In order to accurately model the subsurface of a new salt cavern gas storage facility at the Jemgum site in the Lower Saxony Basin (NW Germany), modern 3D pre-stack depth-migrated seismic data were utilized during an early planning stage. Gas storage projects are often regarded purely as engineering projects. However, the involvement of geoscientists provided an opportunity to further add operational value to the project by applying state-of-the-art geological modelling techniques. As part of the site characterization, a new generic workflow was developed to facilitate a more time-efficient creation of a static, multi-z-valued salt interface, essential for modelling of any complex salt structure. Uncertainties related to the reconstruction of salt interface meshes were analysed accordingly and used to quantitatively determine spatial uncertainties of the final static depth model. Furthermore, seismic-attribute images were created which enabled the detection of a mid-Miocene fluvial system evident at shallow depths of just 100–300 m below mean sea level. The study demonstrates that seismic data, targeting Rotliegend gas sands at depths of more than 4000 m, can be very beneficial to better understand the near-surface hydrogeological processes for gas storage.