In-situ permeability measurements with the Cone Permeameter{trademark} measurement system

The permeability of soil to fluid flow defines the magnitude of soil gas and groundwater flow under imposed pressure gradients. Pressure gradients exist due to natural effects such as hydraulic gradients (in the case of groundwater) and barometrically imposed gradients (in the case of soil gas). Unnatural gradients are imposed by soil vapor extraction air sparging, active venting, pump-and-treat, and other remediation processes requiring the active movement of fluids through the soil. The design of these processes requires knowledge of the flow characteristics of the soil. The most variable of the soil's flow characteristics is its permeability, which can vary by several orders of magnitude in a given geologic and hydrologic setting. Knowledge of soil gas permeability is needed to design soil vapor extraction systems and predict the general movement of gas in soil. Saturated hydraulic conductivity, or the soil's permeability to liquid flow, is required to predict movement of groundwater in saturated soils. The variability of permeability is illustrated by the range of values for different media in a table. It is not uncommon for permeabilities to vary by several orders of magnitude at a given site