Abstract

Numerical representation of the geologic framework and its hydrologic and geochemical properties is an integral part of all vadose zone flow-and-transport modeling. Historically, the geologic framework has been represented by simple homogeneous and horizontally stratified hydrogeologic units. However, as computer-processing capabilities have become more advanced, there has been more emphasis on improving spatial resolution and quantifying uncertainty in key model parameters. One of the more popular approaches has focused on geostatistical simulation of the flow-and-transport properties themselves, with little regard to the geologic strata and sedimentary sequences. Newer approaches are focusing more on geostatistical simulation of the sequence-stratigraphic relations of lithofacies and the geostatistical distributions of flow-and-transport properties within those facies. These approaches require more rigorous quantitative treatment of geologic data than is normally supported by the mostly qualitative nature of borehole geologic information. At the USDOE Hanford Site, efforts are being made to standardize borehole geologic data so they can be used in a systematic and quantitative way to define the spatial distribution of flow-and-transport properties in support of vadose zone flow-and-transport simulations. New detailed procedures translate qualitative descriptive information into categorical data and inconsistent quantitative and semiquantitative data into common parametric data sets. A geologic data-management system is being developed to manage and integrate these standardized categorical data sets with other existing databases to support synergistic analysis and to improve numerical representation of the hydrogeologic architecture. These standardized data sets were used to develop lithofacies-based geostatistical representations of hydraulic conductivity beneath one of Hanford's more complex waste sites.

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