GRAND JUNCTION, Colo. — The U.S. Department of Energy today announced the availability of a Data Summary Report of enhanced characterization fieldwork conducted in August 2012 at the Riverton, Wyoming, Uranium Mill Tailings Radiation Control Act (UMTRCA) Site.
“The Department will use the data to assess why levels of groundwater contamination in monitoring wells increased after the 2010 historic flood event of the Little Wind River,” said Bill Dam, DOE Riverton site manager. “The next step is to analyze and interpret the data.”
The enhanced characterization fieldwork involved installing 103 boreholes along 9 transects with a small, portable drill rig. Water samples were collected at each location, and soil samples were collected at 34 locations. The report presents data from chemical analyses of the samples. Additional interpretation and evaluations will be documented in the annual Verification Monitoring Report that will be available later this year.
Uranium and vanadium ore processed from 1958 to 1963 resulted in contamination of the shallow groundwater at the Riverton site, which is located on the Wind River Indian Reservation. DOE conducted groundwater characterization studies at the Riverton site in the 1990s and recommended a natural flushing compliance strategy, which was approved by the U.S. Nuclear Regulatory Commission. The Department has conducted additional monitoring to verify site conditions and assess the progress of natural flushing since 1998.
Results of the verification monitoring indicated that natural flushing was generally progressing as expected until June 2010, when a record flood caused the Little Wind River to overflow and flood a large area near the former mill site. Groundwater sampling conducted immediately after the flood showed significant increases in contaminant concentrations in monitoring wells where the flooding occurred. The higher contaminant concentrations may be the result of high water levels mobilizing residual contamination in soil above the groundwater.
The Enhanced Characterization of the Surficial Aquifer, Riverton, Wyoming, Processing Site, Data Summary Report is available on the DOE Office of Legacy Management website at http://www.lm.doe.gov/Riverton/S09545_EnhancedChar.pdf. Questions or comments about the data summary can be sent to Riverton@lm.doe.gov.