Co-disposal of waste rock with tailings, neutralants, or geochemically inert overburden can limit the potential for ARD by reducing the potential for infiltration and oxidation by filling voids in the waste rock and maintaining neutral pH conditions. This paper presents the results of a two-stage kinetic leach column program of highly reactive pyrrhotite waste rock. The first stage of tests was conducted to determine if the addition of lime to the waste rock would inhibit the generation of ARD. The second stage of tests is ongoing, and was conducted to determine if co-disposal of non-acid generating tailings with the waste rock would inhibit ARD generation. The results from the first stage of testing show that the treated samples have been able to maintain neutral pH conditions for 20 months. The second-stage results demonstrate that the co-disposal methods are effective in limiting the onset of acid conditions for at least 15 months under laboratory conditions. The second-stage study will continue for another six months. Based on this study, both in-situ neutralization and co-disposal of waste rock with tailings appear to represent promising options for placement of reactive waste rock at this site.
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