10 NOISE AND VIBRATION

Transcription

1 10 NOISE AND VIBRATION 10.1 Introduction 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 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 Scope of Assessment 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 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 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 Objectives of Assessment 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 HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL APPRAISAL VOLUME 2 1

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 Legislation, Policy and Guidance 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) 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 PPG 24 (Ref. 10.1) was introduced by the Department of the Environment in 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 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 ( ) The draft RSS (Ref. 10.3) was published by the South West Assembly in The areas of the Strategy for which noise issues are highlighted are reproduced below: 2 HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL STATEMENT VOLUME 2

3 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 Our Environment: Our Future 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 Somerset A Landscape for the Future 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 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 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; HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL APPRAISAL VOLUME 2 3

4 ii iii 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 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 The implementation of this legislation is the responsibility of the Environmental Health Unit. ii) Sedgemoor District Local Plan ( Adopted Version) 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 Key Consultations 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 A second consultation meeting was held with WSC and SDC in October 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 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 The following advice and direction was provided by WSC and SDC, which has been taken into account within this assessment: 4 HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL STATEMENT VOLUME 2

5 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) Methodology a) Noise and Vibration Principles This section sets out the noise and vibration principles which have formed the basis of the noise and vibration assessment. i) Noise Principles 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) 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. HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL APPRAISAL VOLUME 2 5

6 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 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 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 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 timeaveraged sound energy and as such may be elevated by short term high noise events 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 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). 6 HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL STATEMENT VOLUME 2

7 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) 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 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 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 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 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 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 HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL APPRAISAL VOLUME 2 7

8 routines differ to account for longitudinal (daytime) body position and lateral (night-time) body position 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 quasistatic stresses are induced by, for example, soil compaction 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 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 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 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 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 8 HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL STATEMENT VOLUME 2

9 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 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 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 The proposed criteria for works on the Development Site (including temporary construction areas) are, in general, more stringent than recommended in BS : 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 : 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) 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 : Saturday HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL APPRAISAL VOLUME 2 9

10 Assessment Period Construction Noise Threshold (free-field)* :00 Sunday and Bank Holidays : 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 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 Based on these values, the noise magnitude scale for use in the prediction of potential impacts is presented in Table 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 < > < > :00 < >45 Saturday < > < > :00 < >45 Sunday and Bank Holidays <40 < >60 > :00 < >45 10 HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL STATEMENT VOLUME 2

11 Notes: db re: 20 μpa Noise from Construction Traffic 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 The Design Manual for Roads and Bridges (DMRB) Volume 11 Section 3 Part 7 (HA 213/08) Noise and Vibration (2008) (Ref ) provides an appropriate method for evaluating both the immediate and long-term impact of abrupt changes in the 18-hour traffic flow ( ) in terms of the impacts on people and, principally, occupiers of residential property 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 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 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 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. HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL APPRAISAL VOLUME 2 11

12 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 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 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 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 was selected to represent the worstcase construction year (i.e. the year with peak construction related traffic movements) 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 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; 12 HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL STATEMENT VOLUME 2

13 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 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 ) 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 ) and, Part 2: 1993 Guide to damage levels from ground-borne vibration (Ref ) 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 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 Based on Table B.1 of BS , the proposed PPV significance criteria for typical demolition and construction activities (excluding blasting), measured at a sensitive receptor location, are presented in Table 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. HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL APPRAISAL VOLUME 2 13

14 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 ). 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 Based on Table 1 of BS , the proposed PPV significance criteria for blasting operations, measured at a residential receptor location, are: Very Low: Low: Medium: High: Generation of PPV below 6 mm/s. Generation of PPV in the range of >6 to <10 mm/s. Generation of PPV in the range of >10 to <24 mm/s. Generation of PPV in excess of 24 mm/s 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 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 ). The operational noise emissions have been modelled using Cadna computational predictive software 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 14 HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL STATEMENT VOLUME 2

15 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 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 For the calculation of noise propagation from the built plant, three meteorological scenarios were used: average wind direction based on hourly data ( ); downwind conditions (2.5 m/s northerly); and neutral (no wind) BS 4142 (Ref ) 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 ) British Standard BS 4142: 1997 (Ref ) 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 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 However, BS 4142: 1997 (Ref ) 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 HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL APPRAISAL VOLUME 2 15

16 methodology based on BS 4142: 1997 (Ref ) should therefore be based upon noise propagation under neutral weather conditions (no wind) Furthermore, BS 4142: 1997 (Ref ) 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 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 ) and British Standard BS 8233: 1999 Sound insulation and noise reduction for buildings Code of practice (Ref ), even with windows open 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 = 43dB LAeq,T outside a bedroom window 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 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 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 16 HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL STATEMENT VOLUME 2

17 assessment of the potential noise impact from operational road traffic Baseline Environmental Characteristics a) Noise Sensitive Receptors 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 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 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 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 mN. 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 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 An initial baseline noise survey was undertaken between 27 April and 7 May The survey methodology and the identification of appropriate monitoring locations were agreed with the HEOs of WSC and SDC prior to the survey 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. HINKLEY POINT C PRE-APPLICATION CONSULTATION STAGE 2 ENVIRONMENTAL APPRAISAL VOLUME 2 17