During construction work, a natural gas leak was detected at an underground natural gas aquifer storage facility. The leak was located in a service gutter containing three headers. These headers were locked out and purged. Micro-leakage was located precisely on the manifold of a well when gas operations were resumed two days later. The expert assessment of the leaking section confirmed the presence of a perforation and heavy corrosion (at 6 o’clock, low point of the tube) with significant loss of material. An analysis of the deposits indicated the extensive presence of rust (iron oxide, chloride), limestone (calcium, silicon, magnesium) and chlorine, sodium and potassium used for treating the city water supply. The large quantity of water in the technical gallery may have contributed to the oxidation phenomenon.