The three siting regions with an Opalinus Clay host rock – Zürich Nordost, North of Lägern and Jura Ost – are characterised by a simple and stable underground geological situation.
To allow the repository to be constructed safely, the host rock requires an extent of at least six square kilometres, with a usable width of at least one and a half kilometres.
Each of the three siting regions also comes into question for disposal of low- and intermediate-level waste.
Following a review based on aspects of safety and engineering feasibility, the Swiss Federal Nuclear Safety Inspectorate (ENSI) and other review bodies approved the proposed siting regions. On 30th November 2011, the Federal Council decided to incorporate the siting regions definitively into the Sectoral Plan.