Which of the three siting regions Jura Ost, Nördlich Lägern and Zürich Nordost is the most suitable for hosting a deep geological repository? Nagra aims to answer this question by means of a series of deep borehole investigations. Their purpose is to complete the underground geological picture. Nagra already has a vast knowledge of the underground and “completing” means using the results from the borehole investigations to place the last important pieces of the puzzle. The first borehole in Bülach (Nördlich Lägern) was successfully completed at the end of 2019, and currently, boreholes are being drilled in Trüllikon and Marthalen (both Zürich Nordost). In the spring, drilling will begin in Bözberg (Jura Ost).
Based on earlier investigations – so-called 3D seismic measurements – it has now become clear that the northern part of the Nördlich Lägern siting region is not suitable for hosting a repository. The reason for this is that Nagra has discovered fault zones deep underground in the north. For a deep geological repository, the geology has to be undisturbed. After completing the borehole in Bülach, Nagra decided to refrain from further investigation of the northern part and has withdrawn the permit applications for boreholes in Glattfelden and Weiach. Thanks to 3D seismic measurements and the Bülach borehole investigations, Nagra knows that the southern part of the Nördlich Lägern siting region is suitable in principle for the construction of a repository. This autumn, drilling will thus begin at the Stadel-3 site, which lies to south of the fault zone and is thus more representative for the siting region than the boreholes in the north.
Cover photo: Comet Photoshopping GmbH, Dieter Enz