The<unk>  occurred in the U.S. state of New Mexico on July 16, 1979, when United Nuclear Corporation's tailings disposal pond at its<unk> <unk>  in<unk> <unk>  breached its dam. The accident remains the largest release of radioactive material in U.S. history, having released more radioactivity than the Three Mile Island accident four months earlier. The<unk> , which operated from June 1977 to May 1982, was located on privately owned land about north of Gallup, New Mexico, and was bordered to the north and southwest by Navajo Nation Tribal Trust lands. The<unk> ing of<unk>  ore produced an acidic slurry of ground waste<unk>  and fluid (tailings) that was pumped to the tailings disposal area. The breach released more than of solid radioactive<unk>  waste and of acidic, radioactive tailings solution into the Puerco River through Pipeline Arroyo. An estimated of<unk>  and 46 curies of alpha contaminants traveled downstream to Navajo County, Arizona, and onto the Navajo Nation. In addition to being radioactive and acidic, the<unk>  contained toxic metals and sulfates. The<unk>  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<unk> . 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. 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<unk>  also happened in Native American country, among a community that at that time were not predisposed to speaking out. In 2003, the<unk><unk>  Chapter of the Navajo Nation began the<unk> <unk><unk>  Monitoring Project to assess environmental impacts of abandoned<unk>  mines; it found significant radiation from both natural and mining sources in the area. The EPA National Priorities List currently includes the<unk> <unk>  tailings storage site, where "groundwater migration is not under control."
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