The most important task of the Phase I is to develop techniques to investigate, analyze and evaluate the geological environment at up to 1,000m in depth. Models of the geological environment are constructed in the Phase I-a. A cycle of investigations, analyses and evaluation is repeated in the 2^nd half of the Phase I (2000 FY : henceforth 'Phase I-b') to examine the above-mentioned correlation described in Chapter 3.1.

In the Phase I-a are developed geological, hydrogeological models and rock mechanics conceptual models using the data obtained by the surface-based investigations, including geophysical survey and borehole investigations (Fig.3.2).

In the Phase I-b, investigation plans are made based on the results of the investigations in the Phase I-a and various research restrictions. Models constructed in the Phase I-a are revised according to the results of the analyses and evaluation made during the Phase I-a. The reiteration of the cycle shown in Fig.3.1 enables us to understand how the models are improved by the revision and above-mentioned correlation.

Furthermore, by verifying the above-mentioned revised models in the subsequent Phases, it is expected that the validity of surface-based investigations, analyses/evaluations could be evaluated. Consequently, an appropriate varieties/amount of investigations needed for model construction are shown.