Mine waste dams threaten the environment, even when they don’t fail

Scars from large mining operations are permanently etched across the landscapes of the world. The environmental damage and human health hazards that these activities create may be both severe and irreversible.

Many mining operations store enormous quantities of waste, known as tailings, onsite. After miners excavate rock, a processing plant crushes it to recover valuable minerals such as gold or copper. The leftover pulverized rock and liquid slurry become tailings, which often are acidic and contain high concentrations of arsenic, mercury and other toxic substances.

Mining companies store tailings forever, frequently behind earth-filled embankment dams. Over the past 100 years, more than 300 mine tailing dams worldwide have failed, mainly due to foundation weakening, seepage, overtopping and earthquake damage.

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