Groundwater flow system inferred from hydraulic stresses and heads at an underground LPG storage cavern site

Underground Liquefied Petroleum Gas (LPG) storage caverns were constructed below the groundwater table to contain pressurized gas by groundwater pressure. Continuous and regular groundwater monitoring data were used to analyze whether the gas containment condition was satisfied or not. The monitoring data included time series analysis of hydraulic heads, gas and groundwater pressures, and groundwater chemistry. Through cross-correlation analyses of the time series data, the major factors causing hydraulic head fluctuation were found to be groundwater recharge from precipitation and cavern gas pressures. Hydraulic head and hydrochemical data indicate that a fault zone acts as the groundwater recharge zone and water curtain tunnels reduce head fluctuations.