Vattenfall: Dolphins Unfazed by Offshore Wind Construction Work … – Offshore WIND

Concerns have been raised that the installation of the monopiles of the Vesterhav North wind farm offshore Denmark could cause a small pod of dolphins to leave the area. The dolphins have, however, neither left the area nor have they changed their behaviour, Vattenfall, the owner and developer of the wind farm, said.

In 2020, wildlife and underwater photographer Lars Mikkelsen discovered a pod of seven Common Bottlenose dolphins during a sailing trip in the canal between the North Sea and the Limfjord at the Danish coastal town of Thyborn. Since then, Mikkelsen has been closely following the dolphins that are rare guests in the seas around Denmark.

The small pod of dolphins has for the past three years established residence in the area of the Danish part of the North Sea where Vattenfall is constructing its Vesterhav offshore wind farms.

So, when concerns were raised that the installation of the wind farms monopiles could cause the dolphins to leave the area, Vattenfall initiated a collaborative monitoring effort. Fortunately, it showed that the dolphins were still present and have not changed behaviour after completion of the monopile installation.

Vattenfall said the company is committed to preserving marine life and that it takes the biodiversity crisis just as seriously as the climate crisis. Therefore, the company said that it had already implemented a series of measures to reduce noise caused by pile driving and its potential effect on biodiversity.

Hydro Sound Dumper System

By the end of this year, the 21 turbines from Vesterhav Nord offshore wind farm will supply enough fossil-free electricity to meet the consumption needs of 180,000 Danish households. As part of the construction phase, monopiles are hammered into the seabed using a hydro sound damper system, which is a physical screen deployed around the pile to absorb noise.

The pile driving begins at reduced force, which is gradually increased to give marine mammals such as seals and porpoises an opportunity to move away from the area before noise levels reach a maximum.

At the same time, Vattenfall has also measured the underwater noise approximately 750 metres from the pile-driving site to ensure the noise stays below the desired levels.

When the work driving down the wind farms foundations approached, Lars Mikkelsen contacted Vattenfall as he was concerned that the underwater noise could disturb the dolphins at Thyborn. Vattenfall and Mikkelsen quickly reached an agreement with the University of Southern Denmark (SDU) to carry out additional noise measurements in the canal at about 11.5 kilometres from the construction site.

Dolphins Unaffected by Construction Activities

To understand the dolphins response to the construction activities, Vattenfall collaborated with Mikkelsen and the University of Southern Denmark. The underwater sound measurements and observations took place over several days during construction in April 2023.

University of Southern Denmark has measured the noise levels during piling in the area where the dolphins are typically found. At the same time, our local partner Lars Mikkelsen has observed the dolphins behaviour. What the results indicate is that the dolphins are still there and that they dont seem to have changed behaviour during or after construction, says Matthieu Povidis-Delefosse, a marine biologist at Vattenfall.

When Vesterhav Nord is put into operation later this year, marine mammals are likely to visit the offshore wind farm.

Evidence of sightings of whales, porpoises, and dolphins at our offshore wind farm indicates that marine mammals are not deterred by operating offshore wind farms, and in some case can even be attracted to them, said Povidis-Delefosse.

An offshore wind farm can function as an artificial reef, and due to the offshore wind farm it is protected from activities such as bottom trawling. These conditions allow fish to thrive with potential benefit for marine species at the top of the food chain such as seals, porpoises, and dolphins.

Vattenfall is developing Vesterhav North (Nord) simultaneously with the Vesterhav Syd (South) offshore wind farm.

The two wind farms will comprise 41 Siemens Gamesa 8.4 MW wind turbines and have a combined capacity of 344 MW. The wind farms are scheduled to be commissioned by the end of this year.

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Vattenfall: Dolphins Unfazed by Offshore Wind Construction Work ... - Offshore WIND