9. Noise

9.1. Introduction

1. This chapter presents the assessment of the likely significant effects (as per the “EIA Regulations 2017”) on the environment of the Berwick Bank Wind Farm onshore transmission works (OnTW) (the Proposed Development) due to noise and vibration. 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 assessment is informed by the following technical chapter:

• Chapter 12, Traffic and Transport.
  3. This chapter summarises information contained within Volume 4, Appendix 9.1: Baseline Noise Survey.
  4. This chapter refers to ‘substation’ as opposed to ‘Electricity Transmission Buildings’ or ‘substation/converter station’. However, the assessment considers both the substation (HVAC) and converter station (HVDC) options. The source levels associated with both the substation (HVAC) and converter station (HVDC) are presented in the Maximum Design Scenario section and the predicted levels, secondary mitigation and residual effects of both designs are presented in the Assessment of Significance section. This ensures that the EIA assesses both design scenarios.

9.2. Purpose of this Chapter

5. 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 due to noise and vibration arising from the Proposed Development, and reaches a conclusion on the likely significant effects of noise and vibration based on the information gathered and the analysis and assessments carried out; 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 due to noise and vibration.

9.3. Study Area

6. The noise and vibration study area, in relation to the extent of the onshore Proposed Development area, is shown in Volume 2, Figure 9.1   Open ▸ The noise and vibration study area includes the following elements of infrastructure:

• Cable landfall;
• Onshore cable corridor; and
• Onshore substation.
  7. The spatial scope of the construction noise assessment includes the following geographic coverage:
• Up to 300 m from any construction activities;
• Along the onshore development area where activities have the potential to cause likely significant effects on identified Noise Sensitive Receptors (NSRs); and 
• Traffic routes and routes subject to significant changes in traffic flows (and / or percentage of Heavy Goods Vehicle (HGV)) associated with construction.
  8. The extent of the noise and vibration study area for the construction phase road traffic noise and vibration assessment was based on details provided in Volume 1, Chapter 12. 
  9. The noise and vibration study areas are based on experience from recent major infrastructure projects including the Thames Tideway Tunnel, the A14 Cambridge to Huntingdon Improvement Scheme, High Speed 2 (Phases 1 and 2a) and Crossrail.
  10. The operational phase noise assessment study area is defined as up to 1 km from the onshore substation boundary.
  11. The noise and vibration assessment draws on the information provided within Volume 1, Chapter 5 in order to define a maximum design scenario, which is subsequently assessed in this chapter.

Noise Sensitive Receptors

12. Table 9.1   Open ▸ describes the NSRs included within this assessment, and shown on Volume 2, Figure 9.2. The NSRs have been chosen based on their proximity to the cable landfall, the onshore cable corridor, and the onshore substation and are either individual residential properties or are considered representative of groups of residential properties.

Table 9.1:  Identified Noise Sensitive Receptors

9.4. Policy and Legislative context

13. A summary of the policy provisions relevant to noise and vibration are provided in Table 9.2   Open ▸ below. A summary of the legislative provisions relevant to noise and vibration are provided in Table 9.3   Open ▸ below.

Table 9.2:  Summary of Policy Provisions Relevant to Noise and Vibration

Table 9.3: Summary of Legislative Provisions Relevant to Noise and Vibration

9.5. Consultation

14. A summary of the key issues raised during consultation activities carried out to date specific to noise and vibration is presented in Table 9.4   Open ▸ below, together with how these issues have been considered in the production of this chapter. Further detail is presented within Volume 1, Chapter 2 and the Pre-Application Consultation (PAC) Report.

Table 9.4:  Summary of Key Consultation Carried Out for the Proposed Development Relevant to Noise and Vibration

9.6. Methodology to Inform Baseline

15. Consideration of the surrounding environment was initially conducted using existing available geographical information including aerial and satellite photography and mapping data in order to determine the nearest NSRs and noise sources present within the noise and vibration study area for use in the assessment.
16. Measurements of the existing ambient noise level were required to be taken at locations considered representative of the NSRs that had the potential to be affected by the construction and operation of the Proposed Development.
17. Full details of the baseline noise surveys are discussed in Volume 4, Technical Appendix 9.1. The noise surveys confirmed the initial desk-based assessment that the noise environment is influenced by the A1 trunk road and the East Coast Main Line (ECML) but is generally quiet and rural in nature in areas away from the major transport noise sources.
18. Noise monitoring survey locations were discussed and agreed with ELC’s Environmental Health Officer prior to survey work commencing and are shown in Volume 2, Figure 9.2   Open ▸ and Table 9.1   Open ▸ above. 
19. The surveys were carried out between May and November 2021 (with the findings used to inform the assessment presented within this EIA Report).  Noise measurements were conducted in accordance with BS 7445-1:2003 (BSI 2003) and BS 4142:2014+A1:2019 (BSI 2019).    A baseline vibration survey was not deemed necessary as vibration impacts do not relate to baseline vibration levels, with this approach being agreed during discussion with ELC’s Environmental Health Officer through the EIA Scoping process.

9.6.1.    Desktop Study

20. Information on noise and vibration within the noise and vibration study area was collected through a detailed desktop review of existing studies and datasets. These are summarised in Table 9.5   Open ▸ below.

Table 9.5:  Summary of Key Desktop Studies & Datasets

9.6.2.    Site-Specific Surveys

21. To inform the noise and vibration impact assessment, site-specific surveys were carried out, as agreed with East Lothian Council. A summary of the surveys carried out to inform the assessment of effects is outlined in Table 9.6 below.

Table 9.6:  Summary of Site-Specific Survey Data

9.7. Baseline Environment

9.7.1.    Overview of Baseline Environment

22. In order to characterise the existing acoustic environment within the noise and vibration study area a baseline noise survey was conducted at locations representative of the NSRs as agreed with ELC, detailed in Table 9.1   Open ▸ .  Measurements were conducted between May and November 2021.   Details of the baseline noise survey are contained within Volume 4, Appendix 9.1.
23. Table 9.7   Open ▸ provides a summary of the measured baseline noise data at the landfall and along the cable route.

Table 9.7:  Baseline Noise Data, Landfall and Cable Route, Daytime free-field, decibel (dB)

24. Table 9.8   Open ▸ and Table 9.9   Open ▸ provide a summary of the measured baseline noise data at NSRs in proximity to the onshore substation location during both the daytime and night-time surveys respectively as logarithmic averages over the monitoring period. The LA90,T values are considered in Table 9.10   Open ▸ .

Table 9.8:  Baseline Noise Data, Onshore Substation, Daytime free-field, dB

Table 9.9:  Baseline Noise Data, Onshore Substation, Night-time free-field, dB

25. Surveyor observations at SSR1 during the installation and decommissioning of equipment noted that the acoustic environment was affected predominantly by natural sounds such as wind rustling vegetation and bird calls. Activities at the farm adjacent to the property (such as farm vehicle movements) were occasional contributors, as were infrequent vehicles passing on the road to the northwest.
26. Surveyor observations at SSR2 noted that the acoustic environment was affected predominantly by continuous road traffic on the A1 and intermittent train passes on the ECML adjacent to the property. Natural sounds, such as bird calls and barking dogs, were occasional contributors.
27. Surveyor observations at SSR3 noted that the acoustic environment was affected predominantly by continuous, distant road traffic on the A1 and intermittent train passes on ECML. Natural sounds, such as wind rustling vegetation, were also contributors. Lesser contributions came from nearby residential premises and infrequent vehicles passing through the village.
28. Surveyor observations at SSR4 noted that the acoustic environment within the garden/external amenity area was affected predominantly by continuous noise from the watercourse/burn to the edge of the garden. Lesser contributions came from wind-blown vegetation, distant road traffic on the A1 and intermittent train passes on the ECML. Aircraft were noted passing overhead during the survey set-up.
29. Surveyor observations at SSR5 noted that the acoustic environment was affected predominantly by natural sounds such as wind rustling vegetation, bird calls, barking dogs and noise from livestock (hens) at the farm. Lesser contributions came from distant road traffic on the A1 and intermittent train passes on the ECML.
30. Surveyor observations at SSR6 noted that the acoustic environment was affected predominantly by natural sounds such as wind rustling vegetation. Lesser contributions came from distant road traffic on the A1 and intermittent train passes on the ECML.

Deriving Background Sound Levels

31. Statistical analysis has been carried out on the measured background sound levels[1], LA90,T, at the onshore noise and vibration study area during the night-time (as the constraining time period). The mean, mode and standard deviation are presented in Table 9.10   Open ▸ to show the variability of background sound at each location. Statistical analysis is carried out to ascertain a representative background sound level and is detailed within Volume 4, Appendix 9.1.

Table 9.10:  Background Sound Level Statistical Analysis, Substation, Night-time free-field, dB

9.7.2.    Future Baseline Scenario

32. 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 Onshore EIA Report.
33. 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.
34. The baseline noise monitoring survey provides a clear representation of the existing acoustic environment within the noise and vibration study area of the Proposed Development.
35. Noise is managed and driven by UK and local legislation and policies. The UK’s noise strategy and standards are enacted through management actions at a local authority level. There is a policy trend towards the maintenance and improvement of the noise environment across the UK, which is reflected in national planning policies within Scotland (PAN 1 2011). Predicted noise levels due to a change in land use, new developments and associated vehicles are assessed as part of the development planning and consent process.
36. Potential adverse impacts to the prevailing acoustic environment should be minimised or mitigated to suitable levels (in accordance with current legislation, policy and guidance), preventing and limiting adverse impact, where possible.
37. The acoustic environment in the noise and vibration study area is largely influenced by road traffic noise from the A1. Even with a predicted future movement towards electric vehicles the speed limit on the A1 is such that aerodynamic and tyre noise is more dominant than engine noise. In areas away from the influence of the A1 natural sounds such as wind and birdsong dominate, Consequently, in relation to the Proposed Development and its immediate receiving environment it is reasonable to predict a general steady baseline acoustic environment would be maintained. 

9.7.3.    Data Assumptions And Limitations

38. The key data limitation with the baseline data and their ability to materially influence the outcome of the EIA is the inherent variability of the noise environment. To manage this variability and provide representative noise data for the onshore noise and vibration study area, data were collected over two weeks to allow for day to day variability and reduce uncertainty associated with the characterisation of the baseline environment.  
39. The key data limitation with operational noise predictions is the source level data. Due to the stage of the design process, warranted source level information is not available. In place of site-specific data, worst case assumptions have been made on source levels based on historic data. As a result, there is also a lack of site-specific detailed information regarding the potential tonality. To manage this, and in a conservative and robust approach, an assumed spectral profile was used and appropriate penalties applied to the specific sound level to account for the likely perceptibility of tonality at receptors. Measures to minimise noise levels will be considered, where possible, as part of the design process, further managing this limitation prior to energisation of the Proposed Development.

9.8. Key Parameters for Assessment

9.8.1.    Maximum Design Scenario

40. 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. 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.
41. This section describes the parameters on which the noise and vibration assessment has been based. These are the parameters which are judged to give rise to the maximum levels of effect on noise and vibration sensitive receptors. Table 9.11   Open ▸ and Table 9.12   Open ▸ give the parameters for construction and operation respectively.

Table 9.11:  Parameters for Construction Impacts on Noise and Vibration

42. The majority of construction activities will take place during daytime only. Some plant, such as generators for site security and pumps to maintain water levels, will run overnight. The night-time predicted noise levels for the scenarios detailed in Table 9.11   Open ▸ (excluding trenchless technology (e.g. HDD)) reflect this.
43. For the trenchless technology (e.g. HDD) scenarios where working occurs outside of the hours of Monday to Sunday 7am to 7pm the maximum design scenario includes only the drilling rig and associated drilling fluid recovery system, pumps and generators (i.e. no mobile heavy plant such as excavators or bulldozers).
44. Table 9.12   Open ▸ gives the parameters for operational impacts.  Due to the stage of the design process warranted source level information is not available. In place of site-specific data, worst case assumptions have been made on source levels based on historic data.
45. Sources within buildings are calculated based on worst case sound power levels for internal plant and take into account the building dimensions. It is assumed that buildings will be constructed of single sheet profiled steel. Details of the buildings, including louvred openings and vents, will be clarified at detailed design stage The levels are rounded to the nearest dB.
46. The parameters detail a high voltage alternating current (HVAC) and high voltage direct current (HVDC) Option. This will be refined through the design process.

Table 9.12: Parameters for Operation Impacts on Noise and Vibration

* - internal reverberant sound level within buildings

47. For each impact phase all works have been assessed as occurring simultaneously at each location (e.g. at each jointing bay, each trenchless technology compound in the respective scenarios) along the onshore cable corridor. It is noted that, given the potential spatial extent and programme for the Enabling Works it is unlikely that all aspects of the Enabling Works will be undertaken simultaneously, however, this is considered a conservative approach.
48. Trenchless technology (e.g. HDD) has been assumed to be in operation at the landfall trenchless technology location and where trenchless technology occurs under the railway line and the A1 Trunk Road for 24 hours a day and assessed accordingly.  For all other construction activities at the landfall, onshore cable corridor and onshore substation the assessment is based on construction between the hours of 07:00 to 19:00 Monday to Sunday.
49. 24 hour operations will not happen for the trenchless technology (e.g. HDD) at the Scheduled Monument (SM5849) close to Castledene and Four Acres and it has been agreed that drilling would occur at the western compound which is the furthest from residential properties.
50. Trenchless technology (e.g. HDD) activities at other locations along the onshore cable corridor would be planned to occur during working hours; trenchless technology would only occur outside of these hours should an unforeseen overrun occur.

9.8.2.    Impacts Scoped out of the Assessment

51. Impacts scoped out of the assessment were agreed with key stakeholders through consultation. These, together with a justification, are presented in Table 9.13   Open ▸ .

Table 9.13:  Impacts Scoped Out of the Assessment for Noise and Vibration

9.9. Methodology for Assessment of Effects

9.9.1.    Overview

52. The Noise and Vibration assessment of effects has followed the methodology set out within Volume 1, Chapter 2. Specific to the assessment of noise and vibration, the following guidance documents have also been considered:

• BS 4142:2014+A1:2019 – Method for Rating and Assessing Industrial and Commercial Sound              Describes a method for rating and assessing sound of an industrial and/or commercial nature.  This method uses a rating level to assess the likely effects from sound of an industrial or commercial nature on people using amenity space outside a dwelling or premises used for residential purposes upon which the sound is incident.
• BS 5228-1:2009+A1:2014 Code of Practice for Noise and Vibration Control on Construction and Open Sites – Part 1: Noise              Part 1 provides recommendations for basic methods of noise control relating to construction and open sites where work activities/operations generate significant noise levels.  The legislative background to noise control is described and recommendations are given regarding procedures for the establishment of effective liaison between developers, site operators and Local Planning Authorities.  This BS provides guidance on methods of predicting and measuring noise and assessing its impact on those exposed to it.
• BS 5228-2:2009+A1:2014 Code of Practice for Noise and Vibration Control on Construction and Open Sites – Part 2: Vibration               Part 2 gives recommendations for basic methods of vibration control relating to construction and open sites where work activities/operations generate significant vibration levels.  The Standard includes tables of vibration levels measured during piling operations throughout the UK.  It provides guidance concerning methods of mitigating vibration from construction, particularly with regard to percussive piling.  
• BS 7445: Parts 1 and 2 – Description and Measurement of Environmental Noise              Provides details of the instrumentation and measurement techniques to be used when assessing environmental noise and defines the basic noise quantity as the continuous A-weighted sound pressure level (LAeq,T).  Part 2 of BS 7445 replicates International Standards Organisation (ISO) 1996-2.
• BS 8233:2014 – Guidance on Sound Insulation and Noise Reduction for Buildings              Provides a methodology to calculate the noise levels entering a building through facades and facade elements and provides details of appropriate measures for sound insulation between dwellings.  It includes recommended internal noise levels which are provided for a variety of situations and are based on World Health Organisation (WHO) recommendations.
• Calculation of Road Traffic Noise (CRTN) 1988 Provides a method for assessing noise from road traffic in the UK and a method of calculating noise levels from the Annual Average Weekday Traffic (AAWT) flows and from measured noise levels.  Since publication in 1988 this document has been the nationally accepted standard in predicting noise levels from road traffic.  The calculation methods provided include correction factors to take account of variables affecting the creation and propagation of road traffic noise, accounting for the percentage of heavy goods vehicles (HGV), different road surfacing, inclination, screening by barriers and relative height of source and receiver.
• Design Manual for Roads and Bridges (DMRB), LA 111, 2020 LA 111 provides guidance on the environmental assessment of noise impacts from road schemes.  It contains advice and information on transport-related noise and vibration, which has relevance with regard to the construction and operational traffic impacts affecting sensitive receptors adjacent to road networks.  It also provides guideline significance criteria for assessing traffic related noise impacts.
• ISO 9613-2 Specifies an engineering method for calculating the attenuation of sound during propagation outdoors in order to predict the levels of environmental noise at a distance from a noise source.
• High Speed Two Phase One Information Paper E23: Control of Construction Noise and Vibration (2017)              Provides additional guidance for construction noise and vibration affecting residential premises and details noise and vibration levels above which significant effects are anticipated.

9.9.2.    Impact Assessment Criteria / Method

53. Determining the significance involves firstly defining the magnitude of the potential impacts and the sensitivity of the receptors before an assessment is made on the likely significant effects of the predicted impacts. 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.

Construction Phase Noise Impact Magnitude

54. Following the methodology contained in DMRB LA 111, (Highways England, 2020) an initial screening assessment was carried out to assess the potential for an increase in baseline noise level of 1dB(A) or more as a result of the addition of construction traffic to existing traffic levels.  Any road links with a predicted increase in traffic volume of 25% were identified.  Such changes in traffic volume would correspond to a 1 dB(A) change in noise level at the relevant road link.  Traffic flows on the roads (links) surrounding the Proposed Development site were provided by the traffic consultants (Pell Frischmann) as Average Daily Traffic (ADT) for the following scenarios:

• 2026 – baseline traffic flow;
• 2026 – baseline traffic flow plus construction traffic;
  55. Predictions of the LA10,18hour noise index were carried out in accordance with the method provided in CRTN within noise prediction software CadnaA, using the projected traffic flows and HGV composition converted to Annual Average Weekday Traffic (AAWT).
  56. Construction phase change in road traffic noise at NSRs was assessed using the impact magnitude criteria in Table 9.14. The thresholds for differentiating the criteria are taken from DMRB for short-term impacts and are an indication of the relative change in ambient noise as a result of the Proposed Development.

Table 9.14:  Magnitude Criteria for Relative Change Due to Road Traffic (Short Term)

57. BS 5228-1:2009+A1:2014 (BSI 2014) describes several methods for assessing noise impacts during construction projects. 
58. The assessment approach utilised in this EIA Report is the threshold based “ABC” method.  The method is detailed within BS 5228-1:2009+A1:2014 (BSI 2014), which specifies a construction noise limit based on the existing ambient noise level and for different periods of the day. 
59. The predicted construction noise levels are assessed against noise limits derived from advice within Annex E of BS 5228-1:2009+A1:2014 (BSI 2014).  Table 9.15   Open ▸ , reproduced from BS 5228-1:2009+A1:2014 (BSI 2014) Table E.1, presents the criteria for selection of a noise limit for a specific receptor location (which are adopted in the noise impact magnitude criteria in Table 9.16   Open ▸ , Table 9.17, and Table 9.18   Open ▸ ).

Table 9.15:  Construction Noise Threshold Levels Based on the ABC Method (BS 5228-1:2009+A1:2014)

60. The “ABC” method described in BS 5228-1:2009+A1:2014 and the guidance contained within the HS2 Information Paper E23: Control of Construction Noise and Vibration establishes that there is no significant impact below the thresholds presented above. 
61. BS 5228-1:2009+A1:2014 states:

“If the site noise level exceeds the appropriate category value, then a potential significant effect is indicated.  The assessor then needs to consider other project-specific factors, such as the number of receptors affected and the duration and character of the impact, to determine if there is a significant effect.”

62. The CadnaA noise model used in this construction phase assessment incorporated noise sources located in the noise and vibration study area, nearby residential dwellings and other buildings, intervening ground cover and topographical information.
63. All identified NSRs at landfall, along the onshore cable corridor and at the onshore substation, are considered to fall into Category A, based on the measured noise levels at these receptors and will hence be subject to the most stringent noise limits (see Table 9.15   Open ▸ ).
64. Noise levels for the construction phase were calculated using the methods and guidance in BS 5228-1:2009+A1:2014.  This Standard provides methods for predicting receptor noise levels from construction works based on the number and type of construction plant and activities operating on site, with corrections to account for:

• the “on-time” of the plant, as a percentage of the assessment period;
• distance from source to receptor;
• acoustic screening by barriers, buildings or topography; and
• ground type. 
  65. Construction noise impacts were assessed using the impact magnitude presented in Table 9.16 for the daytime period, Table 9.17 for the evening and weekend periods, and Table 9.18   Open ▸ for the night-time.

Table 9.16:  Day time Construction Noise Impact Magnitude Criteria

Table 9.17:  Evening and Weekends Construction Noise Impact Magnitude Criteria

Table 9.18:  Night-time Construction Noise Impact Magnitude Criteria

Construction Phase Vibration Impact Magnitude

66. Paragraph 3.32 of DMRB   LA 111 (Highways England, 2020) states that:
67. “PPVs [peak particle velocity] in the structure of buildings close to heavily trafficked roads rarely exceed 2 mm/s and typically are below 1 mm/s. Normal use of a building such as closing doors, walking on suspended wooden floors and operating domestic appliances can generate similar levels of vibration to those from road traffic”
68. Construction traffic vibration is, therefore, not assessed.
69. Ground-borne vibration can result from construction works and may lead to perceptible levels of vibration at nearby receptors, which at higher levels can cause annoyance to residents.  In extreme cases, cosmetic or structural building damage can occur, however vibration levels have to be of a significant magnitude for this effect to be manifested and such cases are rare.
70. High vibration levels generally arise from ‘heavy’ construction works such as piling, deep excavation, or dynamic ground compaction.  The use of piling during the construction of the onshore substation may be required as well as drilling in trenchless technology (e.g. HDD) which will be required at landfall and along the cable route.
71. Annex E of BS 5228-2:2009+A1:2014 contains empirical formulae derived by Hiller and Crabb (2000) from field measurements relating to resultant peak particle velocity (PPV) with a number of other parameters for vibratory compaction, dynamic compaction, percussive and vibratory piling, the vibration of stone columns and tunnel boring operations.  Use of these empirical formulae enables resultant PPV to be predicted and for some activities (vibratory compaction, vibratory piling and vibrated stone columns) they can provide an indicator of the probability of these levels of PPV being exceeded.
72. The empirical equations for predicting construction-related vibration provide estimates in terms of PPV.  Therefore, the consequences of predicted levels in terms of human perception and disturbance can be established through direct comparison with the BS 5228-2:2009+A1:2014 guidance vibration levels.
73. Ground-borne vibration assessments may be drawn from the empirical methods detailed in BS 5228-2:2009+A1:2014, in the “Transport and Road Research Laboratory (TRRL) 246: Traffic: Traffic induced vibrations in buildings”, and within the “Transport Research Laboratory (TRL) Report 429 (2000): Ground-borne vibration caused by mechanical construction works”. 
74. However, these calculation methods rely on detailed information, including the type and number of plant being used, their location, and the length of time they are in operation.  Given the mobile nature of much of the plant that has the potential to impart sufficient energy into the ground, and the varying ground conditions in the immediate vicinity of the construction works, it was considered that an accurate representation of vibration conditions using these predictive methods was not possible.
75. Consequently, a series of calculations, following the methodologies referred to above, were carried out based on typical construction activities that have the potential to impart sufficient energy into the ground, applying reasonable maximum design scenario assumptions in order to determine set-back distances at which adverse impacts from vibration levels may occur.

The response of a building to ground-borne vibration is affected by the type of foundation, ground conditions, the building construction and the condition of the building.  For construction vibration, the vibration level and effects detailed in Table 9.19   Open ▸ were adopted based on BS 5228-2:2009+A1:2014.  Limits for transient vibration, above which cosmetic damage could occur, are given numerically in terms of PPV. The onset of structural damage will occur only at magnitudes four times greater than those in Table 9.19.

Table 9.19:  Transient Vibration Guide Values for Cosmetic Damage

76. Table 9.20   Open ▸ lists the minimum set-back distances at which vibration levels of reportable significance for other typical construction activities may occur.  BS 5228-2:2009+A1:2014 calculation methods were used to derive the set-back distances.

Table 9.20:  Predicted Distances at Which Vibration Levels May Occur

77. Vibration associated with typical trenchless technology (e.g. HDD) is discussed in more detail within Section 9.11.
78. Table 9.21   Open ▸ reproduced from research (Rockhill et al. 2014) details minimum safe separation distance for piling activities from sensitive receptors to reduce the likelihood of cosmetic damage occurrence.

Table 9.21:  Receptor Proximity for Indicated Piling Methods

79. For construction vibration from sources other than blasting, the vibration level and effects presented in Table 9.22   Open ▸ were adopted based on Table B-1 of BS 5228-2:2009+A1:2014.  These levels and effects are based on human perception of vibration in residential environments.

Table 9.22:  Construction Vibration - Impact Magnitude

Operational Phase Noise Impact Magnitude 

80. Where there are noise sources such as fixed plant associated with onshore components, the most appropriate assessment guidance is BS 4142:2014+A1:2019.  The guidance describes a method of determining the level of sound of an industrial source and the existing background sound level. 
81. BS 4142:2014+A1:2019 describes methods for rating and assessing sound of an industrial and/or commercial nature.  The methods use outdoor sound levels to assess the likely effects of sound on people who might be inside or outside a dwelling or premises used for residential purposes upon which sound is incident, and combines procedures for assessing the impact in relation to:

“…Sound from fixed installations which comprise mechanical and electrical plant and equipment;...”

82. This standard is the nationally accepted standard for the assessment of operational noise and is applicable to the determination of the following levels at outdoor locations: 

“a) rating levels for sources of sound of an industrial and/or commercial nature; and

b) ambient, background and residual sound levels, for the purposes of:

• investigating complaints;
• assessing sound from existing, proposed, new, modified or additional source(s) of sound of an industrial and/or commercial nature; and
• assessing sound at proposed new dwellings or premises used for residential purposes.”
  83. The standard incorporates a requirement for the assessment of uncertainty in environmental sound measurements and introduces the concepts of “significant adverse impact” rather than likelihood of complaints.  Common principles with the previous edition are consideration of sound characteristics, time of day and frequency of occurrence. 
  84. The standard applies to industrial/commercial and background sound levels outside residential buildings and for assessing whether existing and new industrial/commercial noise sources are likely to give rise to significant adverse impacts on the occupants living in the vicinity. Whilst the standard does not address non-residential receptors, such as Innerwick School (SSR7), adopting this standard for non-residential receptors does present a worst case assessment for these receptors and is considered a conservative approach.
  85. Assessment is carried out by subtracting the measured background sound level from the rating level; the greater this difference, the greater the magnitude of the impact. 
  86. BS 4142:2014 refers to the following:

• “A difference of around +10dB or more is likely to be an indication of a significant adverse impact, depending on the context;
• A difference of around +5dB is likely to be an indication of an adverse impact, depending on the context; and
• The lower the rating level relative to the measured background sound level the less likely it is that the specific sound source will have an adverse impact or a significant adverse impact.  Where the rating level does not exceed the background sound level, this is an indication of the specific sound source having a low impact, depending on the context”.

Context

87. The standard also makes the following comments:

“Where the initial estimate of the impact needs to be modified due to the context, take all pertinent factors into consideration, including the following.

• The absolute level of sound. For a given difference between the rating level and the background sound level, the magnitude of the overall impact might be greater for an acoustic environment where the residual sound level is high than for an acoustic environment where the residual sound level is low.
• Where background sound levels and rating levels are low, absolute levels might be as, or more, relevant than the margin by which the rating level exceeds the background. This is especially true at night.
• Where residual sound levels are very high, the residual sound might itself result in adverse impacts or significant adverse impacts, and the margin by which the rating level exceeds the background might simply be an indication of the extent to which the specific sound source is likely to make those impacts worse.
• The character and level of the residual sound compared to the character and level of the specific sound. Consider whether it would be beneficial to compare the frequency spectrum and temporal variation of the specific sound with that of the ambient or residual sound to assess the degree to which the specific sound source is likely to be distinguishable and will represent an incongruous sound by comparison to the acoustic environment that would occur in the absence of the specific sound. Any sound parameters, sampling periods and averaging time periods used to undertake character comparisons should reflect the way in which sound of an industrial and/ or commercial nature is likely to be perceived and how people react to it.
• The sensitivity of the receptor and whether dwellings or other premises used for residential purposes will already incorporate design measures that secure good internal and/or outdoor acoustic conditions, such as:
• facade insulation treatment;
• ventilation and/or cooling that will reduce the need to have windows open so as to provide rapid or purge ventilation; and
• acoustic screening.”
  88. Whilst the latest revision of BS 4142 does not provide definition of low or very low background and rating levels the previous (1997) version considered that background levels of 30dB(A) and rating levels of 35dB(A) could be considered low. Numerous studies, such as those by Moorhouse for the Health Protection Agency and Berry and Flindell for Defra (referenced within the Further Reading Section of BS 4142), as well as the recent Association of Noise Consultants Working Group report on BS4142 application conclude that impacts at rating levels below 35 dB(A) are unlikely. At night, particularly, where potential sleep disturbance is the key issue, a rating level of below 35 dB(A) results in internal levels significantly below the BS8233 guideline values.
  89. When assessing the noise from a source, which is classified as the Rating Level, it is necessary to have regard to the acoustic features that may be present.  Section 9.1 of BS 4142:2014+A1:2019 states:

• “Certain acoustic features can increase the significance of impact over that expected from a basic comparison between the specific sound level and the background sound level.  Where such features are present at the assessment location, add a character correction to the specific sound level to obtain the rating level.”
  90. These penalty corrections are added based on perceptibility at the receptor location.
  91. An operational assessment in accordance with BS 4142:2014+A1:2019 has been carried out for the onshore substation as it is the only noise source associated with the operational phase. Due to the separation distance, existing acoustic environment and a detailed screening of the onshore substation plant and equipment, no penalty corrections for intermittency or impulsivity are required.
  92. In terms of intermittency, the onshore substation will typically operate for the full 24hrs each day, with no expected stops/starts to the fixed electrical plant. Therefore, no intermittency penalty correction is required. Where there may be air cooling fans that stop/start, this is not considered to be distinctively audible at the receptor, above baseline sound characteristics due to masking effects.
  93. There are no items of fixed electrical plant with impulsive characteristics under typical operating conditions.
  94. Whilst it is known that the sound emissions (i.e. sound level emitted at source) from transformers typically contain a significant proportion of their acoustic energy at 100 Hz and harmonics, this tonal characteristic may also be masked by other noise from the substation (e.g. cooling equipment). This will be understood in more detail at the detailed design stage post consent.  
  95. Therefore, as a precautionary approach it is considered that the maximum +6 dB penalty for tonality would be appropriate. The potential for tonality to be present in the sound emissions from the substation will be revisited at detailed design stage, when more detailed information regarding levels of tonal sound will be sought from the substation equipment provider and designer.    
  96. The specific sound level is measured or predicted in terms of the LAeq,T, where ‘T’ is a reference period of:
• 1 hour during daytime hours (07:00 to 23:00 hours); and
• 15 minutes during night-time hours (23:00 to 07:00 hours).
  97. To predict the noise from the operational aspects of the onshore substation, CadnaA noise modelling software was utilised. The model incorporated proposed buildings based on elevation drawings, proposed fixed plant and additional noise sources (such as temporary generating plant) associated with the onshore substation.  The model also included nearby residential dwellings and other buildings in the onshore development area, intervening ground cover and topographical information.
  98. The calculation algorithm described in ISO 9613-2:1996 (ISO, 1996) was used in the operational noise propagation modelling exercise.
  99. The magnitude of impact that will be applied to the operational assessment, based on a quantitative assessment of noise impact using BS 4142:2014+A1:2019 and TAN, is summarised in Table 9.23   Open ▸ .
  100. TAN states

• “In deciding if a significant impact occurs in regard to the assessment of industrial noise, or noise of an industrial nature, using the methodology of BS 4142 (where appropriate); the Scottish Government consider impacts are normally not significant (in a quantitative sense only) [where] the difference between the Rating and background noise levels is less than 5 dB(A), and that usually the threshold of minor significant impacts is when the difference between the Rating and background noise levels is at least 5 dB(A); and commonly do not become sufficiently significant to warrant mitigation until the difference between the Rating and background noise levels is more than 10 dB(A)”.
  101. Using this principle, a difference in sound level of between +5 dB(A) to +10 dB(A) is detailed as a low magnitude of change. 

 Table 9.23:  Substation Operational Noise Impact Magnitude Criteria