DEME Offshore Bags Hollandse Kust Zuid Rock Installation Contract

Grid Connection

September 21, 2023, by Adnan Memija

Vattenfall has contracted DEME Offshore to carry out rock berm installation works at Hollandse Kust Zuid offshore wind farm site in the Netherlands.

According to Vattenfall, rock installation works will take place between the fourth quarter of 2023 and the first quarter of 2025.

“Based on lessons learned in the offshore wind industry, Vattenfall are taking proactive measures to reduce risk and increase the lifetime integrity by stabilizing the Inter Array Cables (IAC) at HKZ 1-4 with rock berms,” said Sam Gardner, Project Manager.

Prior to rock berm installation works commencing, Vattenfall contracted Fugro to carry out IAC inspections and scour pad surveys.

The surveys, which are currently ongoing and are expected to be completed next month, are executed using one of Fugro’s Blue Essence uncrewed surface vessels (USVs) with Blue Volta, an electric remotely operated vehicle (eROV).

Controlled from Fugro’s remote operations centre based in Aberdeen, this technology is said to reduce fuel consumption by up to 95 per cent compared to conventional support vessels and eliminates the need for personnel to work in high-risk offshore environments.

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The 1.5 GW Hollandse Kust Zuid offshore wind farm, owned by Vattenfall, BASF, and Allianz, is located some 20 kilometres off the Dutch province of Zuid-Holland.

The project features 139 Siemens Gamesa 11.0-200 DD wind turbines, one less than the 140 that were planned for. Last year, one of the foundations was damaged after a collision with bulk carrier Julietta D, after it became rudderless during a storm and drifted through the wind farm.

In alignment with partners, contractors, and authorities it was decided that the foundation was damaged too much to install a turbine and will not be replaced. The damaged foundation will be removed in 2024.

Hollandse Kust Zuid, the world’s first subsidy-free offshore wind farm, is expected to be inaugurated later this year.