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After Deadly Dam Spills, Miners Seek a Better Way—It Isn’t Working Out

Companies hope to develop technology that makes storing waste less dangerous, but it hasn’t been easy

SYDNEY—Global miners searching for new ways to handle mining waste following deadly spills in Brazil in recent years are reaching a frustrating conclusion: Many promising options aren’t proven at large scale.

Companies have traditionally held waste—mixtures of mud, rock and water, known as tailings—behind dams near their mines. However, that practice has come under intense scrutiny following the January collapse of a dam in Brazil owned by Vale SA, which killed 270 people, and another deadly spill four years earlier at an...