Root causes of tailings dam overtopping : the economics of risk & consequence

Abstract

This paper examines overtopping failures of embankments at tailings impoundments from 1915-2015 and compares the severity of consequence for overtopping failures to that of other causes of failure. We find that the distribution by severity of consequence for overtopping at active mines is not significantly different from any of the other established "causes of failure." Further we find that the distribution by severity within and across all active TSF recorded failure causes (N=125) is also reflected in the mean distribution of severity for all of our recorded TSF failures (N=267) suggesting that a common root cause, rather than the individual causes of failure, may determine the severity of failure. We look here at the demonstrated link between severity of consequence of failure and the economic dynamics of the "Mining Metric" over 100 years (Bowker and Chambers 2015) as it applies to overtopping. We offer what is available from authoritative sources on the economics backstory of known overtopping failures and crises. We conclude that the deviations from best available technology and best applicable practices at the mine level are conscious choices driven by economics and that without a reframing of the professional, regulatory, and legal frameworks for mining these choices will continue to be made even where proven technology and new promising technology are available and better suited to a given mining asset. Solutions that will prevent mine failure require not only the work of evolving consensus on best available technology/best applicable practices, but also the recognition of root causes which build to catastrophic failure. A complete solution cannot be attained without accountability to best knowledge, best practice, best effective technology in mining law and regulation, as permit standards, as standards for oversight for life-of-mine and of life-of-tailings storage facilities.