Stability and Seepage Analysis of the Bralorne Gold Mines Tailings Dam Following a Change in Usage from Tailings Dam to Water Reservoir Dam Lefrancois, Anne-Marie
The Bralorne Gold Mines Ltd. operates the historic Bralorne Pioneer Mine, near Goldbridge B.C. The tailings dam construction spanned from 2003 to late October of 2005. The mill discharged tailings for a short period subsequent to construction but since 2004, only the groundwater flowing from the mine adit has been pumped to the tailings impoundment. Some seasonal higher arsenic levels within the groundwater have prompted this action and monitoring of the seepage water leaving the dam consistently shows acceptable arsenic discharge levels. The tailings impoundment has proven very valuable in term of containment and attenuation of arsenic. However, the usage of the dam as a water reservoir versus its design as a tailings impoundment was a concern for the BC Inspector of Mines. A stability and seepage analysis of the dam in its new state was requested. This undergraduate thesis analyzes the slope stability of the dam under this new regime and provides a model for the groundwater flows. 2D Limit Equilibrium Analysis based on data obtained from old reports, site visits and monitoring equipment, confirms that the dam is performing as designed. The computer models maintain a factor of safety greater than 1.5 for static analysis and above 1.15 for various seismic loading conditions.
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