6.5. Cumulative Effect Assessment

6.5.1. Overview

  1. Under the EIA Regulations, a CEA is required to assess the likely significant effects on the environment arising from the Array alone and cumulatively with other relevant plans, projects and activities. Cumulative effects are therefore the combined effect of the Array on the same receptor group or resource as a result of the effects from a number of different plans, projects and activities.
  2. The term ‘cumulative assessment’ is used in this Array EIA Report to describe the assessment of changes caused by other reasonably foreseeable actions alongside the Array.
  3. This section provides an overview of the legislation and guidance associated with the CEA and the approach to CEA.

6.5.2. Cumulative Effect Assessment Legislation and Guidance

  1. An assessment of cumulative effects is required in accordance with the EIA Directive (2011/92/EU, as amended by Directive 2014/52/EU) and the EIA Regulations.
  2. The EIA Directive (Annex IV, Article 5e) states: “A description of the likely significant effects of the project on the environment resulting from: the cumulation of effects with other existing and/or approved projects, taking into account any existing environmental problems relating to areas of particular environmental importance likely to be affected or the use of natural resources”.
  3. Article 5 of the EIA Directive (Annex IV) also states: “The description of the likely significant effects on the factors specified in Article 3(1) should cover the direct effects and any indirect, secondary, cumulative, transboundary, short-term, medium-term and long-term, permanent and temporary, positive and negative effects of the project. This description should take into account the environmental protection objectives established at Union or Member State level which are relevant to the project”.
  4. This is transposed directly into domestic law through the EIA Regulations.
  5. There are several other relevant guidance documents which have been considered in the development of the CEA, including:
  • A Handbook on Environmental Impact Assessment: Guidance for Competent Authorities, Consultees and Others Involved in the Environmental Impact Assessment Process in Scotland (NatureScot, 2018);
  • Environmental Impact Assessment for Offshore Renewable Energy Projects (BSI, 2015); and
  • Renewable UK Cumulative Impact Assessment Guidelines. Guiding Principles for Cumulative Impacts Assessment in Offshore Wind Farms (Renewable UK, 2013).
  1. The Applicant is currently engaging with MD-LOT on the forthcoming release of the Cumulative Effects Framework and will commit to the use of relevant and appropriate guidance, on ornithology and marine mammal assessments, where published and available.

6.5.3. Approach to the Cumulative Effect Assessment

  1. Ahead of the assessment of cumulative effects, other projects, plans and activities were first compiled into a long list of potential projects, and then screened for inclusion in a short list of projects to be considered in the CEA for each Topic. A summary of this process is outlined within this section, and a full description of the CEA methodology is provided in volume 3, appendix 6.4.
  2. The methodology for the screening of potential projects, plans and activities to provide cumulative effects is also presented in Figure 6.2   Open ▸ .

                        Screening stage

  1. A fundamental requirement of undertaking the CEA is to identify those foreseeable developments or activities with which the Array may interact with resulting in cumulative effects. There is the potential for interaction to occur during all phases (construction, operation and maintenance, and decommissioning) in the development of the Array. The process of identifying those projects, plans or activities for which there is the potential for an interaction to occur is referred to as ‘screening’.
  2. A specialised process has been developed to screen the projects, plans and activities that may be considered cumulatively alongside the Array. This involves a staged process that takes into consideration the current level of detail available for projects, plans and activities, as well as the potential for interactions on a conceptual, physical and temporal basis.
                        Compiling the CEA long list
  1. To ensure a thorough and comprehensive approach to identification of potential plans, projects and activities considered in the CEA, an initial ‘long list’ of projects within a defined Zone of Influence (ZoI) was developed. The ZoI for the Array was based on the offshore ornithology study area, the largest topic-specific study area.
  2. The Marine Scotland (2018) Consenting and Licensing Guidance: For Offshore Wind, Wave and Tidal Energy Applications states that “Engagement with MD-LOT is required to identify which plans/projects/ongoing activities should be included in the in-combination element of the cumulative effects assessment (CEA)”.
  3. Offshore wind projects within the Zone of Influence (ZoI) being considered by offshore ornithology have been compiled in the long list, including developments which:
  • have become operational since baseline data was collected;
  • are under construction;
  • have consent;
  • are the subject of an application for consent that has been submitted but not yet determined;
  • are in scoping or have a Scoping Opinion; and
  • are plans and projects which are “reasonably foreseeable” (i.e. developments that are being planned, such as in the case of offshore renewable energy developments, projects which have a Crown Estate Scotland (CES) AfL).
  1. The CEA has considered all other relevant plans, projects and activities that are publicly available six months prior to the Array application where quantitative assessment is required. A qualitative CEA will consider all other relevant projects, plans and activities that are publicly available three months prior to submission of the Array application.
  2. The CEA long list has been developed using datasets from MD-LOT, The Crown Estate (TCE) and others to identify projects and plans in the vicinity of the Array relating to topics such as commercial fisheries, cables and pipelines, energy and oil and gas.
  3. The CEA long list for the Array is provided in volume 3, appendix 6.5.
                        Screening of the CEA long list
  1. For a cumulative effect to occur, the potential of the effect to directly or indirectly affect the receptor(s) in question must be established (i.e. there must be an impact-receptor-pathway). The plans, projects and activities listed in the CEA long list were considered on a topic-by-topic basis to ensure the potential for a relevant receptor-impact pathway in screening each of the plans, activities or projects was identified.
  2. The initial CEA long list was short-listed following consideration of potential for cumulative effects for each potential impact-receptor pathway following the staged process as set out below:
  • conceptual overlap – in instances where an impact has the potential to directly or indirectly affect the receptor(s) in question (i.e. presence of an impact-receptor pathway);
  • physical overlap – ability for impacts arising from the Array to overlap with those from other projects/plans on a receptor basis. This results in an overlap of the physical extents of the impacts arising from the two (or more) projects/plans which must be established for a cumulative effect to arise. Exceptions to this exist for certain mobile receptors that may move between, and are subject to, two or more separate physical extents of impact from two or more projects; and
  • temporal overlap – for a cumulative effect to arise from two or more projects, a temporal overlap of impacts arising from each must be established. Some impacts are, however, active only during certain phases of development, such as piling noise during construction. The absence of a strict overlap however may not necessarily preclude a cumulative effect, as receptors may become further affected by additional, non-temporally overlapping projects. This will be considered for each topic with projects being screened in for cumulative assessment if required.
  1. This screening stage was led by the experience and knowledge of technical specialists, and the current guidance and regulations. The plans, projects and activities that remain after review of the long list are taken forwards to the assessment stage.
  2. In the absence of publicly available information for the Morven Offshore Wind Farm construction phase, a maximum overlap (100%) of the Array construction phase has been assumed for the purposes of CEA, which represents the most precautionary approach for cumulative assessment. This assumes Morven array’s construction phase (which is anticipated to be over seven years (Morven Offshore Wind Farm Limited (MvOWFL), 2023) will take place between 2031 and 2037, with the operational and maintenance phase commencing in 2038.
  3. Furthermore, although there are no publicly available details relating to the required offshore export cable corridor(s) for the Morven Offshore Wind Farm, as this project is reasonably foreseeable, it has been included as a Tier 3 project for the purposes of CEA.

 

 

Figure 6.2:
CEA Methodology for the Screening of Potential Projects, Plans and Activities

Figure 6.2: CEA Methodology for the Screening of Potential Projects, Plans and Activities

 

                        Assessment stage

  1. Following the Screening stage, a tiered approach has been adopted for undertaking the CEA of the Array, as described in Figure 6.2   Open ▸ . This approach provides a framework for placing relative weight on the potential for each project/plan to be included in the CEA to ultimately be realised, based upon the project/plan’s current stage of maturity and certainty in the project’s parameters.
  2. All projects/plans screened in via the previously described screening process have been allocated into one of the three Tiers and assessed in the CEA. It is worth noting that data collection is assessed against the source of this data (i.e. data confidence) to verify its accuracy and reliability.
  3. The CEA presented in this Array EIA Report has been undertaken on the basis of information presented in the EIA Reports (or other similar planning documents) for the other projects, plans and activities. Projects, plans and activities often seek consent for a maximum design scenario, which may be refined during the determination/examination period of the application and during the post-consent phases of the development. Changes made to a project’s design since the publication of the EIA Report for that project have not generally been included in the CEA long list or assessed within the topic chapters due to the uncertainty surrounding whether these are ultimately implemented or not. Where topic or project specific advice has been received in relation to the project design, this will be identified in the topic assessment.
  4. Where practicable, the CEA methodology follows the Array assessment of effects methodology as described in section 6.4.5. By following this approach, a level of consistency is maintained throughout the topic chapters and relevant comparisons can be made. 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.
  5. Where the potential significant effect for the Array alone is assessed as negligible, or where an impact is predicted to be highly localised, these will not generally be considered within the Array CEA, as there is not considered to be a potential for cumulative effects with other plans, projects or activities. Where a specific assessment methodology differs from this approach then this will be outlined within the relevant topic chapter.

                        Transboundary effects

  1. The potential for transboundary effects to arise is a result of an impact from the Array which has the potential to significantly affect the environment of an EEA state(s). Full description of how the transboundary effects assessment has been carried out is found in volume 3, appendix 6.6.
  2. To assist with this process, a screening exercise for potential transboundary impacts was undertaken at the scoping stage and presented in the Ossian Array EIA Scoping Report (Ossian OWFL, 2023).
  3. Volume 3, appendix 6.6 presents the update to the transboundary screening work undertaken at the scoping stage, taking into consideration more recent project information where relevant.
  4. This exercise identified that the following topics may experience transboundary impacts from the Array:
  1. This topic chapter provides an assessment of transboundary effects for each receptor group, which also considers the inter-relationships between effects. The inter-related effects identified within each topic chapter have been summarised in a standalone inter-related effects chapter (volume 2, chapter 20).