Tests will indicate progress of current groundwater remediation strategy
The U.S. Department of Energy will conduct additional characterization work at the Riverton, WY, Uranium Mill Tailings Radiation Control Act (UMTRCA) Site this summer, including extensive groundwater and soil sampling. The Department will use the sampling results to update the site conceptual model and to develop a revised groundwater flow and transport model to more accurately simulate natural flushing processes.
Historical ore processing resulted in contamination of the shallow groundwater at the Riverton site, which is located on the Wind River Indian Reservation and processed uranium ore from 1958 to 1963. 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 verification monitoring to document site conditions and assess the progress of natural flushing since 1998. The Wind River Environmental Quality Commission also conducts studies and provides verification monitoring support.
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 downgradient of the former mill site. Groundwater sampling conductedimmediately after the flood showed significant increases in contaminant concentrations in monitoring wells where the flooding occurred. The spikes in contaminant concentrations are attributed to the flood waters mobilizing residual contamination and potentially accelerating the natural flushing process.
“After the record flood in 2010, we learned that our existing computer models could not account for the spikes in contaminant concentrations,” said April Gil, DOE Riverton site manager. “So we need to update the conceptual model and revise the groundwater flow and transport model to more accurately simulate natural flushing processes.”
The Work Plan for the Enhanced Characterization of the Surficial Aquifer, Riverton, Wyoming, Processing Site is available on the DOE Office of Legacy Management website at http://www.lm.doe.gov/riverton/Documents.aspx. Questions or comments about the work plan can be sent to Riverton@lm.doe.gov.