| Description |
Stable isotopes, dissolved gas concentrations, tritium, and chlorofluorocarbons (CFCs) were used in a groundwater study to characterize groundwater flow, chemical composition, noble gas composition, and age to investigate increasing trace metal concentrations at a uranium processing facility near the town of Blanding in southeastern Utah. Temperature and salinity profiles were used in conjunction with noble gas composition to evaluate the extent of stratification of the water column. Low-flow sampling was employed at two depths in several wells to further characterize water column stratification, collection of samples for tritium, chlorofluorocarbons, hydrogen and oxygen isotopes of water, sulfur and oxygen isotopes of sulfate, nitrate and sulfate, and trace metal concentrations of groundwater. Samples were also collected from a number of surface water sites, including three tailings cell waste ponds. Distinct noble gas compositions, determined using passive diffusion samples at two depths in most wells, indicated significant stratification of the water column. Low-flow sampling, however, failed to delineate stratification in the water column with respect to trace metals, inorganics, stable isotopes of water and sulfate, tritium, and CFCs. Isotope fingerprints of surface water sites at the mill strongly correlated to samples from two wells. Although other factors such as sulfate and trace metal concentrations did not indicate leakage occurring from the tailings cells, the isotope fingerprints suggested some interaction between surface waters and groundwater. Young groundwater ages in wells immediately down-gradient from wildlife ponds and adjacent to tailings cells further indicated a connection between surface waters and groundwater. Data from groundwater ages, stable isotope fingerprints, and dissolved noble gases suggest that active horizontal and vertical groundwater flow is occurring, and that there are clear interactions between surface water sites and groundwater. However, trace metal and other inorganic concentrations suggest that leakage from the tailings cells and contamination of groundwater is not occurring. This study has valuable implications for the potential impact of mining and refining operations on important groundwater resources, as well as the functionality of multi-faceted stable isotope and groundwater age dating techniques. |
