Assessing Credible Modes of Failure: Afton TSF Dam Breach Study
Author: Anna Akkerman, P.Eng., Violeta Martin, Ph.D., P.Eng.
Conference: Tailings and Mine Waste 2015
Date: October 25-28, 2015
The Afton Tailings Storage Facility is located in the semi-arid Interior Region of British Columbia and has been in care and maintenance since 1997, after approximately 20 years of operation. In response to the British Columbia Chief Mine Inspector’s orders issued in August 2014, following a dam breach incident at the Mount Polley Mine, dam breach analysis and inundation studies for the Afton Tailings Storage Facility were conducted.
Defining realistic and credible modes of failure that were consistent with the Canadian Dam Association Dam Safety Guidelines for conducting these studies proved challenging due to the hydrologic conditions and certain features of the Tailings Storage Facility dam design. The selection of initial hydrologic conditions and breach locations has a considerable effect on the predicted volume of tailings mobilized, the characteristics of the flood wave, and the extent of the downstream impact.
Inundation results based on modes of failure that are not credible do not provide real value to the owner, regulators, or the public because they offer little insight into the actual risks posed by a facility. This paper examines the challenges in defining credible modes of failure used in dam breach and inundation studies for mining dams, and presents a case study based on the Afton Tailings Storage Facility.
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