National Wind Watch: Wind Energy News » Porpoises could derail world’s biggest offshore wind farm

Plans for the world’s biggest offshore wind farm have been thrown into doubt over fears the noise of building it will disturb porpoises.

A decision on planning permission for Dong Energy’s 1.8 gigawatt Hornsea Two project, which would see up to 300 giant turbines built 55 miles off the coast of Yorkshire, had been due from the Department of Energy and Climate Change by next week.

But the decision has been delayed after the Department for Environment, Food and Rural Affairs proposed designating a vast, 14,000 square mile tranche of the North Sea – including the entire 115 square mile area of the proposed wind farm – as a Special Area of Conservation (SAC) for the harbour porpoise.

As a result, a Habitats Regulations Assessment must now be carried out to look at “the likely significant effects of the project, both alone and in-combination with other plans and projects” on the porpoise protection zone.

The harbour porpoise is the smallest and most prevalent marine mammal in UK waters and is currently deemed to have “favourable” conservation status.

Designating areas as SACs is designed to ensure this status is maintained by avoiding “deterioration of the habitats of the harbour porpoise or significant disturbance to the harbour porpoise”.

According to evidence from Natural England and the Joint Nature Conservation Committee, “it is well known that porpoise are sensitive to impulsive noise from activities such as pile driving”.

Although the groups say that there are “a range of mitigation measures available that could potentially reduce the noise footprint of the project to acceptable levels”, this could potentially require significant changes to the proposed construction of the wind farm, such as “seasonal restrictions” on turbine installation.

It could also involve Dong Energy using “alternative foundations to remove or reduce the need for piling” or even “potentially emerging technologies that reduce noise levels at source”.

Any such additional measures are likely to be unwelcome at a time when developers are battling to make offshore wind farm construction more efficient in order to hit steep cost-reduction targets set by the Government.

Dong Energy said it already implemented mitigation measures to protect marine mammals, such as “using trained observers to ensure that the area around the offshore construction site is clear of marine mammals before any piling work starts”.

A spokesman added: “Hornsea Project Two is an important part of Dong Energy’s post-2020 pipeline of projects in the UK. This announcement means a very short delay in the planning process, but we look forward to a decision on 16th August.”