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March 31, 2014
Previous investigations identified elevated radiation levels at abandoned uranium mines (AUMs) operated in the 1950s-1960s in the Tachee Wash and Waterfall Canyon areas of Tachee/Blue Gap and Black Mesa Chapters of the Navajo Nation in northeastern Arizona. The occurrence of trace metals in wastes at these sites has not been previously characterized. Community concerns about possible ongoing release of hazardous substances from these sites, and possible contamination of water in a spring used by local families for drinking water, prompted a preliminary field study by UNM METALS Center. Field gamma radiation spot surveys on the largest waste site and geospatial analysis of the proximity of residences to the mine wastes indicate that the Claim 28 Mine site satisfies the Navajo Nation’s screening criteria as a high priority AUM. ICP-MS analysis of a water sample from a local spring confirmed the presence of uranium in concentrations exceeding the federal and tribal drinking water standard. XPS and XRF analyses of soil and waste samples collected from the largest AUM in the area revealed high levels of uranium, vanadium, arsenic, iron and aluminum, compared with non-impacted local soils. SEM analyses of the wastes found sub micron-size U particles, which pose a potential inhalation risk. Further studies are needed to fully characterize the physical and chemical properties of the mine wastes, determine release patterns through runoff, and better understand hydrogeologic relationships between waste sites and natural springs.
*ACKNOWLEDGEMENT: We acknowledge Navajo EPA’s authorization to collect samples from the Claim 28 Mine Complex and dedicate this first report of the UNM METALS Research Center to the memory of Navajo EPA health physicist Eugene Esplain, who worked tirelessly for a quarter century helping Navajo communities remediate abandoned uranium mines. (see link above to read article).
Contributors: Chris Shuey and Wm. Paul Robinson, principal authors (Southwest Research and Information Center); Sadie Bill, (Tachee Uranium Concerns Committee), Adrian Brearley (University of New Mexico Department of Earth and Planetary Sciences), Jose Manuel Cerrato (UNM Department of Civil Engineering), and Abdul-Medhi Ali (UNM Department of Civil Engineering).