In Stage 3 of the Sectoral Plan for Deep Geological Repositories, Nagra completed the picture of the subsurface – thanks in part to the nine boreholes drilled during the 2019 – 2022 deep borehole campaign. Investigations focused on the properties of the underground rock formations – particularly those of the Opalinus Clay in which the deep geological repository will eventually be constructed.
The Bözberg-1 borehole reached a final depth of 1,037 metres. At the time, it was the first deep borehole in the Jura Ost siting region of Nagra’s most recent deep borehole campaign. It was later followed by the Bözberg-2 borehole.
Opalinus Clay penetrated as early as 1983
Data for the Jura Ost region are already available from an earlier deep borehole drilled in the community of Riniken. The earlier Riniken borehole from 1983 as well as the Bözberg 1 and Bözberg 2 boreholes were drilled around the potential underground disposal zone, which was the best way to achieve a complete overview of the geological conditions of the region.
In the Jura Ost siting region, the geological layers drop towards the south. The Bözberg-1 borehole was located at the southern edge of the siting region. As a result, it was possible to investigate all relevant geological layers, including the Opalinus Clay, at their deepest point in the Jura Ost siting region.
Nagra had already encountered the Opalinus Clay while drilling the Riniken exploratory borehole in the 1980s (the picture on the left shows the drill site in 1983). At the time, Nagra was looking for granite, but the crystalline layers at this site are much deeper than was assumed at the time. Around 40 years later, the findings from the Riniken exploratory borehole nevertheless supported the search for a repository in Switzerland: they helped to complete the picture of the subsurface in the Jura Ost siting region.
Find out more about the Riniken exploratory borehole in Technical Report NTB 86-02.
Read report
Further deep boreholes
Bözberg-2 borehole
Bözberg-2 was the second deep borehole to be drilled in the Jura Ost siting region as part of Stage 3 of the site selection process.
Bülach borehole
Bülach was the first deep borehole to be drilled in the Nördlich Lägern siting region as part of Stage 3 of the site selection process for a deep geological repository.
Stadel-3 borehole
Stadel-3 was the second deep borehole to be drilled in the Nördlich Lägern siting region as part of Stage 3 of the site selection process.
Stadel-2 borehole
The Stadel-2 borehole was the third deep borehole to be drilled in the Nördlich Lägern siting region as part of Stage 3 of the site selection process.
Bachs-1 borehole
The Bachs borehole was the fourth deep borehole to be drilled in the Nördlich Lägern siting region as part of Stage 3 of the site selection process.
Trüllikon-1 borehole
The Trüllikon borehole was the first deep borehole to be drilled in the Zürich Nordost siting region as part of Stage 3 of the site selection process.
Marthalen borehole
The Marthalen borehole was the second deep borehole to be drilled in the Zürich Nordost siting region as part of Stage 3 of the site selection process.
Rheinau-1 borehole
The Rheinau borehole was the third deep borehole to be drilled in the Zürich Nordost siting region as part of Stage 3 of the site selection process.
Work report
Photos:
Gerry Thönen
Nagra