8.8. Key Parameters for Assessment

8.8.1. Maximum Design Scenario

  1. The MDSs identified in Table 8.12   Open ▸ are those expected to have the potential to result in the greatest impact on benthic subtidal ecology. These scenarios have been selected from the details provided in volume 1, chapter 3 of the Array EIA Report. Effects of greater adverse significance are not predicted to arise should any other development scenario, based on details within the Project Description (volume 1, chapter 3) (e.g. different infrastructure layout), to that assessed here, be taken forward in the final design scheme.
  2. The impact of increased SSCs and associated deposition has been informed by the assessment presented in volume 2, chapter 7.
Table 8.12:
Maximum Design Scenario Considered for Each Potential Impact as Part of the Assessment of LSE1 on Benthic Subtidal Ecology

Table 8.12: Maximum Design Scenario Considered for Each Potential Impact as Part of the Assessment of LSE1 on Benthic Subtidal Ecology

8.8.2. Impacts Scoped Out of the Assessment

  1. The benthic subtidal ecology pre-Scoping workshop (see Table 8.5   Open ▸ ) was used to facilitate stakeholder engagement on topics to be scoped out of the assessment.
  2. On the basis of the baseline environment and the Project Description outlined in volume 1, chapter 3 of the Array EIA Report, a number of impacts were proposed to be scoped out of the assessment for benthic subtidal ecology. This was either agreed with key stakeholders through consultation as discussed in volume 1, chapter 5, or otherwise, the impact was proposed to be scoped out in the Ossian Array EIA Scoping Report (Ossian OWFL, 2023) and agreement was confirmed through the EIA scoping consultation and subsequent Scoping Opinion (MD-LOT, 2023).
  3. These impacts are outlined, together with justifications for scoping them out, in Table 8.13   Open ▸ .
Table 8.13:
Impacts Scoped Out of the Assessment for Benthic Subtidal Ecology (Tick Confirms the Impact is Scoped Out

Table 8.13: Impacts Scoped Out of the Assessment for Benthic Subtidal Ecology (Tick Confirms the Impact is Scoped Out

8.9. Methodology for Assessment of Effects

8.9.1. Overview

  1. The benthic subtidal ecology assessment of effects has followed the methodology set out in volume 1, chapter 6 of the Array EIA Report. Specific to the benthic subtidal ecology EIA, the following guidance documents have also been considered:
  • Guidelines for Ecological Impact Assessment (EcIA) in the UK and Ireland (CIEEM, 2022);
  • Advances in Assessing Sabellaria spinulosa Reefs for Ongoing Monitoring (Jenkins et al., 2018);
  • Marine Evidence Based Sensitivity Assessment – A Guide (Tyler-Walters et al., 2018);
  • Guidelines for Data Acquisition to Support Marine Environmental Assessments of Offshore Renewable Energy Projects (Judd, 2012);
  • Guidance on Survey and Monitoring in Relation to Marine Renewables Deployments in Scotland – Volume 5: Benthic Habitats (Saunders et al., 2011);
  • Best Methods for Identifying and Evaluating Sabellaria spinulosa and Cobble Reef (Limpenny et al., 2010);
  • Identification of the Main Characteristics of Stony Reef Habitats under the Habitats Directive (Irving, 2009);
  •  Guidance on Environmental Considerations for Offshore Windfarm Development (OSPAR Commission, 2008a); and
  • Defining and Managing Sabellaria spinulosa Reefs (Gubbay, 2007).

8.9.2. Criteria for Assessment of Effects

  1. When determining the significance of effects, a two stage process is used which involves defining the magnitude of the potential impacts and the sensitivity of each receptor. This section describes the criteria applied in this chapter to assign values to the magnitude of potential impacts and the sensitivities of the receptors. The terms used to define magnitude and sensitivity are based on those which are described in further detail in volume 1, chapter 6 of the Array EIA Report.
  2. The criteria for defining magnitude in this chapter are outlined in Table 8.14   Open ▸ . Each assessment considered the spatial extent, duration, frequency and reversibility of impact when determining magnitude, which are outlined within the magnitude section of each impact assessment (e.g. a duration of hours or days would be considered for most receptors to be of short term duration, which is likely to result in a low magnitude of impact).

 

Table 8.14:
Definition of Terms Relating to the Magnitude of an Impact

Table 8.14: Definition of Terms Relating to the Magnitude of an Impact

 

  1. The MarESA has been used to define the sensitivity of benthic subtidal ecology IEFs. MarESA involves the likelihood for damage (thus vulnerability) due to defined pressures and the rate of recovery (i.e. recoverability) once said pressure is removed. Vulnerability is defined as the level at which a receptor can absorb disturbance or stress without changing character. Recoverability is defined as the ability of the habitat or species to return to the state that it existed in prior to the impact which caused the change. However, full recovery does not necessarily mean that every species component of a habitat or population has recovered to its prior condition, abundance, and/or extent. Instead, full recovery is reached if the relevant functional components are present, and the habitat and/or population is structurally and functionally recognisable as it was prior to the change.
  2. MarESA is a database developed through the Marine Life Information Network (MarLIN) of Britain and Ireland and maintained by the Marine Biological Association (MBA). The MarESA database consists of a detailed review of available evidence on the effects of pressures on marine species and habitats. It also contains a scoring of sensitivity against a standard list of pressures, and their benchmark levels of effect. The MarESA evidence base is peer reviewed and is the largest review undertaken to date on the effects of human activities and natural events on marine species and habitats. It is one of the best available sources of evidence regarding the recovery of seabed species and habitats.
  3. The MarESA sensitivity assessment correlates vulnerability and recoverability in order to characterise sensitivity of benthic receptors. This has been used to inform the sensitivity of the benthic subtidal ecology IEFs within the assessment of significance and the CEA (sections 8.11 and 8.12, respectively). The criteria for defining sensitivity in this chapter are outlined in Table 8.15   Open ▸ .
  4. FeAST provides sensitivity assessments for various species and habitats using the same methodology and approach as the MarESA. However, only the ocean quahog IEF had a specific FeAST assessment, with none available for dead man’s fingers, sea tamarisk, or phosphorescent sea pen. The FeAST contained an assessment on the broad seabed habitats ‘continental shelf coarse sediments’, ‘continental shelf mixed sediments’, and ‘continental shelf sands’, which could be used to assess the Offshore subtidal sands and gravels IEF and the Subtidal sands and gravels IEF, however the FeAST assessment does not contain information specific to the representative biotopes identified for these IEFs in Table 8.11   Open ▸ . Therefore, for the assessment of significance and the CEA, the FeAST was not used, only the MarESA and other available background literature.
  5. As noted in section 8.11, there was no MarESA available for sea tamarisk or phosphorescent sea pen, the sensitivities of these IEFs have been assessed using the available literature throughout. For the dead man’s fingers IEF, only the outdated MarLIN sensitivity assessment is available, which was superseded in 2014 by the MarESA for the remaining IEFs. Given that the same representative biotopes were identified within the Array benthic subtidal ecology study area for both the Offshore subtidal sands and gravels IEF and the Subtidal sands and gravels IEF (see Table 8.11   Open ▸ ) these two IEFs have been assessed in-combination throughout.

 

Table 8.15:
Definition of Terms Relating to the Sensitivity of the Receptor

Table 8.15: Definition of Terms Relating to the Sensitivity of the Receptor

 

  1. The magnitude of the impact and the sensitivity of the receptor are combined when determining the significance of the effect upon benthic subtidal ecology. The particular method employed for this assessment is presented in Table 8.16   Open ▸ .
  2. Where a range is suggested for the significance of effect, for example, minor to moderate, it is possible that this may span the significance threshold. The technical specialist’s professional judgement was applied to determine which outcome defines the most likely effect, which takes in to account the sensitivity of the receptor and the magnitude of impact. Where professional judgement is applied to quantify final significance from a range, the assessment hsa set out the factors that result in the final assessment of significance. These factors may include the likelihood that an effect will occur, data certainty and relevant information about the wider environmental context.
  3. For the purposes of this assessment:
  • a level of residual effect of moderate or more will be considered a ‘significant’ effect in terms of the EIA Regulations; and
  • a level of residual effect of minor or less will be considered ‘not significant’ in terms of the EIA Regulations.
  1. Effects of moderate significance or above are therefore considered important in the decision-making process, whilst effects of minor significance or less warrant little, if any, weight in the decision-making process.

 

Table 8.16:
Matrix Used for the Assessment of the Significance of the Effect

Table 8.16: Matrix Used for the Assessment of the Significance of the Effect

 

8.9.3. Designated Sites

  1. As per the conclusions provided in section 8.7.2, this Array EIA Report no LSE1 in EIA terms are predicted on the qualifying interest feature(s) of MPAs, Natura 2000 sites (i.e. nature conservation sites in Europe designated under the Habitats or Birds Directives[5]) and/or sites in the UK that comprise the National Site Network (collectively termed ‘European sites’). This is due to the distance from the Array of designated sites with qualifying interest features relevant to benthic subtidal ecology and the non-mobile nature of their respective qualifying features. These factors result in a lack of potential impact upon these designated sites due to the Array.