1. Introduction

1.1. Project Background

  1. Ossian Offshore Wind Farm Limited (Ossian OWFL) (hereafter referred to as the ‘Applicant’) is proposing to develop Ossian Offshore Wind Farm (the Project), within the E1 Plan Option (PO) Area as following conclusion of the ScotWind Leasing Round. The Project is a joint venture between SSE Renewables Limited (SSER), Copenhagen Infrastructure Partners (CIP) and Marubeni Corporation. 
  2. The Project will include offshore and onshore infrastructure including an offshore generating station (the Array), offshore export cables to landfall and onshore transmission cables leading to an onshore convertor station connecting to the electricity transmission network.  
  3. This document is part of a suite of documents that make up the application to Scottish Ministers to construct and operate the Array. The Applicant is seeking the following consents and licences:  
  • a Section 36 consent under the Electricity Act 1989 for an offshore generating station in the Scottish offshore region (12 to 200 nm) where generating capacity exceeds 50 MW; and  
  • Two Marine Licences under the Marine and Coastal Access Act 2009 (MCAA) (Scottish waters beyond 12 nm) for the following:   

–           generating station (wind turbines, including their floating substructures and mooring and anchoring systems and inter-array cables); and   

–           transmission infrastructure (OSPs and interconnector cables within the site boundary).  

  1. The proposed offshore export cable corridor(s) and proposed onshore cable corridor(s) (including all infrastructure such as onshore converter station(s) at the Proposed landfall location(s)) are not included within the application. This is because the proposed landfall location(s) have yet to be agreed and will be decided following the conclusion of the ongoing Offshore Transmission Network Review (OTNR) and National Grid Holistic Network Design Follow Up Exercise (HNDFUE). 
  2. Key components of the Array include: 
  • wind turbines, including floating foundations and mooring, and anchoring systems; 
  • inter-array cables; 
  • interconnector cables; and 
  • OSPs. 
  1. Mooring and anchoring systems will be used to fix up to 265 floating wind turbines. There will be up to 15 OSPs using piled jackets or suction caisson jackets foundations installed in the Array. Subsea inter-array cables will connect the wind turbines to each other and to the OSPs, while interconnector cables will connect the OSPs to each other.  
  2. At this stage the overall capacity for the Array is not defined. However, the exported capacity for the Array is expected to be 3.6 GW, although this relies on the number and capacity of the wind turbines installed within the parameters of the Project Design Envelope (PDE) defined for this assessment and as set out in volume 1, chapter 3 of the EIA Report (Ossian OWFL, 2024a).
  3. A Report to Inform Appropriate Assessment (RIAA) accompanies the application for the Array (Ossian OWFL, 2024b). The RIAA assesses whether the Array could have an adverse effect, either alone, or in-combination with other plans or projects, on the integrity of any European site. European sites include Special Areas of Conservation (SACs), candidate SACs (cSACs), Sites of Community Importance (SCI), Special Protection Areas (SPAs) and, as a matter of policy (Scottish Government, 2020), possible SACs (pSACs), potential SPAs (pSPAs) and Ramsar Sites (listed under the Ramsar Convention on Wetlands of International Importance). 
  4. For SACs with designated features including diadromous fish and marine mammals, the RIAA concluded ‘No adverse effect on the integrity of the site’, either from the project alone or in-combination with other developments. For SPAs, the RIAA again concluded ‘no adverse effect on the integrity of the site’ for project-alone impacts. However, the RIAA concludes that a potential adverse effect cannot be ruled out, when considered in-combination with other plans and projects, at seven sites and for three qualifying species. This impact is a result of disturbance and displacement and/or collision during the operation and maintenance phase of the Array. The sites and features where ‘adverse effects on the integrity of the site’ cannot be ruled out are: 
  • Fowlsheugh SPA;
  • Buchan Ness to Collieston Coast SPA;
  • East Caithness Cliffs SPA;
  • Flamborough and Filey Coast SPA;
  • Forth Islands SPA;
  • North Caithness Cliffs SPA;
  • Troup, Pennan and Lion’s Head SPA.
  1. As such, the Applicant has proposed a Derogation Case, which includes measures to compensate the adverse effects. The chosen package of compensation measures, comprise of the following:
  • Implementation of invasive species controls including mink in Scotland;
  • Seabird bycatch reduction in Portugal.
  1. Full details, including the evidence underpinning each measure and the plan for delivery, is provided in the Ecological Evidence Report (Derogation Case, Appendix 1) and the Compensation Plan (Derogation Case, Appendix 2).

1.2. Purpose of this Document

  1. This document presents an assessment of the likely significant environmental effects of the compensatory measures being developed as part of the Derogation Case for the Array. Whilst the proposed compensatory measures themselves are relatively small-scale and do not constitute EIA Schedule 1 or Schedule 2 projects (triggering a need for EIA), the compensatory measures are being brought forward as a consequence of the Array’s potential effects on the national site network. Any effects arising from the compensatory measures are, on a precautionary basis, considered to be indirect or secondary to the effects of the Array, and for consideration under the Environmental Impact Assessment (EIA) regulations[1] which requires consideration of indirect and secondary impacts. The purpose of this document is to assess the likely significant effects of the proposed compensation measures on the environment. Full details on the policy and legislative background please see Policy and Legislation (volume 1, chapter 2) (Ossian OWFL, 2024b).

1.3. Structure of this Document

  1. This Environmental Impact Assessment Report (EIAR) is set out in a number of stages as follows:
  • Brief description of the proposed compensation measures:
  • Consideration of alternative compensatory measures
  • Consultation
  • A brief summary of the EIA Methodology used for the assessment.