Abandoned mine shaft

Database aims to help prevent mine-waste disasters

Image credit: Dreamstime

Researchers at the University of Waterloo have created a database as part of a study intended to help mining companies better understand the societal and environmental impacts of mine-waste disasters and hopefully avoid them in future.

The study forms the first global picture of the occurrence rates, behaviours and physical impacts of mine-waste disasters known as tailings flow. Tailings flows are rapid downstream movements of mine waste, following tailing dam failures.

Catastrophic tailings flows have occurred approximately one every two to three years since 1965, causing death, long-term environmental contamination and severe infrastructure damage over distances that can span tens of kilometres. In the past few decades, hazardous weather and inadequate drainage have been the most frequent triggers for these events.

“Despite the strict engineering requirements, tailings dams can fail, sometimes catastrophically, so our research raises awareness of the potential downstream effects for public safety purposes,” said PhD candidate Nahyan Rana, lead researcher on the study. “This study is especially relevant when we consider the global rise 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 cases of tailings flow and make the case to support more dam assessments.

Analysing satellite imagery and historic data pointed them towards the conclusion that tailings flows primarily depend on a high water-to-solids ratio in the tailings, as well as the nature of the downstream terrain. Having excess stored water increases the fluidity of the released tailings.

They found that some tailings flows reached extreme speeds of 100km/h when travelling along semi-dry and narrow channels, causing mass casualties (including fatalities); destruction of communities, and destruction of ecosystems. Other tailings flows occur along active rivers, resulting in slow speeds but longer travel distances (exceeding 10km). Tailings flows on near-flat terrain tend to travel shorter distances; reach moderate speeds of 22-50km/h, and are associated with widespread flooding.

“Since 2014, there have been three high-profile events: two in Brazil and one right here in Canada,” said Professor Stephen Evans, a geological engineering expert and co-author of this study. “While much progress has been made in terms of regulation and oversight, studying past tailings flows enables better prediction of what could happen should a major tailings dam failure occur.”

The Waterloo researchers hope their database will be useful to mining engineers, who will now be able to compare the conditions they are working in with the conditions of previous incidents.

E&T, like the University of Waterloo researchers, used satellite imagery to investigate environmental consequences of mining, specifically lithium mining in Chile. The investigation concluded that lithium mining was damaging the local environmental and communities in the Atacama salt flats, with activities reducing water levels in an already parched region.

Last year, E&T also explored whether mining, with its long history of environmental destruction, can ever make the change and truly go green.

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