The long-term safety of deep disposal of radioactive waste is strongly dependent on the performance of the geological setting. The geology fulfils important safety functions including isolating the waste from human contact or intrusion, providing a stable physical and chemical environment, insulating against external disturbances, and preventing or delaying the transport of radioactive materials away from the waste.  Thus, a sound understanding of the geology's history and evolution is central in supporting assessments that examine the long-term performance and safety of deep disposal. This conference proceedings examines how geoscientific arguments and data are compiled and linked to create a unified description of the geological setting to support a safety case. It also examines practical aspects and limitations in collecting, linking, extrapolating and communicating such information.