East of Toulouse, trucks will shake the earth to map the subsoil

From 23 July to 6 August, vibratory trucks will traverse the streets of L’Union, east of Toulouse, to map the metro. This study is a prerequisite for a possible geothermal heating network project, led by Toulouse Métropole.

What exactly is under our feet? If now the satellites can draw every corner of the surface with precision, the mysteries remain for the cellar. But the metropolis of Toulouse must establish a comprehensive map, to guess the geothermal potential. This is a prerequisite before you can possibly create a heating network.

To carry out the investigation, the metropolis entrusted the mission to Engie and one of its service providers, Smart Seismic Solutions (S3). Its teams will carry out a measurement campaign between 23 July and 6 August in L’Union. The heart of these measures is perched on 4 massive tyres: a vibratory truck.

“Short-term noise pollution”

The method used is based on sensors, “geophones” arranged along circulation axes, every 30 m. Once these devices are in place, the truck will ensure passage along the identified avenues or streets. It will then perform a 48-second vibration, at different frequency pitches, before traveling over 30m to do the same thing. The geophones will then capture the reverberation of the sound on the deep ground, thus allowing us to understand the nature, size and density of the underground layer.

To ensure that these measurements are not disturbed by traffic or other interventions, they must be carried out at night. S3 teams will operate in the evening and until midnight. Although the vibrations pose no risk to the structure of the houses, noise pollution cannot be avoided. But luckily it will only be short-lived for each of the affected roads.

Nine streets affected

The truck will travel most of the avenue de Toulouse, the avenue de Cornaudric up to the boulevard des Fontanelles, the streets of Somport, du Lac d’Oo, de Pau and de Tarbes, and the avenues of Montcalm, Gavarnie and Saint-Caprais.