GoKawiilRadioactive spill in New Mexico, United States
The Church Rock uranium mill spill occurred in the U.S. state of New Mexico on July 16, 1979, when United Nuclear Corporation's tailings disposal pond at its uranium mill in Church Rock breached its dam.[1][2] The spill remains the largest release of radioactive material in U.S. history, having released more radioactivity than the Three Mile Island accident four months earlier.[2][3][4][5]
The mill, which operated from June 1977 to May 1982, was located on privately owned land about 17 miles (27 km) northeast of Gallup, New Mexico, and was bordered to the north and southwest by Navajo Nation Tribal Trust lands. The milling of uranium ore produced an acidic slurry of ground waste rock and fluid (tailings) that was pumped to the tailings disposal area.[6][7] The breach released more than 1,100 short tons (1,000 t) of solid radioactive mill waste and 94 million US gallons (360,000 m3) of acidic, radioactive tailings solution into the Puerco River through Pipeline Arroyo. An estimated 1.36 short tons (1.23 t) of uranium and 46 curies of alpha contaminants traveled 80 miles (130 km) downstream[8] to Navajo County, Arizona, and onto the Navajo Nation.[2] In addition to being radioactive and acidic, the spill contained toxic metals and sulfates.[9] The spill contaminated groundwater and rendered the Puerco unusable to local residents, mostly Navajo peoples who used the river's water for drinking, irrigation, and livestock. They were not warned for days of the toxic dangers from the spill.[2]
The governor of New Mexico, Bruce King, refused the Navajo Nation's request that the site be declared a federal disaster area, limiting aid to affected residents.[10] The nuclear contamination event received less media coverage than that of Three Mile Island, possibly because it occurred in a very rural area not served by major media. The spill also happened in Native American country, among a community who reportedly did not have their concerns addressed by medical authorities.[11]
In 2003, the Church Rock Chapter of the Navajo Nation began the Church Rock Uranium Monitoring Project to assess environmental impacts of abandoned uranium mines; it found significant radiation from both natural and mining sources in the area.[12] As of 2016, the EPA National Priorities List included the Church Rock tailings storage site, where "groundwater migration is not under control".[13]
Dam failure [ edit ]
At around 5:30 am on July 16, 1979, a previously identified crack opened into a 20-foot-breach (6.1 m) in the south cell of United Nuclear Corporation's Church Rock temporary uranium mill tailings disposal pond, and 1,100 short tons (1,000 t) of solid radioactive mill waste and about 93 million US gallons (350,000 m3) of acidic, radioactive tailings solution flowed into Pipeline Arroyo, a tributary of the Puerco River.[2][4][14] Warnings of an impending spill had been ignored by the state and by United Nuclear Corporation.[15] Though the uranium mill only bordered the Navajo Nation, the tailings spilled onto the Navajo Nation as they flowed down the Puerco River.[2]
The 20-foot (6.1 m) breach in the tailings dam formed around 5:30 a.m. on July 16, 1979. [ 2 ]
The tailings solution had a pH of 1.2[16] and a gross alpha particle activity of 128 nanocuries (4.7 kBq) per liter.[17] In addition to radioactive uranium, thorium, radium, and polonium, it also contained various other metals, including cadmium, aluminium, magnesium, manganese, molybdenum, nickel, selenium, sodium, vanadium, zinc, iron, and lead, and also high concentrations of sulfates.[17] The contaminated water from the Church Rock spill traveled 80 miles (130 km) downstream, through Gallup, New Mexico, and reached as far as Navajo County, Arizona. The flood backed up sewers, affected nearby aquifers, and left stagnating, contaminated pools on the riverside.[4][18][19]
As the highly acidic spill traveled downstream, alkaline soils and clays neutralized the acid and adsorbed many of the contaminants. The contaminated sediments were gradually dispersed by the river and diluted by "clean" sediment. In parts of the river system with higher concentrations of contaminants, yellow salt crystals precipitated onto the arroyo bed. These salts, containing metals and radionuclides, were washed away during subsequent rainstorms. Approximately one month after the spill, the Puerco River had regained normal levels of salinity, acidity, and radioactivity at low flow levels, with contaminants being detectable only after heavy rains. The EPA reported no long-term effects of the spill, but noted that contaminant levels from uranium mine effluents and natural sources were "environmentally significant".[9][20]
... continue reading