Butterfly Effect. Or how a seemingly insignificant incident can have devastating effects. What happened on December 16, 2021 at the Marengo metro station in Toulouse illustrates this perfectly. The weather cooled sharply during the night of the 15th to 16th, and at 1 am a pipe made of gray cast iron, in the jargon of water pipe specialists, that is, steel, broke. “The water pumped into the Garonne suddenly reached a temperature below 3°, which can cause breakages”, explains Jérôme Natta, general manager of Setom, the water concession company of Toulouse Métropole. “This material is sensitive to sudden temperature variations”, confirms the DG. The frost itself has no effect on the pipes, but Setom had to intervene in 2021 on 760 leaks and breakages with its service of on-call operates 24 hours a day.

Flooded Marengo station

The water escaping from the ruptured pipe then infiltrated the basements until it entered the Marengo metro station, an important crossroads for line A of the metro near the Matabiau station and the bus station. “We had to close the station to pump the water while line A was interrupted between Marengo and Balma”, explains Tisséo. The agents of Setom and Tisséo had to work day and night to repair the pipeline and restore line A to normal service along its entire length the day after the incident.