Hydrogeochemical investigation in Horonobe Underground Research Center; Changes in groundwater pressure and geochemistry associated with construction of a underground facility

Murakami, Hiroaki  ; Amano, Yuki   ; Nanjo, Isao; Iwatsuki, Teruki  

Constructions such as geological disposal of high-level radioactive waste influence hydraulic and geochemical condition around the facility. Therefore, it is necessary to develop the methodology to evaluate those effects. In this study, we report the results of monitoring for disturbing process of hydrogeochemical conditions of groundwater. Water-collection rings were installed every about 30 m deep in each vertical shafts. The flow rate, physic-chemical parameter (etc. pH, ORP, DO) and chemical composition of groundwater were observed at water-collection rings. Meanwhile, a borehole was drilled at 140 m Niche off the East Shaft. The physic-chemical parameter and hydraulic pressure of groundwater were monitoring at this borehole during drilling of the East Shaft. As a result, it was shown that hydraulic pressure was influenced by drilling the East Shaft in the area from the shaft at least 80 m or more.