Lessons Learnt through Delivery of Ecological Impact Assessments for UK Offshore Wind with Reference to the North American Market

The process of permitting of offshore wind projects within UK waters has developed in complexity over the last five years. This complexity is a direct consequence of the proposal of offshore projects within deeper waters and... [ view full abstract ]

The process of permitting of offshore wind projects within UK waters has developed in complexity over the last five years. This complexity is a direct consequence of the proposal of offshore projects within deeper waters and more complex soil types than were developed in the early phases of European offshore wind development. The final design of a UK offshore wind farm is now not typically fixed until Financial Investment Decision (FID), immediately prior to the appointment of the Principle Contractor for construction. One of the drivers of this approach is that it enables the Developer to de-risk expenditure associated with expensive geotechnical surveys and resulting foundation design studies. This means that foundation design and turbine choice (including rotor diameter) are not known during impact assessment or when a licence application is made. Therefore, the impact assessment and permitting process is undertaken on a range of project designs, termed the Design Envelope, to allow for flexibility in final design.
To achieve an ecological impact assessment against this Design Envelope that complies with the relevant assessment legislation, assessment is conducted against a ‘worst case’ for each receptor. For example, a pinned jacket foundation would constitute worst case with respect to underwater noise impacts to marine mammals, while a gravity foundation would constitute worse case for benthic ecology and scour. Noise propagation modelling will require estimation of the highest blow energies required to pile drive the foundation structure to the greatest depth needed to secure the foundations, as detailed ground conditions at each turbine location are unknown. Conversely, assessments for benthic and water quality impacts will need to consider the largest volume of sediment removal and rock placement required to provide weight bearing substrate and scour protection for large gravity base foundations. With regards to turbine size, a larger number of smaller turbines is often considered worst case for ornithological receptors for displacement and collision risk. This will mean that impact assessments, by design, will conclude that a greater impact than is likely could result from the Project.
This approach to the Design Envelope has required a step change in approach from ecological impact assessment practitioners. It requires ecological consultants with detailed knowledge of receptors to work closely with engineers to determine the Design Envelope. Working together to achieve the required definition where receptor impacts are pivotal to the permitting process can make the difference between permitting and refusal.
Natural Power has been instrumental in working with Developers, Determining Authorities and Stakeholders to refine the Design Envelope to allow ‘most credible’ worst case scenarios to be utilized in impact assessment. In our presentation we will provide key lessons learnt to disseminate knowledge to generate a similar understanding of the drivers of the Design Envelope and impact assessment consequences within a US context. We would hope to promote discussion with regards to the relevancy of the approach within a North American context, as the US offshore market moves to larger projects in deeper water, utlising engineering lessons from delivery in similar conditions in Europe.