Questões de Concurso Comentadas para especialista em recursos minerais - desenvolvimento e economia mineral

   There is no doubt that the resources extracted from mining are critical to our way of life. Likely, you’re reading this on your computer, smartphone, or tablet. Mining touches all our lives daily (in addition to metals used in electronics, think about that can of soda you are drinking, or the aggregate used to pave your driveway). The industry works hard to make sure the net impact is positive. 

   However, the waste associated with mining, both past and present, is an unavoidable result of conventional mineral processing. In the future it may be possible to extract metals like copper and gold without crushing and grinding the ore down to fine particle size and adding considerable quantities of liquid, resulting in conventional tailings.

    What are the challenges associated with conventional tailings? Well, it is all about water. Managing seepage from the tailings themselves, monitoring pore water pressure within the tailings dams or designing facilities to safely store or pass flood events. Because such a significant quantity of water is added during mineral processing, “conventional” tailings dams store the tailings as a slurry. Water within the tailing material is either evaporated, migrates as seepage or remains entrained within the tailings impoundment. Removing water prior to disposal through various means is considered “alternative” disposal. Mining low grades of ore has resulted in increased water use per unit of production. In some cases, the availability of water is one of the greatest constraints on mine development.

Internet: <www.stantec.com> (adapted). 

  A dam holding back mining waste from a Brazilian miner is at risk of collapsing, a government audit says. The same company was responsible for two tailings dam collapses since 2015 that unleashed millions of gallons of toxic sludge and killed hundreds of people in Brazil’s southeastern state of Minas Gerais, which has been known worldwide as the Brumadinho Dam Collapse.

   The retired Xingu dam at Alegria iron ore mine in Mariana — the same municipality where a tailings dam collapsed in November 2015 in what’s considered Brazil’s worst environmental disaster to date — is at “serious and imminent risk of rupture by liquefaction,” according to an audit report from a local state organ. The report says the Xingu dam “does not present stability conditions.” “It is, therefore, an extremely serious situation that puts at risk workers who perform activities, access or remain on the crest, on the downstream slopes, in the flood area and in the area on the tailings upstream of the dam,” the document says.

  The ANM (National Mining Agency) rated the Xingu dam’s safety at level 2 in a September 2020 assessment, after requesting the company to improve the structure. The miner has fulfilled part of the request, but has sought a deadline extension for other repair works, without major changes in the structure. In its most recent inspection, ANM identified structural problems where no corrective measures had been implemented. 

Internet: <news.mongabay.com> (adapted).