ANALYSES OF SLUG TESTS AND HYDRAULIC CONDUCTIVITY VARIATIONS IN THE NEAR-FIELD OF A 2-WELL TRACER EXPERIMENT SITE

Three-hundred eight slug tests were conducted in a 5 x 5 m area in a c oastal, sandy aquifer at the Georgetown site in South Carolina to char acterize three-dimensional aquifer heterogeneity. Methods developed by Hvorslev, Bouwer and Rice, and Cooper et al. were employed to estimat e hydraulic conductivity values from the slug test data. These three m ethods produced similar spatial distributions of the hydraulic conduct ivity but quite different values. Overall, the method of Cooper et al. produces higher conductivity values in high permeability zones but lo wer values in low permeability areas than the Hvorslev method. Varianc es of the natural log of conductivity values derived from Hvorslev's a nd Bouwer and Rice's methods agree with those in the other aquifers un der similar depositional environments. However, the variance calculate d for the data based on the method of Cooper et al. appears unreasonab ly large. Despite these differences, histograms of the three sets of c onductivity values exhibit bimodal distributions, reflecting stratific ation of the aquifer. Geostatistical analyses show that correlation le ngths and statistical anisotropy of the hydraulic conductivity spatial structure varies with depth.