Cover Trials on Tailings Storage Facilities in Arid Hypersaline Regions

A field study was established in 2001 to evaluate a range of cover designs for the rehabilitation of tailings storage facilities in arid hypersaline regions. The success of a cover system in this environment is dependent on the extent to which the cover limits the upward evaporation-driven migration of salts from the tailings into the cover. A “discontinuous cover” (that is, cover mounds) is one particular system that was trialled. Aside from being a cost-effective alternative to placing a conventional continuous cover, the concept of a discontinuous cover system was built on the idea that water rising to the surface due to capillary action would not rise further than the low points between the cover mounds, as the cover materials are far coarser than the tailings. The sides and tops of the mounds would then in theory be suitable for the growth of vegetation, while the low points would become salinas where vegetation could not grow, mimicking a natural salt pan.

The current research has demonstrated that the development of a salt crust on the bare tailings surface has reduced the rate of evaporation from the bare tailings, to the point where there is evidence of lateral migration of salts from beneath the bare tailings surface into the adjacent cover mounds. This has resulted in higher salt concentrations within the cover mounds than within a continuous cover of corresponding materials and cross-section. This outcome questions the potential effectiveness of a discontinuous cover system for hypersaline areas where revegetation is the aim. Further trials are recommended to further understand the mechanisms limiting the success of the current discontinuous cover system design. A key element in developing a vegetated cover on hypersaline tailings in an arid climate is an effective and sustainable capillary break between the tailings and the growth medium.