Geochemical investigation of UMTRAP designated site at Riverton, Wyoming

The objectives of the investigation are to characterize the geochemistry, to determine the contaminant distribution resulting from the former milling activities and tailings, and to infer chemical pathways and transport mechanisms from the contaminant distribution. The results will be used to model contaminant migration and to develop criteria for long-term containment media, such as a cover system which is impermeable to contaminant migration. This report assumes a familiarity with the hydrologic conditions of the site and the geochemical concepts underlying the investigation. The results reported are based on a one-time sampling of waters and solid material from the background, the area adjacent to the site, and the site. The solid samples were water extracted to remove easily soluble salts and acid extracted to remove carbonates and hydroxides. The water extracts and solid samples were analyzed for the major and trace elements. A limited number of samples were analyzed for radiological components. The report includes the methods of sampling, sample processing, analysis, land data interpretation. Four major conclusions are: (1) salts containing uranium, vanadium, radium, and other contaminants have migrated to the surface and have activities and concentrations nearly as great as within the tailings; (2) contaminants have migrated about onemore » meter into the soils below the tailings but were retarded by the precipitation as carbonates, hydroxides, and oxides; (3) the soils off the northeast corner of the tailings are contaminated with uranium, nickel, aluminum, and iron which were deposited by a single event of fluid transport; and (4) the surface and shallow subsurface waters adjacent to the tailings are contaminated but the source of contamination can not be conclusively related to the tailings.« less