Waste Dump Design and Underdrain Assessment

Thompson Creek Mining Company retained BGC to undertake a geotechnical assessment of the Pat Hughes and Buckskin waste dumps as part of Thompson Creek’s proposed expansion of the mine. BGC used information provided by Thompson Creek, including reports on the soil and rock types in the foundation, groundwater condition, waste characterization, approximate waste distribution and seismic hazards of the site, to develop stability analysis models of the waste dumps.  Surface water flows and water management systems were also evaluated to confirm that the underdrain performance was adequate to maintain waste dump stability.

Results of the analysis indicated that a lower buttressing, or “wrap-around” lift, approximately 150 m high and 120 m wide would be required in order for the proposed Buckskin waste dump to meet industry standards.  Several waste dump geometries were evaluated for the proposed Pat Hughes expansion, including various heights and widths of the lower wrap-around and a re-sloped lower lift face.  In addition, it was determined that the long-term stability of the Pat Hughes dump would be positively impacted by extending the underdrain.