A team representing two Federal agencies—U.S. Department of Energy (DOE) Office of Legacy Management and U.S. Geological Survey—is evaluating redistribution of contaminants at the Riverton, Wyoming, Processing Site. The Riverton site, a Uranium Mill Tailings Radiation Control Act Title I site, located on the Wind River Indian Reservation in central Wyoming, processed uranium ore from 1958 to 1963. DOE relocated 1.8 million cubic yards of tailings waste offsite and completed surface remediation by 1989. Contaminant concentrations in shallow groundwater (located about 6 feet below ground surface) generally declined until June 2010, when a historic flood of the Little Wind River resulted in significant increases in dissolved contaminants.
The field team, managed by DOE, employed Geoprobe Systems® technology to collect groundwater samples from 103 locations for chemical analyses.The Geoprobe Direct Push machine allowed coring of the unsaturated zone to observe the soil profile. Soil samples collected from 34 locations will be analyzed at DOE’s Environmental Sciences Laboratory in Grand Junction, Colorado, to determine amounts of uranium in the solid form that may affect groundwater concentrations. The investigation will provide a better understanding of the geochemical reactions that occurred when dilute river water contacted the soil-aquifer and will enable development of new models for predicting the duration of natural flushing in the future.
April Gil, LM Environment Team Lead and Grand Junction Site Manager, provided interviews to several media outlets during the sampling event, which were distributed to the Associated Press. She also met with local stakeholders, including the Wind River Environmental Quality Commission and congressional representatives.
Results of the investigation will be provided in an upcoming data report, followed by interpretative reports and a presentation at the 2013 Waste Management Conference.