Against a highly complex consenting landscape, Tetra Tech led the Environmental Impact Assessment (EIA) for three of Ørsted’s flagship offshore wind projects.
In the UK, consent to build major infrastructure projects such as large offshore wind farms is ultimately granted by the Secretary of State. The EIA process is highly regulated and is critical to securing consent. Support provided by Tetra Tech included project management, consenting and technical services throughout the pre-application and examination phases of all three of the Hornsea projects.
Each Hornsea project has set new records for proposed offshore wind farms, and Hornsea Project Three will be the largest proposed to date, anywhere in the world. It has the potential to generate up to 2.4 GW of electricity and will cover an area offshore of approximately 700 sq km.
Challenge
Obtaining permission from the UK Government to build huge, utility-scale, offshore wind farms is challenging. A cornerstone of the process is the successful acceptance of the EIA by the Planning Inspectorate. Consent to build is dependent on accurately assessing the cumulative, and in combination, environmental impact of an increasing number of multiple wind farms and existing, and often competing, sea uses (for example oil and gas, fisheries, commercial navigation).
Furthermore, significant areas of the sea bed and coastal regions have been designated as protected areas which limits infrastructure development. Adding to the complexity are the statutory regulators and consultees which are becoming increasingly active in their defence of these protected marine areas.
Offshore wind projects can also include complex onshore elements such as an onshore substation and lengthy cable runs to the grid connection. Both require nuanced engagement with multiple landowners and stakeholders.
Tetra Tech was engaged by Ørsted to deliver the EIA for three separate flagship Ørsted projects.
Solution
Tetra Tech has deep expertise in the delivery of offshore renewables. Our team of project managers, EIA experts and technical leads bring a comprehensive understanding of a range of potential marine and terrestrial, human, biological, and physical environmental impacts to meet the challenges of each of the Hornsea projects.
We provided key support for public and stakeholder consultation, completion of the Preliminary Environmental Information Report (PEIR), drafting the environmental assessment, and submission of a final environmental statement.
The project potentially impacted ecologically sensitive areas so Tetra Tech led on a wide range of technical issues including assessment of visual impact concerns (key to onshore substation consent), environmental planning for cable-routing, and extensive ornithological studies to monitor potential impacts for seabirds.
Project timeline
- 2014: Consent for Project One was granted in December
- 2016: Project Two offshore wind farm was consented in August
- 2018: Project Three Development Consent submitted in May 2018
- 2020: Project One commenced operation. Project Three Development Consent granted, December 31
- 2022: Project Two is scheduled to commence operation
Benefits
- 1.2 GW Hornsea Project One capacity: enough power for 1 million homes
- 1.8 GW Hornsea Project Two capacity: enough power for 1.6 million homes
- 2.4 GW Proposed Project Three capacity: enough to power over 2 million homes
- 4.6 million homes can be powered by Hornsea once all three projects have commenced operation
During the Examination phase, Tetra Tech supported Ørsted providing responses to the Examining Authority’s questions, authoring additional documents, and input into the Development Consent Order and Marine Licence conditions. We also provided expert witnesses during the hearings.
As lead EIA consultant, Tetra Tech project managers:
- Coordinated the EIA
- Managed the team of technical specialists
- Liaised with engineering teams
- Supported the Development Consent Orders and deemed Marine Licences.
At a glance
Client
Ørsted
Location
North Sea
Services
EIA coordination and project management, expert witness advice during hearings, lead EIA consultants, pre-application and examination phase support, provision of majority of offshore technical specialists (in-house), provision of majority of onshore technical specialists (in-house), stakeholder engagement / consultation
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The project featured in this article was undertaken by RPS, A Tetra Tech Company and originally published on RPSgroup.com. In March 2026 RPS rebranded to Tetra Tech.