Technology for Safe Tailings Disposal

This week witnessed yet another tailings dam accident. The event took place in China’s Heilongjiang province and water up to 110km downstream has been polluted. Tailing dams came back into the limelight last year, when a Brazilian dam operated by Vale collapsed killing 270 people. As reported by Reuters, “Brazilian authorities recently halted operations in 47 mining dams that failed to certify their stability, including at least 25 belonging to Vale.” Mexico has also had its share of tailings accidents in its books. In 2014 a Grupo Mexico dam burst, contaminating Sonora’s main river.

Mining Technology notes that “in this century alone, there have now been 11 serious dam failures. This number also appears to be on the rise, according to figures produced by researchers at World Mine Tailings Failures (WMTF).” In fact, WMTF predicts 19 very serious failures in the following 10 years, if major changes to law and industry practices are not introduced.

New technology for better controlling of all key variables is also crucial for achieving greater tailing safety. Dry-stacking is a case in point. As explained in an infographic by Reuters, “this method sucks water from mine waste so that it can be stored safely, effectively as dry dirt. The approach holds potential to boost water recycling in arid climates while substantially reducing the footprint and geo-technical risks of massive dams that store wet tailings.”

Although dry-stacking is expensive and suitable mainly for smaller mines, it is an exciting alternative. To this point, Luiz Camargo, Country Head of Fortuna Silver, said to Mexico Business News: “Our tailings management begins with how we process ore to ensure that our tailings are as nontoxic as possible. Then, instead of disposing our industrial waste in a tailings dam we use a dry stack method for two reasons. First, we use a zero-water-discharge cycle, which means that we treat and reuse approximately 95 percent of the water in our process that is not lost due to evaporation. Second, as tailings dams occupy such a huge space, the environmental impact during the mine operation is greater. The dry stack implies disposing of our filtered tailings in a space covered by a geomembrane to prevent any filtrations through rain into the soil. We filter the tailings to recover their water, then put them in the dry stack and flatten them. While this is a significantly costlier process compared to a tailings dam, the environmental return on investment pays for itself by far.”