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. He measured them, reported them to his supervisors, and didn't think anything more of it.

A few weeks later, at 5:30 a.m. on July 16, 1979, the dam failed, releasing 1,100 tons of uranium waste and 94 million gallons of radioactive water into the Rio Puerco and through Navajo lands, a toxic flood that had devastating consequences on the surrounding area.

"The water, filled with acids from the milling process, twisted a metal culvert in the Puerco," according to Judy Pasternak's book Yellow Dirt: A Poisoned Land and the Betrayal of the Navajos. "Sheep keeled over and died, and crops curdled along the banks. The surge of radiation was detected as far away as Sanders, Arizona, fifty miles downstream." According to a Nuclear Regulatory Commission report, radioactivity levels in the Puerco near the breached dam were 7,000 times that of what is allowed in drinking water.

The heavily contaminated water flowed over the river banks, creating radioactive pools. "There were children up and down the river playing in those stagnant pools, and they were deadly poisonous," Jorge Winterer, a doctor with Indian Health Service in Gallup, New Mexico, said after the spill.

Earlier this year, standing in his yard next to an old Chevy, King pointed in the direction of the now dry Rio Puerco. "It came right through there," said King. The unleashed river of waste had flowed through his family's land just a half-mile from his house. "I remember the terrible odor and the yellowish color of the water." He recalls seeing an elderly woman who had burned her feet crossing the Puerco while watering her sheep that day.