This Tuesday, October 13, the “Kermor”, one of the boats chartered by Ailes Marines, went to bring up about thirty traps submerged for two weeks, next to the drilling area of the Saint-Brieuc bay wind farm.
“This is a complementary follow-up, after studies carried out in the laboratory and in the harbor of Brest by the CNRS researcher Laurent Chauvaud. It is a question of evaluating their behavior, a possible stress ”, states Marie Thabard, who manages the environmental watch for Ailes Marines.
Shells in tank then in trap
“The shells were first placed in a tank for a week for acclimatization and then each in a box to avoid interactions. The traps were arranged in six lines 400 m, 600 m and 3 km from the drilling point, ”she says.
Approaching the Aeolus, the drilling platform boat, Delphine Mathias, doctor and engineer in underwater acoustics at SUM (Brest), for its part, designates a yellow buoy anchored about 400 m from the site. “It measures in real time the sound level emitted by the work, also captures ambient noise. Every 10 minutes, we receive a value of the average noise on a web interface, ”explains the scientist from this independent research office commissioned by Ailes Marines.
What do these data say? “We have noise levels of the order of 178 to 190 decibels at the primary borehole and at a distance of 500 m we have already lost 40 to 50 decibels”, she assures us. “These are measures in line with those carried out in other wind farms in Europe and also with those carried out in 2018 and 2020, in the bay of Saint-Brieuc, in the test phase before the works”, adds Delphine Mathias. What impact, then? “This does not indicate that there is no impact, but that for the species for which we know the hearing and impact thresholds, there is no need to worry”, means she does.
Noise is also the business of another research firm, Biotope, and associated partners. In addition to observations of marine mammals, birds and fish made during 70 boat trips and 37 by plane, from before construction to today, its scientists rely on seven underwater acoustic stations, including two in the site area and five on the outskirts. They record continuously.
“We do not have a conclusive hindsight, but …”
“We collect these data every three months for marine mammals: we then analyze the physical and biological noise for two and a half months,” says Florian Lecorps. What do the observations and data collected indicate? “We are at the start of the analysis, we have not taken a conclusive step backwards, but, for the moment, we have not spotted any fundamental modification of the diversity or the density of species, nor of behavior and movements. compared to 2012-2014 ”, means the ecological engineer specializing in birds and marine mammals.
The investigation area covers 2,600 km2. “The area of the park is not the most frequented by alcids – Torda penguins, murres, loons, etc. – which are quite sensitive species. Between 2021 and 2024, we will continue these studies ”, he means.
Turbidity, the second opinion of the Shom
As for turbidity, “we positioned three fixed buoys and two displaced buoys in 9 positions in the work area, 400 m from the drilling point. They are equipped with sensors 1.5 m from the surface and 3 m from the bottom, knowing that there is between 30 and 50 m of bottom ”, describes Marie Thabard. “Here too, the results are consistent. A second opinion of Shom, the hydrographic and oceanographic service of the Navy, agreed on a low turbidity during the work ”, she reports.
Ailes Marines ensures that it devotes € 2 million per year to scientific monitoring. In addition, € 40 million for impact studies related to the project.