Spread all over the place, they capture the waves emitted by vibrating trucks conducting a geothermal prospecting campaign in the basement.
First there is some blue spray and a ribbon of the same color tied to a branch or bush. Then, a few days later, a strange orange and white plastic electronic box appeared in the same place. These small wireless devices located throughout the canton did not cease to intrigue the Genevans.
Speculation abounds on social media, most often in the tone of laughter: “It is a device to occupy the conspiracy now that the pleasant winter is coming,” jokes one user. “Transmitters to control 5G chips in vaccines,” another responds, still jokingly. Others, more prosaically, assume that it has a link to the set of households that the Geneva Industrial Services (GIS) and the state recently released to announce a geothermal prospecting campaign. Bingo!
In fact, these boxes are “geophones”, that is, instruments used to listen to the earth. They capture the echoes of the waves emitted by vibrating trucks to draw a 3D image of the basement, on exactly the same principle as an ultrasound. The goal is to identify the water tables that can potentially be used to heat buildings. Going into action on Monday, these trucks will cross the municipality for six weeks, at night.
In total, 20,000 sensors are scattered throughout the cantonal territory, twenty meters away, in lines 160 to 240 meters apart. “Their geographic locations are determined with extreme precision,” explains Michel Meyer, director of geothermal energy at SIG. A grid of almost 55,000 points has been drawn to have the best possible mesh in the canton ”. The “geophones” remain in the same place for about a week at a time, before being moved as the vibrator trucks advance in their prospecting campaign. Therefore, everyone has a chance to see one close to home.
For those who want to know more, an information stand is set up on the Uni Mail esplanade, boulevard du Pont-d’Arve, until November 6 (open from 11 a.m. to 7 p.m., Thursday at 9 p.m.). This Saturday there is an “open house” day, from 10 am to 4 pm. An interactive map (www.geothermies.ch/plan) It allows to know the exact dates of passage of the trucks in the communes, by address. Finally, a free hotline is made available to the public, from 8:00 p.m. to 12:00 p.m., on 0800 99 20 21.