Researchers at the University of Waterloo have created a database as part of a study designed to help mining companies better understand and hopefully prevent the social and environmental impacts of mining waste disasters in the future.
The study provides the first global picture of the frequencies, behavior, and physical consequences of mining waste disasters, the so-called tailings flow. Waste streams are rapid downstream movements of mining waste following the failure of tailings dams.
Since 1965, catastrophic waste streams have occurred approximately once every two to three years, resulting in fatalities, long-term environmental pollution, and serious damage to infrastructure over distances that can span tens of kilometers. In recent decades, hazardous weather and insufficient drainage have been the most common causes of these events.
“Despite strict technical requirements, tailings dams can fail, sometimes catastrophically, so our study raises awareness of the potential downstream impacts for public safety purposes,” said Ph.D. student Nahyan Rana, lead researcher on the study. “This study is especially relevant when looking at the global increase in mining activity.”
The study involved researchers in three provinces and brings together detailed information on 63 tailings flows that have occurred worldwide since 1928. They used satellite imagery to map dozens of tailings flow cases and to support more dam assessments.
Analyzing satellite images and historical data led them to conclude that tailings flow depends primarily on a high water-to-solids ratio in the tailings, as well as on the nature of the downstream terrain. Having excess stored water increases the fluidity of the released residues.
They found that some waste streams reached extreme speeds of 100 km/h when traveling along semi-arid and narrow channels, causing massive casualties (including fatalities); destruction of communities, and destruction of ecosystems. Other waste flows occur along active rivers, resulting in slow speeds but longer travel distances (more than 10 km). Waste streams on nearly flat terrain tend to travel shorter distances; reach moderate speeds of 22-50 km/h and are associated with widespread flooding.
“Since 2014, there have been three high-profile events: two in Brazil and one here in Canada,” said Professor Stephen Evans, a geological engineering expert, and co-author of this study. “While much progress has been made in regulation and oversight, studying the flows of waste streams in the past allows a better prediction of what could happen if a major failure of the waste dam were to occur.”
The Waterloo researchers hope their database will be useful to mining engineers, who can now compare the conditions in which they work with the conditions of previous incidents.
E&T, like researchers at the University of Waterloo, used satellite imagery to investigate the environmental impact of mining, particularly lithium mining in Chile. The study concluded that lithium mining was detrimental to the local environment and communities in the Atacama Salt Flats, with activities decreasing water levels in an already parched region.