Remediation works conducted on tailings management areas are aimed at providing long-term safe encapsulation of processing residues. The primary aim of such encapsulation is the significant reduction of pollutant loads via the atmospheric and aquatic pathways. Integrating state-of-the art remedial technologies from around the world into the Wismut project, various remedial options were investigated on how to achieve safe long-term tailings stabilisation. As a result, dry in-situ stabilisation was identified as the most cost effective option.
Stabilisation is a multi-stage process. In a first phase, contaminated supernatant water, known as free water, is removed from the tailings surface and pumped for treatment. In a following step, the tailings pond surface is capped with a multi-layered cover system. Exposed tailings surfaces are then covered with geotechnical means such as geofabrics, drain mats and geogrids. In addition, vertical drains are stitched up to five meters deep into the tailings. Also known as wicks, these geotextile drains speed up tailings dewatering. At a later stage, in interim cover consisting predominantly of waste rock is placed on top of this load-bearing working platform. The load of the waste rock has the effect of accelerating further dewatering of the tailings. With sufficient shear strength gained, the site’s final contour is shaped by front fill, excavation, and relocation of mineral material in the dam and centre-pond areas.
The final phase includes the placement of a final cover using site-specific soil types and subsequent surface vegetation. Planting of suitable woody species alternating with grassland and succession areas will help emerge a varied landscape structure.