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Reduction measures

The wind farm off the Bay of Saint-Brieuc, carried by Ailes Marines, obtained on 18 April 2017, from the Prefecture of Côtes-d'Armor, the administrative authorisation known as "Autorisation Unique IOTA" under the provisions of Articles L.214-1 et seq. of the Environment Code.

This authorisation prescribes several measures for monitoring, reducing, compensating or accompanying the environment. The reduction measures are intended to limit the negative impacts of the project on the environment. They may attempt to reduce its duration, extent or intensity.

Reduction measures for marine mammals in the construction phase

During construction:

Effective habitat loss due to avoidance
Disturbance due to boat noise
Communication masking due to noise
Risk of death/injury due to noise

In order to meet IOTA reduction measures 1 and 2, a Marine Mammal Mitigation Plan (MMMP) was prepared by Ailes Marines. This plan will be deployed in the construction phase during the threshing operations and includes :

  • Visual detection by Marine Mammals Observers (MMOs) ;
  • Acoustic detection by Passive Acoustic Monitoring (PAM) operators ;
  • Installation of acoustic deterrent devices to keep away marine mammals (pingers) ;
  • Soft-start of threshing activities.

The main objective of the MMMP is to prevent hearing injuries to marine mammals in the vicinity of threshing activities. This plan has been integrated into the wind turbine installation contract and will be followed by the contractor during threshing operations.

Details of the procedure :

Planning and Status

Measure under development

Between 2021 and 2022, and only during threshing activities in the construction phase.

Reducing the disturbance of the Balearic Shearwater in periods of interbreeding presence

During construction:

Habitat Loss/Habitat Change
Disturbance from Vessels
Risk of Collision with Vessels

During operation:

Risk of Collision
Habitat Loss / Modification

The objective of the measure is to inform yard personnel to enable the avoidance of shearwater rafts by Personnel Transfer Vessels (PTVs) during work at sea and to raise public awareness.

This measure was aimed at departures from Saint-Quay-Portrieux (the initial port of the construction phase), as the impact study had revealed that shearwater rafts were present between this port and the offshore construction area. However, the location of the port has changed and it will be located in Lézardrieux. The shearwater rafts are no longer on the shipping lanes and the risk of encountering them is now negligible, thereby reducing the impact identified in the impact study. The measure has therefore been adapted to meet the new needs.

The measure has a double scope:

Awareness-raising operations will be organised in two coastal communities to the east and west of the Bay of Saint-Brieuc.

Planning and Status

Measure under development


  • Awareness program for the construction phase 1% 1%


  • Raising awareness of the public and sea users 1% 1%

Photoattraction reduction in construction

The impact study showed that some species of birds in flight were more sensitive to light than others. In the absence of mitigation measures, the potential effects of light attraction were rated as moderate for petrels and shearwaters and low to negligible for other bird species. Although limited information is available on their (migratory) behaviour.

This measure is intended to reduce the impact of lights on ships in the construction phase.

In accordance with the conditions attached to AU IOTA, the effects of light attraction can and should be mitigated:

These requirements have been transcribed in the specifications of the construction companies that will have to follow these obligations.

Initial feedback from the works contractors during the analysis of the tenders shows that, in general, each vessel participating in the project will be equipped with all the external lights necessary to carry out its operations at night, namely :

Navigation lights, complying with international regulations, classification and flag administration rules (i.e. oriented horizontally (parallel to sea level), with prescribed angular sectors) ;

Traffic lights for warning aircraft and helicopter landings, in accordance with international aviation rules and regulations (oriented towards the sky, but put into service only when necessary) ;

Searchlights for search and rescue operations and passage through the channels (the orientation is variable but these are only used in emergencies) ;


Floodlights for launching life-saving equipment and boarding, in the event of emergency abandonment of the vessel, always directed downwards and towards the boat systems and the sea directly surrounding it, if necessary ;

Common deck lights for safe movement of personnel (facing down) ;

Floodlights to illuminate the work area, ensuring the operational safety of the project.

This initial feedback shows that most lighting, unless prescribed by regulations or specific needs (to ensure the safety of flight and working personnel in particular), will be directed downwards.

On construction ships.

Planning and Status

Measure under development

This measure is planned for the entire duration of the construction phase.