Dogger Bank Wind Farm — a joint venture between SSE Renewables, Equinor, and Vårgrønn, developed in three 1.2 GW phases — required 277 monopile foundations and transition pieces installed across a North Sea site 130 km off the Yorkshire coast, one of the most demanding wave environments any offshore wind foundation campaign has faced.

The commercial interest is less the scale than the sequencing: three consecutive phases requiring repeated vessel and equipment mobilisation under Seaway7's overall foundation-installation scope, running across three years, while a new transition-piece design was deployed in the field for the first time.

277
Foundations installed
3.6 GW
Total capacity
1,424 t
Heaviest monopile
8 m
Record flange diameter
3 phases
A, B, C
Phase 1
Fabrication and mobilisation
Monopiles and transition pieces were manufactured by the Sif-Smulders consortium and dispatched from Sif's Maasvlakte 2 terminal in Rotterdam. Foundations for Dogger Bank B reached 72.8 m in length and up to 1,424 t, connected via a then record-breaking 8 m flange.
Phase 2
Monopile and transition-piece installation by jack-up, monohull, and semi-submersible vessels
Seaway7 held the tier-one foundation installation contract across all three phases. DEME was subcontracted to deploy the jack-up vessel Innovation for the opening foundation work at Dogger Bank A in July 2022; Seaway Strashnov, a monohull crane vessel, then carried monopile installation through the remainder of the campaign, with the semi-submersible Seaway Alfa Lift installing transition pieces across all three phases once it entered service in 2023.
Phase 3
Substation jacket and topside installation
Each phase required its own HVDC offshore substation. Heerema Marine Contractors' semi-submersible crane vessel Sleipnir installed the Dogger Bank C jacket and topside; Saipem's Saipem 7000 installed the Dogger Bank B substation topside onto a jacket foundation designed and fabricated by Saipem.
Design detail with an operating-life rationale

The split-level transition piece was designed specifically for safe technician access directly into the turbine tower from service and operations vessels — a decision made to reduce manual handling and lifting operations across the wind farm's roughly 35-year operational life, not just to simplify installation.

Three installation phases, three years, and a transition-piece design decided before a single foundation went in the water — made to save handling risk decades into the asset's operating life.

Dogger Bank's installation campaign is a case study in phased vessel, equipment, and subcontractor mobilisation at scale: Seaway7's tier-one foundation scope continued across all three sequential phases, with DEME subcontracted for opening foundation work at Dogger Bank A, while separately contracted heavy-lift campaigns installed the substations documented here — Saipem for Dogger Bank B, Heerema for Dogger Bank C.

For further reading, see Heavy Lift Engineering for Offshore Wind and Jacket Lift System Interfaces, which cover the foundation types used across this campaign.

Related case studies: Vindeby · Borssele · London Array

Core concepts: What is erection engineering? · What is heavy lift engineering?

A jack-up installation vessel loaded with wind turbine blades and tower sections at a quayside, with further towers and crawler cranes behind
Components for Dogger Bank at Able Seaton Port, Hartlepool, the marshalling hub for the wind farm's turbines, April 2024. Cropped from the original for web display.
Photo: David Robinson (Geograph), Wikimedia Commons, CC BY-SA 2.0.
Three-panel schematic of the Dogger Bank foundation campaign: monopiles up to 72.8 m long and 1,424 t with an 8 m flange shipped from Rotterdam; monopile and transition-piece installation by the jack-up Innovation at Dogger Bank A from July 2022, the monohull Seaway Strashnov for monopiles, and the semi-submersible Seaway Alfa Lift for transition pieces from 2023; HVDC substations installed by Sleipnir at Dogger Bank C and Saipem 7000 at Dogger Bank B.
Dogger Bank — one foundation campaign, three phases, several vessel types.
Diagram: EE&HL Network, 2026. Conceptual schematic — not to scale.
Tap or click the diagram to open it full size.

Sources: New Civil Engineer — turbine count, monopile foundations and HVDC substation programme; Offshore Wind — substation jacket dimensions and water depths; Equinor — developer announcement of the completion of all 277 foundations, November 2025. Figures are reported as published and reflect a project still under construction.