1.6. Environmental Impact Assessment Methodology

  1. This section outlines the EIA methodology used for the assessment of LSE1 associated with the Array on physical, biological and human environment receptors.
  2. This Array EIA Report has been prepared in accordance with the EIA Regulations and relevant policy and legislation as described in section 1.2.

1.6.1. Key Principles of the Assessment

                        Overview

  1. The EIA methodology used in this Array EIA Report has been included as a separate chapter (volume 1, chapter 6). In addition, the following is included in each topic chapter:
  • identification of the study area for the topic specific assessments;
  • description of topic specific policy, guidance and legislation;
  • summary of topic specific consultation activity, including comments received from MD-LOT and stakeholder representation as part of the Ossian Array Scoping Opinion (MD-LOT, 2023);
  • description of the methodology to inform the baseline conditions, including detail on desktop study sources and site-specific surveys where relevant;
  • description of the environmental baseline conditions, including future baseline scenario;
  • presentation of the assessment of LSE1 (further details of what this includes are listed in volume 1, chapter 6);
  • presentation of the CEA;
  • presentation of the transboundary effects; and
  • presentation of the inter-related effects.
  1. The following sections describe the approach taken as part of the offshore EIA process in more detail.

                        Evidence-based approach

  1. The area of the North Sea in the vicinity of the Array has an existing base of data/knowledge acquired through surveys and assessments undertaken for existing and proposed offshore wind farms including Berwick Bank, Seagreen Alpha/Bravo (referred to as Seagreen 1 Offshore Wind Farm and Seagreen 1A Project when considered as part of the CEA for the Array), Inch Cape and Neart na Gaoithe (NnG). The Applicant has further commissioned site-specific surveys carried out as part of the Array baseline studies. Where possible in this Array EIA Report, the Applicant has made use of these data to:
  • characterise the baseline environment to inform the EIA where data are sufficient and appropriate;
  • identify data gaps;
  • draw upon the pre-existing evidence base in addition to site-specific and recent data as appropriate; and
  • support scoping out of impacts where there is clear evidence of lack of a receptor-impact pathway.
  1. Where possible, additional data to inform the Array assessment of effects have been identified and described within the relevant topic chapter of this Array EIA Report (volume 2, chapters 7 to 20).

                        Maximum design scenario

  1. The PDE approach (also known as the Rochdale Envelope approach) has been adopted for the assessment of the Array, in accordance with current best practice and the “Rochdale Envelope Principle[3]” (volume 1, chapter 3) (PINS, 2018). This approach follows the assessment of LSE1 of the realistic ‘maximum design scenario’ parameters of the Array.
  2. Volume 1, chapter 3 presents the project design parameters for relevant components of the Array. For each of the topic chapters within this Array EIA Report (volume 2, chapters 7 to 20) and for each of the effects assessed, the project design parameters considered constitute the scenario which would give rise to the greatest potential effect (i.e. a ‘most adverse’ scenario; hereafter referred to as the ‘maximum design scenario’ or ‘MDS’).
  3. Through identifying and assessing the MDS for any given potential impact, it can be assumed that the potential impact (and therefore the effect) will be no greater for any other design scenario. This approach enables the Applicant to retain necessary flexibility in design of the Array, within the maximum scenarios which are fully assessed in the Array EIA Report.

                        Designed in measures and mitigation measures

  1. There are three different forms of mitigation including:
  • Primary mitigation (inherent): “Modification to the location or design of the development made during the pre-application phase that are an inherent part of the project, and do not require additional action to be taken” (IEMA, 2016).
  • Secondary mitigation (foreseeable): “Actions that will require further activity in order to achieve the anticipated outcome. These may be imposed as part of the planning consent, or through inclusion in the ES” (IEMA, 2016).
  • Tertiary mitigation (inexorable): “Actions that would occur with or without input from the EIA feeding into the design process. These include actions that will be undertaken to meet other existing legislative requirement, or actions that are considered to be standard practices used to manage commonly occurring environmental effects” (IEMA, 2016).
  1. Both primary (inherent) mitigation and tertiary (inexorable) mitigation are considered as “designed in measures” within this Array EIA Report. The iterative approach to the assessment process has been utilised to inform the design of the Array (through the identification of LSE1 and development of designed in measures to address these). Commitment to implementing the identified measures is demonstrated through incorporation of such measures within the design as “designed in measures”.
  2. This approach ensures that the significance of effect presented in the Array EIA Report is considered representative of the maximum effect of the Array should the application for consent be approved and the Array be developed.
  3. Secondary (foreseeable) mitigation is an additional measure which is implemented after the assessment process has been completed. The aim of a secondary mitigation measure is to prevent, reduce and offset LSE1 which could not be avoided through designed in measures. Secondary mitigation proposed to reduce significance of impact are detailed within the topic chapters of the Array EIA Report and summarised in volume 2, chapters 7 to 20.

                        Identification of impacts and significance of effect

  1. The Array has the potential to create a range of impacts and effects with regards to the physical, biological and human environment, for both coastal and marine receptors.
  2. For the purposes of the Array EIA Report, the term ‘impact’ is defined as a change as a result of an action. For example, the laying of an inter-array cable (action) is likely to result in seabed disturbance (impact). Impacts can be defined as direct, indirect, temporary, irreversible, secondary, cumulative and inter-related. They can also be either beneficial or adverse, although the relationship between them is not always straightforward and relies on available evidence and professional judgement.
  3. The term ‘effect’ is defined as the consequence of an impact. For example, the laying of an inter-array cable (action) results in seabed disturbance (impact), with the potential to disturb benthic habitats and species (effect).
  4. The overall significance of an effect is determined through the correlation of the potential magnitude of impact and the sensitivity of the receptor. To ensure consistency in defining the significance of an effect, a matrix approach has been adopted, and is presented in Table 1.1   Open ▸ . In cases where a range of significance is possible for an effect, there remains the possibility that this may span the significance threshold (i.e. the range is given as minor to moderate). In such cases the final significance is based upon the technical specialist’s professional judgement as to which outcome is the most likely effect, with an explanation as to why this is the case.

 

Table 1.1:
Matrix Typically Used for the Assessment of the Significance of the Effect

Table 1.1: Matrix Typically Used for the Assessment of the Significance of the Effect

 

  1. The standard approach for the purposes of this assessment:
  • a level of significance of effect of moderate or more will be considered a ‘significant’ effect in terms of the EIA Regulations; and
  • a level of significance of effect of minor or less will be considered ‘not significant’ in terms of the EIA Regulations.
  1. Certain topic chapters have applied an EIA methodology which deviates from the one described in volume 1, chapter 6; these are listed in volume 1, chapter and explained in the relevant topic chapters (volume 2, chapters 7 to 19).
  2. As part of the topic assessment, further mitigation measures have been identified after the assessment of significance as required. Following this, the assessment re-evaluates the significance of effect using the methodology previously described.

                        Cumulative Effects Assessment

  1. The CEA considers the impacts arising from the Array cumulatively with other relevant plans, projects and activities, such as other offshore wind farms, oil and gas projects, cables, and ports and harbours projects. Cumulative effects are therefore the combined effect of the Array with the effects from a number of different plans, projects and activities, on the same receptor group or resource.
  2. A process has been followed for the screening of plans, projects and activities that may be considered in the CEA alongside the Array (volume 3, appendix 6.4). This process involved a screening stage, which identified those foreseeable developments or activities with which the Array may interact to result in cumulative effects.
  3. After the screening, a list of all projects, plans and activities screened in for assessment was produced for each topic and a tiered approach was adopted to complete the CEA. The tiers are described in volume 3, appendix 6.4.
  4. The CEA follows the Array assessment of effects methodology, as described in volume 1, chapter 6, as far as practicable. This approach however differs between topic chapters according to several factors, such as the nature of the topic, the cumulative projects, plans and activities included for that topic, the data available for each project, plan and activity, and the specific practicalities around undertaking CEA for that discipline. Where quantitative assessment has not been practicable, a mix of qualitative and quantitative or wholly qualitative assessment has been undertaken.

                        Transboundary effects

  1. Transboundary effects may have the potential to arise if an impact from the Array has the potential to significantly affect the environment on the interests of European Economic Area (EEA) states. A full description of how the transboundary effects assessment has been carried out is found in volume 3, appendix 6.6.
  2. The following topic has been identified as having a potential for transboundary impacts associated with the Array: