Researchers at the University of Waterloo have used historical satellite imagery to map a database showing 63 tailings flow incidents that have occurred worldwide since 1928. They hope their work will help to illustrate the environmental impacts of mining disasters, while also offering opportunities for industry to learn from their mistakes.
The new database is part of a study that presents the first global picture of the occurrence rates, behaviours and physical impacts of tailings flows, which are rapid downstream movements of mine waste following failures of tailings storage areas. Although predominantly produced from mining activities, the study also notes tailings generated from some industrial and power plant operations.
In the study, the researchers found that the behaviour of tailings flows primarily depends on a high ratio of water to solids in the tailings and the nature of the downstream terrain. Having excess stored water increases the fluidity of failed tailings, they suggest.
“Despite the strict engineering requirements, tailings impoundments can fail, sometimes catastrophically, so our research raises awareness of the potential downstream effects for public safety purposes,” announced the study’s lead researcher, Nahyan Rana, a PhD student of earth and environmental sciences at Waterloo, in a statement. “This study is especially relevant when we consider the global rise in mining activity,” he added.
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The new research suggests that catastrophic mining tailings flows have happened once every two to three years on average since 1965, with many of these events causing death, long-lasting environmental contamination and severe infrastructure damage over distances that can span tens of kilometres.
The database documents several breaches of tailings storage areas across Canada, such as the 2012 Gullbridge Mine incident in Newfoundland, the 2013 Obed Mountain coal mine waste spill in Alberta, and the 2014 Mount Polley copper mine breach in British Columbia.
Hazardous weather and inadequate drainage systems have been the most frequent triggers for tailings flows since 1996, researchers found.
Some tailings flows have attained maximum speeds of 100 kilometres per hour when travelling along semi-dry, narrow channels. On near-flat, open terrains they have travelled shorter distances but caused widespread flooding with maximum speeds of 22 to 50 kilometres per hour.
“Since 2014, there have been three high-profile events – two in Brazil and one right here in Canada,” said Stephen Evans, a professor of geological engineering and co-author of the 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 impoundment failure occur,” he added.
The study, Catastrophic mass flows resulting from tailings impoundment failures, was recently published in the journal Engineering Geology. The database, A Comprehensive Global Database of Tailings Flows, can be accessed through Scholars Portal Dataverse.