Nagra submitted its proposals for siting regions to be further investigated in Stage 3 of the site selection process in January 2015: these were the regions Jura Ost and Zürich Nordost. In the supporting documentation, Nagra explained that safe repositories could be constructed in all six of the siting regions in the process, but proposed that the regions Nördlich Lägern, Südranden, Jura-Südfuss und Wellenberg be placed in reserve. This was justified based on the clear disadvantages of these regions in terms of safety when compared with Jura Ost and Zürich Nordost. In November 2015, ENSI called for Nagra to provide additional documentation on the indicator „depth with respect to engineering feasibility“ and the material was prepared and submitted in August 2016. Nagra adhered to its view that a repository could be constructed safely in the Nördlich Lägern region, but that realising a repository at greater depth in the Opalinus Clay would be very challenging. This was considered to be a clear disadvantage in terms of safety.
With today´s recommendation to carry out further investigations in Nördlich Lägern besides Jura Ost and Zürich Nordost, the regulatory authority has adopted a different stand. Nagra accepts the outcome of the ENSI analysis. As only the conclusions are available at present and not the full review, Nagra is not currently in a position to comment on the content.
Following ENSI´s call for additional documentation in November 2015, Nagra announced that it would begin planning an investigation programme for the Nördlich Lägern siting region in order to be prepared for every eventuality. 3D seismic measurements are currently ongoing in the region and applications for exploratory boreholes will be submitted in spring 2017.