At the feasibility stage of a high-level radioactive waste facility in the eastern Paris Basin, the French National Radioactive Waste Management Agency (Andra) has conducted innovative and extensive characterization of the Callovo-Oxfordian argillaceous rock (Cox) and neighboring Oxfordian and Dogger limestones; High resolution 3D seismic data were used to model the distribution of mechanical and hydrogeological properties of the geological formations. Assessing the reliability of the geophysical modelling is crucial for making decision on the design of the radioactive waste facility. Probabilistic modeling (geostatistics) has been successfully introduced in the geophysical workflow to quantify uncertainty attached to processing and modeling outputs. The result of such a hybrid geophysical- geostatistical processing is increased confidence in seismic interpretation and modeling and reliable operational risk assessment.