The Permeafor: A Rapid Tool for Field Hydraulic Conductivity Testing in Granular Soils

There are currently several in situ and laboratory methods of determining the hydraulic conductivity of soils. However, it remains difficult to obtain representative hydraulic conductivity profiles rapidly and economically, especially on projects in which values are required over large areas and at numerous depths. Furthermore, there is an emerging need in geotechnical and geoenvironmental engineering to profile this parameter in situ, such as for the design of water infiltration systems and retention ponds or for evaluation of contaminant fate and transport, which has resulted in a greater demand to improve existing methods or develop new, rapid, and reliable techniques. A proposed alternative to measure hydraulic conductivity in granular soils is to use a Permeafor, an instrument originally developed in France to evaluate variations in hydraulic conductivity in situ. This variation is assessed by observing water flow into the soil, at any given depth, under an applied hydraulic head. The ratio of flow to hydraulic head is used as an indicator of hydraulic conductivity variations with depth. A Permeafor system was designed, built, and field tested at several sites across New Hampshire. The results from more than 120 field tests at sites with granular soils demonstrated the potential of the Permeafor to rapidly generate profiles of hydraulic conductivity. The Permeafor is a useful tool in bridging the gap between timeconsuming testing of few locations and large-scale hydraulic conductivity testing. This article introduces the Permeafor design, its supporting equipment, and control software and provides some examples of results obtained at a test site in New Hampshire.