Monitoring of petroleum contamination in soils surrounding underground storage tanks is an important issue for the effective remediation of soil and groundwater. In this study, a method for the detection of oil leakage from underground storage tanks was developed using time domain reflectometry (TDR), which has a sensible capacity for soil resistance, and a hydraulic control system. Without the hydraulic control system, TDR-measured impedance was not sensitive to the input of oil. The ability of the new system to detect diesel leakage in a sandy soil was verified by conducting leakage detection experiments. Impedance changes measured by TDR installed in the cylinder are useful as a sign of oil leakage. The sensitivity of oil leakage detection was dependent on the configuration of the hydraulic control system. The applicability of the sensor system in subsurface environment was validated by conducting oil release detection test in the sand tank. Results indicate that TDR, combined with a hydraulic control system, can be used for the detection of oil leakage from the storage tank. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.