The hydraulic conductivity of shallow subsurface sediments is the most important field parameter measured during property characterizations in projects driven by RCRA or CERCLA regulations. Studies to establish the rate of contaminant transport depend on reliable values of hydraulic conductivity. Methods to calculate hydraulic conductivity have evolved over the last 50 years to evaluate different subsurface conditions, ranging from low permeability sediments to fractured rocks. Some methods have been found to produce widely varying results over a range greater than one order of magnitude. Laboratory produced results are being rejected with increasing frequency as field-produced results, through the use of slug test in low permeability conditions and of pumping tests in medium and high permeability conditions, indicate substantially higher values of hydraulic conductivity and, therefore, higher rates of transport of conservative contaminants. Field methods produce data from induced water-level changes for manipulations by a variety of mathematical techniques, most of which have been programmed in numerous commercial software packages. Comparisons of software-produced results and results produced by hand plotting and calculation indicate significant differences that would not be acceptable for use in realistic evaluations of contaminant transport.

End_of_Record - Last_Page 19---------------