Abstract
This Evidence Review Note (ERN) provides overarching guidance on Environmental Impact Assessment (EIA) for offshore wind development in the UK. It forms the foundation of the OWEKH ERN series, offering a consistent, strategic framework to support proportionate, transparent, and high-quality assessment practice across all environmental topics. Drawing on insights from 79 offshore windfarms (OWF) EIAs, sector guidance,and stakeholder consultation, this ERN addresses common weaknesses in current practice and proposes a shared approach to scoping, reporting, cumulative assessment, and post-consent delivery. It is designed to support developers and regulators to produce clearer, more consistent Environmental Statement (ES) to achieve more efficient consenting. This ERN identifies recurring challenges,including:
- Excessive or inconsistent scoping effort and protracted assessments
- Fragmented terminology – vague and confusing text that reduces accessibility and consistency
- Disjointed structure – incoherent or repetitive
- Disconnected strategic- and project-level assessments
- Weak tracking of mitigation delivery and post-consent commitments
- Insufficient recognition of beneficial effects and sector learning
To address these, this ERN presents nine core recommendations (Section 5):
1. Strategic Approach to Risk Assessment: Address key risks early through strategic planning e.g. Strategic Environmental Assessment (SEA), and potentially through a future option of Environmental Outcome Reports (EOR) to reduce uncertainty and avoid unmitigable effects at project level.
2. Address Sector-Level Evidence Gaps: Collaborate to close key data gaps in baselines, thresholds, impacts, environmental effects and monitoring, and improve integration of digital tools and shared evidence platforms. Be clear where evidence gaps mean an assessment is not possible, and where resource would be best concentrated on mitigation and monitoring.
3. Standardisation of Scoping: Adopt a consistent UK-wide scoping approach using a three-tier (A-C) framework to focus assessment on Likely Significant Effects (LSE) and reduce unnecessary effort.
4. Consistency and Clarity of Reporting: Use a standard chapter structure and consistent terminology (Annex B) to improve accessibility, comparability and clarity across the ES.
5. Proportionality of Reporting and Survey: Ensure reporting and survey effort is proportionate to risk and project design stage. Use digital tools to enhance clarity and reduce duplication (Annex B). Reference to pre-agreed ERNs may reduce volume and enhance consistency across documentation.
6. Monitoring, Verification and Enforcement: Secure mitigation through enforceable conditions and proportionate monitoring, supported by clear, standardised, post-consent plans and standardised wording (Annex C).
7. Use of Cumulative Effects Assessment: Apply consistent, proportionate cumulative effects methods, using shared baselines and supporting sector-wide meta-reviews where possible.
8. Acknowledge Beneficial Effects: Clearly identify and provide evidence of positive outcomes, such as improved data or environmental enhancements, and agree how they are reported. This could also be addressed at the strategic stage, refined at project level and incorporated into monitoring and reporting at project, regional and national level.
9. Maintain and Evolve Guidance Through Collaborative Learning: Review and update the ERNs regularly using new evidence, stakeholder input, and post-consent learning to support continuous improvement. This could, for example, be based on the best practice approach for continual improvement in ISO 9001.
This ERN does not replace topic-specific guidance, but complements it, providing a common structure and direction for all OWF EIAs. This guidance is not legal advice on EIA or advice about the application process in the UK. By implementing the recommendations, the offshore wind sector can reduce duplication, improve confidence and deliver more effective environmental decision making, while supporting the UK’s transition to Net Zero.