EN 
DE When planning a construction project, the subsoil must always be investigated. Sometimes the subsoil harbours increased risks, so-called geohazards. In northern Germany, for example, salt dome highs pose a potential risk of sinkholes due to leaching processes. In this case, there are recommendations for constructive measures to reduce the risk of sinkholes for a planned development.
In a construction project in Sarstedt, the positioning of the actual salt dome edge was imprecise due to the available data, so that the client decided in favour of a detailed exploration in order to be able to rule out a possible subsoil risk.
In addition to the exploration work for the preparation of a geotechnical report, two deep boreholes were drilled on the construction site to determine whether leachable rock is actually present in the subsurface of the investigation area. No signs of leachable rock or cap rock of the salt dome were found during the drilling work.
Cretaceous bedrock was encountered beneath the Quaternary cover in both boreholes, whereby one of the boreholes exposed Upper Cretaceous limestones over the course of the depth, while Lower Cretaceous clay to clay marlstones were encountered in the borehole closer to the salt dome. These are the Cretaceous layers deposited in the course of the halokinesis of the Sarstedt salt dome on the northern flank of the salt dome.
The exploratory drillings thus proved that the edge of the salt dome was located outside the planned construction project and that the risk of sinkholes is therefore not increased.
This meant that nothing stood in the way of building on the site without further safety measures.
