Air permeability measurements on Neogene and Quaternary sediments from the Campine area: using outcrop analogues for determining hydrodynamic aquifer properties

To move beyond the traditional scales of aquifer characterisation, outcrop studies may be used to serve as an analogue for determining the true small-scale spatial variability in subsurface hydrodynamic properties. Moreover, natural analogues can provide a means to study characteristics and long-term behaviour of engineered barriers, including disposal facility earth covers. A very convenient and cost-effective method for measuring hydraulic conductivity in the field is the use of hand-held air permeameters. This has been done by several authors in the past for instance for studying the relationship between small-scale sedimentary structures and hydraulic conductivity. In the framework of characterising the influence of the small-scale variability (centimeter- to meter-scale) in hydraulic conductivity (K) on subsurface hydrological processes of interest to SCK•CEN, air permeability measurements were performed on several outcrops in the Campine area. The results of this campaign are presented in this document, together with the validation of the method through lab analyses on the samples that were taken in the field. As a final step, the integration of these results into the existing knowledge is discussed, and some recommendations are made for guiding future characterisation efforts.