Water Cover Technology for Reactive Tailings Management: A Case Study of Field Measurement and Model Predictions

Abstract

Environmentally safe disposal of sulfiderich reactive mine tailings is one of the major challenges facing the mining industry in Canada, Scandinavia, USA, and many other parts of the world. Placing tailings under a water cover is one of the effective methods to reduce the influx of oxygen to the tailings. Wind-induced turbulence and subsequent resuspension of the tailings, however, are major concerns with this approach. In this paper, a study of wind-induced resuspension at the Shebandowan tailings storage facility, northwestern Ontario, Canada, is discussed. The study compares computer modeling of required water cover depths and resuspended tailings concentrations to observed field data. The calculated minimum water cover depths required to eliminate resuspension were found to be higher than the existing implemented water cover depths in each cell. The predicted resuspended tailings concentrations for the west cell were 6-22 mg/l with an average value of 15 mg/l and, for the east cell, 1-10 mg/l, with an average of 6.0 mg/l. In comparison, optical backscatter sensors, deployed in situ, recorded average resuspended tailings concentration up to 25 mg/l, indicating that the model results were similar to the field-measured values. Results from sediment trap measurements did not show any correlation between the amount of resuspended tailings and water cover depth. Sediment traps collect not only sediments eroded and suspended at the location of deployment but also those that have been transported from elsewhere and redeposited at the trap location. The amount of resuspension occurring at Shebandowan does not raise a major concern because discharge from the tailings area is collected and managed before it reports to the final effluent.

Impacts and prognosis of natural resource development on water and wetlands in Canada’s boreal zone

“…Sherriff et al (2011) showed that despite high oxidation rates and metal concentrations in tailings ponds of a copper-zinc mine in Manitoba (closed in 2002), metal concentrations in a downstream lake receiving tailings outflow water were stable indicating that the tailings management activities at that site were effective to date. Kachhwal et al (2011) also demonstrated that current water cover technologies and other tailings management efforts at a nickel-copper mining site in northwestern Ontario (closed in 1998) were effective at preventing downstream export of metals in the final effluent. Water cover technologies in rehabilitation efforts at uranium mining sites in north-central Ontario (closed as recently as the mid-1990s) have successfully reduced acid generation such that only limited effluent treatment is required for pH control and radium removal (Davé 2011).…”