19. Water quality

19.1. Introduction

1. This chapter of the Offshore Environmental Impact Assessment (EIA) Report presents the assessment of the likely significant effects (as per the “EIA Regulations”) on the environment of the Berwick Bank Wind Farm offshore infrastructure which is the subject of this application (hereafter referred to as “the Proposed Development”) on water quality. Specifically, this chapter considers the potential impacts of the Proposed Development seaward of Mean High Water Springs (MHWS) during the construction, operation and maintenance, and decommissioning phases.

2. “Likely significant effect is a term used in both the “EIA Regulations” and the Habitat Regulations. Reference to likely significant effect in this Offshore EIA Report refers to “likely significant effect” as used by the “EIA Regulations”. This Offshore EIA Report is accompanied by a Report to Inform Appropriate Assessment (RIAA) (SSER, 2022c) which uses the term as defined by the Habitats Regulations Appraisal (HRA) Regulations.
3. The assessment presented is informed by the following technical chapters:

• volume 2, chapter 7: Physical Processes;
• volume 2, chapter 8: Benthic Subtidal and Intertidal Ecology; and
• volume 2, chapter 9: Fish and Shellfish Ecology.

19.2. Purpose of this Chapter

4. The primary purpose of the Offshore EIA Report is outlined in volume 1, chapter 1. It is intended that the Offshore EIA Report will provide the Scottish Ministers, statutory and non-statutory stakeholders, with sufficient information to determine the likely significant effects of the Proposed Development on the receiving environment.
5. In particular, this Water Quality Offshore EIA Report chapter:

• presents the existing environmental baseline established from desk studies;
• identifies any assumptions and limitations encountered in compiling the environmental information;
• presents the likely significant environmental impacts on water quality arising from the Proposed Development and reaches a conclusion on the likely significant effects on water quality, based on the information gathered and the analysis and assessments undertaken; and
• highlights any necessary monitoring and/or mitigation measures which are recommended to prevent, minimise, reduce or offset the likely significant adverse environmental effects of the Proposed Development on water quality.

19.3. Study Area

6. The Offshore EIA Report water quality study area includes the intertidal area. This intertidal area overlaps with the onshore topic of Geology, Hydrology, Soils and Flood Risk (landward of MLWS) and Ecology and Ornithology (landward of MHWS) ( Figure 19.1   Open ▸ ).

Figure 19.1: Water Quality Study Area

19.4. Policy and Legislative Context

7. Policy and legislation on renewable energy infrastructure is presented in volume 1, chapter 2 of the Offshore EIA Report. Policy and legislation specifically in relation to water quality, is contained in the Water Environment (Controlled Activities) (Scotland) Regulations 2011 (as amended), Marine Strategy Regulations 2010, the Bathing Waters (Scotland) Regulations 2008, the Water Environment and Water Services (Scotland) Act 2003, the Conservation (Natural Habitats, &c.) Regulations 1994, the Sectoral Marine Plan for Offshore Wind Energy (SMP) 2020, the Scottish National Marine Plan (NMP) 2015, and the United Kingdom (UK) Marine Policy Statement (MPS) 2011. A summary of the legislative provisions relevant to water quality are provided in Table 19.1   Open ▸ to Table 19.5   Open ▸ , with other relevant policy provisions set out in Table 19.6   Open ▸ to
8. Table 19.8   Open ▸ . These are summarised here with further detail presented in volume 3, appendix 19.
9. All the policy and legislation provided in Table 19.1   Open ▸ to
10. Table 19.8   Open ▸ is also relevant to the intertidal area.

Table 19.1 Water Environment (Controlled Activities) (Scotland) Regulations 2011 (as Amended)

Table 19.2: Summary of Marine Strategy Regulations 2010 Relevant to Water Quality

Table 19.3: Summary of Bathing Waters (Scotland) Regulations 2008 Relevant to Water Quality

Table 19.4: Summary of Water Environment and Water Services (Scotland) Act 2003 Relevant to Water Quality

Table 19.5: Summary of Conservation (Natural Habitats, &c.) Regulations 1994 Relevant to Water Quality

Table 19.6: Summary of Sectoral Marine Plan for Offshore Wind Energy (SMP) 2020 Relevant to Water Quality

Table 19.7: Summary of Scottish National Marine Plan (NMP) 2015 Relevant to Water Quality

Table 19.8: Summary of UK Marine Policy Statement (MPS) 2011 Relevant to Water Quality

19.5. Consultation

11. A summary of the key issues raised during consultation activities undertaken to date specific to water quality is presented in Table 19.9   Open ▸ , together with how these issues have been considered in the production of this Water Quality Offshore EIA Report chapter. Further detail is presented within volume1, chapter 5 where appropriate.

Table 19.9: Summary of Key Consultation of Relevance to Water Quality

19.6. Methodology to Inform Baseline

19.6.2.              Desktop Study

12. Information on water quality within the water quality study area was collected through a detailed desktop review of existing studies and datasets. These are summarised in Table 19.10   Open ▸ .

Table 19.10: Summary of Key Desktop Reports

19.6.3.              Identification of Designated Sites

13. All designated sites within the water quality study area, and qualifying interest features that could be affected by the construction, operation and maintenance, and decommissioning phases of the Proposed Development were identified using the three-step process described below:

• step 1: All designated sites of international, national and local importance within the water quality study area were identified using a number of sources. For SACs and SPAs, these sources included the JNCC Marine Protected Area (MPA) mapper and the Marine Scotland NMPi maps, and for WFD water dependent protected areas, including bathing water sites, the SEPA water classification hub, SEPA water bodies data sheets and SEPA bathing waters pages;
• step 2: Information was compiled on the relevant WFD water bodies and bathing water sites for each of these sites; and
• step 3: Using the above information and expert judgement, sites were included for further consideration if:

–           a designated site directly overlaps with the Proposed Development array area and the Proposed Development export cable corridor; and/or

–           sites and associated features were located within the potential Zone of Influence (ZoI) for impacts associated with the Proposed Development.

14. The ZoI for water quality was defined through physical processes modelling undertaken in volume 3, appendix 7.1. and followed that identified in volume 2, chapter 8. The ZoI identified designated sites within one tidal excursion (12 km) of the Proposed Development array area and Proposed Development export cable corridor and are therefore at the maximum range of the impacts of the Proposed Development. However, a precautionary approach has been taken, based on the largest ZoI estimated for receptors in the supporting chapters (see paragraph 3). The greatest of these is the ZoI for fish and shellfish ecology (volume 2, chapter 9) which is 25 km, or approximately two tidal excursions.

19.6.4.              Site-Specific Survey Data

15. Table 19.11   Open ▸ summarises data used to inform the water quality assessment. Sampling of bathing water quality is undertaken by SEPA, and is conducted 18 times between 1 June and 15 September, in fulfilment of WFD obligations as set out in Table 19.2   Open ▸ , and sampling of sediment contamination was conducted as part of the benthic ecology assessment.

Table 19.11: Summary of Site-Specific Survey Data

19.7. Baseline Environment

19.7.2.              Overview of Baseline Environment

Water Framework Water Bodies

16. The WFD establishes a legislative framework for the protection of surface waters (including rivers, lakes, transitional waters and coastal waters) and groundwater throughout the EU. Under the WFD, coastal waters, estuaries, rivers, man-made docks and canals are divided into a series of water bodies. Within each water body, the WFD sets ecological and chemical objectives. The aim of the WFD is for all water bodies identified in the WFD to achieve “good status” by 2015. This aim was not achieved in Scotland by 2015, but by 2021 87% of water bodies had achieved good status (Scottish Environment Protection Agency (SEPA), 2021). SEPA is aiming to maintain this, and to achieve, or return to, good status in 94% of waters by 2027 (SEPA, 2015). Under all conditions, it requires that there should be no deterioration in status of any water bodies.
17. The Proposed Development export cable corridor overlaps with two WFD water bodies (Barns Ness to Wheat Stack (ID: 200038) and Firth of Forth Outer - Offshore (ID: 20055) and lies within 25 km of two WFD water bodies (North Berwick to Barns Ness (ID: 200467) and Wheat Stack to Berwick-upon-Tweed (ID: 200031)). The most recent sampling results and status classifications available for these water bodies is 2020 (SEPA, 2022a), and details are presented in paragraphs 18 to 21. Locations of WFD water bodies and bathing locations with respect to the Proposed Development are illustrated in Figure 19.1   Open ▸ .
18. The Barns Ness to Wheat Stack water body covers approximately 98.3 km2, all of which lies within the water quality ZoI, and 13.5 km2 of which overlaps with the Proposed Development export cable corridor. This water body had an overall status in 2020 of Good, with a water quality status of Good, an ecological status of Good and a physico-chemical status of High. The status of the water body has deteriorated from an overall High status in 2012 and has an objective of maintaining Good overall status by 2027. There are currently no pressures identified on this water body that would cause long term deterioration from Good status.
19. The Firth of Forth Outer - Offshore water body covers approximately 446.6 km2, of which 31.0 km2 overlaps with the Proposed Development export cable corridor, and 408.4 km2 lies within the water quality ZoI. This water body had an overall status in 2020 of Good, with a water quality status of Good, an ecological status of Good and a physico-chemical status of High. The status of the water body has deteriorated from an overall High status in 2012 and has an objective of maintaining Good overall status by 2027. There are currently no pressures identified on this water body that would cause long-term deterioration from Good status.
20. The North Berwick to Barns Ness water body covers approximately 134.5 km2, all of which lies within the water quality ZoI, and does not overlap with the Proposed Development export cable corridor. This water body had an overall status in 2020 of Good, which it has maintained since 2007, an ecological status of Good and a physico-chemical status of High. The water body has an objective of maintaining Good overall status by 2027, and there are currently no pressures identified on this water body that would cause a deterioration from Good status.
21. The Wheat Stack to Berwick-Upon-Tweed water body covers approximately 115.2 km2, all of which lies within the water quality ZoI, and does not overlap with the Proposed Development export cable corridor. This water body had an overall status in 2020 of Good, with a water quality status of Good, an ecological status of Good and a physico-chemical status of High. The water body has an objective of maintaining Good overall status by 2027. There are currently no pressures identified on this water body that would cause long-term deterioration from Good status.
22. Maintaining and improving water quality in WFD water bodies is achieved via measures described in the river basin management plan for Scotland (SEPA, 2021), which include regulating new and existing discharges, abstractions, impoundments and engineering works in accordance with the Water Environment (Controlled Activities) (Scotland) Regulations 2011.
23. Assessment of the potential impacts of the Proposed Development upon hydromorphological, biological (habitats and fish), water quality, protected sites, and INNS receptors is considered in detail in volume 3, appendix 19.1.

European Commission Bathing Water Sampling Locations

24. The Bathing Water (Scotland) Regulations 2008 transpose Council Directive 2006/7/EC (the Bathing Water Directive) concerning the management of bathing water quality into Scottish law and reporting commenced in 2015.
25. Compliance with the Bathing Water Regulations is measured using two microbiological parameters: Escherichia coli (E. coli) and intestinal Enterococci, and bathing waters are classed as either poor, sufficient, good or excellent. The revised Bathing Water Directive introduces a new classification system with more stringent water quality standards, requiring all bathing waters to be classed as at least ‘sufficient’. It also puts an emphasis on providing information to the public.
26. Eight European Commission (EC) bathing water sampling locations lie within 25 km of the Proposed Development export cable corridor. In the 2021 to 2022 sampling season one location (Eyemouth) was classified as Sufficient, two locations (Dunbar (East) and Dunbar (Belhaven)) were classified as Good and five locations (Thorntonloch, Whitesands, Pease Bay, Coldingham and Seacliff) were classified as Excellent (SEPA 2022b). There is no explicit statutory requirement for bathing waters to achieve or maintain a given status, but summary information on water quality status must be available to the public at bathing locations.

Onshore and intertidal

27. The Berwick Bank Wind Farm Onshore EIA (SSER, 2022a) considers the potential for pollution to enter inland watercourses, and the Thorntonloch Bathing Water indirectly, as a consequence of runoff from construction areas, chemical/fuel spills and untreated foul water discharge. This impact was assessed as having a negligible magnitude on a high sensitivity receptor (the WFD water bodies at ‘Good’ status) and considered to be of minor adverse significance, and the potential cumulative effects are considered in section 19.12.
28. The intertidal area is considered as part of the WFD assessment in volume 2, appendix 19 since WFD water bodies include the area up to MHWS. Direct impacts of the Proposed Development upon receptors in the intertidal area will be avoided due to the use of trenchless techniques resulting in no pathway for impacts to occur within this area. Further assessment will therefore not be required and information on this is presented in section 19.8.3.

19.7.3.              Designated Sites

29. A number of designated sites identified for water quality receptors are located in the vicinity of the Proposed Development, and are described in Table 19.12   Open ▸ below and illustrated in Figure 19.1   Open ▸

Table 19.12: Designated Sites and Relevant Qualifying Interest Features for the Water Quality Chapter

19.7.4.              Important Ecological Features

30. There are no Important Ecological Features (IEFs) appropriate to water quality specifically, within the ZoI. This has been determined in line with CIEEM guidelines which indicate that as the marine environment is sufficiently widespread and a highly dynamic habitat and is expected to remain viable and sustainable throughout the project, detailed assessment is not necessary (CIEEM, 2018). Deterioration of water quality is, however, a potential impact to benthic ecology, fish and shellfish ecology, and offshore and intertidal ornithology receptors. The IEFs appropriate to these topics are addressed fully in volume 2, chapters 8 , 9 and 11 respectively, and a summary of those features potentially affected by changes to water quality are detailed in Table 19.13   Open ▸ .

Table 19.13: IEFs within the Water Quality Study Area

19.7.5.              Future Baseline Scenario

31. The EIA Regulations (The Electricity Works (Environmental Impact Assessment) (Scotland) Regulations 2017; The Marine Works (Environmental Impact Assessment) (Scotland) Regulations 2017; The Marine Works (Environmental Impact Assessment) Regulations 2007; and The Town and Country Planning (Environmental Impact Assessment) (Scotland) Regulations 2017), require that “a description of the relevant aspects of the current state of the environment (baseline scenario) and an outline of the likely evolution thereof without development as far as natural changes from the baseline scenario can be assessed with reasonable effort, on the basis of the availability of environmental information and scientific knowledge” is included within the Offshore EIA Report for the Proposed Development.
32. In the event that the Proposed Development does not come forward, an assessment of the future baseline conditions has been carried out and is described within this section.
33. The baseline environment for water quality is not static and will exhibit a degree of natural change over time. Such changes will occur with or without the Proposed Development in place due to natural variability and the impact of existing and future anthropogenic pressures (e.g. sewage storm discharge events, accidental release of pollutants into water catchments, coastal and offshore pollution events).
34. Future baseline conditions would also be altered by climate change, resulting in sea level rise and increased storminess, and this may have the effect of altering water quality both offshore at the Proposed Development array area and export cable corridor, and in coastal areas. Recent, current, and long term objectives for water quality indicators at WFD water bodies in the water quality study area are presented in Table 19.14   Open ▸ , and these broadly involve the long-term maintenance of the current ‘Good’ and ‘High’ classifications across all categories.

Table 19.14: Recent and Current Classifications, and Future Objectives, for WFD Water Bodies

35. The criteria for inclusion of designated sites in the water quality assessment do not entirely coincide with the criteria on which the WFD assessment in volume 2, appendix 19 is based. The designated sites considered for each, and, where appropriate, the justification for their omission are summarised in Table 19.15   Open ▸ .

Table 19.15: Differences in designated sites corresponding between water quality assessment and WFD assessment

19.7.6.              Data Limitations and Assumptions

The water quality study area has been the focus of study for both academic and government institutions, and coincides with a number of designated sites, which contain a range of biological, physical and geological qualifying features. In particular for water quality, regular monitoring of WFD water bodies and bathing water sampling locations under the statutory obligations of the WFD and the Bathing Water Directive (as transposed into Scottish law) have ensured a largely continuous water quality dataset since 2007, covering a broad range of physical, chemical and biological parameters. It is therefore considered that the baseline data employed with respect to water quality measures are robust and sufficient for the purposes of the assessment of effects presented.

19.8. Key Parameters for Assessment

19.8.2.              Maximum Design Scenario

36. The maximum design scenarios identified in Table 19.16   Open ▸ have been selected as those having the potential to result in the greatest effect on an identified receptor or receptor group. These scenarios have been selected from the details provided in volume 1, chapter 3 of the Offshore EIA Report. Effects of greater adverse significance are not predicted to arise should any other development scenario, based on details within the Project Design Envelope (e.g. different infrastructure layout), to that assessed here, be taken forward in the final design scheme.

Table 19.16: Maximum Design Scenario Considered for Each Impact as Part of the Assessment of Likely Significant Effects on Water Quality

19.8.3.              Impacts Scoped out of the Assessment

37. On the basis of the baseline environment (see section 19.7), and the project description outlined in volume 1, chapter 3 of the Offshore EIA Report, a number of impacts have been scoped out of the assessment for water quality. These impacts are outlined, together with a justification for scoping them out, in Table 19.17   Open ▸ . Discussions with consultees about the scoping of these impacts that took place after the publication of the Berwick Bank Wind Farm Scoping Opinion (MS-LOT, 2022) are included in the Audit Document for Post-Scoping Discussions (volume 3, appendix 5.1).

Table 19.17: Impacts Scoped Out of the Assessment for Water Quality (tick confirms the impact is scoped out)

19.9. Methodology for assessment of effects

19.9.2.              Overview

38. The water quality assessment of effects has followed the methodology set out in volume 1, chapter 6 of the Offshore EIA Report. Specific to the water quality assessment, the following guidance documents have also been considered:

• Guidelines for Ecological Impact Assessment (EcIA) in the UK and Ireland. Terrestrial, Freshwater and Coastal (CIEEM, 2018);
• Guidance on Environmental Considerations for Offshore Wind Farm Development (OSPAR, 2008); and
• Clearing the Waters For All: Guidance on WFD assessment: estuarine and coastal waters (Environment Agency, 2017).

39. In addition, the water quality assessment of effects has considered the legislative framework as defined by:

• Marine Strategy Regulations 2010;
• Bathing Waters (Scotland) Regulations 2008;
• Water Environment and Water Services (Scotland) Act 2003; and
• Conservation (Natural Habitats, &c.) Regulations 1994.

19.9.3.              Criteria for Assessment of effects

40. The process for determining the significance of effects is a two-stage process that involves defining the magnitude of the potential impacts and the sensitivity of the receptors. This section describes the criteria applied in this chapter to assign values to the magnitude of potential impacts and the sensitivity 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 Offshore EIA Report.
41. The criteria for defining magnitude in this chapter are outlined in Table 19.18   Open ▸ . When defining the magnitude of an impact, factors such as the duration, frequency, spatial extent and reversibility of the impact have been taken into account.
42. The criteria for defining magnitude in this chapter are outlined in Table 19.18   Open ▸ . In determining magnitude within this chapter, each assessment considered the spatial extent, duration, frequency and reversibility of impact and these are outlined within the magnitude section of each assessment of effect (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 19.18: Definition of Terms Relating to the Magnitude of an Impact

43. The criteria for defining sensitivity in this chapter are outlined in Table 19.19   Open ▸ .

Table 19.19: Definition of Terms Relating to the Sensitivity of the Receptor

44. The significance of the effect upon water quality is determined by correlating the magnitude of the impact and the sensitivity of the receptor. The particular method employed for this assessment is presented in Table 19.20   Open ▸ .
45. In cases where a range is suggested for the significance of 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 conclusion is based upon the author's professional judgement as to which outcome delineates the most likely effect, with an explanation as to why this is the case. Where professional judgement is applied to quantify final significance from a range, the assessment will 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.
46. 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.
  47. 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 19.20: Matrix Used for the Assessment of the Significance of The Effect

19.9.4.              Designated Sites

48. Where Natura 2000 sites (i.e. nature conservation sites in Europe designated under the Habitats or Birds Directives[4]) or sites in the UK that comprise the National Site Network (collectively termed ‘European sites’) are considered, this chapter makes an assessment of the likely significant effects in EIA terms on the qualifying interest feature(s) of these sites as described within section 19.7.3 of this chapter. The assessment of the potential impacts on the site is deferred to the RIAA (SSER,2022c) for the Proposed Development). A summary of the outcomes reported in the RIAA is provided in section 19.15 of this chapter.
49. With respect to locally designated sites and national designations (other than European sites), where these sites fall within the boundaries of a European site and where qualifying interest features are the same, only the features of the European site have been taken forward for assessment. This is because potential impacts on the integrity and conservation status of the locally or nationally designated site are assumed to be inherent within the assessment of the features of the European site (i.e. a separate assessment for the local or national site is not undertaken). However, where a local or nationally designated site falls outside the boundaries of a European site, but within the water quality study area, an assessment of the likely significant effects on the overall site is made in this chapter using the EIA methodology.
50. No European sites have been designated with water quality as a qualifying feature, but where European sites within 25 km of the Proposed Development array area and Proposed Development export cable corridor have been designated on the basis of relevant qualifying features for which changes to water quality may have a direct effect (i.e. fish and shellfish ecology and benthic ecology), these sites, and their relevant qualifying features, are included in Table 19.13   Open ▸ .

19.10. Measures Adopted as part of the Proposed Development

51. As part of the project design process, a number of measures have been proposed to reduce the potential for impacts on water quality (see Table 19.21   Open ▸ ). As there is a commitment to implementing these measures, they are considered inherently part of the design of the Proposed Development and have therefore been considered in the assessment presented in section 19.11 (i.e. the determination of magnitude and therefore significance assumes implementation of these measures). These measures are considered standard industry practice for this type of development.

Table 19.21: Designed In Measures Adopted as Part of the Proposed Development

19.11. Assessment of Significance

52. The potential impacts arising from the construction, operation and maintenance and decommissioning phases of the Proposed Development are listed in Table 19.16   Open ▸ , along with the maximum design scenario against which each impact has been assessed.
53. An assessment of the likely significance of the effects of the Proposed Development on water quality receptors as a result of the identified impacts is given below.
54. The impacts of increased suspended sediment concentration (SSC) and hydrodynamics are assessed in the physical processes chapter (volume 2, chapter 7), and the impact of release of seabed contamination is considered in the benthic ecology chapter (volume 2, chapter 8).

Increased risk of introduction and spread of invasive and non-native species

55. The risk of introduction and spread of INNS during the construction, operation and maintenance and decommissioning phases has been considered in this assessment.
56. INNS within the Proposed Development area may increase during the construction, operation and maintenance, and decommissioning phases as detailed in Table 19.16   Open ▸ .
57. Introduction of INNS can result from activities involving any vessel, including installation, survey, crew transfer, and cable repair vessels, entering the Proposed Development area.
58. Colonisation by INNS can result during and after installation of hard substrates that may create suitable habitat, including foundation and scouring protection for wind turbines and OSPs/Offshore convertor station platforms, and cable protection.

Construction Phase

Magnitude of Impact

59. The installation of hard substrates and the presence of construction vessels may lead to an increased risk of introduction and spread of INNS. The maximum design scenario is represented by up to 11,484 vessel round trips during the construction phase, which will occur over a maximum duration of up to 96 months ( Table 19.16   Open ▸ ).
60. There are a number of existing vessel movements occurring within the Proposed Development area area, including cargo vessels, tankers, fishing vessels, recreational vessels and service vessels (volume 3, appendix 13.1). The baseline identified in volume 3, appendix 13.1 identified an average of 14 unique vessel movements per day over a 14-day survey period in August 2022 within a 10 nm buffer around the Proposed Development array area (hereinafter, the Proposed Development shipping and navigation study area). Cargo vessels, tankers and commercial fishing vessels were the most common vessel type. The vessel traffic survey of August 2022 showed an average of three to four vessels intersecting the Proposed Development array area per day, over summer. Throughout the 14-day period, a maximum of 25 vessels were recorded within the Proposed Development array shipping and navigation study area over one day. Provided the INNS provisions of the EMP are implemented, the additional vessels associated with the Proposed Development are unlikely to significantly add to the risk of introduction and spread of INNS.
61. As presented in Table 19.16   Open ▸ , the risk of introduction and spread of INNS will be increased due to the creation of 10,198,971 m2 of hard substrate from the installation of jacket foundations, associated scour protection and any cable protection. There are already natural hard substrates within the vicinity of the Proposed Development array area and offshore Proposed Development export cable corridor (e.g. moderate energy subtidal rock, cobble/stony reefs, and rocky reefs in the nearshore section of the Proposed Development export cable corridor). Furthermore, there are pre-existing wind turbine foundations from Seagreen as well as the Neart na Gaoithe and Inch Cape projects currently under construction.
62. There are multiple marine INNS that are now widespread and well established in Scotland. Some of which have been reported in the Firth of Forth as well as the surrounding area (based on NBN Atlas data) and therefore have the potential to colonise the Proposed Development infrastructure and surrounding area. These include Japanese skeleton shrimp Caprella mutica (MSS, 2020), carpet sea-squirt Didemnum vexillum, green sea fingers Codium fragile subsp. fragile, wakame Undaria pinnatifida and wire weed Sargassum muticum (NatureScot, 2021).
63. There are several other marine INNS which are of only patchy distribution or are currently only known from the rest of the UK. These include American lobster Homarus americanus, Pacific oyster Crassostrea gigas, Chinese mitten crab Eriocheir sinensis, and slipper limpet Crepidula fornicata (NatureScot, 2021).
64. The vessels used for construction will largely be local therefore the introduction of species from outside the region is unlikely. Some of the species already in the region however are known to spread as fouling on ships hulls which could introduce then to the Proposed Development array area and Proposed Development export cable corridor, including wakame, green sea fingers and carpet sea-squirt (Beveridge et al., 2011; CABI, 2019).
65. As set out in Table 19.21   Open ▸ , an INNS Management Plan and EMP (see volume 4, appendix 22), which will include measures such as ensuring any new infrastructure coming from another marine environment are cleaned and checked prior to installation and that vessels comply with the IMO ballast water management guidelines will be developed and adhered to for the Proposed Development. This will ensure that the risk of potential introduction and spread of INNS will be minimised.
66. The latest post-construction monitoring data from the Beatrice Offshore Wind Farm (APEM, 2021) found no evidence for the presence of INNS on turbine foundations following the presence of installation vessels from international ports, which is evidence to suggest that the introduction of structure such as offshore wind turbine foundation into the benthic environment doesn’t necessarily lead to the spread of INNS in Scottish waters.
67. There is no evidence to suggest that INNS are likely to cause a detrimental effect upon water quality, and in some cases have been found to improve water quality, for example by increasing water clarity and decreasing E. coli densities of sewage-enriched water (Neves et al., 2020).
68. The impact is predicted to be of local spatial extent, long term duration, continuous and low reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be negligible.

Sensitivity of the Receptor

69. All WFD water bodies within 25 km of the Proposed Development are currently classified by SEPA as High for freedom from INNS, and in the long term all water bodies have the objective to maintain this classification. INNS are already widespread within the Firth of Forth, and these objectives have been established in this context, and in the context of the existing offshore wind farm project detailed in Table 19.23   Open ▸ . Maintaining a High classification for freedom for INNS for all WFD waterbodies will be contingent upon successful implementation by construction vessels of the INNS provisions contained within the EMP.
70. The risk of introduction and spread of INNS is unlikely to be an impact on bathing water sampling locations as INNS are not a criterion on which bathing water status is classified.
71. Areas of water in the water quality study area which are not classified as WFD water bodies or as a bathing site (i.e. the remainder of the water quality study area), are expected to be of comparable sensitivity. This is especially true where the water quality study area coincides with the Firth of Forth Banks Complex MPA.
72. These water quality receptors have been considered individually and are all deemed to be of negligible vulnerability, high recoverability and high value. The sensitivity of the receptor is therefore considered to be low.

Significance of the Effect

73. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the water quality receptors is considered to be low. The effect for all receptors will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Secondary Mitigation and Residual Effect

74. No water quality mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 19.10) is not significant in EIA terms.

Operation and Maintenance Phase

Magnitude of Impact

75. Following the construction phase when hard substrates required for colonisation by INNS are present, the movement of operation and maintenance vessels may lead to an increased risk of introduction and spread of INNS. The maximum design scenario is represented by up to 2,324 vessels round trips per year during the operation and maintenance phase ( Table 19.16   Open ▸ ) which is a reduction from the construction phase. Furthermore, the long term creation of 10,198,971 m2 hard substrate, in the form of jacket foundations, associated scour protection and cable protection, has the potential to contribute to the introduction and spread of INNS. The estimate for habitat creation is considered to be conservative as the lattice nature of jacket foundations will result in a smaller area of habitat created than has been assumed for a foundation with solid sides.
76. The removal of encrusted growth may also occur during the operation and maintenance phase; however, no quantitative assessment can be made as the volume of encrusting is not known. Removal of marine growth has the potential to release invasive species if these have colonised hard structures of the Proposed Development, or if the materials and equipment used in the process have not been properly cleaned after use at a previous location that may have had invasive species present. To control this however, an invasive species management plan has been introduced to reduce the transmission of species through actions involved in the various phases of the Proposed Development ( Table 19.21   Open ▸ ).
77. Details of INNS of concern in this region of Scotland are as outlined previously in paragraphs 62 and 63.
78. As set out in Table 19.21   Open ▸ , an INNS Management Plan and EMP (see volume 4, appendix 22), which will include measures such as ensuring any new infrastructure coming from another marine environment are cleaned and checked prior to installation and that vessels comply with the IMO ballast water management guidelines will be developed and adhered to for the Proposed Development. This will ensure that the risk of potential introduction and spread of INNS will be minimised.
79. The impact is predicted to be of local spatial extent, long term duration, continuous and low reversibility. It is predicted that the impact will affect the receptor indirectly. The magnitude is therefore considered to be negligible.