GEOCHEMICAL MODELING OF URANIUM ISL GROUNDWATER RESTORATION

Geochemical modeling with the computer code, PHREEQC, was used to illustrate the possible evolution of groundwater quality during and after groundwater restoration following in-situ uranium leach mining. Several simple geochemical scenarios were considered as part of the modeling exercise, including whether oxic or anoxic groundwater flowed into the mined region at the end of the restoration process. Alternative assumptions with respect to the formation of various stable and metastable mineral phases after introduction of reductant to the groundwater system had a significant impact on the resulting groundwater quality. Among the various scenarios, perhaps the most important issue with respect to achieving water quality objectives of groundwater restoration is whether oxic or anoxic groundwater flows into the mined region after the active phase of restoration.