Tailings is an area of mining where the industry is constantly seeking new approaches and ideas. They are an inevitable byproduct of the mining process but require extensive management to protect people and the environment. Recent catastrophic failures have rightly resulted in enhanced oversight and calls for change. Through the Global Industry Standard for Tailings Management (GISTM), mining companies are now actively adopting new levels of governance to increase the safety of tailings storage facilities (TSFs).
Governance alone is not the solution, however. Identifying new methods and technologies for managing tailings is imperative. Those methods must be robust, practical, and economical at scale; ideally, they should also minimize any increase in operational complexity at the facility. An innovative tailings management concept, hydraulic dewatered stacking (HDS), appears to tick all these boxes. It is being developed by global mining major, Anglo American, who partnered with WSP to conceptualize and design the new approach.
Innovation breeds innovation
The idea for HDS was born out of the adoption of coarse particle recovery (CPR) at Anglo American’s El Soldado copper mine in Chile. CPR results in a free-draining sand byproduct, which the mine believed could be put to beneficial use. Reaching out to WSP, Anglo American’s question was a simple one: could this waste be turned into a resource? The answer quickly became a resounding yes.
The concept devised by the combined Anglo American-WSP team uses CPR sand as a filter, co-disposing it with tailings to deliver passive drainage and gravitational dewatering of the tailings. The water is then managed separately for re-use in the mining process.
The key benefits
The HDS concept thus delivers benefits well beyond just finding a use for CPR sand. The three main advantages studied relate to water, stability, and closure.
Conventionally deposited tailings contain a large amount of entrained water with supernatant water typically managed on the surface. This results in large amounts of water being lost through entrainment and evaporation: water losses from tailings are in fact the most significant water loss at the majority of mining operations.
In contrast, HDS liberates the water entrained in the tailings and allows it to be recycled. This reduces demand for fresh water (or desalination), and therefore the overall water sustainability of the mine. In water-stressed regions, this is a significant benefit, not only for the environment, but also to the mine’s bottom line, as the financial cost of water is expected to increase substantially over time.