[en] The present situation at a specific site in the Baltic Shield is viewed in the light of its geologic history. Prediction, at a given level of confidence and from a limited number of drillholes, of the minimum average spacing of conductive zones in subsurface rocks of low hydraulic conductivity is based on a combination of the binomial and Poisson distribution, regarding the holes as a profile sampling and assuming a cubic pattern of fractures. The data provide an empirical basis for linking the nature and frequency of past geologic events to their local effects. Special attenetion is given to the preservation of tectonic blocks of large rock-volumes with very low hydraulic conductivity throughout the present cratonic stage, during which intermittent movement took place in marked fault-zones bordering the Shield, and three different orogenies affected the surrounding regions. Rock-mechanical, stochastic and deterministic approaches are utilized to predict future effects from this basis. (Author)