Deep boreholes provide a direct insight into the underground geological environment and its structure.

Two drilling techniques are widely used:

In destructive drilling, the rock is crushed in the borehole. A fluid is pumped through the drill-pipe, which flushes the rock fragments (cuttings) to the surface. The drilling fluid is circulated in a closed circuit.

In cored boreholes, which are more costly to drill, hollow drill-bits grind only the rock at the edge of the borehole and the core in the centre remains intact. The core is loosened and pulled to the surface where the rock can be investigated in more detail.

The investigations are also supplemented by a range of borehole measurements - so-called logs - as well as hydrogeological and rock mechanical tests.

According to the Nuclear Energy Act, Nagra’s exploratory boreholes require a permit from the Federal Department of the Environment, Transport, Energy and Communications (DETEC). Nagra intends to submit the necessary in 2016. The federal authorities will review the applications together with the affected Cantons and communities. The decision of the Federal Council on Stage 2 of the Sectoral Plan is expected for 2018. Up-to-date information on the status of these exploratory boreholes can be found on the website "Tiefbohrungen" (in German).

To date, Nagra has drilled around 1000 to 2500 metres of borehole in Northern Switzerland as part of the investigation programme for the demonstration of disposal feasibility (Entsorgungsnachweis). The boreholes are:

Böttstein 1501 meters (1982 to 1983)
Weiach 2482 meters (1983)
Riniken 1801 meters (1983 to 1984)
Schafisheim 2006 meters (1983 bis 1984)
Kaisten 1306 meters (1984)
Leuggern 1689 meters (1984 to 1985)
Siblingen 1522 meters (1988 to 1989)
Benken 1007 meters (1998 to 1999)


Exploration applications

With a view to Stage 3 of the Sectoral Plan process, Nagra submitted applications for permits for eight exploratory boreholes in each of the siting regions Jura Ost and Zürich Nordost in September 2016. The applications for the Nördlich Lägern region followed in August 2017.

The applications were open for public inspection in the affected communities in the Jura Ost region between 27th February and 28th March. The inspection period in Zürich Nordost ran from 13th March until 26th April. The public inspection in Nördlich Lägern began on on 1st November 2017. All public inspections were completed on 16th January 2018. On 21th August 2018, the first three permits (Bülach, Marthalen and Trüllikon 1) have already been granted by DETEC and others are expected in the coming months.

The planned exploratory boreholes in the Jura Ost region are Zeihen, Effingen 1, Riniken 2, Remigen 1, Remigen 2, Bözberg 1, Bözberg 2 and Effingen 2.

The planned exploratory boreholes in the Nördlich Lägern region are Weiach, Bülach, Stadel 1, Eglisau, Stadel 2, Glattfelden, Stadel 3.

The planned exploratory boreholes in the Zürich Nordost region are Uhwiesen, Laufen, Trüllikon 1, Trüllikon 2, Rheinau, Dachsen, Marthalen, Trüllikon 3.