Demonstration of the groundwater observation network system in backfilled underground facility

Murakami, Hiroaki  ; Takeuchi, Ryuji  ; Iwatsuki, Teruki  

Japan Atomic Energy Agency (JAEA) has been conducting the hydro-pressure and hydrochemical monitoring for more than two decades to understand the hydrochemical disturbance due to the excavation of tunnels at Mizunami Underground Research Laboratory (MIU). To understand the environmental influence due to the backfilling of research tunnels that started in 2019, environmental monitoring of groundwater has been performed and recovery status of groundwater is being confirmed. In order to observe the deep-groundwater environment from the ground, the groundwater pressure monitoring and sampling, which have been performed in the research tunnel, are to be performed from the ground. However, backfilling of a large-scale underground facilities such as MIU is globally unprecedented, thus it was necessary to develop a new observation system. Accordingly, we developed a new observation network to observe the environment around the research tunnels of the MIU. This system enables monitoring of groundwater pressure and water sampling of the backfilled tunnel from the ground while utilizing the existing-monitoring system installed in the tunnels. Accordingly, we demonstrated its technology through the environmental monitoring of groundwater. The results of the environmental monitoring and the existing groundwater data of MIU indicate that this system is able to monitor the groundwater environment in the backfilled tunnels.