry. The consequence classifications should be informed by a dam break study and the stability analyses for the dams should be updated. The report should contain key reference information such as site investigation data and cross sections with best known conditions of the dams.
Willms, D.A., M.J. Cronk, H.N. McLeod and L.M. Murray. 2018. “An Approach to Dam Safety Assessment,” in CIM Convention 2018, May 6-9, 2018. Vancouver, BC, Canada.