Seaway 7 installs first Hollandse Kust Zuid foundation

4C Offshore | Tom Russell
By: 16/07/2021 Seaway 7
Seaway 7 has installed the first monopile foundation for the Hollandse Kust Zuid Wind Farm, off the coast of the Netherlands.

Seaway 7 is transporting and installing all 140 wind turbine monopile foundations and 315km of 66kV inner array grid cables. Offshore installation will continue through 2021 and 2022 using Seaway 7's heavy lift, cable lay and support vessels.

Each foundation is designed specifically for the location where it will be installed. The heaviest and largest monopile weighs 955 tons and is 75 metres long, while the lightest and shortest foundation still weighs 735 tons and is 62 metres long. The monopiles will be installed in water depths varying from 17 to 28 metres.


An installation vessel transports the foundations to their offshore location and positions itself at the exact location. The ship's crane then lifts the monopile into the water and lowers it until it reaches the seabed at a depth of 17 to 28 metres. Once the foundation is in position on the seabed, a hydraulic hammer is used to drive the pile to the desired depth.


The project consists of two sites,
Hollandse Kust Zuid 1&2 and Hollandse Kust Zuid 3&4, and is being developed by Vattenfall, which secured the rights to the projects with subsidy free bids in March 2018 and July 2019. They are located between 18 and 36 kilometers off the Dutch coast, between The Hague and Zandvoort. They will be fitted with 140 units of Siemens Gamesa 11 MW, SG 11.0-200 DD offshore turbines. Once the wind farm is operational, the 140 wind turbines will produce more than 6 TWh of green electricity annually.

For more information on offshore wind farms worldwide, click here.