6.4. Key Principles of the Array Assessment

6.4.1. Overview

  1. Within this Array EIA Report, the assessment of each topic (e.g. benthic subtidal ecology, offshore ornithology, shipping and navigation, etc.) is presented in a separate topic specific chapter (volume 2, chapters 7 to 19). Within each of the topic chapters, the following matters have been considered:
  • 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; and
  • presentation of the assessment of likely significant effects, which includes:

–           presentation of a MDS considering each potential impact;

–           detail on impacts scoped out of the assessment with appropriate justification;

–           a description of the designed in measures adopted as part of the Array;

–           identification of likely impacts and assessment of the significance of their identified effects through the construction, operation and maintenance, and decommissioning phases of the development. This assessment includes consideration of designed in measures that have been considered within the Project Design;

–           identification of any further mitigation measures required in respect of likely significant effects (in addition to designed in measures) along with the assessment of any residual effects;

–           assessment of any likely significant cumulative effects between the Array and other developments on a single receptor. These will include projects which have become operational since collection of baseline data, projects under construction, those with consent, projects for which an application for consent has been submitted but not yet determined, projects in scoping and where an Agreement for Lease (AfL) has been granted;  

–           identification of any future monitoring that may be required;

–           assessment of any transboundary effects (i.e. effects on European Economic Area (EEA) states); and

–           summary of the inter-related effects and ecosystem assessment.

  1. Inter-related effects (i.e. inter-relationships between environmental topic areas) have been assessed in a standalone chapter (volume 2, chapter 20). Where appropriate, this includes consideration of ecosystem assessment of relevant receptor groups.
  2. The effects of climate change on future baseline conditions have been considered in the description of baseline conditions, and therefore are inherently considered in the assessment of likely significant effects on the receptors in the respective topic chapters (volume 2, chapters 7 to 20). The climate assessment for the Array is included in the Climatic Effects chapter and appendices (volume 2, chapter 17; volume 3, appendices 17.1, 17.2 and 17.3).
  3. The consideration of impacts of the Array on human health is an inherent part of a number of technical assessments presented within the Array EIA Report. Table 6.4   Open ▸ signposts to those technical assessments relevant to human health. It is considered that where there is no significant impact within the technical assessments there can be no significant impacts on human health.
  4. A number of key principles which have been applied to each topic chapter are detailed in sections 6.4.2 to 6.4.5.

6.4.2. Evidence Based Approach

  1. The Array is located in the North Sea, approximately 80 km south-east from Aberdeen at its nearest point. This area of the North Sea has an existing base of data/knowledge acquired through surveys and assessments undertaken for existing and proposed offshore development applications for Berwick Bank, Seagreen Alpha/Bravo (referred to as Seagreen 1 and Seagreen 1A Projects 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).

6.4.3. 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[1]” (volume 1, chapter 3) (PINS, 2018). This approach follows the assessment of likely significant effects of the realistic ‘maximum adverse scenario’ parameters of the Array.
  2. Volume 1, chapter 3 presents the PDE parameters and identifies the range of potential project design values for relevant components of the Array. For each of the topic chapters (volume 2, chapters 7 to 20) within this Array EIA Report and for each of the effects assessed, the PDE considered will be the scenario which would give rise to the greatest potential effect (hereafter referred to as the ‘maximum design scenario’ or ‘MDS’).
  3. An example of the PDE approach would be where several types of piling scenarios are being considered. The assessment in this case would be based on the scenario known to have the greatest potential for impact on a given receptor. In this instance, the PDE for the piling scenario with the greatest noise potential would be the foundation with the largest footprint (i.e. the maximum design scenario for e.g. marine mammals and fish and shellfish ecology). It can be assumed that any project parameters equal to or less than those assessed will have environmental effects of the same level or less upon the receptors for the topic under consideration.
  4. Through identifying and assessing the MDS for any given impact, it can be assumed that the 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. Flexibility in design is required to ensure the most appropriate and up-to-date wind turbine technology for the site is procured and installed, which may be a matter of years after EIA Report production.

6.4.4. Measures to Avoid, Prevent, Reduce or, if Possible, Offset Likely Significant Adverse Effects

                        Overview

  1. Where likely significant effects are identified, the EIA Regulations require ‘a description of the measures envisaged to avoid, prevent, reduce or, if possible, offset any identified significant adverse effects on the environment and, where appropriate, of any proposed monitoring arrangements’ to be included in the EIA Report.
  2. The iterative approach to the assessment process for the Array involves a feedback loop, as illustrated in Figure 6.1   Open ▸ . An impact, and the resulting significance of effect, is initially assessed, and if this is deemed to be a significant adverse effect in EIA terms, changes are made (where reasonably practicable) to relevant project design parameters, or specific mitigation measures are introduced to avoid, reduce or offset the magnitude of the potential impact. The assessment is then repeated, and the process continues, until the EIA practitioner is satisfied within the bounds of the Project objectives, that:
  • the effect has been reduced to a level that is not significant in EIA terms; or
  • having regard to other constraints, no further changes may be made to project design parameters or no practicable mitigation measures are available to reduce the magnitude of impact (and hence significance of effect). In such cases, an overall effect that is still significant in EIA terms may be presented in the Array EIA Report.

 

Figure 6.1:
Proposed Iterative Approach to Mitigation Within the Array EIA

Figure 6.1: Proposed Iterative Approach to Mitigation Within the Array EIA

 

                        Designed in measures (primary mitigation)

  1. IEMA (2016) describe primary (inherent) mitigation as: “Modifications 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”.
  2. Primary mitigation has been referred to as “designed in measures” within this Array EIA Report.
  3. As described in paragraph 24, the iterative approach to the assessment process has been utilised to inform the design of the Array (through the identification of likely significant effects 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”.
  4. 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.

                        Secondary mitigation

  1. IEMA (2016) describe secondary (foreseeable) mitigation as: “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 Environmental Statement”.
  2. Secondary 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 likely significant effects which could not be avoided through designed in measures.

                        Tertiary mitigation

  1. IEMA (2016) describe Tertiary (inexorable) mitigation as: “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”.
  2. Both primary (inherent) mitigation and tertiary (inexorable) mitigation are considered 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.

6.4.5. Identification of Impacts and Significance of Effect

                        Impacts and effects

  1. The Array has the potential to create a range of impacts and effects with regards to the physical, biological and human environment.
  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.

 

Table 6.3:
Definition of Impact Terms Relevant to the Array EIA Report

Table 6.3:  Definition of Impact Terms Relevant to the Array EIA Report

 

  1. The term ‘effect’ is defined as the consequence of an impact. For example, following the inter-array cable laying example described in paragraph 34, the laying of an inter-array cable (action) results in seabed disturbance (impact), with the potential to disturb benthic habitats and species (effect).
  2. The significance of effects is determined by consideration of the magnitude of impact alongside the sensitivity of each receptor/receptor group in accordance with the defined significance criteria.

                        Scope of the assessment

  1. The scope of this Array EIA Report complies with the requirements set out by the EIA Regulations as discussed in volume 1, chapter 2.
  2. In March 2023, the Applicant submitted the Ossian Array EIA Scoping Report (Ossian OWFL, 2023) to MD-LOT to support a request for a formal Scoping Opinion in relation to the Array application from Scottish Ministers. The Scoping Opinion (Ossian Array EIA Scoping Opinion (MD-LOT, 2023)); was received in June 2023.
  3. Due to the nature, size and location of the Array and advice provided through the EIA process, the Array EIA Report focuses on the following topic areas:
  • Physical Processes (volume 2, chapter 7);
  • Benthic Subtidal Ecology (volume 2, chapter 8);
  • Fish and Shellfish Ecology (volume 2, chapter 9);
  • Marine Mammals (volume 2, chapter 10);
  • Offshore Ornithology (volume 2, chapter 11);
  • Commercial Fisheries (volume 2, chapter 12);
  • Shipping and Navigation (volume 2, chapter 13);
  • Aviation, Military and Communications (volume 2, chapter 14);
  • Infrastructure and Other Users (volume 2, chapter 15);
  • Major Accidents and Disasters (volume 2, chapter 16);
  • Climatic Effects (volume 2, chapter 17);
  • Offshore Socio-economics (volume 2, chapter 18);
  • Marine Archaeology (volume 2, chapter 19); and
  • Inter-Related Effects (volume 2, chapter 20);
  1. Table 6.4   Open ▸ outlines the requirements of the EIA Regulations and where these requirements have been considered within this Array EIA Report.

 

Table 6.4:
EIA Regulations Requirements and Where in this Array EIA Report these are Addressed

Table 6.4: EIA Regulations Requirements and Where in this Array EIA Report these are Addressed

 

                        Determining magnitude of impacts

  1. The magnitude of an impact is the spatial extent, duration, frequency, and reversibility of an impact from the construction, operation and maintenance or decommissioning of the Array. A magnitude is assigned to each of the impacts assessed within this Array EIA Report.

 

Table 6.5:
Definition of Terms Relevant to Defining the Magnitude of an Impact (Highways Agency et al., (2008) and CIEEM (2019))

Table 6.5: Definition of Terms Relevant to Defining the Magnitude of an Impact (Highways Agency et al., (2008) and CIEEM (2019))

 

  1. The magnitude of an impact is defined within each topic chapter according to the following scale:
  • negligible;
  • low;
  • medium; and
  • high.
  1. Definitions for each of these categories is set out in Table 6.6   Open ▸ , which describes both potential beneficial and adverse magnitudes of change (adapted from Highways Agency et al. (2020)). Each of the technical chapters contain topic-specific definitions for each of these categories which are based upon topic-relevant external policy, guidance, standards and other material, including specialist knowledge.

 

Table 6.6:
Definition of Terms Relating to the Magnitude of an Impact (Highways Agency et al., 2020)

Table 6.6: Definition of Terms Relating to the Magnitude of an Impact (Highways Agency et al., 2020)

 

                        Determining sensitivity of receptors

  1. Receptors can be the physical or biological resource or human user group that have the potential to be affected by impacts as a result of the Array. These receptors are identified through available data and baseline studies compiled in the development of the Array EIA Report.
  2. In defining the sensitivity for each receptor/receptor group, the vulnerability, recoverability and value/importance of that receptor/receptor group has been considered. These are defined in Table 6.7   Open ▸ and are used in each topic chapter as appropriate. In instances where these considerations are not included in the assessment, the reason for this is explained within the relevant topic chapter.

 

Table 6.7:
Definition of Terms Relevant to Defining the Sensitivity of a Receptor

Table 6.7: Definition of Terms Relevant to Defining the Sensitivity of a Receptor

 

  1. Sensitivity is defined within each topic chapter according to the following scale:
  • negligible;
  • low;
  • medium;
  • high; and
  • very high.
  1. Definitions for each of these categories is set out in Table 6.8   Open ▸ , based on the Highways Agency et al. (2020). Each technical chapter contains topic-specific definitions for each of these categories and these are based upon topic-relevant external policy, guidance, standards and other material, or specialist knowledge.

 

Table 6.8:
Definition of Terms Relating to the Sensitivity of the Receptor (based on Highways Agency et al., 2020)

Table 6.8: Definition of Terms Relating to the Sensitivity of the Receptor (based on Highways Agency et al., 2020)

 

  1. The following topic chapters have applied an EIA methodology which deviates from the one described in this chapter. These include:
  • marine mammals;
  • commercial fisheries;
  • shipping and navigation;
  • aviation, military and communications;
  • climatic effects;
  • offshore socio-economics; and
  • marine archaeology.
  1. The topic specific EIA methodology is described within these chapters.

                        Determining significance of effect

  1. 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 6.9   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 delineates the most likely effect, with an explanation as to why this is the case.
  2. The matrix approach is consistent with the general approach described in the Design Manual for Roads and Bridges (DMRB, Highways England et al., 2020) and Environmental Impact Assessment for Offshore Renewable Energy Projects – Guide (BSI, 2015). A number of modifications have however been made in the interest of proportionality, including:
  • an impact of ‘negligible’ magnitude will always lead to a non-significant effect due a maximum possible significance of ‘minor’ as per the matrix approach included in Table 6.9   Open ▸ ; and
  • receptors of ‘negligible’ importance, value or sensitivity will always lead to a non-significant effect due to a maximum possible significance of ‘minor’ as per the matrix approach included in Table 6.9   Open ▸ .
  1. Effects to be assessed as part of the Array EIA Report have been agreed with statutory nature conservation bodies (SNCBs) and stakeholders as part of the Scoping Opinion and Stakeholder Engagement Plan (SEP).

 

Table 6.9:
Matrix Used for the Assessment of the Significance of the Effect

Table 6.9:  Matrix Used for the Assessment of the Significance of the Effect

 

  1. 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. The definition of each of these significance levels are presented within Table 6.10   Open ▸ .
  2. A level of significance of effect of moderate or more is considered important in the decision-making process, whilst effects of minor significance or less entitle little, if any, weight in the decision-making process.
  3. Where significant effects (in terms of the EIA Regulations) are identified during the assessment these may be subject to secondary mitigation to reduce or offset the effect (paragraph 57 and paragraph 58). If resulting residual effects are still significant taking into account mitigation these will require further consideration as part of the decision-making process to determine whether the effects are acceptable (paragraph 59).

 

Table 6.10:
Definition of Significance Levels for the Array (based on Highways Agency et al., 2020)

Table 6.10: Definition of Significance Levels for the Array (based on Highways Agency et al., 2020)

 

                        Mitigation measures

  1. If, during the preparation of the Array EIA Report, the effect of an impact presents a major significant adverse outcome, changes are typically made to the Array design (primary mitigation) to reduce or offset the magnitude of impact or secondary mitigation is proposed to reduce magnitude of impact. If the effect of an impact presents a moderately significant adverse outcome, mitigation such as engineering controls or construction methods (secondary mitigation) are employed to reduce or offset the magnitude of the impact as outlined in section 6.4.4 paragraph 24.
  2. Volume 3, appendix 6.3 provides a summary of the mitigation commitments, including the designed in mitigation (primary and tertiary) and secondary mitigation measures detailed within the topic chapters of the Array EIA Report. The means of implementation of these mitigation measures is also specified for each of the mitigation commitments, along with any caveats to these commitments as requested by Scottish Ministers within the Array EIA Scoping Opinion (MD-LOT, 2023).

                        Residual effects

  1. Residual effects are those effects remaining once all mitigation measures have been taken into consideration in assessment. Following the identification of secondary mitigation measures as described above and as required, in addition to primary and tertiary mitigation, the assessment re-evaluates the significance of effect utilising the methodology outlined above. The assessment of likely significance of residual effects provides the following conclusions for the purposes of the assessment:
  • a residual level of significance equal to or greater than moderate will be considered a ‘significant’ effect in terms of the EIA Regulations; and
  • a residual level equal to or less than minor will be considered ‘not significant’ in terms of the EIA Regulations.