Technischer Bericht NTB 85-01

Nagra, the National Cooperative for the Storage of Radioactive Waste, is carrying out a comprehensive geological research programme in an area of approximately 1200 km² in northern Switzerland. This study, begun in 1980, will provide the scientific knowledge required to judge the suitability of the subsurface bedrock for the final storage of nuclear waste.

The various investigations comprise a programme of deep boreholes, a regional geophysical reconnaissance of the petrographic and structural conditions, a hydrogeologic programme to classify groundwater chemistry and describe groundwater flow systems in the deep subsurface, and neotectonic observations to detect and measure active crustal movements in the area under study.

The Böttstein well was the first borehole on the drilling programme. Located in the community of Böttstein on coordinates 659'340.8 / 268'556.0, at an altitude of 347.46 m above sea level it lies approximately 10 km to the North of the town of Brugg (Ct. Aargau). Its total depth is 1501 m.

This well was drilled to investigate in great detail the sedimentary cover and the uppermost 1000 m of the crystalline basement. An extensive programme, comprising continuous coring, sampling of formation fluids, hydraulic testing, and geophysical logging was conducted to provide a solid geologic data base; and to assess the predictive capabilities of the respective analytic methods and investigative tools in order to optimise costs versus benefits in successive wells.

Drilling operations at Böttstein started in October 1982 and, with interruptions for scientific investigations, continued until the end of July 1983. Additional tests and surveys were carried out in the completed well until December 1983. Finally, during January 1984 a system of multiple packers was installed in the borehole to observe hydraulic conditions in both the Buntsandstein and crystalline sequence over an extended period of time. The programme for these investigations was successfully realized.

Drilling operations as well as scientific investigations were planned and managed by Nagra staff with the aid of consultants. More than 50 university institutes, consultants, and service firms with a total of approximately 150 scientists and technicians from Switzerland, the German Federal Republic, France, Britain, Denmark, Canada and the USA were engaged in the investigations.

The present report is an extensive synopsis of the most important results achieved. It also contains comments on the methodology applied. The detailed reporting on the individual investigations is contained in the technical reports of Nagra. At present, 10 reports dealing with the Böttstein well have been published in this series, and further reports are in preparation.

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