Hydrochemical and stable isotope assessment of tailings pond leakage, Nickel Plate Mine, British Columbia

An integrated hydrogeochemical and stable isotope study was undertaken to a ssess tailings pond leakage at the Nickel Plate Mine site in British Columb ia, Canada. The approach used consisted of a hydrochemical mixing model for sulfate in conjunction with stable isotope data (18O and 2H) to estimate p ossible levels of contamination reaching surface waters from leakage throug h the dam and to determine the relative percentages of "seepage" that can b e attributed to leakage through the dam and to natural groundwater flow ben eath and around the dam. Results suggest that tailings pond waters are dilu ted by groundwaters by approximately 50% before their arrival in the collec tion swamps, and that the leakage from the tailings pond partially by-pass the collection (and pump-back) system at a rate of between 0.09 and 0.12 l/ s. Stable isotope data indicate that tailings pond waters and swamp waters are enriched in the heavier isotopes as a result of evaporation line of slo pe 3.9 (D/18O). The isotope date indicate that seepage beneath the dam cons ists of approximately 50% real seepage and 50% meteoric waters (both surfac e water and groundwaters).