Experimental Evaluation of a Drive‐Point Ground‐Water Sampler for Hydraulic Conductivity Measurement

Abstract Drive‐point ground‐water samplers, designed to enable delineation of the vertical and areal extent of a contaminant plume, have been modified to obtain an in situ measurement of hydraulic conductivity in aquifers. The multlevel drive‐point sampler (MLDPS) consists of a 30‐cm long screen pushed to a desired depth within a retractable outer sleeve and a pressure transducer to monitor the rate of fill within a sample chamber. The accuracy and variability of a MLDPS to measure hydraulic conductivity was evaluated in a 50‐m 3 laboratory aquifer comprised of a uniform medium sand. Twelve measurements were performed using the MLDPS followed by duplicate slug tests performed at identical locations and depths within the aquifer. MLDPS and slug test data were analyzed using the method of Widdowson et al. (1990). The MLDPS provided an estimation of hydraulic conductivity at least one order of magnitude below slug test‐derived hydraulic conductivity and the range of hydraulic conductivity associated with a medium sand. MLDPS‐derived hydraulic conductivity values also show greater variability and range relative to the slug test‐derived values. Hydraulic conductivity ranges from 0.072 to 2.3 m/d using the MLDPS (coefficient of variation = C v = 1.3) compared to a range of 10 to 16 m/d (C v = 0.14) for the slug test values. Variability and magnitude of the MLDPS‐derived hydraulic conductivity is attributed to disturbance of aquifer material and experimental factors inherent to the design of the instrument.