ABSTRACT

ABSTRACT: The flooded pit created after closure of a surface mine was subsequently used during the 1980s to contain pyritic tailings from an adjacent mill, thus becoming a Tailings Disposal Facility (TDF). A mining company proposes to place new tailings from sulfide ore processing in the TDF. Investigation of the water chemistry in the TDF reveals a water column stratified with respect to temperature, dissolved oxygen, oxidation-reduction potential and the concentrations of many metals. Further research strongly indicates that upward diffusion of high concentrations of metals in bottom waters is limited by an active scavenging process mediated by iron hydroxides. Iron cycling maintains the scavenging process and is possible due to reducing conditions at the bottom of the TDF maintained by the sulfide tailings.