A collapsed dam owned by Brazilian mining company Vale SA, in Brumadinho, Brazil. Its failure in January caused 270 deaths. Photo: washington alves/Reuters By Alistair MacDonald June 7, 2019 7:02 p.m. ET
Related Four of Toronto-based Barrick’s dams had come under question, the company said. For instance, a recent independent review of a dam in Ontario showed “an inadequate factor of safety against liquefaction,” according to footnotes on Barrick’s disclosure. Liquefaction, a process whereby seemingly solid materials suddenly behave like a liquid, occurred during the Brazil disaster. Barrick said in its notes that it plans to add a buttress to further stabilize the dam.
Switzerland’s Glencore also disclosed several dams that outside engineers had questioned. Two of those dams, both in Peru, had a hazard classification of extreme, indicating that the collapse of either could cost more than 100 lives and cause significant damage to local infrastructure. “We have confidence in the integrity of our facilities around the world, which are subject to the highest global safety and stewardship standards,” a spokesman for Anglo American said in an email.
Upstream dams are considered the cheapest type to build, but are also seen by experts as the most prone to failure. They are built from the same mining waste they are designed to hold back. Unlike other dam types, upstream structures mainly depend on the actual waste, or tailings, for their stability, whereas in other types the waste is contained behind an engineered structure.
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