Offshore construction

This page features the latest updates on Sofia's offshore construction progress and upcoming activity. It includes details of the main contractors that will ensure the successful delivery of the project's infrastructure offshore, from the array site on Dogger Bank to landfall in Teesside.


Offshore map with turbine locations


Following the completion of the landfall horizontal directional drill to install ducts in 2022, offshore construction is due to start in mid-2023 with the first phase of the installation of Sofia's two 220 kilometres long export cables. Being installed by brand new vessel Leonardo da Vinci the work is set to be carried out in two phases. Work on the Dogger Bank site will start in 2024 with the installation of the first of the project's 100 extended monopile foundations. The year of 2024 will be a busy one with the completion of the export cables, foundations, 350 kilometres of array cables and, at the heart of the wind farm, the 10,000 tonne offshore converter platform and its 7000 tonne jacket foundation. Next will be the arrival and installation of the 14MW turbines. Construction is anticipated be completed by the end of 2026.


Throughout summer 2021, Sofia was busy with offshore surveys as part of the project's pre-construction commitments and site preparation works. 

The works included the pre-construction benthic survey programme, investigation of an archaeological feature found during a previous geophysical survey and the start of pre-construction bird surveys using a new technique combining LiDAR technology and aerial photography data.

The first of two unexploded ordnance (UXO) investigations and clearance campaigns starts in September with the second due in 2022. Potential UXOs will be investigated, identified and, if confirmed, removed prior to construction using innovative methods to reduce underwater noise impacts to marine mammals and fish. Any UXOs found are likely to be British buoyant mines or German ground mines from WW2. This work will also include further archaeological investigations, as well as underwater noise monitoring.


Mid 2021

Offshore surveys and site clearance to prepare for construction.

Manufacture of the project’s two 220 kilometre export cables underway.

Late 2021

Start of fabrication of offshore converter platform and jacket foundation.

Mid 2022

Ducting for export cable installed at landfall in Redcar, Teesside.

Early 2023

Start of fabrication of Sofia's 350 kilometres of array cables.

Start of fabrication of the project’s 100 extended monopile foundations.

Mid 2023

First phase of export cable installation.

Start of manufacture and fabrication of the project's 100 turbines.

Early 2024

First extended monopile foundation installed on Dogger Bank site.

Array cable installation gets underway. 

Mid 2024

Offshore converter platform and jacket foundation sail to site ready for installation.

Late 2024

Completion of installation of the export cables, offshore converter station, array cables and the 100 turbine foundations.


Turbine installation underway


Installation and commissioning of the 100 turbines continues.

Late 2026

Sofia is fully operational.


Sofia submits documents related to the offshore activity to the Marine Management Organisation to approve and then store and make publicly available. To view the documents related to Sofia you can access the MMO Public Register and search under DCO/2016/00021 and DCO/2016/00019.

One of the key offshore construction documents is the Project Environmental Management and Monitoring Plan.  It sets out how environmental impacts will be managed during Sofia’s offshore construction and operation, covering the environmental frameworks and procedures that will be followed by all contractors and sub-contractors in relation to marine pollution, chemicals, waste and disposal.



Siemens Gamesa Renewable Energy (SGRE) will manufacture, fabricate and install Sofia's 100 wind turbines.

Siemens Gamesa Renewable Energy

GE’s Grid Solutions will be responsible for the engineering, procurement, construction and installation of the offshore (and onshore) HVDC converter stations capable of transmitting 1,400 megawatts of power at 320 kilovolts.

GE's Grid Solutions

Working in a consortium with GE's Grid Solutions, Sembcorp Marine will build and install the offshore platform and jacket foundation.

Sembcorp Marine

Van Oord will deliver the project's 100 foundations and 350 kilometres of array cables.

Van Oord

Prysmian Group will design, supply, install and commission Sofia's HVDC export link including 440 kilometres of offshore export cables and installation work.


Prysmian Group


Heerema Marine Contractors will transport and install Sofia's offshore converter platform using Sleipnir, the world's largest sustainable semi-submersible crane vessel.


Heerema Marine Contractors

Cadeler has commissioned two brand new X-class vessels to transport and install the project's 100 turbines. They will be completed in late 2024 and early 2025 respectively.