Technischer Bericht NTB 85-07

Feldmethoden zur Grundwasserentnahme aus Tiefbohrungen und zur hydrochemischen Überwachung der Bohrspülung

Between 1982 and 1985, six drill holes with depths approaching 2,500 m were executed in northern Switzerland by the National Cooperative for the Storage of Radioactive Waste (Nagra). Investigations were aimed at describing geologic conditions with respect to waste disposal, particularly within the crystalline basement.

One of the main efforts was directed at identifying properties and behavior of the encountered groundwater. Among the activities involved was the collecting of representative groundwater samples for an entire suite of laboratory investigations.

The present report deals with the methods used and experience gained during drilling fluid tracing and monitoring, water sampling and quality control of extracted groundwater. The technical constraints (depth, temperature, borehole diameter) led to the deployment of specialized equipment, parts of which were still at the experimental stage.