Two cross-hole tracer tests and one infiltration tracer test were completed at a former uranium mill site in Grand Junction, Colorado. Reactive transport modeling was completed to derive physical and geochemical parameters. The observed data from saturated zone cross-hole tracer testing was adequately simulated using PHT-USG (reactive transport model) and PEST++ (calibration routine) with reasonable estimates of hydraulic conductivity, dispersion, effective porosity, cation exchange, calcite saturation index, and uranium sorption potential. The use of multiple layering in one cross-hole model was able to capture hydraulic conductivity variations with depth, which produced a double hump in the tracer concentrations. The complete article can be downloaded here: https://www.mdpi.com/2075-163X/13/7/947

100-series well constructions with injection and pumping pattern in relation to hydrogeology and solid-phase uranium concentrations. Red shading indicates depths with solid-phase uranium concentrations that are above background. Depths are to scale with two times horizontal exaggeration. Well 0105 is beyond the plane of the page (Figure 2). Arrows indicate flow directions.