The use of Wireless Sensor Networks (WSNs) in support of Dynamic Risk Assessment regarding oil spills still lacks a proper integration. WSNs enable prompt responses to such emergencies through an appropriate inspection, thus avoiding possible larger disasters. This work proposes a methodology for the setup of a WSN as a Leak Detection System in which a Fusion Center collects sensors’ binary decisions and provides a more reliable decision about the presence/absence of a leak. The detection rules are based on statistical signal processing techniques, and the choice of the optimal thresholds is made through the optimization of three objective functions tailored to the Oil&Gas industry. Detection performances are assessed in terms of the Receiver Operating Characteristic (ROC) curve. The case study is the Goliat FPSO, a production platform located in the Barents Sea, and related requirements dictated by Norwegian authorities to prevent oil spills. The considered WSN monitors the subsea manifolds through passive acoustic sensors.