In 1968, the United Nuclear Corporation initiated mining operations in the largest underground uranium mine in the United States. Located in Church Rock, New Mexico, in the Navajo Native American Reservation, the Church Rock Mill produced more than two million pounds of uranium oxide per year. Waste from the mining process was disposed of in three lined lagoons fortified by a man-made dam built on geologically unsound land—of which both the United Nuclear Corporation and state and federal agencies were aware. On 16 July, 1979, the dam breached and 1100 tons of uranium waste and 94 million gallons of radioactive water seeped into the Puerco River. Scientists estimate that the amount of radiation released in the Church Rock uranium mill spill was larger than the amount released at Three Mile Island, just four months prior. Surrounding residents of the mill, almost entirely Navajos, relied on the Puerco River as a watering source for livestock. They have since suffered severe health problems due to substantial increases in radioactivity found in the water, soil, and air. Despite several selective investigations and cleanup efforts by the US Environmental Protection Agency, ramifications of the spill remain evident in the Navajo Nation today.
Interview with Larry King, who worked on-site at the United Nuclear Corporation mine the day of the tailings pond spill, and still lives in the area.