"Some of the worst mining disasters do not happen in mines.

They take place at dams.

After minerals are extracted from mines, there are waste materials — including sand, rock and chemicals. They're known as "tailings" and are permanently stored in dams constructed of earth, rock-fill or concrete.

But the dams can fail — from chemical erosion caused by the tailings and from disasters like floods and earthquakes. And the toll can be devastating."

Jose Olivares reports for NPR December 2, 2017. [2]