Abstract
This paper describes observed attenuation of constituents in tailings dam seepage along groundwater flow pathways and potential implications for future design of tailings embankments. Near-complete attenuation of selenium, nitrogen, and some oxyanions has been observed in seepage emerging downstream of tailings embankments at several operating mines. These processes are functionally equivalent to active water treatment processes, but they come at no capital and operating costs for the operations above the costs of maintaining the embankments. This paper explores the attenuation processes and options for deliberately designing embankments with such attenuation/water treatment properties. The attenuation mechanisms are likely a combination of biotic and abiotic mechanisms related to suboxic and anoxic conditions that develop to varying degrees in the water column profile, at the water-tailings interface, in the tailings mass, and along the flow path through the dam construction materials and/or in the natural materials beneath the facility. The reduction potential of inorganic sulphide minerals likely also plays a role. Tailings seepage water chemistry data from three operating sites are presented. Conservative species, such as sulfate and chloride, were used to estimate seepage travel time. Selenium, nitrogen species, antimony, molybdenum, and arsenic attenuation was observed at all mine sites. Work is ongoing to survey a wider range of seepages from operating and closed tailings facilities to map out factors that affect attenuation. The long-term goal is to identify specific tailings properties and construction materials that facilitate attenuation of constituents in seepage, which could be incorporated into bases of design for tailings embankments.
Authors
Shauna Litke (Presenter) | SRK Canada
Soren Jensen | SRK Canada
Click here to view all presentations at this event.
