A PORTABLE AIR-MINIPERMEAMETER FOR RAPID IN-SITU FIELD-MEASUREMENTS

Measurements of air-permeability in outcrops provide a means of obtaining numerous spatially distributed measurements for statistical analysis and subsequent parameterization of ground-water flow and transport modeling. The air-minipermeameters previously used for such studies generally consist of a compressed air source, rotameters, and diaphragm gauges. We present a lightweight syringe-based air-minipermeameter (LSAMP) design that is significantly more portable than previous instruments. The prototype model is contained in a 12.7 X 15.2 X 23 centimeter (5 X 6 X 9 inch) electrical box and weighs approximately 2 kilograms. The prototype LSAMP has a sampling range of 0.5 to 200 darcys. Individual measurements in this range require less than one minute. Permeability measured with the LSAMP closely correspond to permeability measured with a traditional minipermeameter and those measured on cores. Measurement error caused by soil moisture is less than 5 percent for volumetric water contents less than 5 percent. An analysis of variance on 38 triplicate measurements indicates that the variability associated with measurement error is much less than the range of measured values. Repeated permeability measurements under field conditions on two standard cores indicate that while the measurement error is greater under field conditions, the prototype device field performance is consistent with laboratory calibration results.