Early in the summer of 1979, Larry King, an underground surveyor at the United Nuclear Corporation’s Church Rock Uranium mine in New Mexico, began noticing something unusual when looking at the south side of the tailings dam. That massive earthen wall was responsible for holding back thousands of tons of toxic water and waste produced by the mine and the nearby mill that extracted uranium from raw ore. And as King saw, there were “fist-sized cracks” developing in that wall.