ABSTRACT
During the period 1981–1983, SKB (Swedish Nuclear Fuel and Waste Co.) performed surface and borehole investigations at the Gideå site, North-east Sweden as part of a site selection program for a spent nuclear fuel repository. This study presents structural and lithological models to be used as input for hydraulic modelling. A three dimensional lithology model demonstrates that paragneiss is intermingled by elongated bodies of orthogneiss. The gneiss complex is intersected by steeply dipping dolerites. Rock contacts between dolerites and gneisses are not extensively fractured, implying no hydraulic pathways along dolerite dykes. There is no correlation of statistical significance between log k and rock type. Lithological sequence does not change within repository depth, whereas the hydraulic conductivity is higher down to 200 m of depth than at repository depth (500 m). Twelve fracture zones have been identified in the area, many of which are highly water conductive, and strike NNE to ENE, parallel with the main regional stress.
