Site selection in Switzerland: parallelization of implementer data collection and technical–political decision-making
Authors: Vietor Tim 
Published: September 2023

Abstract. The ambition of the Swiss radioactive waste program is to store waste at the
best-suited, safest site in Switzerland. In September 2022 the announcement
of Nördlich Lägern as the best-suited site was a major milestone of
this site selection process. The full documentation of the site selection
and the safety assessment will be submitted with the general license
application at the end of 2024. The total time of the site selection process
from its formal initiation in 2008 until submission of the general license
application will be 16 years. The three-phase site selection process consisted of (1) initial screening, (2)
de-selection of less favourable sites and (3) identification of the best-suited region. The database was refined for each selection step, but
detailed site characterization was restricted to the final phase. The
selection criteria were kept unchanged in the entire process. Four groups
were used: (1) properties of the host rock; (2) long-term evolution of the
geological situation; (3) quality of the geological findings; (4) engineering
feasibility. The requirements for the criteria were re-adjusted in each phase
to honour the available data and to adopt the requirements to the increasing
quality of the sites as less-suited regions were continuously screened out.
Initial estimates for the duration of the site selection were in the range
of 8–10 years. Soon it became clear that the technical work and the
decision-making process for each phase would take additional time. To
minimize phases of low activity, NAGRA started data collection campaigns for each step as soon as possible. This led to overlapping of regulator reviews
and decision-making by the government for the previous step and data
collection by NAGRA for the next step. Step-1 data collection started as
soon as enough information about the process was available. This allowed the
proposal of the initial selection of sites a few months later. Data collection
for step 2 with seismic data reprocessing, outcrop work, investigations of
third-party boreholes, regional seismic and geodetic monitoring and 2D fill-in lines began in 2009/10, well before the decision on step 1 by the
federal government in 2011. This overlap allowed the proposal for the detailed sited investigations in 2014 to be prepared. Step 3 data collection with
3D seismic campaigns started in 2015. To minimize the delay between the
3D seismic investigations and the start of deep drillings, drill sites were
planned on available 2D seismic information. In 2017 initial 3D seismic data
became available, the drilling sequence was adopted accordingly and the
first applications for the drill sites were handed in. The licensing of the
drill sites was continuously adjusted together with the involved
authorities. The decision of the federal government on completion of the
second phase, confirming three sites for the third and last phase, was taken in
2018. The data collection in the third and final step was completed with the
ninth deep borehole in early 2022. Close monitoring of the incoming data
allowed the announcement of the best-suited site in September of the same year.