Geoscientific characterization of flat bedded rock salt as part of the German Repository Site Selection Act – Part II “Thuringian Basin”

According to the Repository Site Selection Act (Standortauswahlgesetz – StandAG), the German Site Selection Procedure is an iterative process and consists of three phases with increasing levels of detail in which the assessed area is continuously reduced during the process. Starting with an empty, so-called “white map of Germany,” BGE (implementer of the German Site Selection Procedure) completed Step 1 of Phase I in September 2020 with the submission of the Sub-areas Interim Report (BGE 2020/88), where BGE identified 90 individual sub-areas (in claystone, rock salt, and crystalline rock).

In Step 2 of Phase I, BGE aims to localize siting regions within the 90 sub-areas by applying preliminary safety assessments and other scientific criteria. Within the preliminary safety assessments, subsurface data are interpreted and the results documented. The workflow comprises the detailed characterization and interpretation with a focus on the host rock formation that acts as the main geological barrier but also considers the surrounding rock formations.

Part II of this contribution describes the integration of different data for a geological interpretation of individual criteria in the preliminary safety assessments using the Zechstein rocks salts of the Thuringian Basin as an example. The assessment of the spatial geometry (thickness of the main geological barrier and minimum depth) as well as the internal configuration of the rock salt are important features that were combined in the categorizations for the Thuringian Basin, which were published as a preliminary working status in 2024.