Evaluation of a single-layer desulphurized tailings cover

Abstract

The potential effectiveness for long-term closure of a desulphurized tailings cover placed on reactive tailings at the Detour Lake Mine was assessed. The single-layer cover was aimed at reducing oxygen ingress using high water saturation to limit oxygen diffusion and consumption of oxygen in the cover by residual sulphide minerals. The cover was 1.0 to 1.5 m thick and met desulphurization targets, but was coarser grained than the design. One-dimensional unsaturated flow and oxygen diffusion modelling was used to predict water content profiles, depth of oxygen penetration, and diffusive oxygen fluxes. Effective diffusion and reaction rate coefficients estimated from field data matched laboratory measurements. Depth to water table was identified as the most important factor for reducing tailings oxidation. The deeper (4 m) water tables measured at the cover edges led to a lower degree of saturation and higher oxygen flux. Finer grain size and higher air-entry values in the cover materials helped maintain saturation, and a capillary break (fine over coarse) cover reduced oxygen fluxes to <5% of fluxes to uncovered tailings. The as-built cover (coarse over fine) reduced oxygen influx by at most 50% and as low as <1% of uncovered tailings.

Award-winning papers published in 2013

“…Papers published in CGJ are eligible for the award. The 2013 Keefer Medal was awarded to Bonnie Dobchuk, Craig Nichol, G. Ward Wilson, and Michel Aubertin: Evaluation of a single-layer desulphurized tailings cover (Dobchuk et al 2013) ABSTRACT: The potential effectiveness for long-term closure of a desulphurized tailings cover placed on reactive tailings at the Detour Lake Mine was assessed. The single-layer cover was aimed at reducing oxygen ingress using high water saturation to limit oxygen diffusion and consumption of oxygen in the cover by residual sulphide minerals.…”

Mine Drainage: Characterization, Treatment, Modeling, and Environmental Aspect

“…Passive treatment systems do not require the continuous input of materials, energy or human intervention once the systems are constructed. The single-layer cover, 1.0 to 1.5 m thick, was placed on reactive tailings to provide long-term closure by reducing oxygen ingress using high water saturation to limit oxygen diffusion and consumption of oxygen in the cover by residual sulfide minerals (Dobchuk et al, 2013). The asbuilt cover reduced oxygen influx by most 50% and oxygen level was as low as 1% of that in uncovered tailings.…”

Effectiveness of alkaline amendments in acid mine drainage remediation

“…In mine waste system, the buffer capacity of tailings is a function of their mineralogical and chemical composition. Laboratory testing and numerical simulation model highlighted the importance of the infiltration rate, the oxygen diffusion rate, the location of acidity production, and the buffering capacity of the engineered cover and tailings material in assessing acidity and metals production from cover and tailings profile (Dobchuk et al, 2003). Acid-buffering minerals such as calcite, dolomite, carbonate or bicarbonate in tailings provide high buffering capacity resulting in rapid neutralization of pore and surface water (Ritcey, 1989;Wilkin, 2007).…”