The computations done so far rely on the data available concerning the site in the east of France. Those pertaining to the geological medium rest first on existing documentation, and second, between 1994 and 1996, on non — (or only slightly) invasive methods.

• Through drillings, the characteristics of the geological formation have been measured at the local scale; the samples taken were used to measure and establish geological, geomechanical and geochemical properties.

• The non-intrusive methods are those of geophysics, particularly 3D geo­physics, effected on the whole of the projected underground laboratory. No tectonic events were detected, thus confirming the seismotectonic stability of the site, one of the selection criteria.

Evolutions due to external causes are also considered, especially the geomorphologic and hydrogeologic consequences of climate change. The surveys have not detected any significant influence of such changes on radio­nuclide transfer times, even under extreme conditions. A succession of climate change events is also examined.