11. Geology, Hydrology, Soils & Flood Risk

11.1. Introduction

1. This chapter presents the assessment of the likely significant effects on the environment of the Berwick Bank Wind Farm onshore transmission works (OnTW) (the Proposed Development) on Geology, Hydrology, Soils & Flood Risk. Specifically, this chapter considers the potential impact of the Proposed Development landward of Mean Low Water Springs (MLWS) during the construction, operational and maintenance, and decommissioning phases.
2. This chapter summarises information contained within Volume 4, Appendix 11.1 (Berwick Bank Wind Farm: Flood Risk Assessment) and Appendix 11.2 (Berwick Bank Wind Farm: Drainage Strategy).

11.2. Purpose of this Chapter

3. This chapter:

• Presents the existing environmental baseline established from desk studies, site-specific surveys and consultation with stakeholders;
• Identifies any assumptions and limitations encountered in compiling the environmental information;
• Presents the potential environmental impacts on geology, hydrology, soils & flood risk arising from the Proposed Development, and reaches a conclusion on the likely significant effects on geology, hydrology, soils & flood risk  based on the information gathered and the analysis and assessments undertaken; and
• Highlights any necessary monitoring and/or mitigation measures recommended to prevent, minimise, reduce or offset the likely significant adverse environmental effects of the Proposed Development on geology, hydrology, soils & flood risk.

11.3. Study Area

4. The geology, hydrology, soils & flood risk study area will cover the Proposed Development site and any potential effects up to 1 km from the site (refer to Volume 4, Figure 11.1   Open ▸ ). It is considered that this geology, hydrology, soils & flood risk typical study area buffer distance is appropriate considering the size of the development and allows potential effects on downstream receptors to be identified. The geology, hydrology, soils & flood risk study area includes the intertidal area and considers potential effects on offshore receptors that may arise as a result of the upgradient works.

11.3.1.              Intertidal Area

5. The planning application boundary for the Application extends to MLWS.  The infrastructure to be located between Mean High Water Springs (MHWS) and MLWS consists of cables to be installed via trenchless technology (e.g. horizontal directional drilling (HDD)).  Impacts associated with this infrastructure have been assessed in the Offshore EIA Report (Volume 2, Chapter 7), although given the commitment to use trenchless technology no likely significant effects have been predicted.
6. The Offshore EIA Report is available online at the Berwick Bank Wind Farm website; www.berwickbank.com. An electronic copy has been submitted to East Lothian Council Planning Department.
7. The potential effects of the onshore infrastructure located above MHWS on the intertidal area have been assessed in this chapter.

11.4. Policy and Legislative context

8. A summary of the policy provisions relevant to Geology, Hydrology, Soils & Flood Risk are provided in Table 11.1   Open ▸ below. A summary of the relevant legislative provisions are provided in Table 11.2   Open ▸ below.

Table 11.1:  Summary of Scottish Policy and East Lothian Policy (Local Development Plan (LDP) 2018) Relevant to Geology, Hydrology, Soils & Flood Risk

Table 11.2: Summary of Legislative Provisions Relevant to Geology, Hydrology, Soils & Flood Risk

11.5. Consultation

9. A summary of the key issues raised during consultation activities undertaken to date specific to geology, hydrology, soils & flood risk is presented in Table 11.3   Open ▸ below, together with how these issues have been considered in the production of this Geology, Hydrology, Soils & Flood Risk chapter. Further detail is presented within Volume 1, Chapter 2 of the Onshore EIA Report and the Pre-Application Consultation (PAC) Report.

Table 11.3:  Summary of Key Consultation Undertaken for the Proposed Development Relevant to Geology, Hydrology, Soils & Flood Risk

11.6. Methodology to Inform Baseline

10. This section sets out a summary of the methodology to inform the analysis of the baseline within the geology, hydrology, soils & flood risk study area.
11. A desk-based assessment has been undertaken to establish the catchments’ characteristics and baseline geological and hydrological conditions of the geology, hydrology, soils & flood risk study area. As part of the desk-based assessment, information regarding Private Water Supplies (PWS), historic landfill sites, water quality and flood risk data, abstraction licences and monitoring locations have been obtained to inform the assessment. Where available, classification of waterbodies has been referenced as determined by SEPA through River Basin Management Planning, under the Water Framework Directive.
12. Site surveys have been undertaken to further assess baseline conditions from information gathered from the desk-based assessment. Site surveys included a hydrological / geological walkover, watercourse assessments and flood risk assessments.

11.6.1.              Desktop Study

13. Information on geology, hydrology, soils & flood risk within the geology, hydrology, soils & flood risk study area was collected through a detailed desktop review of existing studies and datasets. These are summarised in Table 11.4   Open ▸ below.

Table 11.4:  Summary of Key Desktop Studies & Datasets

11.6.2.              Site-Specific Surveys

14. To inform the Geology, Hydrology, Soils & Flood Risk chapter, site-specific surveys were undertaken. A summary of the surveys undertaken to inform the geology, hydrology, soils & flood risk assessment of effects is outlined in Table 11.5   Open ▸ below.

Table 11.5:  Summary of Site-Specific Survey Data

11.7. Baseline Environment

11.7.1.              Overview of Baseline Environment

15. This section sets out a summary of relevant baseline data for the geology, hydrology, soils & flood risk study area under the following headings:

• Hydrology;
• Water Resources;
• Hydrogeology;
• Flood Risk;
• Geology;
• Soils; and
• Other Designated Sites.

Hydrology

Surface Water Catchments

16. The geology, hydrology, soils & flood risk study area is situated within six surface water catchments as shown in SEPA’s Baseline Confluence Nested Catchments data file;

• East Lothian Coastal between Dry Burn and Spott Burn (ID 12575);
• Dry Burn @ mouth (ID 18113);
• East Lothian Coastal between Thornton Burn and Dry Burn (ID 12687);
• Thornton Burn @ mouth (ID 13453);
• East Lothian Coastal between Dunglass Burn and Thornton Burn (ID 19745); and
• Dunglass Burn @ mouth (ID 16994).
  17. An overview of the surface water catchments is provided in Volume 2, Figure 11.2   Open ▸
  18. Of the above catchments “East Lothian Coastal between Dry Burn and Spott Burn” and “Dunglass Burn @ mouth” are outwith the site and not hydraulically connected with the Proposed Development.
  19. The “Dry Burn @ mouth” catchment is approximately 19 km2 and the Dry Burn watercourse is classified by SEPA as being of ‘Moderate’ status (SEPA, 2020). The north western extents of the Proposed Development are located within the “Dry Burn @ mouth” catchment. A small number of minor unnamed tributaries to the Dry Burn are located within the geology, hydrology, soils & flood risk study area.
  20. The “East Lothian Coastal catchment between Thornton Burn and Dry Burn” is approximately 4km2. The main watercourse in this catchment is unnamed and originates from the agricultural land to the west of Innerwick and flows to the settlement of Skateraw. The watercourse (hereafter referred to as the Innerwick Burn) is not classified by SEPA. The Innerwick Burn has been surveyed for the purpose of informing the drainage strategy for the onshore substation and it has been identified that it is heavily modified with multiple culverts and discharges to the Dry Burn to the north of the settlement of Skateraw. The onshore substation is located within this catchment area. No other watercourses are located within this catchment.
  21. The “Thornton Burn @ mouth” catchment is approximately 14 km2 and is classified by SEPA as being of ‘Good’ status (SEPA, 2020). The main watercourse within the catchment is known as the Thornton Burn within the downstream reaches. Within the geology, hydrology, soils & flood risk study area, the Thornton Burn is also known as the Braidwood Burn (predominant watercourse) and the Ogle Burn (tributary to the Braidwood Burn) is located further upstream near to Thorntonloch. The southern extents of the Proposed Development are located within this catchment.
  22. The “East Lothian Coastal between Dunglass Burn and Thornton Burn” catchment is approximately 17 km2 with no named watercourses present. Several minor unnamed watercourses are present draining the catchment area to the coastline. The southern extents of the site are located within this catchment but no Proposed Development is located within this catchment with the exception of a short section of access track to the proposed Branxton grid substation. This short section of track is located within the western extents of the catchment.
  23. The coastal waters at the site are classified by SEPA under the Barns Ness to Wheat Stack coastal water body and are considered to be of Good status (SEPA, 2020).
  24. Thorntonloch Beach is a Bathing Waters protected area, classified as being of Excellent status (SEPA, 2020). No Proposed Development infrastructure is located in the vicinity of the Bathing Waters but development is located within the catchment of the Thornton Burn which drains to the Bathing Waters.  

Water Resources

Public Water Supplies

25. In the scoping response, Scottish Water confirmed there are no Scottish Water drinking water catchments or water abstraction sources, which are designated as Drinking Water Protected Areas under the Water Framework Directive, within the geology, hydrology, soils & flood risk study area. The geology, hydrology, soils & flood risk study area is located within a groundwater Drinking Water Protected Area (DWPA) – as is the case for the majority of Scotland with the exception of the Scottish Borders and Dumfries and Galloway council areas.

Private Water Supplies

26. In response to a Freedom of Information (FOI) consultation request ELC provided the details of PWS within 5 km of the coordinates X 374080, Y 673982 (the centre of the site). ELC identified nine PWS supplies serving a total of 28 properties and one factory.
27. All supplies are located outside of the geology, hydrology, soils & flood risk study area, inland and therefore upgradient of the site. The closest PWS is located over 1.4km from the site.

SEPA CAR Abstractions

28. In the scoping response ELC note “The nearest SEPA licensed groundwater abstractions (CAR/S/1014268) is ~320m north of the proposed Skateraw and Crowhill substation locations on the opposite side of the railway line and trunk road. The next nearest licensed or registered groundwater abstractions are over 2km away at Dunbar Cement Works.” CAR/S/1014268 is recorded by SEPA as a “pumping test” in the received information from the FOI and is located within the geology, hydrology, soils & flood risk study area and site. The Dunbar Cement Works is not located within the geology, hydrology, soils & flood risk study area.
29. Locations of PWSs and abstraction locations are provided in Volume 2, Figure 11.3   Open ▸

Hydrogeology

Aquifer Classification

30. The geology, hydrology, soils & flood risk study area is situated within Torness (bedrock) and Torness Coastal (superficial) aquifers. The aquifers are classified as having Good status (SEPA, 2020).

Aquifer Productivity

31. The geology, hydrology, soils & flood risk study area is underlain by moderately productive aquifers.
32. Aquifer flow within the geology, hydrology, soils & flood risk study area is described as virtually all through fractures and other discontinuities.
33. A summary of the hydrogeology within the geology, hydrology, soils & flood risk study area is provided in Volume 2, Figure 11.4   Open ▸

Groundwater Dependent Terrestrial Ecosystems

34. The geology, hydrology, soils & flood risk study area does not contain any peatlands or wetlands. Therefore no Groundwater Dependent Terrestrial Ecosystems (GWDTE) are present.

Flood Risk

35. A Flood Risk Assessment (FRA) has been carried out and included as Volume 4, Appendix 11.1.
36. All potential sources of flooding to the site have been considered with respect to the following Proposed Development permanent infrastructure:

• Landfall,
• Cable Route and
• Onshore Substation.
  37. Assessment of flood risk to the landfall is confirmed to be overall at ‘no risk’ or ‘low risk’ of flooding from all sources. Following initial screening, further assessment was undertaken to accurately determine the coastal flood extent in relation to the landfall which was found to be at ‘low risk’ from coastal flooding.
  38. Assessment of flood risk to the cable route is confirmed to be overall at ‘no risk’ or ‘low risk’ of flooding from all sources. Following initial screening, further assessment was undertaken to determine the fluvial flood risk in relation to the cable route watercourse crossings which were found to be at ‘negligible risk’ from fluvial flooding.  
  39. Assessment of flood risk to the onshore substation is confirmed to be, with mitigation applied, overall at ‘low risk’ of flooding from land or from sewers / artificial drains, and at ‘no risk’ of flooding from all other sources (see Volume 4, Appendix 11.2).

Geology

Bedrock Geology

40. Review of the BGS 1:50k geological mapping indicates the very west of the geology, hydrology, soils & flood risk study area is underlain by Great Conglomerate Formation consisting of conglomerate and sandstone and Stratheden Group and Inverclyde Group consisting of sandstone and argillaceous rocks in the very south west.
41. The majority of the southern and central area of the geology, hydrology, soils & flood risk study area is underlain by the Ballagan Formation consisting of Sandstone, Siltstone and Dolomitic Limestone.
42. The bedrock geology in the north of the geology, hydrology, soils & flood risk study area is dominated by various limestone units including Hurlet Limestone, Lower Limestone Formation (consisting of Limestone, Argillaceous Rocks and Subordinate Sandstone), Blackhall Limestone and Main Hosie Limestone.
43. Several faults are recorded across the geology, hydrology, soils & flood risk study area, predominantly in the northern areas and along the western and southern extents.
44. An overview of the bedrock geology within the geology, hydrology, soils & flood risk study area is provided in Volume 2, Figure 11.5   Open ▸

Superficial Geology

45. Review of the BGS 1:50k geological mapping indicates the very west of the geology, hydrology, soils & flood risk study area is underlain by predominantly Till deposits with some areas of Alluvial deposits along watercourse extents.
46. Glaciofluvial Deposits - Gravel, Sand and Silt is the dominating superficial deposit across the remainder of the geology, hydrology, soils & flood risk study area in addition to Alluvial deposits along watercourse extents and Raised Marine deposits Of Holocene Age - Sand and Gravel, Marine Beach Deposits - Gravel, Sand and Silt and Blown Sand along areas of the coastline.
47. Areas of no superficial deposits are also recorded, primarily at the steep sides of watercourses.
48. Review of the BGS 1:50k geological mapping indicates the intertidal area is underlain by Marine Beach Deposits - Gravel, Sand and Silt and Blown Sand along areas of the coastline and Raised Marine Deposits Of Holocene Age - Sand and Gravel, as well as areas where no superficial deposits are recorded.
49. An overview of the superficial geology within the geology, hydrology, soils & flood risk study area is provided in Volume 2, Figure 11.6   Open ▸ : Superficial Geology.

Review of Ground Investigation Information

50. A site-wide ground investigation was undertaken in September 2020 (report published January 2021) to inform the Proposed Development layout and design. The results of the ground investigation broadly concur with the published geology from BGS. Bedrock was generally encountered at depths between 3 – 10m and its nature varied dependent on the location, similar to the BGS findings. Superficial deposits were confirmed to be Glaciofluvial in nature, generally with considerable clay content and poor infiltration capacity. No ‘made ground’ was encountered and no indication of any ground contamination. A potential source of contamination has been identified at the area defined as the ‘Skateraw Borrow Pit’. Further ground investigation undertaken in 2022 identified pulverised fuel ash (PFA) within the subsoil. Further chemical composition testing of the PFA will be undertaken to determine the level of contamination. This further analysis will inform the approach to manage the contamination, which will be determined post consent and agreed with ELC and other relevant stakeholders prior to the commencement of construction.

Mineral Reserves

51. Existing and historic quarries are present across ELC for the extraction of hard rock, limestone and sands and gravels. Skateraw quarry lies within the geology, hydrology, soils & flood risk study area, previously used for extraction of sands and gravels. Planning permission was originally granted in 2001 with an extension in 2011. The planning consent for the quarry expired in 2017.
52. No hard rock or limestone quarries are present within the geology, hydrology, soils & flood risk study area.
53. The superficial deposits and bedrock geology underlying the Proposed Development are widely present within the geology, hydrology, soils & flood risk study area and beyond.

Geologically Designated Sites

54. The landfall passes through the Barns Ness Coast Site of Special Scientific Interest (SSSI) and Geological Conservation Review Site. This is designated for the presence of biologically important habitats and for Lower Carboniferous Limestone which is rich in fossils. This geology is of particular interest as there is an exposed almost complete, though heavily faulted, section through the whole lower limestone group. The Landfall location avoids the ‘crucial areas’ of the feature (a term defined in the EIA Scoping Opinion (Volume 4, Appendix 2.2).
55. The use of trenchless technology (e.g. HDD) from offshore to onshore transition allows for the landfall site and transition pits to be located inland of the Barns Ness Coast SSSI. In addition, the use of trenchless technology will ensure that the works will pass underneath the SSSI as agreed within the EIA Scoping Opinion (Volume 4, Appendix 2.2).
56. The Local Geodiversity Site at Thorntonloch is located within the geology, hydrology, soils & flood risk study area, and is a very good example of rock coast landforms in sedimentary rocks. The Local Geodiversity Site is not within the site boundary and no Proposed Development works will be undertaken near to this location.
57. Locations of the relevant designated sites are provided in Volume 2, Figure 11.7   Open ▸ Designated Sites.

Soils

58. The geology, hydrology, soils & flood risk study area is located in predominantly agricultural land. Impacts on agriculture are included in Land Use, Tourism and Recreation Volume 1, Chapter 14.
59. Soils within the geology, hydrology, soils & flood risk study area are predominantly classified within the generalised soil type of Brown Soils, with isolated areas of mineral gleys and alluvial soils.
60. Topsoil compaction risk within the geology, hydrology, soils & flood risk study area (Volume 2, Figure 11.9) is predominantly moderate, interspersed with areas of high risk.
61. Subsoil compaction risk within the geology, hydrology, soils & flood risk study area (Volume 2, Figure 11.10   Open ▸ ) ranges from moderate to extreme. Areas of extreme vulnerability are predominantly within the area of the site around the A1 and East Coast Main Line, and along the Braidwood Burn.
62. Soil runoff risk within the geology, hydrology, soils & flood risk study area (Volume 2, Figure 11.11) is predominantly low to moderate.

11.7.2.              Future Baseline Scenario

63. The Town and Country Planning (Environmental Impact Assessment) (Scotland) Regulations 2017, require that a “a description of the relevant aspects of the current state of the environment (the “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 relevant information and scientific knowledge” is included within the Onshore EIA Report.
64. In order to ensure that the Proposed Development is assessed against a realistic baseline scenario, i.e. what the baseline conditions are likely to be once the Proposed Development is operational, a description of the likely future baseline conditions is provided within this section.
65. The relevant climate change projections using the UK Climate Change Projections 2018 (UKCP18) are:

• winter rainfall is projected to increase and summer rainfall is most likely to decrease; and
• an increase in frequency of winter storms over the UK.
  66. Increased winter rainfall and increased frequency of winter storms may increase the probability of flood risk and drainage systems may require increased capacity.
  67. Decrease in summer rainfall may affects water supplies dependent on local rainfall, surface water and / or groundwater.
  68. SEPA’s most recent climate change allowances guidance published in 2022 are partially based on UKCP18 findings and provides climate change allowances for sea level rise, rainfall intensity and river flows for Scotland. Relevant allowances for all types of flooding described have been used within the assessment and in the FRA and surface water drainage design.
  69. The relevant climate change allowances for the Proposed Development which is situated in the Forth River Basin are:
• Peak river flow allowance: Total change to 2100 – 56%
• Seal level rise allowance: Cumulative rise from 2017 to 2100 in metres – 0.86
• Peak rainfall intensity allowance: Total change to 2100 – 39%

11.7.3.              Data Assumptions And Limitations

70. Data limitations include:

• No water quality or flow monitoring has been undertaken to date. Baseline water quality monitoring is typically undertaken 12 months prior to commencement of construction (i.e., post consent).
• The Flood Estimation Handbook (FEH) Web service, used for determining catchment characteristics, only analyses catchments greater than 0.5 km2 and does not account for any in-channel artificial modifications to watercourses (i.e. culverting, weirs etc).
• SEPA do not provide flood risk mapping for watercourses with a total catchment area of less than 3km2 or water framework directive (WFD) classification for watercourses with a total catchment area of less than 10km2 (unless they require specific management).

11.8. Key Parameters for Assessment

11.8.1.              Maximum Design Scenario

71. The maximum design scenario(s) summarised here 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 5 of the Onshore 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.
72. The geology, hydrology, soils & flood risk assessment has been based on the maximum Proposed Development footprint and areas of temporary infrastructure along with a construction programme of 40 months. Assessment of flood risk has been on 1 in 200 year return period flood events with associated climate change uplifts.
73. This assessment has considered the following potential impacts:

• temporary direct impacts to statutory designated sites due to the maximum temporary footprint of the Proposed Development during construction;
• changes to natural drainage patterns due to construction activities;
• temporary increase in erosion of soils due to construction activities;
• increase in flood risk due to construction activities and the maximum temporary and permanent infrastructure footprint;
• pollution of watercourses and waterbodies due to surface water runoff during construction, operation, and decommissioning; and
• indirect impacts on private and public water supplies.

11.8.2.              Impacts Scoped out of the Assessment

74. Impacts scoped out of the assessment were agreed with key stakeholders through consultation within the Scoping Opinion or through the additional information provided in the Section 11.7 Baseline Environment within this chapter. Section 11.7 summarises the Baseline Environment specific to areas of Proposed Development, therefore enabling an assessment of potential pathways to be undertaken and more accurately determine potential impacts in comparison to the Scoping Report (which was assessed on the full site boundary). These, together with a justification, are presented in Table 11.6   Open ▸ .

Table 11.6:  Impacts Scoped Out of the Assessment for Geology, Hydrology, Soil and Flood Risk (tick confirms impacts scoped out)

11.9. Methodology For Assessment of Effects

11.9.1.              Overview

75. The geology, hydrology, soils & flood risk assessment of effects has followed the methodology set out in Volume 1, Chapter 2 of the Onshore EIA Report. Specific to the assessment of geology, hydrology, soils & flood risk, the following guidance documents have also been considered:

• Pollution Prevention Guidelines (PPGs) are a series of documents developed by the Environment Agency for England and Wales, the Northern Ireland Environment Agency (NIEA) for Northern Ireland, and SEPA for Scotland. A review plan for PPGs is currently underway, resulting in a replacement guidance series, titled Guidance for Pollution Prevention (GPPs). GPPs provide good practice guidance for the whole of the UK, and environmental regulatory guidance to Scotland, Wales and Northern Ireland. The following PPGs and GPPs have been considered to be of particular relevance as part of this assessment:

–           PPG1: General guide to the prevention of pollution (EA, SEPA & EHSNI, 2013);

–           GPP2: Above ground oil storage tanks (EA, SEPA & EHSNI, January 2018);

–           GPP5: Works and maintenance in or near water (EA, SEPA & EHSNI, January 2017);

–           PPG6: Working at construction and demolition sites (EA, SEPA & EHSNI, 2012); and

–           GPP21: Pollution incidence response planning (EA, SEPA & EHSNI, 2017).

• SEPA Supporting Guidance (SAT-SG-75) – Sector specific guidance: construction sites (SEPA, 2018);
• SEPA (2010) Engineering in the Water environment: Good Practice Guide, River Crossing, 2nd Edition;
• SEPA Guidance Note 2a: Development Management Guidance on Flood Risk (2018)
• SEPA Guidance Note 31: Guidance on Assessing the Impacts of Development Proposals on Groundwater Abstractions and Groundwater Dependent Terrestrial Ecosystems (2017);
• SEPA Policy 19: Groundwater Protection Policy for Scotland (Version 3, 2009);
• SEPA Policy 41: Planning Authority Protocol - Development at Risk of Flooding: Advice and Consultation (2016);
• Technical Flood Risk Guidance for Stakeholders - SEPA Requirements for Undertaking a Flood Risk Assessment (Version 12, 2019);
• Special Requirements for Civil Engineering Contracts for the Prevention of Pollution v2 (SEPA, 2006);
• CIRIA C532: Control of Water Pollution from Construction Sites - Guidance for Consultants and Contractors (CIRIA, 2001);
• CIRIA (2015) The SuDS Manual, Report C753;
• SEPA (2014) Regulatory Method (WAT-RM-08) Sustainable Urban Drainage Systems, Version 5.2; and
• IEMA (2022) A New Perspective on Land and Soil in Environmental Impact Assessment.

76. In addition, the assessment of geology, hydrology, soils & flood risk has considered the legislative framework as defined by:

• Directive 2007/60/EC on the assessment and management of flood risks (EC, 2007);
• 2000/60/EC Water Framework Directive (EC, 2000);
• The EC Groundwater Directive (Directive 2006/118/EC);
• The Control of Pollution Act 1974 (COPA), as amended;
• Environment Act 1995 (UK Government, 1995);
• Flood Prevention and Land Drainage (Scotland) Act 1997 (Scottish Executive, 1997);
• The Water Environment and Water Services (Scotland) Act 2003 (WEWSA);
• Flood Risk Management (Scotland) Act 2009 (Scottish Government, 2009);
• The Water Environment (Controlled Activities) (Scotland) Regulations 2011 as amended (Scottish Government, 2011);
• The Private Water Supplies (Scotland) Regulations  2006;
• The Water Intended for Human Consumption (Private Supplies) (Scotland) Regulations 2017;
• The Water Resources (Scotland) Act 2013 (Scottish Government, 2013); and
• The Private and Public Water Supplies (Miscellaneous Amendments) (Scotland) Regulations 2015.

11.9.2.              Impact Assessment Criteria

77. 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 2 of the Onshore EIA Report.
78. The criteria for defining magnitude in this chapter are outlined in Table 11.7   Open ▸ below.

Table 11.7:  Definition of Terms Relating to the Magnitude of an Impact

79. The criteria for defining sensitivity in this chapter are outlined in Table 11.8   Open ▸ below.

Table 11.8:  Definition of Terms Relating to the Sensitivity of the Receptor

80. The significance of the effect upon geology, hydrology, soils & flood risk is determined by correlating the magnitude of the impact and the sensitivity of the receptor, as outlined in Table 11.9   Open ▸ below.

Table 11.9: Matrix Used for the Assessment of the Significance of the Effect

11.10. Primary & tertiary mitigation

81. As part of the Proposed Development design process, a number of measures have been proposed to reduce the potential for impacts on geology, hydrology, soils & flood risk (see Table 11.10   Open ▸ ). These include measures which have been incorporated as part of the Proposed Development’s design (referred to as ‘primary mitigation’) and measures which will be implemented regardless of the impact assessment (referred to as ‘tertiary mitigation’). 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 11.11 below (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 11.10:  Measure Adopted as Part of the Proposed Development (Primary & Tertiary Mitigation)

11.11. Assessment of Significance

82. The potential impacts arising from the construction, operational and maintenance and decommissioning phases of the Proposed Development, along with the maximum design scenario against which each impact has been assessed is given below.
83. An assessment of the likely significance of the effects of the Proposed Development on geology, hydrology, soils & flood risk receptors caused by each identified impact is given below.

Impacts on Hydrology

84. During the construction phase, there is potential for pollution to enter watercourses (and Thorntonloch Bathing Waters indirectly) as a consequence of runoff from construction areas, chemical / fuel spills and untreated foul water discharge. Provision and implementation of the CEMP including construction drainage measures seeks to put in place appropriate measures to limit the likelihood of any such impact on watercourses local to the Proposed Development. In addition, a minimum buffer of 50m to all classified watercourses has been maintained except where watercourse crossings are required (see Volume 4, Appendix 11.1) and a small section around the Landfall Location. In addition, a WQMP would be implemented to monitor the quality of local watercourses before, during and after construction that are in hydraulic continuity with the Proposed Development.
85. During the operational and maintenance phase, there is potential for pollution to enter the Innerwick Burn adjacent to the onshore substation as a consequence of runoff from the onshore substation. Provision of a permanent surface water drainage strategy seeks to provide appropriate treatment for the Proposed Development runoff prior to discharge to the watercourse. There is potential for pollution to enter local watercourses during maintenance of the cable route (e.g., cable replacement). Any maintenance works of the cable route would mimic the construction phase processes albeit in a more minor and short-term fashion and the relevant appropriate measures will be undertaken following a specific method statement maintenance events.
86. During the decommissioning phase, there is potential for pollution to enter watercourses as a consequence of decommissioning activities (similar to the construction phase but to a lesser degree).

Construction phase

Magnitude of impact

87. The impact is predicted to be of local spatial extent across watercourse extents downstream of construction areas and coastal waters adjacent to landfall, medium term duration, intermittent and high reversibility (given the relatively small near coast catchment areas). It is predicted that the impact will affect the receptor directly. Considering the tertiary measures in place to control drainage during construction within the CEMP, the magnitude is therefore considered to be negligible.

Sensitivity of the receptor

88. The watercourses within the assessment range from high to negligible sensitivity based on their classification. The Thornton Burn is of high sensitivity (due to Good Status Classification), the Dry Burn of medium sensitivity (due to Moderate Status Classification), other unnamed watercourses of negligible sensitivity (due to being unclassified) and the Barness to Wheat Stack coastal water body is of high sensitivity (due to Good Status Classification. The overall sensitivity is considered to be high.

Significance of the effect

89. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptor is considered to be up to high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Secondary mitigation and residual effect

90. No secondary mitigation is considered necessary because the likely effect in the absence of secondary mitigation is not significant in EIA terms.

Operation and maintenance phase

Magnitude of impact

91. The impact is predicted to be of local spatial extent of watercourse extents downstream of the Proposed Development, long term duration, intermittent and high reversibility. It is predicted that the impact will affect the receptor directly. Considering the tertiary measures in place to control drainage during the operational and maintenance phase through the implementation of the surface water drainage strategy, the magnitude is therefore considered to be negligible.

Sensitivity of the receptor

92. The Innerwick Burn adjacent to the onshore substation is heavily modified and unclassified therefore is considered to be of negligible sensitivity. All other watercourses within the study area will not be impacted during the operational phase as the remaining Proposed Development outwith the Innerwick Burn catchment will be below ground (i.e., cable routes).

Significance of the effect

93. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptor is considered to be negligible. The effect will, therefore, be of negligible adverse significance, which is not significant in EIA terms.

Secondary mitigation and residual effect

94. No secondary mitigation is considered necessary because the likely effect in the absence of secondary mitigation is not significant in EIA terms.

Decommissioning phase

Magnitude of impact

95. The magnitude of impact for the decommissioning phase is assumed to be equivalent to the construction phase due to similar processes of plant use, excavation and stockpiling. The magnitude is therefore considered to be negligible.

Sensitivity of the receptor

96. The watercourses within the assessment range from high to negligible sensitivity based on their classification. The Thornton Burn is of high sensitivity, the Dry Burn of medium sensitivity and other unnamed watercourses of negligible sensitivity. The overall sensitivity shall be considered high.

Significance of the effect

97. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptor is considered to be up to high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.