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Aerial view of the drillsite for the Leuggern deep borehole (Canton Aargau). Drilling was carried out between 9th July 1984 and 10th February 1985. (Image: Comet Photoshopping)
Drillsite for an exploratory borehole at Oberrickenbach (Wellenberg region). Drilling was carried out between 12th November 1990 and 4th December 1991. (Image: Comet Photoshopping)
Rig for the Benken borehole in the Zürcher Weinland. Drilling began on 3rd September 1998, reaching a final depth of 1007 metres in the crystalline basement on 4th May 1999. (Image: Comet Photoshopping)
Changing the drill pipe
Each time the drilling head is exchanged, the entire drill pipe has to be removed and then re-installed. (Image: Comet Photoshopping)
Guided tour of the Benken drillsite during the open day in September 1998. (Image: Comet Photoshopping)
Drillcores from the Siblingen borehole (Canton Schaffhausen, 1st September 1988 to 2nd April 1989). (Image: Comet Photoshopping)
Ammonite found at a depth of 652 metres in the Opalinus Clay of the Benken borehole. The remains of this creature that once lived in the ocean have been preserved and protected by the clay from external influences for more than 180 million years. (Image: Comet Photoshopping)
Imprint of a fossil fern (Percopteris subelegans, around 285 million years old) from a drillcore from the Weiach borehole (10th January to 12th November 1983). Coal deposits with a total thickness of around 30 metres were encountered in this borehole. (Image: Nagra)
Once investigations are complete and boreholes can no longer be used, they have to be backfilled to isolate groundwater levels from one another and from the surface. The photograph shows backfilling of the Schafisheim borehole in October 1997. (Image: Comet Photoshopping)
In 2003, the measurement systems installed in the boreholes at Wellenberg were removed and the boreholes were backfilled. The photograph top right shows an abandoned drillsite after recultivation (immediately to the right of the road). (Image: Nagra)