Multi-Level Slug Tests to Measure 3-D Hydraulic Conductivity Distributions

Abstract

The accurate determination of the transport and fate of pollutants through an aquifer begins with a complete understanding of the complexities of the hydraulic conductivity in that aquifer. Slug tests have been a popular method to define in situ hydraulic conductivity in an aquifer. However, traditional slug tests will provide information about the hydraulic conductivity across the entire screened interval of a well and not provide information about variations that may exist in the vertical direction. Equipment was developed that allowed multi-level slug tests to be conducted at discrete intervals within fully screened 5-cm (2 in) diameter wells. Ten such wells at the Geohydrologic and Experiment Monitoring Site were tested in order to provide a more complete spatial definition of the hydraulic conductivity and to determine the utility of the double-packer apparatus for such studies. Results from multi-level slug tests produced vertical profiles of hydraulic conductivity throughout each well’s screened interval. These vertical profiles provided information about spatial variations in hydraulic conductivity, when they were incorporated into cross-sections and a 3-D fence diagram. This research determined the greatest complexity in hydraulic conductivity in a northeast to southwest trend across the study site. Techniques presented here are valuable tools for greater definition of the hydraulic conductivity distribution in similar hydraulic settings.