Technischer Bericht NTB 85-06

Sondierbohrung BöttsteinErgebnisse der Isotopenuntersuchungen zur hydrogeologischen Charakterisierung der Tiefengrundwässer

In the following report NTB 85-06 the hydrogeological and hydrogeochemical interpretation of the results of isotopic investigations on groundwater samples from the Nagra deep borehole Böttstein are presented.
The Nagra deep borehole Böttstein is the first time it has been possible in Switzerland to investigate and to take groundwater samples from deep sedimentary and crystalline aquifer during drilling. All isotope methods of interest in hydrogeological studies have been applied to investigate these deep groundwaters:
2H, 3H, 13C, 14C, 18O in H2O, 18O in SO4, 34S, 36Cl, 39Ar, 85Kr, 81Kr, 3He/4He, 4He, noble gases, 40Ar/36Ar and the isotopes of the Uranium-and Thorium decay series.

In addition studies on rock-samples from the drilled core have been carried out as a cross-check for the interpretation of the isotopic results on groundwater samples. Starting from a description of the acceptable limits of contamination of groundwater samples from boreholes for isotope analyses, and the necessary adaptions for sampling on boreholes, the following subjects are treated: description of the basics of each applied method (as far as not already discussed in the report NTB 83-04) and interpretation of the results of each isotope-method for the groundwaters of the different aquifer formations. A synthesis of all results of the different methods, discussed for each aquifer formation is given in the summary chapter. In the final chapter, the conclusions concerning the spatial hydrogeological picture, as far as can be concluded from the results of one borehole, and a first interpretation of the results of the isotopic investigations with the aim to characterise the hydrodynamic flow directions is presented.

The responsibility for the hydrogeological investigation program lies with the Geological Division of Nagra, headed by Dr. M. Thury. The project Ieader is Dr. W. Kanz.