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10 Noise and Vibration

1HINKLEY POINT C PRE-APPLICATION CONSULTATION – STAGE 2 |

ENVIRONMENTAL APPRAISAL – VOLUME 2

10 NOISE AND VIBRATION

10.1 Introduction

10.1.1 This chapter of the Environmental Appraisal assesses the potential noise and vibration impacts associated with the construction and operation of Hinkley Point C (HPC) on human receptors. Potential noise and vibration impact on terrestrial and marine ecological receptors are addressed in Chapters 18 and 19 on terrestrial ecology and marine ecology respectively.

10.1.2 Noise and vibration effects arising from the construction and operation of HPC relate to:

Site preparation and ground terracing activities; Construction operations including the movement and operation of a wide range of mobile or

stationary construction plant equipment, and specifically with regard to ground compaction, piling activities or blasting;

Off-site construction-traffic effects that may influence noise and vibration sensitive premises;

HPC operational noise; and Off-site operational transport-related movements.

10.2 Scope of Assessment

10.2.1 The scope of the assessment undertaken includes:

Prediction of noise and vibration generation and propagation during the site preparation, ground terracing and construction works;

Prediction of the potential noise impacts associated with road traffic during the construction phase; and

Computational modelling of noise propagation from the main components of the operational HPC.

10.2.2 At present, this Environmental Appraisal does not include an assessment on the impact of potential noise impacts from operational road traffic on public highways. This assessment will be completed in due course once operational traffic generation figures have been finalised.

10.2.3 This section is complemented by a baseline noise survey report, henceforth referred to as the “Factual Noise Report” (see Appendix 10a). The Factual Noise Report includes details of background noise monitoring completed at representative receptor locations in the vicinity of the Development Site as well as additional locations that could be affected during the development construction.

10.3 Objectives of Assessment

10.3.1 The objectives of the assessment were to assess the potential effects of noise and vibration on human receptors. It is unlikely that the construction and operation of the development will lead


2 | HINKLEY POINT C PRE-APPLICATION CONSULTATION – STAGE 2

ENVIRONMENTAL STATEMENT – VOLUME 2

to immediate ‘acute’ noise or vibration effects i.e. hearing damage, as the levels necessary for such effects are generally confined to work places with very high levels of noise or vibration. What effects there may be, will generally be associated with disturbance to living conditions and amenity value, either due to short term, temporary activities or long term operational sources.

10.4 Legislation, Policy and Guidance

10.4.1 The relevant legislation, policy and guidance applicable to the assessment of noise and vibration impacts are listed and described below. Requirements and methods in both determining noise levels, their evaluation and management, particularly during construction works, are set out in a series of guidance notes, of which Planning Policy Guidance Note 24 (Ref. 10.1) is of particular relevance.

a) National Legislation

i) The Control of Pollution Act, 1974 (COPA)

10.4.2 Section 60 of the Control of Pollution Act, 1974 (Ref. 10.2) provides powers to local authority officers to serve an abatement notice in respect of noise nuisance from construction works, whilst Section 61 provides a method by which a contractor can avoid such action by applying for consent to conduct construction activities in advance of their occurrence (a ‘prior consent’). The prior consent is drawn up between the local authority and the contractor and may contain a range of agreed working conditions designed to minimise or prevent the occurrence of noise nuisance from construction activities. Application for a Section 61 ‘prior consent’ is a commonly used mitigation technique in respect of potential noise and vibration impacts from major construction works.

b) National Policy

i) Planning Policy Guidance PPG 24 ‘Planning and Noise’

10.4.3 PPG 24 (Ref. 10.1) was introduced by the Department of the Environment in 1994. Paragraph 1 on page 1 of PPG 24 indicates that it was issued to:

‘…provide advice on how the planning system can be used to minimise the adverse impact of noise without placing unreasonable restrictions on development or adding unduly to the costs and administrative burdens of business. It outlines some of the main considerations which local planning authorities should take into account in drawing up development plan policies and when determining planning applications for development which will either generate noise or be exposed to existing noise sources’.

10.4.4 For new developments that would introduce noise into an area PPG 24 confirms, in Annex 3, that it is appropriate to continue using previously established assessment routines, for example when assessing ‘Noise from road traffic’ (Annex 3, paragraph 1), ‘Noise from industrial and commercial developments’ (Annex 3, paragraphs 19-20) and ‘Noise from construction sites’ (Annex 3, paragraph 21). The appropriate assessment routines applicable to this development are discussed in the relevant assessment methodology sections below.

c) Regional Policy

i) Draft Regional Spatial Strategy (RSS) for the South West (2006-2026)

10.4.5 The draft RSS (Ref. 10.3) was published by the South West Assembly in 2006. The areas of the Strategy for which noise issues are highlighted are reproduced below:




Enhancing Distinctive Environments and Cultural Life:

“Utilising the potential of indigenous assets sustainably, to assist economic regeneration and diversification, is a key component of the ‘environment driver’. However, the changing nature of man’s activities produces outcomes that are often individually small, but cumulative in impact – the effect of noise and light on remaining areas of tranquillity for example”.

ii) The Regional Strategy for the South West Environment 2004 – 2014 “Our Environment: Our Future”

10.4.6 The Regional Strategy (Ref. 10.4) was published by the South West Regional Assembly in association with the South West Regional Environment Network. The following aspect highlights noise related issues:

Spatial Planning:

“Increased development also brings with it pressures on tranquillity, light and noise pollution, increased demand for natural resources such as minerals, water, energy, and increased production of waste. The planning system has a key role to play in managing these pressures and helping to protect and enhance the environmental assets that people value in the region.”

iii) Somerset Sustainable Community Strategy 2009 – 2026 “Somerset – A Landscape for the Future”

10.4.7 The Sustainable Community Strategy (Ref. 10.5) was published by the Somerset Strategic Partnership. The document does not provide specific guidance for the management of noise, but the following component of the Strategy is of relevance:

Challenge 4: Increase people’s quality of life through the use of Somerset’s environment, nature and heritage:

“Manage the precarious balance between the needs of economic and housing growth and the impact it has on the quality of our natural environment and heritage.”

d) Local Policy

10.4.8 Local policies relating to the control and management of noise, including pollution control and nuisance, have been identified below. Whilst Local Plans (LP) are due to be superseded by Local Development Frameworks (LDF), both West Somerset Council and Sedgemoor District Council are yet to publish and/or formally adopt LDFs. The relevant policies within the respective LPs are therefore identified below.

i) West Somerset Local Plan

10.4.9 The West Somerset Local Plan (Ref. 10.6) highlights relevant national policy documents as follows:

“PPG24 states, however, that 'noise can have a significant effect on the environment and on the quality of life enjoyed by individuals and communities.' This is particularly relevant in rural areas where background noise levels are very low and the introduction of noisy activities will often be very disruptive. Furthermore, the Government's White Paper (1990) emphasises that 'noise not only irritates and annoys, but can also do irreparable damage to hearing'.

The planning system has the task of controlling developments which may give rise to or suffer from noise. The Local Planning Authority will ensure that:-

i noise-sensitive developments are located away from existing or potential sources of significant noise;




ii new development involving potentially noisy activities are sited in areas where noise will not be an important consideration or where its impact can be minimised; and

iii potentially noisy developments are strictly controlled in areas which have remained relatively undisturbed by noise nuisance and are a valued recreational and amenity resource for this reason.

The Local Planning Authority, through the process of development control, will seek to ensure the introduction of one or more mitigation measures as appropriate, to reduce the effects of noise either in the development's design or by the use of planning conditions and planning obligations.

Additional powers which control noise exist outside the planning system and the granting of planning permission does not give exemption from these, for example the Noise and Statutory Nuisance Act 1993. The implementation of this legislation is the responsibility of the Environmental Health Unit.”

ii) Sedgemoor District Local Plan (1991-2011 Adopted Version)

10.4.10 Policy PCS15 of the Sedgemoor District Local Plan (Ref. 10.7) relates to noise pollution and specifies that:

“Noise generating development will not be permitted if it would:

(a) be liable to unacceptably increase the level or disruptive character of noise experienced in any area to the detriment of its character; or

(b) be liable to unacceptably increase the noise experienced by the users of existing or proposed noise sensitive development to the detriment of those users.

Noise sensitive development will not be permitted if its users would be unacceptably affected by noise generating uses.”

10.5 Key Consultations

10.5.1 In undertaking this assessment, consultations have been undertaken with the Environmental Health Officers (EHOs) of West Somerset Council (WSC) and Sedgemoor District Council (SDC). A scoping consultation meeting with both parties on December 2008 was undertaken. During this meeting the specific requirements for the assessment of noise impacts were discussed. This included agreements regarding the choice of noise sensitive reference positions to be used for determining noise impacts at community positions closest to the proposed construction sites.

10.5.2 A second consultation meeting was held with WSC and SDC in October 2009. At this meeting, the progress of the impact assessment was described, along with presentation of a summary of the baseline noise monitoring survey. The proposed construction noise limits as detailed in the methodology section below were presented to the consultees, as well as the proposed operational noise threshold discussed in Section 10.6 below. The methodology and scenario assumptions for the operational noise prediction modelling exercise (presented in detail in Appendix 10b) were also described.

10.5.3 Following the second consultation meeting, SDC and WSC requested further clarification on the derivation of the proposed noise threshold values for the construction and operational phases. This further detail was provided in March 2010.

10.5.4 The following advice and direction was provided by WSC and SDC, which has been taken into account within this assessment:




Baseline noise survey scope and methodology was agreed (refer to Factual Noise Report in Appendix 10a);

Impacts of plant noise during the operational phase should be assessed in accordance with BS 4142:1997 (Ref. 10.8), with a target criterion of 5dB above the prevailing background not to be exceeded; and

Due to the large separation distance, vibration due to construction and operation is unlikely to significantly affect the nearest residential locations. It was agreed, during the initial consultation, that a baseline vibration assessment was not required. However, it is now possible that some blasting of bedrock may be required during the construction phase and noise and vibration measurements were undertaken during test blasting in April 2010 in the vicinity of the power station. The details of this are provided in the report ‘Blasting Tests - Noise and Vibration Monitoring Factual Report’ (see Appendix 10c).

10.6 Methodology

a) Noise and Vibration Principles

10.6.1 This section sets out the noise and vibration principles which have formed the basis of the noise and vibration assessment.

i) Noise Principles

10.6.2 Between the quietest audible sound and the loudest tolerable sound, there is a million to one ratio in sound pressure (measured in Pascals, Pa) and due to this wide range, a noise level scale based on logarithms is used in noise measurement, called the decibel (dB) scale. Audibility of sound in humans generally covers a range of approximately 0dB to 140dB (see Table 10.1).

10.6.3 The human hearing mechanism does not respond uniformly to sound across the detectable frequency range, being less effective at hearing particularly high or low frequency sounds and, consequently, instrumentation used to measure noise is ‘weighted’ to reflect the performance of the ear. This is known as the 'A weighting' and annotated as dB LA. The annotation ‘L’ denotes the fact that the descriptor refers to a level on the dB scale.

Table 10.1: Sound Pressure Level in dB LA for Common Situations

Typical Noise Level, dB LA Example

0 Threshold of hearing.

30 Rural area at night, still air.

40 Public library.

Refrigerator humming at a distance of 2m.

50 Quiet office, no machinery.

Boiling kettle at a distance of 0.5m.

60 Normal conversation.




Typical Noise Level, dB LA Example

70 Telephone ringing at a distance of 2m.

Vacuum cleaner at a distance of 3m.

80 General factory noise level.

90 Heavy goods vehicle from pavement.

Powered lawnmower, operator’s ear.

100 Pneumatic drill at a distance of 5m.

120 Discotheque loudspeaker a distance of 1m.

140 Threshold of pain.

10.6.4 The noise level at a measurement point is rarely steady, even in rural areas, and varies over a range dependent upon the effects of local noise sources. Close to a busy motorway, the noise level may vary over a range of 5dB LA, whereas in a suburban area this may increase up to 40 dB LA and more due to the multitude of noise sources in such areas (cars, dogs, aircraft etc.) and their variable operation. Furthermore, the range of night-time noise levels will often be smaller and the levels significantly reduced compared to daytime levels. When considering environmental noise, it is necessary to consider how to quantify the existing noise (the ambient noise) to account for these continuous variations, generally through the use of one of a number of time-averaged parameters.

10.6.5 A parameter that is widely accepted as reflecting the underlying ‘background’ noise level is the LA90 index. This is a statistical value representing the noise level exceeded for 90% of the measurement period and generally reflects the noise level in the lulls between individual noise events. Over a 1-hour period, the LA90 will be the noise level exceeded for 54 minutes. Because it is a statistical value, this parameter is regarded as being relatively ‘stable’ and immune to being adversely affected by short term high noise events.

10.6.6 The equivalent continuous A-weighted sound pressure level, LAeq, is the single number that represents the total sound energy measured over that period. LAeq is the sound level of a notionally steady sound having the same energy as a fluctuating sound over a specified measurement period. It is commonly used to describe environmental noise from individual sources that vary in level over their operational cycle. This value is a measure of the time-averaged sound energy and as such may be elevated by short term high noise events.

10.6.7 The index historically adopted by the Government since the early 1970s to assess road traffic noise is the LA10. This is the noise level exceeded for 10% of the measurement time. Over a 1-hour period the LA10 will therefore be the noise level exceeded for 6 minutes.

10.6.8 Time weighting determines how quickly the sound level meter responds to changes in noise level. The ‘fast’ time weighting averages the measured level every eighth of a second, whereas the ‘slow’ weighting averages every one second. The ‘fast’ time weighting most closely follows the response of the human ear to sound level changes and is most commonly specified for environmental noise measurement purposes (including the LA10 and LA90 statistical parameters).




10.6.9 Most environmental noise measurements and assessments are undertaken in ‘free-field’ conditions, away from any existing reflecting surfaces (other than the ground). However, it is sometimes necessary to consider noise levels immediately external to a façade when considering the impact on residents inside properties and this normally requires the addition of up to 3dB LA to the predicted (or measured) free-field level due to noise reflection from the façade. The assessment of road traffic noise in the UK, for example, is based on a predicted (or measured) ‘façade’ noise level (using the LA10 statistical parameter).

10.6.10 Under normal conditions, human subjects are generally only capable of noticing changes in steady levels of 3dB LA or more (PPG 24, 1994), although noise level changes as low as 1 dB may be perceived under laboratory conditions. It is generally accepted that a change of 10 dB LA in an overall, steady noise level is perceived to the human ear as a doubling (or halving) of the noise level (PPG 24, 1994 (Ref. 10.1). These findings do not necessarily apply to transient, non-steady or intermittent noise sources.

ii) Vibration Prinicples

10.6.11 When an object is in contact with a vibrating surface, it is displaced about its reference (stationary) position. Displacement (in mm) is therefore one parameter that can be used to describe the magnitude of a vibration. For sinusoidal signals, displacement, velocity (m/s) and acceleration (m/s2) amplitudes are related mathematically by a function of frequency and time. If phase is neglected (as is always the case when making time-averaged measurements), then the velocity can be obtained by dividing the acceleration signal by a factor proportional to frequency (measured in Hertz, Hz) and the displacement can then be obtained by dividing the acceleration signal by a factor proportional to the square of frequency.

10.6.12 For a complex acceleration signal giving rise to a complicated time history, there are several additional quantities that may be used to describe the vibration:

The root mean square value (rms) is obtained by taking the square root of the mean of the sum of the squares of the instantaneous acceleration measured during the total measurement time (T);

The peak value is the maximum instantaneous acceleration measured during the measurement time, (T). It is a useful indicator of the magnitude of short duration shocks;

The Peak Particle Velocity (PPV) is the maximum instantaneous velocity of a particle at a point during a given time interval.

10.6.13 The limit of human perception to vibration is of the order of 0.15mm/s to 0.3 mm/s PPV, in the frequency range 0.1 Hz to 1500 Hz. The human body is not equally sensitive to all frequencies of vibration and weighting curves to reflect the frequency dependency of the body have been developed and are contained within the International Organisation of Standardisation (ISO) Standards. The weighting gives a good correlation between the measured vibration level and the subjective feeling or impact produced by the vibration.

10.6.14 The weightings can be incorporated into modern vibration meters, thus enabling measurement of vibration levels that correspond to human perception. Those vibrations occurring between 1-80 Hz are of particular interest when measuring exposure to whole-body vibration.

10.6.15 Sensitivity to vibration is also known to be dependent on the direction of excitation and the human body responds differently when standing (longitudinal) compared to when lying down (lateral). Whole-body vibrations are measured in the directions of an orthogonal co-ordinate system having its origins at the location of the heart, and day and night-time assessment




routines differ to account for longitudinal (daytime) body position and lateral (night-time) body position.

10.6.16 Vibration-induced damage to buildings can arise in different ways, making it difficult to arrive at universal criteria that will adequately and simply indicate damage risk. Damage can occur directly due to high dynamic stresses, due to accelerated ageing, or indirectly when high quasi-static stresses are induced by, for example, soil compaction.

10.6.17 Figure B.1 of British Standard BS 5228: 2009 ‘Code of practice for noise and vibration control on construction and open sites’, Part 2 (Ref. 10.9). ‘Vibration’ indicates, for example, that for a residential building (line 2) a PPV of greater than 15mm/s at 4Hz or greater than 50mm/s at 40Hz or above, measured at the base of the building, may be expected to result in cosmetic damage.

b) Baseline Noise Monitoring

10.6.18 A combination of short-term attended and medium-term unattended measurement were undertaken at the following locations:

North of the Development Site on the site boundary adjacent to the coastal path; Knighton Farm approximately 450m to the south-west of the Development Site; Doggets approximately 30m to the south-east of the Development Site; Wick House approximately 810m to the east of the Development Site; South of the Development Site on the site boundary, approximately 180m north of the

nearest residential receptor location (Bishops Farm House); Hinkley Point Power Station Visitor Centre approximately 500m to the east of the

Development Site; Rodway Road to the south-east of the Development Site and north of Cannington; Chad’s Hill, to the south-east of the Development Site and north-west of Cannington; Combwich to the east of the Development Site; and Northbrook Road to the south-east of the Development Site and south-east of Cannington.

10.6.19 Further details on the monitoring regime and details of the microphone position, as well as a commentary of the significant noise sources at each location are provided in the Factual Noise Report in Appendix 10a.

c) Impact Assessment Methodology

10.6.20 With regard to noise and vibration effects, the standard impact assessment methodology, as set out in Volume 1 Chapter 5, is not readily applicable. This is largely due to the fact that noise and vibration effects are assessed in relation to quantitative noise level criteria and thresholds (see sections below). However, for the purposes of this assessment and in line with the methodologies set out in the Environmental Appraisal, the overall sensitivity and value relates to human receptors living in proximity to either the Development Site or affected highways,have been nominally rated. The overall importance and sensitivity is therefore judged to be Medium for private dwellings within 1km of a source of noise or vibration effects, and Low for dwellings beyond 1km from the nearest noise source.

10.6.21 The significance of identified impacts can therefore be related to the Impact Significance Matrix presented in Volume 1 Chapter 5, once the magnitude of each impact has been predicted in accordance with the relevant guidance methodologies described.

i) Construction

Noise from Construction Equipment




10.6.22 Construction site noise is assessed differently to noise from permanent installations, as it is recognised that construction noise is an inevitable by-product of required works and that the construction works are a transient operation.

10.6.23 Noise levels generated by demolition and construction activities are regulated by guidelines and subject to Local Authority control. Advice is contained within British Standard BS 5228: 2009 ‘Noise and vibration control on construction and open sites’ - Part 1 ‘Noise’ (Ref. 10.9). This document contains a database of the noise emission from individual items of equipment and activities and routines to predict noise from demolition and construction methods to identified receptors. The prediction method gives guidance on the effects of different types of ground, barrier attenuation and how to assess the impact of fixed and mobile plant. Whilst not mandatory, Annex E of this document provides informative advice to aid the development of assessment criteria based on previous published guidance and methodologies adopted successfully for other planning applications.

10.6.24 In assessing the requirement for noise limits, or operating period controls relating to construction works, Government Agencies and Local Authorities generally give consideration to the following aspects of the planned works, all of which have a bearing on the ‘significance’ of the impact:

The duration of the planned construction activities (weeks, months, years); Whether some construction works are planned through the night-time period; The proximity of the construction works relative to residential areas; and The predicted noise level and noise level impact at residential areas.

10.6.25 The proposed criteria for works on the Development Site (including temporary construction areas) are, in general, more stringent than recommended in BS 5228-1: 2009 (Ref. 10.9) Annex E, in light of the proposed duration of construction works. Recommended criteria for construction works are typically referenced to longer time periods (i.e. 12-hour daytime, 4-hour evening or 8-hour night), which allow for more intensive, and more noisy work over shorter periods if the working schedule is well managed. The shorter reference period of 1-hour for all periods as proposed,would therefore provide a stricter control on construction noise emissions throughout the long-term construction schedule. This takes account of the recommendation, in BS 5228-1: 2009 Annex E, for a 1-hour reference period to be adopted for long-term earthworks (i.e. for working periods greater than 6-months).

10.6.26 The proposed noise emission limits for construction activities undertaken within the Development Site are presented in Table 10.2 below.

Table 10.2: Proposed Noise Emission Limits for Construction of Hinkley Point C

Assessment Period Construction Noise Threshold (free-field)*

Day of Week Time of Day dB LAeq,1hour

Monday – Friday 07.00 – 19.00

19.00 – 23.00

23.00 – 07:00

65

60

45

Saturday 07.00 – 19.00 65




Assessment Period Construction Noise Threshold (free-field)*

19.00 – 23.00

23.00 – 07:00

60

45

Sunday and Bank Holidays 07.00 – 19.00

19.00 – 23.00

23.00 – 07:00

60

55

45

Notes: dB re: 20 μPa

* Measured at a noise sensitive receptor location (free-field)

Where LAeq = the equivalent continuous A-weighted sound pressure level, being the single number that represents the total sound energy measured over that period.

Noise levels may be permitted up to 75dB LAeq,1hour for specific works of short duration (such as blasting) where “best practicable means” have been demonstrated to WSC and noise sensitive premises have been informed at least 48 hours in advance.

10.6.27 It should be noted that the noise levels presented in Table 10.2 are limits rather than target values. As the majority of works will occur at a significant distance from receptors in the locality of the site, construction noise levels are, on the whole, predicted to be well below the proposed threshold values.

10.6.28 Based on these values, the noise magnitude scale for use in the prediction of potential impacts is presented in Table 10.3. It should be noted that the values in Table 10.3 are ‘façade’ levels and, therefore a +3dB correction has been applied in accordance with BS 5228:2009.

Table 10.3: Noise Magnitude Scale for Construction of Hinkley Point C

Assessment Period Construction Noise Magnitude (associated with the Development Site) dB LAeq,1hour (free-field)

Day of Week Time of Day Very Low Low Medium High

Monday – Friday 07.00 – 19.00

19.00 – 23.00

23.00 – 07:00

<45

<40

<35

45-55

40-50

35-40

55-65

50-60

40-45

>65

>60

>45

Saturday 07.00 – 19.00

19.00 – 23.00

23.00 – 07:00

<45

<40

<35

45-55

40-50

35-40

55-65

50-60

40-45

>65

>60

>45

Sunday and Bank Holidays

07.00 – 19.00

19.00 – 23.00

23.00 – 07:00

<40

<35

<35

40-50

35-45

35-40

50-60

45-55

40-45

>60

>55

>45




Notes: dB re: 20 μPa

Noise from Construction Traffic

10.6.29 There is no specific guidance for assessing the impact of construction road traffic on public highways. However, given the duration of the proposed construction programme, an assessment has been undertaken using the methodology usually employed for permanent operational road traffic noise impacts.

10.6.30 The Design Manual for Roads and Bridges (DMRB) Volume 11 Section 3 Part 7 (HA 213/08) ‘Noise and Vibration’ (2008) (Ref. 10.17) provides an appropriate method for evaluating both the immediate and long-term impact of abrupt changes in the 18-hour traffic flow (06.00-24.00) in terms of the impacts on people and, principally, occupiers of residential property.

10.6.31 DMRB requires that an assessment is undertaken where an increase in a road traffic flow of 25% or greater is predicted (equivalent to an increase or decrease in road traffic noise of approximately 1dB LA), implying that road traffic flow increases of up to 25% offer no significant impacts in environmental noise terms.

10.6.32 It is generally accepted that changes in road traffic noise levels of up to 3dB LA are not widely perceptible. This is equivalent to a road traffic flow increase or reduction of 50%. Confirmation is provided in Department of Transport ‘Transport Analysis Guidance’ (2007 update), where it is stated:

“For freely flowing traffic, a difference of about 3dB in noise level is required before there is a statistically significant change in the average assessment of nuisance. The assessment of nuisance however could still be affected even if there is only a 1dB change in the noise level if the change is associated with changes in the view of traffic, or if the change occurs suddenly.”

10.6.33 In order to assess the level of community disturbance from potential changes in local road traffic characteristics during the construction phase of the proposed development, an assessment has been undertaken based on the principles of the DMRB Simple Assessment methodology. Although this methodology is designed for the assessment of permanent traffic impacts, it is also considered the most appropriate tool available for the assessment of the long-term construction phase proposed.

10.6.34 The change in Basic Noise Level (BNL), calculated according to the methods given in Calculation of Road Traffic Noise (CRTN), for each road section affected (detailed in Table D1 of Appendix 10d) can then be compared with noise impacts criteria presented in Table 10.4 (the change can be an increase or decrease of noise).

Table 10.4: Guidelines for the Assessment of Magnitude for 18-hour Traffic Noise

Magnitude Guidelines

High Considerable increase in the perceived noise levels typified as a difference of more than 5 dB LA10,T from the existing ambient level.

Medium Noticeable change in the perceived noise levels, typified as a difference of 3 to 4.9 dB LA10,T from the existing ambient level.

Low Perceptible change in the perceived noise levels, typified as a difference of 1 to 2.9 dB LA10,T from the existing ambient level.




Magnitude Guidelines

Very low Generally imperceptible change in the perceived noise levels typified as a difference of 0.1 to 0.9 dB LA10,T from the existing ambient level.

10.6.35 The traffic data used for the road traffic noise impact assessment has been taken from the Paramics micro-simulation traffic model built to assess the effects of the Hinkley Point C development proposals. The Paramics model includes Cannington and Bridgwater and Junctions 23 and 24 of the M5 motorway. The bus and HGV trips are fixed to the network and the remaining development trips are dynamically assigned through the network. For each modelling scenario the output traffic data from the Paramics model was factored using Automatic Traffic Count data to provide 18-hour Annual Average Weekly Traffic (AAWT) data.

10.6.36 In order to determine the overall potential road traffic noise impacts of construction of the Hinkley Point C Project, the following assessment scenarios are examined:

2009 ‘Baseline Year’ (09BY); 2016 ‘Do-Nothing’ (16DN), including forecast traffic growth including committed

development only; 2016 ‘Do-Something’ (16DS), including: forecast traffic growth including committed development; construction of HPC (peak manpower); construction of a Western Bypass of Cannington; and construction of the on and off-site associated developments and incorporated travel plan

measures to mitigate traffic impacts.

10.6.37 2009 was chosen as the baseline year for the assessment as this is the most recent year for which monitoring and traffic data were all available. 2016 was selected to represent the worst-case construction year (i.e. the year with peak construction related traffic movements).

10.6.38 Comparison of impacts determined for each of the scenarios described above will therefore represent an assessment of the overall impacts of the construction traffic relating to the Hinkley Point C Project.

10.6.39 The forecast 2016 ‘Do-Something’ scenario uses data from the ‘with development’ road traffic scenario (Table D2 of Appendix 10d) provided by the traffic consultants. This assumes that a number of travel plan measures are in place during the construction phase of the Hinkley Point C Project. These additional measures (which include the Associated Developments) have been designed to alleviate impacts on the local highway network. As well as reducing traffic congestion and potential impacts on local air quality, these measures will help to reduce noise and vibration impacts from road traffic during the proposed HPC construction phase. These Associated Developments include:

J23 Park and ride facility and freight logistics facilities close to Junction 23 of the Motorway; J24 Park and ride and freight logistics facilities close to Junction 24 of the M5 Motorway; Bridgwater A Contractor accommodation and residential facilities of the A39 Bath Road; Bridgwater C Contractor accommodation and residential facilities at Bridgwater Rugby Club,

off College Way; Cannington Park and ride facility located off the A39, south of Cannington village; Williton Park and ride facility located off Mamsey Lane, west of Williton;




Combwich Upgrade of the existing wharf, and construction of a water-borne freight logistics facility;

Hinkley Point C Workers Accommodation Campus on the main site Southern Construction Phase Area; and

Cannington Bypass to the west of Cannington Village, connecting the A39/High Street roundabout with the C182 Rodway, south of Putnell Barn.

Vibration during Construction

10.6.40 Guidance on assessment of the potential vibration impacts associated with construction activities is provided within British Standard BS 5228: 2009 ‘Noise and vibration control on construction and open sites’ - Part 2 ‘Vibration’ (Ref. 10.9). This document refers to measurement and assessment guidance provided in BS 6472 ‘Guide to evaluation of human exposure to vibration in buildings’ - Part 1: 2008 ‘Vibration sources other than blasting’ (Ref. 10.11) and BS 7385 ‘Evaluation and measurement for vibration in buildings’ - Part 1: 1990 ‘Guide for measurement of vibrations and evaluation of their effects on buildings’ (Ref. 10.11) and, Part 2: 1993 ‘Guide to damage levels from ground-borne vibration’ (Ref. 10.13).

10.6.41 For this type of development, plant such as compressors, pumps, generators and Heavy Goods Vehicles (HGVs) are likely to be the most significant sources of low frequency noise with the potential to cause resonance in nearby buildings, often perceived as vibration by occupants.

10.6.42 Demolition and construction works generally give rise to impulsive and intermittent vibration. In such circumstances, it is necessary to be able to quickly compare the levels against simple criteria which give an immediate evaluation of the likelihood of a problem without recourse to complex post-processing of results. Under these conditions, assessment criteria based on peak particle velocities (PPVs) are most appropriate.

10.6.43 Based on Table B.1 of BS 5228-2, the proposed PPV significance criteria for typical demolition and construction activities (excluding blasting), measured at a sensitive receptor location, are presented in Table 10.5.

Table 10.5: Vibration Significance Criteria (excludes blasting)

Significance Vibration Level (mm/s PPV)

Impact

Very Low 0.14 Vibration might be just perceptible in the most sensitive situations for most vibration frequencies associated with construction. At lower frequencies, people are less sensitive to vibration.

Low 0.3 Vibration might be just perceptible in residential environments.

Medium 1.0 It is likely that vibration of this level in residential environments will cause complaint, but can be tolerated if prior warning and explanation has been given to residents.

High 10 Vibration is likely to be intolerable for any more than a very brief exposure to this level.




10.6.44 In the case of blasting and ripping operations that will be required during the deep foundation excavation phase, the potential impacts have been assessed in accordance with British Standard BS 6472 ‘Guide to evaluation of human exposure to vibration in buildings’ - Part 2: 2008 ‘Blast-induced vibration’ (Ref. 10.14). This document provides a methodology for the prediction of the likely vibration magnitude based on the Maximum Instantaneous Charge (MIC) in kg, and the slant distance from the blast to the receptor in metres. In order to ensure that there are no adverse effects on both existing buildings and fresh concrete, a vibration monitoring scheme will be put in place during this phase of works.

10.6.45 Based on Table 1 of BS 6472-2, the proposed PPV significance criteria for blasting operations, measured at a residential receptor location, are:

Very Low: Generation of PPV below 6 mm/s. Low: Generation of PPV in the range of >6 to <10 mm/s. Medium: Generation of PPV in the range of >10 to <24 mm/s. High: Generation of PPV in excess of 24 mm/s.

10.6.46 The above assumes that blasting and ripping will only be undertaken during daytime hours (08:00-18:00 Mon-Fri, 08:00-13:00 Sat), and that that there will be no more than three blast events per day.

ii) Operation

Industrial Noise

10.6.47 The propagation of operational noise emissions from sources on the proposed HPCC site including: machinery; building vents; and building façades has been predicted in accordance with the International Standards Organisation (ISO) 9613: ‘Attenuation of sound during propagation outdoors’ - Part 2 ‘General method of calculation’ (Ref. 10.15). The operational noise emissions have been modelled using Cadna computational predictive software.

10.6.48 This section provides a summary of the modelling undertaken and full details, including all assumptions made. Input and output data are provided in Appendix 11b. Cadna noise modelling has been used to predict the levels of environmental noise at a distance from a variety of sources. Parameters used within the noise modelling include:

Topography: The existing topography was modelled using 1m LIDAR (Light Reflection and Ranging) data and beyond this area, 10m Ordnance Survey contours were imported into the model. The local topography of the Development Site was adjusted to reflect the proposed platform levels as set out in Volume 2 Chapter 2. Landscaping has not been incorporated into the model predictions as Unit 1 will be operational before the proposed landscaping is complete.

Buildings and other Obstacles: Proposed and existing buildings and cylinders (including chimney stacks) were incorporated within the model. The height of buildings located on the existing Hinkley Point A and B nuclear power generation sites have been estimated, whilst the height of all sensitive receptor buildings has been set to 6m, allowing for properties of up to two storeys.

Noise Sources (Emission Points): Three types of noise sources were included in the model, including point sources, area sources and line sources. The directivity of noise emissions was based upon the source type (e.g. chimney stack exit or building façade) and the source location (openings in building façades).

Ground absorption: All land outside of the Development Site and the existing nuclear power generation sites at Hinkley Point was assigned a sound absorption factor of 1.00 (soft




ground) for the purpose of noise propagation calculations. The remaining ground was assigned a ground absorption factor of 0.20, to account for hard surfaces and small obstacles (machinery, vehicles etc.).

Meteorological conditions: Annual hourly sequential meteorological data generated using the United Kingdom Meteorological Office (UKMO) Numerical Weather Prediction Model was used to define meteorological condition in the noise propagation model. The industrial noise calculation utilises the ISO 9613-2 methodology for the determination of meteorological correction (Cmet). Meteorological conditions assumed for the prediction and calculation of sound emissions include a temperature of 10 ºC and a relative Humidity of 70 %. Additional sensitivity testing was undertaken as detailed in Appendix 10b.

Foliage/woodland areas: Areas of existing foliage have been identified within the model. However, these areas have no acoustic features and are therefore not accounted for within noise propagation calculations.

Reflections: Given the distance separation between the Built Development Areas and the nearest noise sensitive receptors, a single order of reflection was permitted within the model.

Noise Sensitive Locations: Noise sensitive receptors used include Knighton Farm, Doggets and Wick Farm (see Figure 10.1 and Figure 10.2). The baseline noise conditions for these receptors are described in the Factual Noise Report in Appendix 10a.

10.6.49 For the calculation of noise propagation from the built plant, three meteorological scenarios were used:

average wind direction based on hourly data (2004-2008); downwind conditions (2.5 m/s northerly); and neutral (no wind).

10.6.50 BS 4142 (Ref. 10.13) does not specify how wind effects should be accounted for in propagation predictions, only that the calculation method should be reported and reasoned appropriately. Operational noise propagation has been determined based upon all three scenarios to provide an indication of the meteorological effects. The study utilised Cadna A noise prediction model software. Noise propagation calculations were undertaken in accordance with the International Standards Organisation guidance document ISO 9613: Part 2: 1996 ‘Attenuation of sound during propagation outdoors’ (Ref. 10.14).

10.6.51 British Standard BS 4142: 1997 (Ref. 10.13) sets out methodology for rating the acceptability of increases in the background noise level LA90 at noise-sensitive receptors affected by noise from existing or proposed fixed developments including factories and commercial or industrial units.

10.6.52 In Section 9 of BS4142: 1997 ‘Assessment Method’, it is stated that an excess above the existing background noise level LA90 of up to 5dB LA due to the rating noise level from fixed plant at a new development, is of 'marginal significance'. This has been interpreted since the introduction of the Standard in 1967, that a 5dB LA excess due to new, fixed plant noise sources is, in general, acceptable. For this reason, the WSC and SDC EHOs recommended its use within this assessment.

10.6.53 However, BS 4142: 1997 (Ref. 10.13) does not specify how wind effects should be accounted for in propagation predictions, only that the calculation method should be reported and reasoned appropriately. Given the distance separations involved, meteorological conditions may have significant effects on the propagation of noise from the site. Any assessment




methodology based on BS 4142: 1997 (Ref. 10.13) should therefore be based upon noise propagation under neutral weather conditions (no wind).

10.6.54 Furthermore, BS 4142: 1997 (Ref. 10.13) is not suitable for assessing the noise impacts when the background and rating noise levels are both very low (below 30 LA90,T and 35dB LAeq,T respectively), as occurs around the proposal site (refer to Factual Noise Report). Given the rural setting, it is therefore more appropriate to set a fixed target criterion of 43dB LAeq,T for all plant at the façade of nearest noise sensitive receptors, taking into account meteorological conditions that are likely to promote noise propagation from the Site to the receivers. Operational noise impacts have therefore been assessed based on the average wind direction and the worst-case down-wind scenario for comparison with the proposed criterion.

10.6.55 This proposed target noise level would minimise the potential for sleep disturbance in accordance with guidance provided in WHO document ‘Guidelines for Community Noise’ (1999) (Ref. 10.15) and British Standard BS 8233: 1999 ‘Sound insulation and noise reduction for buildings – Code of practice’ (Ref. 10.16), even with windows open.

10.6.56 The rating noise criterion of 43dB LAeq,T is derived based upon achieving an internal noise level of 30 dB LAeq,night within bedrooms. The WHO Guidelines for Community Noise indicates that this represents the noise level at which it is possible to start detecting effects and below which effects can be assumed to be negligible. This is generally considered a conservative and precautionary approach to noise impact assessment. PPG 24 states that a sound reduction of 13 dB LA is expected for a partially open window, therefore 30 + 13 = 43dB LAeq,T outside a bedroom window.

10.6.57 In terms of potential daytime disturbance, this criterion is 7 dB below the level at which the WHO consider to be the onset of moderate annoyance in a small minority (10 %) of the population (50 dB LAeq,16hours).

d) Operational Traffic Noise

10.6.58 As noted in Section 10.2, the impact assessment does not include an assessment of the potential noise impacts associated with road traffic during the operational phase. This assessment will be completed in due course once operational traffic generation figures have been finalised. It is intended that operational road traffic emissions will be assessed for the full Environmental Statement (ES) as part of the application for the DCO. As with the assessment of construction traffic, it is intended that assessment will be undertaken in accordance with the Design Manual for Roads and Bridges (DMRB) Volume 11 Section 3 Part 7 (HA 213/08) ‘Noise and Vibration’ (2008).

e) Further Assessment Work

10.6.59 As described in Volume 1 Chapter 1 this Environmental Appraisal draws upon work undertaken to date to inform the Environmental Impact Assessment (EIA) that will form the basis of an Environmental Statement which will be prepared following the Stage 2 consultation. It is proposed that further assessment work will be undertaken on the potential noise and vibrations effects resulting from the construction and operation of HPC, this is likely to include:

Cadna modelling of the site preparation and ground terracing works; assessment of potential in-combination effects of construction plant and traffic; assessment of potential impacts to other footpaths in the area during construction; assessment of the potential impacts from the construction and operation of the temporary

jetty (however due to the location of nearby sensitive receptors (greater than 1km from the proposed jetty) it is anticipated that these impacts will be negligible); and




assessment of the potential noise impact from operational road traffic.

10.7 Baseline Environmental Characteristics

a) Noise Sensitive Receptors

10.7.1 A noise sensitive receptor is identified as a location where significant changes in environmental noise levels have the potential to cause either detrimental or beneficial impacts. Considered effects typically include influence to the amenity of an area, potential disturbance to sleep, comfortable conversation or entertainment, degradation of an educational environment, or interruption of a religious ceremony.

10.7.2 Noise sensitive receptors in the vicinity of the Development Site have principally been selected according to the likelihood of the impacts listed above to occur, and also to represent a group of locations, on a ‘worst-case’ basis, where similar impacts may occur.

10.7.3 The area around the proposed power station is primarily arable farmland, punctuated by scattered residences, farmhouses, and a number of small hamlets. Three noise sensitive receptors were selected from these, each at a distance greater than one kilometre from the nearest proposed UK EPR reactor unit. The distance to the Development Site boundary for each of these receptors is less than one kilometre as outlined in Section 10.6. During the construction phase, it is proposed that the majority of the works will be undertaken within the Development Site north of the latitudinal line 144750mN. There will be no construction works south of the line during enabling and site preparation, and only limited activities carried out during the main phase. These will include some bunding and surface water attenuation associated with the construction of the accommodation campus and the construction of an emergency access road incorporating a bridge over Bum Brook. The location of noise sensitive receptor locations relative to the Hinkley Point C construction and operation is identified in Figure 10.1 and Figure 10.2.

10.7.4 A summary of the key elements of each phase with respect to potential noise impacts on nearby receptor locations is provided below so that the appropriateness of monitoring location selection is apparent.

b) Baseline Noise and Vibration Surveys

10.7.5 An initial baseline noise survey was undertaken between 27 April and 7 May 2009. The survey methodology and the identification of appropriate monitoring locations were agreed with the HEOs of WSC and SDC prior to the survey.

10.7.6 The baseline noise survey was undertaken to establish the existing acoustic climate at the nearest noise sensitive receptors. Full details of the survey are provided in the Factual Noise Report in Appendix 10a along with a complete set of monitoring data. Table 10.6 below provides a summary of the recorded range of noise levels in measured daytime and night-time LAeq and LA90 data.




Table 10.6: Summary of the Range in Baseline Noise Measurements at Key Noise Sensitive Receptor Locations (Baseline noise survey April – May 2009)

Receptor location Sound pressure level, dB

Day Evening Night

LAeq,T LA90,T LAeq,T LA90,T LAeq,T LA90,T

Northern Development Site boundary (Coastal footpath)

42 - 45 36 - 37 45 41 47 42

Knighton Farm (residential) 44 - 48 30 - 33 37 - 41 26 - 31 43 - 46 26 – 31

Doggets (residential) 40 - 59 32 - 45 35 - 63 30 - 37 35 - 52 27 – 45

Wick Farm (residential) 46 - 60 37 - 46 41 - 45 35 - 41 44 - 47 36 – 38

Southern boundary of the Southern Construction Phase Area

40 - 50 32 - 35 37 29 39 29

Hinkley Point power station – visitors centre

49 - 50 46 - 48 50 48 56 50

10.7.7 Baseline noise measurements were undertaken at a height of between 1.2m and 1.5m above ground level, in free-field conditions, in accordance with BS 7445: 2003 Part 1 ‘Description and measurement of environmental noise – Guide to quantities and procedures’ (Ref. 10.14). All measurements were undertaken during suitable meteorological conditions, conducive to obtaining reliable and accurate baseline data, in accordance with the relevant Guidance documents.

10.7.8 Monitoring locations were selected to be representative of the nearest noise sensitive receptors, which are primarily residential dwellings in a rural setting. In addition, baseline noise measurements were also undertaken at a location in proximity to the coastal public footpath immediately to the north of the Development Site, to assess the potential impacts on this public amenity.

10.7.9 The dominant noise sources identified during the baseline noise survey included local road traffic, birdsong and surf movement (at a coastal monitoring location). The determined ambient noise levels were typical of a rural environment, dropping very low during the night time, and wind noise masking having an observable effect. Further details of baseline noise levels and existing localised noise sources can be found in the Factual Noise Report.

10.7.10 Further noise and vibration surveys were undertaken between Tuesday 20th and Thursday 29th April 2010 in relation to trials to determine noise and vibration levels that might be associated with blasting works. This survey comprised continuous monitoring, at Bayleys Brook House, approximately 1,600m south of the proposed trial blasting pits within Built Development Area West as illustrated in Figure 10.3. A second continuous monitoring was positioned approximately 800m east of the trial blasting pits and approximately 30m west of the Hinkley Point A boundary fence and access gate.




10.7.11 Throughout the monitoring period, the weather was generally dry and with above average temperatures for the time of year. On the day of the blasting tests (22/04/10), an easterly wind prevailed at a speed of 2-7mph; the ambient temperature just exceeded the average maximum high (13°C); and, there was no rainfall.

10.7.12 The results of the second noise monitoring survey are presented in Tables 10.7 and 10.8 and the results of the vibration measurements are presented in Tables 10.9 and 10.10.

Table 10.7: Summary of Ambient Noise Levels – Bayleys Brook House

Monitoring period (start date)

Measurement duration (T)

Sound Pressure Level, dB (fast time-weighting)

LAeq,T LA90,T * LAmax,T

Night (20/04/10) 8 hours 43.2 35.7 72.1

Day (21/04/10) 16 hours 53.8 37.5 93.7

Night (21/04/10) 8 hours 44.9 36.7 80.0

Day (22/04/10) 16 hours 45.9 37.1 80.0

Night (22/04/10) 8 hours 43.5 35.1 65.4

Day (23/04/10) 16 hours 46.5 35.3 86.9

Night (23/04/10) 8 hours 43.9 34.0 73.5

Day (24/04/10) 16 hours 63.8 36.1 103.9

Night (24/04/10) 8 hours 43.8 33.9 67.8

Day (25/04/10) 16 hours 48.2 37.1 83.5

Night (25/04/10) 8 hours 45.8 33.7 75.7

Day (26/04/10) 16 hours 46.1 37.6 78.9

Night (26/04/10) 8 hours 45.2 35.9 74.5

Day (27/04/10) 16 hours 49.9 36.4 80.5

Night (27/04/10) 8 hours 44.0 31.9 68.0

Day (28/04/10) 16 hours 45.1 36.5 74.7

Night (28/04/10) 8 hours 49.4 33.2 82.6

Notes: All values are in dB re 20 μPa, Free-field.

* LA90 values are arithmetic averages of individual 1-minute measurements.




Table 10.8: Summary of Ambient Noise Levels – North of Hinkley Point B Training and Visitors Centre



Sound Pressure Level, dB (fast time-weighting)

LAeq,T LA90,T * LAmax,T

Night (20/04/10) 8 hours 47.3 45.7 66.2

Day (21/04/10) 16 hours 47.0 44.3 72.3

Night (21/04/10) 8 hours 48.8 47.4 69.4

Day (22/04/10) 16 hours 46.8 44.8 72.6

Night (22/04/10) 8 hours 48.9 46.4 85.0

Day (23/04/10) 16 hours 48.2 46.5 71.0

Night (23/04/10) 8 hours 47.5 46.1 69.2

Day (24/04/10) 16 hours 47.7 46.0 74.2

Night (24/04/10) 8 hours 47.5 46.1 68.8

Day (25/04/10) 16 hours 46.3 43.8 71.9

Night (25/04/10) 8 hours 47.8 45.8 69.1

Day (26/04/10) 16 hours 48.1 45.5 81.8

Night (26/04/10) 8 hours 49.0 46.7 66.5

Day (27/04/10) 16 hours 49.1 47.3 70.7

Night (27/04/10) 8 hours 48.7 47.2 67.0

Notes: All values are in dB re 20 μPa, Free-field.

* LA90 values are arithmetic averages of individual 1-minute measurements.




Table 10.9: Summary of Measured Vibration Levels – Bayleys Brook House



Maximum vibration level, dB (fast time-weighting)

Average* Maximum

Night (20/04/10) 8 hours 0.156 0.161

Day (21/04/10) 16 hours 0.158 0.281

Night (21/04/10) 8 hours 0.157 0.161

Day (22/04/10) 16 hours 0.159 0.201

Night (22/04/10) 8 hours 0.155 0.161

Day (23/04/10) 16 hours 0.159 0.161

Night (23/04/10) 8 hours 0.157 0.161

Day (24/04/10) 16 hours 0.160 0.763

Night (24/04/10) 8 hours 0.160 0.161

Day (25/04/10) 16 hours 0.160 0.201

Night (25/04/10) 8 hours 0.160 0.161

Day (26/04/10) 16 hours 0.160 0.402

Night (26/04/10) 8 hours 0.156 0.161

Day (27/04/10) 16 hours 0.160 0.161

Night (27/04/10) 8 hours 0.160 0.161

Day (28/04/10) 16 hours 0.160 0.161

Night (28/04/10) 8 hours 0.160 0.161

Notes: * Average of the ‘30-second maximum’ recorded values.




Table 10.10: Summary of Measured Vibration Levels – North of Hinkley Point B Training and Visitors Centre



Maximum vibration level, dB (fast time-weighting)

Average* Maximum

Night (20/04/10) 8 hours 0.110 0.161

Day (21/04/10) 16 hours 0.090 0.402

Night (21/04/10) 8 hours 0.118 0.161

Day (22/04/10) 16 hours 0.086 0.402

Night (22/04/10) 8 hours 0.113 0.161

Day (23/04/10) 16 hours 0.084 0.161

Night (23/04/10) 8 hours 0.119 0.161

Day (24/04/10) 16 hours 0.079 0.161

Night (24/04/10) 8 hours 0.098 0.361

Day (25/04/10) 16 hours 0.091 0.241

Night (25/04/10) 8 hours 0.104 0.161

Day (26/04/10) 16 hours 0.075 0.161

Night (26/04/10) 8 hours 0.111 0.361

Day (27/04/10) 16 hours 0.073 0.161

Night (27/04/10) 8 hours 0.097 0.161

Day (28/04/10) 16 hours 0.079 0.161

Notes: * Average of the ‘30-second maximum’ recorded values.

10.8 Assessment of Impacts

10.8.1 For assessing the impact of increased noise and vibration levels, the point of reference is either the noise levels identified in Tables 10.2 and 10.3, for construction effects, or the parameters outlined at paragraph 10.6.45 for blasting. With regard to operational noise, the existing noise environment at noise sensitive receptor locations are described above, and detailed in the Factual Noise Report in Appendix 10a.




a) Construction Impacts

i) Potential Noise and Vibration-generating Activities during the Construction Phase

10.8.2 The primary noise and vibration sources during the construction phase are those typical of an industrial construction site. Potential impacts will vary through the following major stages of the development:

Mobilisation; Construction of temporary and permanent access roads and parking areas; Construction of the sea wall defences; Construction and operation of the temporary jetty; Deep excavations and tunnelling; Construction of a workers accommodation campus; Building construction; Construction of the electrical substation; and Blasting operations.

10.8.3 Throughout these stages, the volume of construction traffic on local roads will vary considerably, with the potential to affect noise sensitive receptors along the main road network connecting the Development Site with the M5 motorway to the south-east.

10.8.4 In addition to the above construction activities, noise resulting from occupation of the proposed workers accommodation campus on the Southern Construction Phase Area could have the potential to impact upon existing neighbouring dwellings.

ii) Construction Equipment Noise

10.8.5 In order to evaluate the noise generation during the construction phase, it is necessary to define the various activities that will be undertaken. Construction contractors may use different working methods and plant. However, it is possible to undertake a generic construction assessment of noise and vibration impacts based on expected methods of working gained from experience with previous similar developments. For the purpose of predicting construction noise levels, a series of typical activities have been assessed based on likely closest approach and typical working techniques.

10.8.6 Construction plant that are likely to be used on-site include the following:

excavators; cranes; earthmoving plant; batching plant; compressors; diesel generators; road-going HGVs removing spoils and delivering material (to be minimised by the

construction of a jetty to be used for aggregates and cement delivery); hand held tools such as disc cutters, grinders and nut runners; piling plant; concrete pumping plant and trucks; rock breakers and crushing plant; dewatering pumps; and tunnel boring plant.




10.8.7 For each phase of the development, a full complement of assumed plant, associated sound power level (SWL) and prediction routines, to the requirements of BS 5228-1, is included in the tables in Appendix 10e. The BS 5228-1 prediction method uses the shortest distance from the receptor to the construction activities. The nearest edge of the relevant construction site has been used as the calculation point for equipment/plant classed as ‘mobile’ (loaders, excavators etc.) and similarly the edge of the site has been used as the calculation point for equipment/plant classed as ‘fixed’ (generators, compressors etc.).

10.8.8 Predictions of construction activity noise levels at the receptor locations has taken into account of features that may affect propagation, such as ground absorption; and, screening by the natural and/or formed topography. Other factors, such as the length of the working traverse and the machinery ‘on-time’ are also included within the calculations.

10.8.9 Predicted noise levels, detailed in Appendix 10e and summarised in Table 10.11, are therefore a worst-case basis, and in practice, the actual noise levels may not attain those predicted. It should be noted that predicted noise levels are based upon the assumption that standard good construction practice measures will be applied. Such measures to control noise nuisance impacts are outlined in BS5228-1: 2009. Therefore, source noise data, used in the construction noise calculations, for specified plant (provided in BS5228-1) is based upon well-maintained equipment, and where appropriate,integral acoustic enclosures.

10.8.10 Further assumed standard good construction practice outlined in BS5228-1: 2009 will include:

Continuous noisy plant to be housed in acoustic enclosures; Use of electrical items of plant instead of diesel plant in especially sensitive locations; Exhaust silencing and plant muffling equipment to be maintained in good working order; Avoid unnecessary revving of engines and switch off equipment; Keep internal haul routes well maintained and avoid steep gradients, where possible; Minimise drop height of materials; Start up plant and vehicles sequentially rather than all together; and Loading/unloading sites to be located away from residential properties and shielded from

those properties, where practicable.

10.8.11 These measures will be included within the Construction Environmental Management Plan (CEMP) for the consruction of HPC.




Table 10.11: Summary of Worst-case Predicted Construction Noise Levels at the Nearest Receptor Locations to Hinkley Point C Construction Works based on BS 5228 Calculations (excluding existing ambient noise)

Residential Location

Predicted worst-case night-time noise levels#, dB LAeq,1h

Construction phase

1 2 3 4 5 6 7 8 9 10 11

Knighton Farm 32 23 46 45 46 30 24 34 29 29 45

Doggets 41 26 46 34 44 40 26 38 58 32 69

Bishops Farm House

31 23 56 70 49 31 24 34 43 37 48

Wick Farm 30 22 28 27 42 30 22 33 40 34 41

Notes: Key for construction phases:

1. Upgrade of roads

2. Seawall construction

3. Construction of bridge over Bum Brook

4. Construction of emergency access road

5. Deep excavation and concrete substitution

6. Construction of temporary and permanent buildings (non-nuclear)

7. Tunnelling

8. Construction of nuclear island buildings

9. Construction of on-site accommodation campus

10. Construction of the substation

11. Final landscaping

# Predicted construction noise levels do not include existing ambient noise levels

10.8.12 The predicted construction noise levels do not include existing ambient noise levels at the respective receptor locations and are therefore, not measurable for comparison with the proposed noise limits in Table 10.2. Baseline ambient noise levels have therefore been added to the predicted construction noise levels above, and presented in Table 10.12 below. The baseline ambient values used are the arithmetic mean of the measured daytime (07:00-19:00) LAeq,15min values.




Table 10.12: Summary of Worst-case Predicted Daytime Construction Noise Levels at the Nearest Receptor Locations to Hinkley Point C Construction works based on BS 5228 Calculations

Residential Location

Predicted worst-case night-time noise levels#, dB LAeq,1h

Construction phase

1 2 3 4 5 6 7 8 9 10 11

Knighton Farm 46 46 49 48 49 46 46 46 46 46 48

Doggets 46 45 48 45 47 46 45 46 58 45 69

Bishops Farm House

41 41 56 70 50 41 41 42 45 42 49

Wick Farm 46 46 46 46 47 46 46 46 47 46 47

Notes: Key for construction phases:

1. Upgrade of roads

2. Seawall construction

3. Construction of bridge over Bum Brook

4. Construction of emergency access road

5. Deep excavation and concrete substitution

6. Construction of temporary and permanent buildings (non-nuclear)

7. Tunnelling

8. Construction of nuclear island buildings

9. Construction of on-site accommodation campus

10. Construction of the substation

11. Final landscaping

# Predicted construction noise levels include the arithmetic mean of the measured baseline ambient daytime noise levels (LAeq,15min) at receptor locations between 07:00 and 19:00. (Ambient noise levels: Knighton Farm = 42 46 dB LAeq,T; Doggetts = 44 45 dB LAeq,T; Bishops Farm House = 40 41 dB LAeq,T; Wick Farm = 46 dB LAeq,T).

10.8.13 From Tables 10.11 and 10.12 and the detailed calculations in Appendix 10e, it can be seen that, during short-term activities associated with construction of the emergency access road, close to Bishops Farm House, the daytime 65dB LAeq,1h criterion is likely to be exceeded.

10.8.14 Similarly, worst-case predicted noise levels during final landscaping operations at the closest approach to the south boundary of the Southern Construction Phase Area are likely to exceed the adopted 65dB LAeq,1h daytime criterion proposed for residential dwellings. It has been assumed that the closest approach for these activities would be 50m, 400m and 540m for Doggets, Bishops Farm House and Knighton Farm, respectively.




10.8.15 The duration of works along the southern site boundary will be limited, and therefore it is proposed that less stringent noise threshold criteria be adopted for the period during which spoil placement is taking place in proximity to the southern site boundary. To justify this, it is proposed that topsoil removed from the Development Site during the preliminary site preparation works may be stored at this southern area. This could form an earth bund wall, to be located approximately 30m north of Doggets property boundary line, constructed in an east-west orientation. With an approximate height of 5m, this could screen subsequent activities to the north. Permitting these works, with higher noise levels in the shorter-term (up to six weeks), will provide a significant benefit to the long-term noise impacts at Doggets, and may provide slight benefits at other nearby dwellings.

10.8.16 As a result of this worst-case assessment with all plant working at the closest approach, the overall impact for the closest properties (Doggets and Bishop’s Farm House) of construction noise during construction of the emergency access road and for short periods during the final landscaping operations is assessed as Major adverse. However, it should be noted that the nature of construction work means that the worst-case situation with the plant working at closest approach may exist for only a matter of days or even hours and there would be regular periods, even during the course of a single day, when the assumed noise plant would not be in operation during breaks or changes of working routine.

10.8.17 The noise impact of all other construction activities associated with the Development Site as identified in Tables 10.9 and 10.10, without mitigation, is assessed as Negligible to Moderate adverse due to a combination of the additional distance attenuation and physical screening by the natural and formed topographical features.

iii) Occupation of the Construction On-site Accommodation Campus

10.8.18 This on-site accommodation campus will be located north of the proposed landscape bund, with the nearest residential accommodation blocks positioned approximately 100m north of Doggets.

10.8.19 The closest campus amenities (such as shops and leisure facilities) will be approximately 180m north of Doggets. Mechanical service units (including air-conditioning and refrigeration plant) associated with amenity buildings will therefore be located at a significant distance from existing residential dwellings. Furthermore, there is the opportunity for these items of plant to be located on the northern facades of the respective buildings, thereby providing significant acoustic screening. Similarly, building elements of leisure facilities will be designed to sufficiently reduce noise breakout, notably from the sports hall and cinema.

10.8.20 Acoustic design and control measures will be incorporated to ensure that noise emissions for occupation and amenity use do not exceed 5dB above the LA90,T background level at the nearest existing residential properties. The overall noise impact upon existing residential dwellings is therefore assessed as Minor adverse. As set out in Volume 1 Chapter 5 on EIA methodology, only those impacts which have been assessed as being of potentially greater than minor adverse significance require mitigation to reduce predicted impacts to acceptable levels. However, the creation of the proposed landscaped bund could provide some screening to nearby sensitive receptors. Further modelling and assessment is required to determine the level of screening the landscaped bund would provide, this will be undertaken for the main EIA and ES as part of the application for the DCO.

iv) Construction Traffic Noise

10.8.21 Noise from road traffic generated during the construction phase will have the potential to impact upon occupants of residential dwellings and other sensitive receptors, such as schools




and places of worship, aligning the local highway network. The peak levels of construction traffic are expected to be generated in 2012 (peak HGV movements) and 2016 (peak manpower). The predicted distribution of the generated construction works traffic on the local highway network in these years has been used to assess the potential noise impacts by comparison with the ‘Do-Nothing’ scenario in the corresponding year, as described in Section 10.6.

10.8.22 Table E.3 of Appendix 10e presents the calculated Basic Noise Level (BNL), including correction for percentage HGV content and average vehicle speed, for each assessed road section.

10.8.23 Comparison of the calculated BNL for the 2016 ‘Do-Nothing’ and ‘Do-Something’ scenarios indicates that the potential change in road traffic noise due to construction traffic ranges from +0.1 to +0.5dB for all but one road section. A change of -2.5 dB in road traffic noise is predicted along the C182 Rodway between High Street and the proposed Cannington bypass roundabout.

10.8.24 Therefore, in 2016 the magnitude of construction traffic noise is considered to be ‘Very Low’ when compared with the criteria in Table 10.4, and the overall noise impact of construction traffic in 2016 is assessed as Minor adverse, and therefore no mitigation is necessary.

v) Blasting Noise and Vibration

10.8.25 During deep excavation, blasting of the bedrock will be required. This is likely to involve drilling of a number of boreholes within a rock face, into which are placed the necessary explosive charges. Blast events will be localised and therefore a minimum explosive charge will used to achieve the required rock extraction rate.

10.8.26 Blasting events, however, can be a cause for concern for neighbouring residents due to the sound, which will heighten senses, followed by the possibility of secondary vibrations at audible frequencies caused by air overpressure. This is only likely to occur following surface blasting, where topographical screening of the air overpressure is minimal. In respect of possible effects of this, BS 6472-2 states that there is “…no known evidence of structural damage occurring in the United Kingdom as a result of air overpressure levels from blasting associated with mineral extraction”. The subjective response of a receiver to this air overpressure is often unrelated to the magnitude of the associated groundborne vibration, which in some cases is not actually perceptible.

10.8.27 Three trial blasts (B-BBH1, B-BBH2 and B-BBH3) were undertaken within the Built Development Area West April 2010, to determine the reaction of the bedrock to blasting, and to assess the potential vibration impacts. During this time, continuous monitoring of both noise and vibration was undertaken at two locations:

west of the Hinkley Point A site boundary; and Bayleys Brook House (residential dwelling) in Shurton.

10.8.28 The monitoring results are presented in the survey report ‘Blasting Test Noise and Vibration Monitoring Factual Report’ (see Appendix 10c).

10.8.29 Figures 10.4 to 10.7 present the noise and vibration levels measured during trial blasting studies within the Development Site which were undertaken to determine the nature of the levels that could occur at potentially sensitive receptors. As set out in Section 10.6, measurements were undertaken at Bayleys Brook House and close to the boundary of Hinkley Point A. The figures clearly indicate that vibration levels from blasting operations are unlikely to exceed the negligible significance criteria (6mm/s) identified in section 10.6.45. Only blast event B-BBH2 registered an observable increase in vibration above the background level at Bayleys Brook House. This maximum recorded PPV level (0.201 mm/s) is below the 0.3 mm/s




level that BS 5228-2 suggests “…might be just perceptible in residential environments”. It is however, above 0.14 mm/s, the level at which BS 5228-2 states that “…might be just perceptible in the most sensitive situations for most vibration frequencies associated with construction.”

10.8.30 It should be noted that good practice for community relations and health and safety, i.e. notifying the community of planned blast events, and the pre-blast alarm, both serve to raise the sensitivity of local residents to both noise and vibration. Therefore, vibrations may have been perceived by alerted residents.

10.8.31 Peak vibration levels from the blast events are more clearly discernible in the measurement data obtained at the Hinkley Point A monitoring location, approximately half the distance (but in a different direction) from the blast site. However, the generated vibration levels at this location were again well below the negligible significance criteria (6mm/s).

10.8.32 It is difficult to be certain of the exact cause of the measured LAmax during a given 1-minute measurement period. However, the maximum A-weighted instantaneous noise level at Bayleys Brook House did not exceed 65dB LAmax,T as a result of the trial blasts.

10.8.33 Overall, it is concluded that the vibration magnitude of blast events, although possibly perceptible to alerted residents, was determined to be ‘Very Low’ in relation to nuisance impacts. Cosmetic damage to buildings is highly unlikely as threshold values for buildings are much higher than those for perception and disturbance used in this study.

10.8.34 It is, therefore, predicted that the blasting noise and vibration would have a Negligible impact on the nearest potentially affected receptors of low to medium importance and sensitivity.

Figure 10.4: Measured Noise and Vibration Levels at Bayleys Brook House during Blast Event B-BBH2

B-BBH2 (Bayleys Brook House) 22/04/10

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Figure 10.5: Measured Noise and Vibration Levels at Hinkley Point A during Blast Event B-BBH2

Figure 10.6: Measured Noise and Vibration Levels at Bayleys Brook House during Blast Events B-BBH3 and B-BBH1

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Figure 10.7: Measured Noise and Vibration Levels at Hinkley Point A during Blast Events B-BBH3 and B-BBH1

vi) Non-blasting Vibration Impacts

10.8.35 Surface plant such as cranes, compressors and generators are not recognised as sources of high levels of environmental vibration. Reference to Figure 1 of ‘Control of Vibration and Noise during Piling’ (British Steel, 1998) confirms that, even at a closest distance of 10m, peak particle velocities (PPV) significantly less than 5 mm/s are generated by such plant. For example, a bulldozer may generate a PPV of approximately 0.6mm/s and a ‘heavy lorry on poor road surface’ a PPV of less than 0.1mm/s at 10m. These values are well below limits at which even cosmetic building damage becomes likely (5mm/s).

10.8.36 Two methods of piling are presently proposed on the Development Site. These are vibratory sheet piling and continuous flight augur (CFA) piling. Each of these generate relatively low levels of vibration compared with hammer driven piling techniques. Given the distance separations between the site of potential piling operations and the nearest residential dwellings (greater than 1km), vibration levels generated during normal construction activities on the Southern Construction Phase Area are likely to be well below the perceptibility level. Notwithstanding this, vibration impacts will be minimised to ensure sensitive activities and machinery associated with nuclear power generation at the operational Hinkley Point B site (approximately 600m to the east) are not adversely affected by the works. Vibration impacts of typical construction activities on the Development Site are assessed as Negligible at the nearest residential receptors.

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b) Mitigation of Construction Impacts

10.8.37 British Standard BS 5228: Part 1: 2009 gives detailed advice on standard good construction practice for minimising nuisance from construction noise. This can take the form of reduction at source, control of noise spread, and in areas of very high noise levels, insulation at receptors. It is likely to be a requirement of any construction contract that the constructors comply with the recommendations in this standard, in order to achieve specific noise limit criteria for each site.

10.8.38 With regard to the blasting operations, as with standard construction activities, blasting events (if required) will be designed to ensure Hinkley Point B operations are not adversely affected. This provision will also ensure that impacts at the nearest residential dwellings (a further 400m from events) are suitably minimised.

10.8.39 Additional, site-specific mitigation measures may be agreed with HEOs of WSC and SDC through the use of their prior approval powers under Section 61 of the Control of Pollution Act 1974. Potential mitigation measures being explored by EDF Energy to reduce potential noise and vibration impacts include:

Development of landscape bunds to protect sensitive receptors near to the site; Noisy night time working on the Development Site to be kept to a minimum and the normal

working day to be used, wherever possible; During blasting operations, measurement of vibration in terms of PPV will be required at the

nearest respective receptor location to ensure compliance with the exposure criteria; and Blasting activities will be conducted during daytime hours only and local residents will be

given advance warning of their occurrence.

10.8.40 It is proposed that an east-west landscape bund will be created to the south of the on-site accommodation campus as part of the construction of this facility following the site preparation and ground terracing works in 2012. The bund will help to mitigate potential construction-related impacts (visual, noise and air quality) on local residents and users of the surrounding area, in particular Doggets. It is also proposed that a landscape bund will be provided to the west of the Development Site along Benhole Lane, north of OS 144750mN to screen site preparation and storage activities undertaken during this part of the construction phase.

c) Residual Construction Impacts

10.8.41 The proposed landscaped bund to be constructed to the south of the on-site accommodation campus will screen subsequent works from noise sensitive receptors. During this initial period before the bund in constructed, the operation of earthworks machinery such as dozers and spoil trucks in closest possible proximity to Doggets, and to a lesser extent Bishops Farm House, is likely to result in the proposed daytime noise criteria of 65dB LAeq,1hr being exceeded. However, given the short-term nature of these works at this location (likely to be less than one month), the predicted noise levels should be acceptable when balancing the potential long-term benefits of an landscape bund construction. It is therefore considered that the residual impacts for the entire construction phase, with the exception of blasting, will be long-term, temporary and Negligible to Minor.

10.8.42 The potential noise impacts of blasting are predicted to be of negligible significance; the mitigation measures suggested will not alter the quantitative blasting noise but will ensure that perceived disturbance is minimised. The residual noise impact of blasting, therefore, remains as Negligible significance.

10.8.43 Controls measures adopted to ensure no adverse construction vibration impacts to ongoing nuclear power generation at Hinkley Point B should provide sufficient protection to the nearest




sensitive receptors. It is therefore assessed that vibration impacts during the construction phase, including blasting, will be Negligible.

10.8.44 Potential noise impacts on nearby sensitive receptors, in particular Doggets which is considered to be of medium sensitivity (see paragraph 10.6.20), from the occupation of the on-site accommodation campus, including operation and use of the proposed amenities have been assessed as Minor adverse. No mitigation is necessary, however the proposed landscaped bund could provide a level of screening.

10.8.45 Residual construction traffic noise impacts will be included, once traffic data are available. Analysis of the predicted change in 18-hour daytime road traffic noise during construction of the proposed nuclear power station in the peak construction year (2016) is assessed as Minor adverse. This is based upon all proposed Associated Development sites being in operation.

d) Operation Impacts

i) Potential Noise-generating Activities during the Commissioning and Operational phase

10.8.46 Once the construction phases are complete for each UK EPR reactor unit, they will undergo commissioning which will last approximately two years per unit. The commissioning phase will involve a number of activities that are likely to generate noise emissions with atypical characteristics; especially during the testing of essential standby plant such as the diesel generators and the overspeed tests of the steam turbines, which may emit high frequency sounds during high pressure leak tests of the water circulation and nuclear steam supply systems.

10.8.47 The primary sources of noise during the operation of HPC relate to the operation UK EPR reactor unit include the following:

The discharge stack; Air entry and exit openings; Ventilation openings; Pumping stations; Steam pipes situated on the Reactor building; and Equipment situated in the Turbine Hall (such as transformers).

10.8.48 In addition to site plant noise, the there will also be operational traffic-related noise effects; the operation of HPC will require a workforce of approximately 900 staff in total, which will generate additional traffic on the highway network. Additional heavy vehicular traffic and workforce traffic will also be generated for materials delivery during maintenance and refuelling outages, where it is anticipated that a further 600-1000 staff would be required.

10.8.49 This impact assessment does not include an assessment of the potential noise impacts associated with road traffic during the operational phase. This assessment will be completed in due course once operational traffic generation figures have been finalised.

ii) Commissioning Activities

10.8.50 During the commissioning tests, some activities are likely to generate noise emissions with atypical characteristics; such high frequency sounds emitted during high pressure leak tests of the water circulation and nuclear steam supply systems. Given the possible magnitude of sound pressure levels likely to be generated, and the distinctive nature, pressure release following these tests may be audible at a number of the nearest receptor locations. However, events are likely to be very short-term (no more than a few minutes each), and short-term. Other




activities undertaken during the commissioning phase are unlikely to generate noise emissions in excess of the fully operational HPC. Given the short-term nature of these activities, the overall noise impact of commissioning testing is assessed as Negligible, and therefore no mitigation is necessary.

iii) On-site Plant Equipment Noise

10.8.51 The propagation of operational noise emissions from sources on the HPC, including machinery, building vents and building façades, have been modelled using Cadna computational predictive software. The model scenarios and assumptions of this modelling study are described in detail in Appendix 10b. Table 10.11 below provides a summary of the predictive façade noise level at three neighbouring noise sensitive receptor locations. These locations correspond to background noise measurement locations detailed in the Factual Noise Report (note: background measurements were undertaken in free-field conditions).

10.8.52 Table 10.13 below provides a summary of the results of the predictive modelling work for façade noise level at three neighbouring noise sensitive receptor locations. These locations correspond to background noise measurement locations detailed in the Factual Noise Report (note: background measurements were undertaken in free-field conditions). Figure 10.8 presents the predicted noise contours for the of operational noise emissions. However it should be noted that this figure represents a worst-case scenario, assuming that all plant and machinery is operating simultaneously, including worst-case operation of emergency and stand-by generators, which would only operate for maximum of 81 hours per year during down periods (see Chapter 4 of this volume). Figure 10.8 presents a 10m x 10m contour grid, at 4m AOD, calculated using the worst-case downwind scenario.

Table 10.13: Predicted Operational Noise Level at Nearest Receptor Dwellings (façade) in Proximity to the Development Site based on Prediction Modelling

Ref. * Receptor Predicted Sound Pressure Level, dB (Façade)

LAT (Average wind direction)

LAT(DW) Downwind (Northerly 2.5 m/s)

LAT Neutral (no wind)

ML2 Knighton Farm 34.7 41.6 36.4

ML3 Doggets 33.6 40.3 35.8

ML4 Wick Farm 33.9 35.0 35.0

Note: * Reference locations identified in Figures B6 and B.8 in Appendix 10b, and refer to Factual Noise Report identifiers.

10.8.53 The acceptable operational noise criterion typically recommended by West Somerset Council is 5dB above background. However, this criterion is based upon the BS 4142: 1997 assessment methodology which states that it is not applicable “when background and rating noise levels are both very low” (below 30 LA90,T dB and 35dB LAr,T). The baseline noise survey, detailed in the Factual Noise Report, subsequently determined that background noise levels do fall below the 30dB LA90,T criterion at night (refer to Table 10.4), as typical of a rural location. Table 10.14 shows the predicted impacts under neutral conditions which neither favour nor discriminate against propagation from source to receiver, in accordance with this methodology. The




background noise levels used in this assessment are the lowest measured values to provide an absolute worst-case assessment.

Table 10.14: Assessment of Predicted Specific Noise Levels during Operation of two UK EPR Units at Hinkley Point C against the Lowest Measured Background Noise Levels at the Nearest Receptor Locations

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ML2 Knighton Farm 33.4 30 26 +3.4 +7.8 No

ML3 Doggets 32.8 32 27 +0.8 +5.8 No

ML4 Wick Farm 32.0 37 36 -5.0 -5.0 Yes

Note: * Reference locations identified in Figures B.6 and B.8 in Appendix 10b, and refer to Factual Noise Report identifiers.

10.8.54 The assessment indicates that predicted noise levels could prove unacceptable during quiet night-time periods in accordance with the guidance recommended by WSC, and based upon BS4142. However, BS 4142 states that it is not applicable in low noise level situations such as determined at all three locations (except background levels at Wick Farm). It is therefore more reasonable to adopt the specific target criterion of 43dB LAr,T for the total noise emissions from all plant operating on the HPC site, measured at the façade of the nearest residential property. This is derived based upon achieving an internal noise level of 30dB LAeq,night within bedrooms. The WHO Guidelines for Community Noise indicates that this represents the noise level at which it is possible to start detecting effects and below which effects can be assumed to be negligible. This is generally considered a conservative and precautionary approach to noise impact assessment.

10.8.55 In terms of potential daytime disturbance, this criterion is 8dB below the level at which the WHO consider to be the onset of moderate annoyance in a small minority (10 %) of the population (50dB LAeq,16hours).

10.8.56 The predictions in Table 10.14 indicate that even during worst-case meteorological conditions (light wind from the site to the receiver point) it is unlikely that this limit criterion of 43dB LAeq,T would be exceeded. Therefore, the overall noise impact of operation of the proposed Hinkley Point C nuclear power station will be Minor adverse. The application of noise mitigation measures should be considered to attenuate noise emissions from the most significant sources identified by the modelling exercise. These include:

Main stack exhaust points; Roof-mounted refrigeration plant; Steam pipes;




Transformer buildings; and Turbine buildings.

10.8.57 In particular these measures should ensure that no noise emissions contain acoustic features which may accentuate the likelihood of disturbance, as defined in Section 8 of BS 4142: 1997. Possible acoustic features include:

a distinguishable, discrete, continuous note (whine, hiss, screech, hum etc.); distinct impulses (bangs, clicks, clatters, or thumps); or a noise irregular enough to attract attention.

10.8.58 Potential sound mitigation to minimise the possible long-term impacts of operational noise are discussed below.

e) Mitigation of Operational Noise

i) Tonal and Impulsive Quality

10.8.59 The 'rating' of a noise automatically increases when tones, whines or impulses are noticed in the audible noise. Care will therefore be taken, both in identifying particular tonal and impulsive sources on the plant and to ensure that these will be adequately silenced by design. The most significant sources of tonal energy are likely to be fans, which will produce tonal noise typically at blade passing frequency. Transformers will also contain middle to low frequency tonal energy at the second and fourth harmonics (100 Hz and 200 Hz).

ii) Equipment Noise Control Treatment

10.8.60 The final noise emissions from selected equipment items may require variations in the nature and extent of required noise control treatments. Treatments that will be considered for the scheme, as appropriate, are listed below:

acoustic attenuators on exhaust stacks, ventilation intakes and discharge points; steam vents to be fitted with vent silencers; acoustic barriers and enclosures; and lagging of steam pipes and control valves.

10.8.61 The noise prediction modelling exercise indicated that, even during worst-case meteorological conditions, the proposed target criterion is unlikely to be exceeded.

f) Residual Operation Impacts

10.8.62 The detailed noise propagation modelling exercise identified that the most significant noise sources include the two main stack exhaust points, roof-mounted refrigeration units, the turbine buildings and the main transformer buildings.

10.8.63 The overall operational noise impact of the proposed nuclear power station is therefore assessed as long-term Minor.

10.8.64 Vibration attenuation measures adopted to ensure no adverse operational impacts to ongoing nuclear power generation at Hinkley Point B, as well as the proposed Hinkley Point C power station itself, should provide sufficient protection to the nearest sensitive receptors. It is therefore assessed that vibration impacts once fully operational, will be Negligible.




References

10.1 Planning Policy Guidance: Planning and Noise PPG 24, September 1994, Department of the Environment.

10.2 Report 15011/TR/00155 ‘Blasting Tests - Noise and Vibration Monitoring Factual Report’. Amec, 2010.

10.3 Draft Regional Spatial Strategy to the South West (2006-2026). South West Assembly in 2006

10.4 The Regional Strategy for the South West Environment 2004-2014 – “Our Environment: Our Future”. The South West Regional Assembly in association with the South West Regional Environment Network

10.5 West Somerset Local Plan. West Somerset Council, 2006

10.6 Somerset District Local Plan (1991-2011 Adopted Version). Somerset County Council

10.7 British Standard BS 5228: 2009 ‘Code of practice for noise and vibration control on construction and open sites’. Part 1. ‘Noise’. British Standards Institution, 2008. ISBN 978 0 580 56048 4.

10.8 Calculation of Road Traffic Noise. The Department of Transport and The Welsh Office, 1975 and 1988. ISBN 0 11 550847 3.

10.9 British Standard BS 5228: 2009 ‘Code of practice for noise and vibration control on construction and open sites’. Part 2. ‘Vibration’. British Standards Institution, 2008. ISBN 978 0 580 56049 1.

10.10 British Standard 6472: 2008 ‘Guide to evaluation of human exposure to vibration in buildings’ Part 1: Vibration sources other than blasting’. British Standards Institution, 2008. ISBN 978 0 580 53027 2.

10.11 British Standard 7385: 1990 ‘Evaluation and measurement for vibration in buildings — Part 1: Guide for measurement of vibrations and evaluation of their effects on buildings, 1990.

10.12 British Standard 7385: 1993 ‘Evaluation and measurement for vibration in buildings — Part 2: Guide to damage levels from groundborne vibration, 1993. ISBN 0 580 22188 1.

10.13 British Standard BS 4142: 1997 ‘Rating industrial noise affecting mixed residential and industrial areas’. British Standards Institution, 1997. ISBN 0 580 28300 3.

10.14 British Standard BS 7445:2003 Part 1 ‘Description and measurement of environmental noise – Guide to quantities and procedures’. British Standards Institution, 2003. ISBN 0 580 43032 4.

10.15 Guidelines for Community Noise, World Health Organisation, 1999.

10.16 British Standard BS 8233: 1999 ‘Sound insulation and noise reduction for buildings – Code of practice’ British Standards Institution, 1999. ISBN 0 580 33009 5.

10.17 Design Manual for Roads and Bridges - Volume 11 “Environmental Assessment” – Section 3 – “Environmental Assessment Techniques”, Part 7 HA 213/08, Noise and Vibration1994. The Highways Agency, 2008.

10.18 WebTag ‘Transport Analysis Guidance’ Website: http://www.webtag.org.uk/. Department for Transport. Update February 2007.

10.19 British Steel, 1998. ‘Control of vibration and noise during piling’.

10.20 The Control of Pollution Act 1974. The Stationary Office.

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