Case study fractured aquifer – Characterization of an aquifer in a Rotliegend sandstone of the Saar-Nahe-Basin | Fallbeispiel Kluftgrundwasserleiter – Charakterisierung eines Grundwasserleiters im Rotliegendsandstein des Saar-Nahe-Beckens
2018
Altenbockum, Michael | Berens, Katharina | Enzmann, Frieder | Kersten, Michael | Rüde, ThomasR. | Wieber, GeorgH. E.
The present case study brings together different field- and laboratory methods and shows how the combination of different methods is able to lead to a plausible geological and hydrogeological conceptual model. The motivation for the study is a large groundwater-contamination site with volatile chlorinated hydrocarbons (CHC). The field work included core drilling, borehole geophysics, field mapping, remote sensing as well as pumping and packer tests. In the laboratory, thin section analyses, computed tomography, mercury porosimetry, compressed permeability measurements and triaxial cell tests were carried out. The Kreuznach- and Standenbühl-Formations can be identified as two types of aquifers by their hydrochemical composition. The hypothesis of continuous porous sandstone-layers in the Kreuznach-Formation as published in former articles (Fürst et al. 1987) was not confirmed. The primary strike of the joint system was identified as N‑S and E‑W with joint spacings of 3 to 8 m. The laboratory tests show an effective porosity of at most 4% and a high retention capacity for the sandstone of the Kreuznach-Formation. About 9% of the joints are water conduits. The results show that because of heterogeneities in the fractured aquifer, the efficiency of hydraulic remediation of groundwater contamination by pumping wells is unpredictable. Furthermore, the high matrix retention capacity has a negative impact on the release of contaminants and on groundwater remediation.
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