Late January marked the fifth anniversary of the world's worst modern-day tailings dam disaster at an iron ore mine in Brumadinho, Brazil. The collapse killed at least 270 people. They were mostly Vale company employees eating lunch in a canteen directly below a dam that gave way, sending a tidal wave of 12 million cubic metres of toxic orange sludge eight kilometres downstream, bulldozing houses, offices and people.

Brumadinho remains a stark reminder that a modern mine is not just a source of valuable metals. It's also a permanent toxic waste storage facility. The need to store and manage mine tailings — the waste created by grinding up and processing ore — is modern mining’s greatest environmental liability and long-term expense. It’s also a huge concern moving forward, as production ramps up of critical metals like copper, needed for the electrification of our civilization to fight climate change. Many new, increasingly large, tailings dams will be required.

In the wake of Brumadinho — with B.C.'s Mount Polley tailings disaster in 2014 still fresh in memories — investors representing trillions in assets, led by the Church of England Pensions Board, vowed never again. Together, with the biggest mining industry group and the UN, the group set about creating a new system of rules to better manage the thousands of tailings dams scattered across the globe.

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