The overall goal of the project Cosma-1: “Geological CO2 storage and other emerging subsurface activities” is the assessment of potential impacts of subsurface activities on shallow aquifers used for drinking water production. The first two deliverables (D 1.1 and D 1.2) dealt with general approaches for risk assessment and a description of potential hazards and hazardous events, which might be a risk for shallow freshwater aquifers, as well as lessons learned from existing geothermal energy production and storage sites in Germany. This Technical Report describes the activities of the second phase of the project COSMA-1 and focuses on the compilation of geological and hydrogeological background data (average values) and the development of a simplified conceptual hydrogeological model for a setting typical for the Northern German Sedimentary Basin. The hydrogeological model of the Cenozoic includes Quaternary and Tertiary aquifers down to the layer beneath the Rupelian clay. On this basis, a numerical model with the program Modflow (PMWIN 5.3) was implemented as no complex geometries had to be considered. The structural geological model of the target formation for underground utilisation, the Detfurth Formation (Middle Bunter), incorporates four different fault systems with nine faults in total enclosing the area of interest. Further, a concept for modeling the interaction between deep, consolidated, saline aquifers with unconsolidated freshwater aquifers in a setting typical for the Northern German Sedimentary Basin was developed. This included the model selection, model parameterization, definition of boundary conditions and implementation in hydrogeological flow model software packages. In the further course of the project, a scenario analysis will be performed by using the numerical hydraulic model of the Middle Bunter and the simplified numerical groundwater model of the Cenozoic. The numerical models will be used to assess the key parameters, having an impact on the upconing of deeper saline groundwater beneath the well fields of water works (in shallow aquifer) due to imposed pressure signals.