Hydrogeochemical research and development at Mizunami Underground Research Laboratory up to 500m depth

Iwatsuki, Teruki ; Yuguchi, Takashi; Omori, Kazuaki; Hasegawa, Takashi; Munemoto, Takashi

We evaluated the Phase I - hydrogeochemical model constructed by Surface-based investigation phase (Phase I), and observed hydrogeochemical change resulting from facility construction in Phase II research. Additionally we developed investigation technique on redox condition, colloid/organics, etc. at gallery in Phase III research. Hydrogeochemical changes in sedimentary rocks and granite resulting from facility construction have been caused by the change of mixing ratio among salinity-distinct groundwaters. Multivariate numerical analysis shows that the groundwater chemistry around drifts would change to that of shallow groundwater in the future. The know-hows on hydrochemical monitoring at the hydrogeological structures and numerical analysis were summarized to infer the hydrochemical changing processes during the facility construction.