HYDROGEOLOGICAL INVESTIGATIONS OF SURFACE-BASED INVESTIGATION PHASE OF HORONOBE URL PROJECT

Abstract

Japan Atomic Energy Agency has been conducting the Horonobe Underground Research Laboratory (URL) project in Horonobe, Hokkaido, as a part of the research and development program on geological disposal of high-level radioactive waste. This paper shows the synthesis results of hydrogeological investigations in the surface-based investigation phase of the project. Hydrological and meteorological investigations show that the infiltration rates of the drainage basins depend on the flora and the topography. The hydraulic tests using the deep boreholes reveals that hydraulic conductivity of the in situ test scale varies widely and decreases with depth in the same formation and that of laboratory test scale is influenced by the stress history. The groundwater flow analysis based on the investigations shows that the groundwater flows over topographic watershed and that the groundwater pressure is kept high in the deep underground.