Geostatistical site characterization of hydraulic head and uranium concentration in groundwater

The first case study presented in this paper describes an assessment of the spatial distribution and temporal changes in hydraulic head pressure in the groundwater beneath a retired federal government uranium processing facility. Analysis of the hydraulic heads involved ordinary kriging which was found to be a better mapping method than such alternatives as inverse-distance weighting, mainly because kriging provides measures of estimation uncertainty. The objective of this kriging was to provide estimated steady-state head values for use in calibrating a groundwater flow model for the site. In the second case study, the spatial distribution of potential uranium contamination in the aquifer was assessed with lognormal kriging. Uranium measurements for this analysis were available at roughly three-month intervals across a four-year time period. The objective of the analysis was to assess where the uranium concentrations were highest. A second objective, not addressed in this paper, was to determine if the concentrations were changing significantly during the four-year time period