The performance of natural barriers at high-level radioactive waste disposal sites heavily depends on the regional groundwater system, which regulates the leakage of waste and radionuclides. Waste disposal sites require homogeneous and mechanically stable formations, making groundwater characterization difficult due to restricted discontinuities like fractures and faults. In the fractured media, conventional groundwater level observation methods in a single borehole only provide averaged hydraulic head data, failing to distinguish individual permeable fractures. To improve the interpretation of the groundwater monitoring results in the fractured media, it is essential to separate each of permeable fractures within a borehole and implement independent hydraulic head observation systems. Flow-logging is currently the most effective method for identifying permeable fractures from each others, supplemented by lithologic and geophysical loggings. Once permeable fractures are identified, their hydraulic connectivity can be examined, and multi-level monitoring wells can be designed accordingly. Despite this, Korea still lacks sufficient technical expertise in constructing various observation wells, highlighting the need for further development in this area.

Keywords: Crystalline rock, Conductive fractures, Connectivity, Design of monitoring well, Investigation procedure