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Short-term, field-scale transient vadose zone pumping tests were performed on several wells at the Savannah River Site, located near Aiken, South Carolina. A total of 18 vacuum extraction tests were conducted in shallow coastal-plain vadose zone sediments, which yielded 38 data sets for analysis. Data collected during these tests were analyzed using two different modified Hantush-Jacob models to estimate the physical properties of the unsaturated sediments. The first model used was a commercially available software package used to estimate aquifer properties. This model assumed the test fluid (air) to be incompressible. The second model used was provided by Clemson University and accounted for the compressibility of the test fluid. This model was used primarily to provide confirmation of results from the first model. Comparisons between the results of the two models showed that both produced similar estimates of permeability for a given data set. Results from the analysis of the 38 data sets showed that the radial air permeability values ranged from 4.7 to 84.0 d. Vertical air permeability values were found to range from 0.93 to 11.7 d. The permeability values for the overlying semiconfining layer ranged from 2.7 × 10−10 to 2.01 d. The results from these tests can be used to establish a general range of air permeabilities for shallow coastal-plain vadose zone sediments.
Kenneth Dixon is a principal engineer at the Savannah River National Laboratory, where he has conducted research related to soil and groundwater characterization and remediation for 14 years. He received his B.S. and M.S. degrees in agricultural engineering from the University of Georgia and an M.E. degree in civil engineering from the University of South Carolina. His primary research interests are in pilot-scale testing of innovative remedial technologies and numerical modeling of contaminant fate and transport in the vadose zone.Ralph Nichols is a fellow engineer at the Savannah River National Laboratory, where he has conducted research related to soil and groundwater characterization and remediation for 17 years. He received a B.S. degree in geological engineering from the University of Missouri–Rolla and an M.S. degree in civil engineering from the University of Oklahoma. His primary research interests are in the collection and synthesis of data from multiple scales into conceptual models that are used to develop sustainable environmental management strategies.