Until 2008, the Aldermac mine was considered one of the most problematic abandoned mines sites in Québec due to the high production of acid mine drainage caused by mine tailings spread over a large area. The site was reclaimed between 2008 and 2009 to reduce the ecological footprint and to minimize any further tailings oxidation (production of acid mine drainage). For this purpose, a monolayer cover with an elevated water table was used as an oxygen barrier on the north zone of the site. To assess the performance of the monolayer with an elevated water table cover, a network of observation wells was set up to monitor the water table level and collect groundwater samples for the analysis of physical and chemical parameters. Results of water table level measurements show that the cover successfully maintains the tailings within the water table at all times, thus preventing further tailings oxidation. Hydrogeochemical results, interpreted with principal component analysis, show that the quality of water is improving, thus indicating that reclamation is helping to reduce groundwater contamination at the site.

Acid mine drainage is an important environmental risk linked to the surface storage of reactive mine tailings. To manage this problem, a cover with a capillary barrier effect (CCBE) can be used. This oxygen barrier cover relies on maintaining a fine-grained material layer (moisture-retaining layer, MRL) with a high degree of saturation. CCBEs can be colonized by surrounding plants. Plant roots pump water and could impact CCBE’s performance. This performance is predicted with unsaturated water flow numerical models in which vegetation parameters can be included. Vegetation parameters may be specific in a CCBE environment. Therefore, analyzing and quantifying the vegetation that colonizes this type of cover is necessary. Plant colonization was investigated through cover and density surveys on 12 transects on a 17-year-old CCBE in the mixed forest of Quebec, Canada. Then, aboveground vegetation and root colonization intensity at three depths in the MRL were characterized on 25 plots of five dominant vegetation types (Salix, Populus, Alnus, Picea sp., and herbaceous species). The mean root length density under plots dominated by Salix sp. was higher than in the other plots. Root colonization of the MRL was concentrated in the first 10 cm and occurred under all woody and herbaceous species as well. This work quantitatively describes, for the first time, the vegetation colonizing a CCBE both at the above- and belowground levels. These data will be useful to better predict the long-term performance of this engineered reclamation cover.

Traditional deposition of tailings slurry in a tailings storage facility (TSF) can create risks of dike failure. In order to minimize these risks and slurry spillage, the surface deposition technique of densified tailings (DT) through dewatering of the slurry has emerged. The DT technique has the potential to maximize water reuse, improve the shear strength of surface tailings, and reduce the ecological footprint of TSF. The consistency of DT covers a continuum ranging from thickened state, to paste state, to dry state. Despite its efficiency and economic feasibility, DT densification using thickeners sometimes proves unable to achieve the design target solids mass concentration (C_w%). Hence, the use of superabsorbent polymers (SAPs) seems to represent a promising alternative, owing to their higher water absorbent capacity. In this paper, superabsorbent polymers (SAPs) reclaimed from industrial reject of baby diapers (Na-polyacrylates) are explored as a promising alternative to mine tailings slurries dewatering. To this end, laboratory-scale dewatering tests have been performed using two grades of Na-polyacrylate SAPs (grade 1 SAP = SAG-A06P coarse-grained, and grade 2 = SAG-M01P-100 medium-grained) for the tailings slurries densification. A higher water absorbency (or swelling capacity) was observed using the coarser SAPs (SAG-A06P) compared to the finer SAPs (SAG-M01P-100). The preliminary results showed that a SAP volume dosage in the range 10–13 kg of SAP/m³ of slurry allowed achieving a final solids mass concentration (C_{w%_final}) ≥ 70%, despite the occurrence of gel-blocking phenomenon.

The modified Kovács (MK) model can predict fairly well the water retention curve (WRC) of different types of soils, using basic geotechnical properties. Considering its relative simplicity and its ability, a study was initiated to compare this model to an alternative predictive approach involving a one-point measurement method (OPMM). The comparison result indicates that there is generally a good agreement between volumetric water content values predicted using the OPMM and the MK model and those obtained from direct measurements. However, the OPMM typically leads to a better correlation than the predicted values obtained with the MK model for cohesive fine-grained soils because shrinkage induced by suction is not taken into account. Hence, the MK model is deemed as a valuable tool that gives realistic estimates of the WRC using easy to obtain basic geotechnical parameters, when there is no direct measurement available for a point on the WRC, and this predictive model can be particularly useful at the preliminary phase of a project.