Technischer Bericht NTB 88-12

Sondierbohrung KaistenUntersuchungsbericht

In 1980, Nagra (the National Cooperative for the Storage of Radioactive Waste) launched an extensive geological investigation programme covering an area of some 1,200 km2 in Northern Switzerland. The aim of the programme was to collect the geological information necessary for assessing the suitability of the crystalline basement as a disposal medium for high-level radioactive waste. The wide range of investigations carried out can be divided logically into a deep drilling programme, geophysical reconnaissance of the rock formations and structures in the region, a hydrogeological programme for investigation of water flow paths deep in the bedrock and a neotectonic programme for identification of active crustal movements in the area.

The Kaisten borehole was the fifth in the deep drilling programme. The drill-site (coordinates 644'641/265'623; 320.38 m a.s.l.) lies within the community of Kaisten in Canton Aargau, some 3 km to the south-west of the Laufenburg railway station. The final depth of the borehole was 1,306 m.

It was intended with the Kaisten borehole to drill through the sedimentary overburden and around 1,000 m deep into the crystalline bedrock. A wide range of investigations was carried out in the borehole itself, as well as on drill-cores and water samples. The most up­to-date methods were used to provide a detailed picture of the geology of the basement and the deep groundwater regime.

Drilling began on 13th February 1984 and continued, with regular interruptions for scientific investigations, until the end of June 1984. Further tests were then carried out during the following months up to the end of April 1985. A multiple packer system was installed between 30.4.1985 and 3.5.1985, with a view to carrying out long-term monitoring of the hydraulic conditions in the Buntsandstein, a sandstone horizon in the Rotliegendes and the crystalline basement. The investigation programme was carried out more or less completely as planned, and with a considerable degree of success.

The drilling and investigation programmes were planned and managed by Nagra employees with the cooperation of external advisers. More than 40 technical colleges, contractors and service companies from Switzerland, Germany, France, Great Britain, the Netherlands, Canada and the USA, representing a total manpower of over 150 scientists and technicians, were involved in the programmes.

This report is a summary of the most significant results obtained during the course of the Kaisten programme. The series of investigation reports for the deep boreholes (Böttstein, Weiach, Riniken, Leuggern, Schafisheim, Kaisten and Siblingen) is structured in such a way that cross-comparisons can easily be made between the results and data-sets for the different locations. The conclusions to be drawn from the data will be reserved for a final synthesis report. Detailed documentation of individual experiments is provided in Nagra's Technical Report series (see NTB list at the end of this report).

Komplette Zusammenfassung / Résumé complet / Full abstract: NTB 88-12 Zusammenfassung – Résumé – Summary.pdf