Japanese first underground LPG storage plants have been constructed by JOGMEC at two sites, Namikata and Kurashiki site. The principle of underground LPG storage employs groundwater pressure to contain LPG within an unlined rock cavern. Therefore, groundwater management during construction is essential to employ appropriate countermeasures in a timely manner to maintain pore pressure around the storage caverns.
At Namikata site, a three-dimensional hydrogeological model was developed as one of the key tools for the observational construction based on the groundwater monitoring. The model takes account of the spatial distribution of hydraulic properties, excavation progress and change in boundary conditions such as water injection pressure.
This paper describes the iterative process of the model development during the cavern construction based on the various monitoring data and its applications to groundwater management during the cavern construction and also to planning and data evaluation of the cavern gas-tightness test.