ABOUT THE GTMI
About Tailings
What Are Tailings?
Tailings is a common by-product of the process of extracting valuable minerals and metals from mined ore. They usually take the form of a liquid slurry made of fine mineral particles, created as mined ore is crushed, ground and processed. Tailings often contain hazardous material, heavy metals (like arsenic, cadmium, mercury, lead), processing chemicals (like cyanide used in gold extraction), and radioactive materials. This will depend on the type of ore mined, the waste material, and the processing method used.
Effective tailings management is integral to the safe and sustainable production of metals and minerals.
Tailings can be stored in a variety of ways: which way depends on numerous factors, for instance the local topography, how much rainfall an area gets, whether there is regular or irregular seismic activity recorded, the type of mineral being mined and how close the mine is to populated areas. There is no one-size-fits-all solution, each tailings facility (also commonly known as a tailings storage facility) is unique.
Identifying the most appropriate method of tailings construction is important to ensure the safe and sustainable operation of a facility. Tailings facilities follow one of three wall construction designs: these are downstream, upstream and centreline.
Downstream
Downstream designs start with an impervious starter dam. Tailings are then discharged into the dam and as the embankment is raised, each new wall is constructed and supported on top of the downstream slope of the previous section, so the dam crest moves downstream with each raise. The downstream design was developed for areas with seismic activity and high rainfall or water collection.
Upstream
Upstream construction begins with a starter dam. The tailings are then discharged into the facility where they form a tailings beach. The deposited tailings adjacent to the dam wall are allowed to drain and then can be compacted to be used to form the foundation for subsequent levels of the wall as the dam is raised. As such, the crest of the dam moves upstream with each raise.
Upstream tailings dams need to be raised slowly, to allow the solid tailings time to dry and consolidate enough to support a new level of the dam. These are suitable for facilities in areas of low rainfall and low seismic activity.
Centreline
The centreline method is a hybrid of upstream and downstream designs. In Centreline construction, the dam is raised vertically from the starter dam. The dam crest therefore remains fixed relative to upstream and downstream directions as the dam is sequentially raised. This design method can also incorporate internal drainage to improve stability.
Single stage
A single stage dam is built to full height in one stage with no further raises. This design is most commonly used for smaller tailings facilities.
Risk of design methods
While upstream dam designs are suitable for areas of low rainfall and low seismic activity, they are considered the most dangerous and least stable, as demonstrated by the Brumadinho (2019) and Fundão (2015) failures in Brazil.
Managing tailings facilities effectively
Tailings facility failures can result in catastrophic, long-term, and generational consequences for people, ecosystems, and economies. Consequently, the highest standards of safety and accountability in tailings management—from design, to post-closure—are an absolute imperative for the industry.
Building effective tailings management and preventing major catastrophes, requires the industry to form genuine partnerships with Indigenous Peoples and local communities, to secure their Free, Prior, and Informed Consent (FPIC) for facility locations and management.
The Global Industry Standard on Tailings Management provides a framework for safer tailings facility management, while affording operators flexibility as to how best to achieve this goal.