British Columbia Mine Reclamation Symposium

Selenium management challenges at Kemess Mine Bent, Harold; McConnachie, Jennifer; Lysay, Georgia J.


In 1997, Kemess Mine began to place waste rock in permanent storage immediately west of the open pit. Waste rock placement occurred within the watershed boundary of a second-order tributary to Attichika Creek in the larger Finlay River watershed. Although diversion systems were constructed around the Waste Rock Dump, much of the small watershed remains intact, with several perennial and ephemeral sources of water, such as localized wetlands south of the Waste Rock Dump, interception ditches diverting water away from the Pit, and seepage water from the toe of the Waste Rock Dump. All of these sources inevitably report to Waste Rock Creek, and provide habitat for a resident Dolly Varden population. Although the waste rock is non-acid generating, the third source, seepage water from a portion of the Waste Rock Dump, was found to contain elevated selenium concentrations. Selenium concentrations in Waste Rock Creek have consistently exceeded the BC Approved Water Quality Objective since late 2003. In 2004, following a review of cumulative water quality data for Waste Rock Creek and discussions with Kemess staff, selenium was recognized as an element of concern at Kemess Mine by the BC Ministry of Environment (MOE). As a result, comprehensive investigations have followed to: identify the predominant selenium source through data analysis of material characterization and geochemical modeling; develop monitoring programs to adequately characterize trends in the receiving environment water, sediments, benthos, and fish; and develop strategies for effective risk assessment and mitigation. This paper summarizes the findings of enhanced monitoring programs and maps the challenges faced while developing an appropriate mitigation strategy.

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