We are Nexa. We’ve changed to go further. To extract deeper, to mine with greater responsibility, to build a more valuable future. A company that believes that mining is the basis for society to evolve. The key ingredient that will sustain the essence of the products and services that we need to develop.
Nexa’s dams and tailings deposits
Nexa prioritizes the reuse of materials through new technologies, as an alternative in the treatment of tailings and waste. This proposal is applied at the Morro Agudo Mine, where tailings are a commercially viable by-product. When this is not applicable, Nexa uses three different forms of disposal, preferably returning the material to the mine (backfill), secondly by dry stacking, and – when these solutions are not possible – we dispose of them in dams. Currently, roughly 15% of the tailings/waste generated by Nexa in Brazil and Peru is disposed of in dams.
Some operations may combine one or more disposal methods. At the Atacocha, El Porvenir and Cerro Lindo units in Peru, we adopted the backfill system, whereby 46% of the tailings are returned to the mines at the Pasco Complex (Atacocha and El Porvenir), and 38% is returned to the Cerro Lindo mine, in which part of the waste is filtered, separating water and solids. The water is recirculated and the filtered tailings are sent to the dry stacks to be compacted.
In Brazil, we already operate in the Vazante mine, disposing of the tailings in dry stacks, which reduces environmental impacts and risks to the operation. This same model will be adopted in the Aripuanã operation, still under construction.
Backfilling refers to filling the mine with tailings, inserted into the voids of underground mines, for the purpose of increasing the structural stability of the mine, providing platforms, improving ore recovery, and disposing of tailings.
The underground disposal of tailings in mining pits can only occur when the tailings are considered inert, eliminating the possibility of contaminating water or soil.
Also called a filtered (or dewatered) tailings stack/deposit, the pulp tailings that remain after processing the ore undergo filtering, drying and handling (whether combined or single method), until obtaining moisture content below 20%.
By extracting water from the pulp (the mixture of liquid plus ore or tailings), the solid part is stored or placed in stacks, ensuring reduced environmental impact.
A dam is a structure built for the purpose of containing, impounding or storing water, liquid substances, or mixtures of liquids and solids, whether permanently or temporarily.
The term “dam” comprises not only the levee or embankment itself, but also all associated structures, such as: spillways and sluices, reservoir, headrace, diversion structures, tailrace, water intakes, impoundment intakes, saddle dike, among others.