Disposal of waste

Overburden, rocks, tailings, slime and other waste from the mining process are stored at pre-defined places based on available space, material and terrain characteristics. Both the Codemin II Project and Barro Alto Project have studied and defined places for deposition of overburden and developed programs for drainage of these deposits and revegetation.

Quality and water flow monitoring procedures are in place in the surrounding of these deposits – downstream and upstream – for identification of possible contamination focuses or carrying of solid particles to waterways. Downstream these deposits, when applicable, sediment containment basins are built.

In Niquelândia, mining activities are stopped, so there was no generation of overburden in 2009. As the overburden is the actual soil and there is no chemical treatment, such as acid lixiviation for instance, there is no need for specific studies. In mountain ranges, as the ore outcrops, no mine overburden is generated.

The Codemin slag is magnesium silicate – classified by NBR 10004 as an inert waste after lixiviation and solubility tests. Therefore, it is deposited in a controlled manner according to ABNT standards for inert and non-inert waste. In Ouvidor, the slag produced in the niobium metallurgy process is stocked in a controlled deposit, according to CNEN standards. The material contains uranium and thorium and is considered a radioactive mining waste. Therefore, the company develops procedures for stocking, periodical inspections and surface and underground water monitoring.

Tailings dams are structures of compressed soil, built to receive and contain tailings arising from ore beneficiation. In general, most of the material is dumped in dam reservoirs, and the solid material is segregated by means of decantation and the liquid phase is eliminated through soil seepage, evaporation and extravasation. For all dams stability inspection and monitoring programs (piezometers) are in place.

Surface and underground water monitoring programs are in place for its area of influence, in addition to emergency and closing plans. In 2009, slime and tailings generated in Ouvidor were forwarded to new waterproof dams.

In Niquelândia, no slime is produced in the process.

Dust collected in exhausters was deposited in a dam in the form of slurry. With the Codemin II Project, all this dust started to be recirculated for reuse of the nickel contained in it and is no longer deposited in the dam. Gradually, the material has been used to feed the process.