Key points:

  • Hydraulic conductivity of the Opalinus Clay is very low and shows only little scatter. There is no relevant difference between the siting regions related to the different depth.
  • The Opalinus Clay hydraulic conductivities from in-situ packer testing are in the same range as lab-tests on drill cores. That is, the tested faults do not act as preferential flow paths.
  • The highest observed fault transmissivity at relevant depth in Northern Switzerland of
    1 × 10-11 m2/s is from a prominent thrust zone in the Schafisheim borehole outside the siting regions.
  • Hydraulic conductivity in the confining units is also low but can be several orders of magnitude higher than in the Opalinus Clay. There is no indication of elevated matrix conductivities related to hard beds in the Lias Group – Dogger Group section.
  • Formation hydraulic heads in the Opalinus Clay are affected by transient processes which are indicative of very low hydraulic conductivities.