 The investigation covered drilling 44 boreholes in the salt table, geophysical investigations, including reflection seismic measurements, hydro-geological studies, approximately 500 outcrop- and groundwaterlevel drillings, four deep boreholes to approximately 2,000 m at the edges of the salt stock, two shaft boreholes to approximately 1,000 m depth to confirm the starting points of the selected slot, a seismic networkstation to monitor earthquake activity as well as numerous other studies.The exploration results and their evaluation were carried out in two reports by the Physikalisch-Technische Bundesanstalt (1983) and the Bundesamt für Strahlenschutz (1990) and are summarized below.It says (PTB 1983)