ABSTRACT
The radioactive waste in the former Asse II salt mine has to be retrieved prior to the legally demanded decommissioning. In this context, the construction of a new mine and shaft is necessary, whereby detailed geological information about the salt structure is indispensable. Knowledge of the evaporite sequence, the internal composition, and the external shape of the Asse salt structure has been significantly enhanced by drill core investigations, borehole measurements, ground penetrating radar, and a new 3D seismic survey in recent years. The combined results indicate a highly complex internal structure with intensely folded Zechstein layers, contradicting earlier geological assumptions about this part of the salt structure. Furthermore, the strong tectonic influence during salt structure development is evidenced by complex structures in the cap rock and overburden, and by the formation of a salt wing on the steep southern flank. Additionally, a considerable narrowing of the salt structure to the southeast reduces the available space for the new mine. Our research shows that planning of waste repositories in complex salt structures has to be based on reliable, site-specific geoscientific data sets to reduce the risk of complications in the construction phase.
