Tailings erosion and resuspension in two mine tailings ponds due to wind waves

Abstract

One of the approaches used for environmental management of mine tailings is the implementation of shallow water covers, typically up to 2 m. As oxygen is one of the key factors in the oxidation of reactive iron-bearing sulfide minerals present in the tailings, water covers provide an effective control measure, owing to the low diffusivity and solubility of oxygen in water. However, wind-induced waves can resuspend flooded tailings, thus increasing the possibility of oxidation and acid generation. Summer field measurements of wind velocity and wave heights at two mine tailings sites in New Brunswick and Ontario are presented and discussed. Frequency diagrams of winds show that in summer wind speeds as high as 15 m/s are anticipated at these sites. Bottom shear stresses are calculated using measured wave heights and compared to critical shear stress of the tailings. Calculated bottom shear stresses exceeded the critical shear stress of the tailings at wind speeds higher than 9 m/s. Based on sediment trap data at the two sites, it is shown that resuspension is not a function of depth and wind-generated stresses alone, but also depends on other factors, such as cohesion and self-consolidation of tailings and site topography. Areas of erosion and accumulation were delineated at the two sites using particle size distribution, metal concentrations and an erosion–transportation–accumulation (ETA) diagram. The findings confirm resuspension work carried out by previous researchers at these two sites.