Report number: 2776.01

STERN WIND LTD PROPOSED ADDITIONAL WIND TURBINE T682A PARK, ,

ASSESSMENT OF ENVIRONMENTAL NOISE

Prepared for: Stern Wind Ltd c/o Planning Consultations 1 Melmount Park Strabane Co Tyrone BT82 9SU

ACIA Engineering Acoustics 39 Garners Lane Stockport SK3 8SD 0161 487 2225 www.acia-acoustics.co.uk 2776.01 page 1

1. INTRODUCTION

1.1 Brief

ACIA was commissioned by Stern Wind on behalf of the applicant to undertake a study of the noise likely to arise from the installation of a second wind turbine at Scoveston Park, Steynton, Milford Haven, .

Planning permission was given by Pembrokeshire County Council on 30 May 2013 for a turbine at Scoveston Park (reference 13/0222/PA). No background noise survey was undertaken in connection with that planning application, and therefore none was required for the present application. Preliminary calculations were made which indicated that the noise immission levels at neighbouring non-involved residential properties, as a results of the proposed additional turbine, were likely to remain below 35dB LA90,10min. This would allow the use of the ‘simplified’ noise assessment methodology in ETSU-R-97, provided that the cumulative effect of all wind turbines in the area did not cause a breach of Condition 6 of the existing consent: this sets a noise limit of 38dB LA90,10min.

1.2 Methodology

In view of the preliminary results, the levels of noise likely to occur at local residential properties as a result of the operation of the proposed turbine were calculated according to the usual best practice applicable to wind energy developments in . The environmental implications were then considered at each of the nearest potentially noise-sensitive properties.

The results are assessed against the guidelines available for wind energy developments, which are contained in Technical Advice Note 8: Planning for Renewable Energy (TAN 8) dating from July 2005. This recommends the use of the ETSU-R-97 report The Assessment and Rating of Noise from Wind Farms and the latest Onshore wind energy planning conditions guidance note (Renewables Advisory Board and the Department for Business, Enterprise and Regulatory Reform, BERR).

The March/April 2009 issue of Acoustics Bulletin contained an article describing an agreement among a number of acousticians with considerable experience in the wind energy field, and this article made a number of recommendations for the interpretation of ETSU-R-97 in the light of recent knowledge.

The Institute of Acoustics’ working group published the Good Practice Guide to the Application of ETSU-R-97 for the Assessment and Rating of Wind Turbine Noise in May 2013, with six supplementary guidance notes following in 2014. These documents confirmed many of the recommendations from the Acoustics Bulletin article and provided some additional details. It is the view of the Welsh Assembly Government policy that this Good Practice Guide represents guidance on best practice, and that it should be followed in carrying out wind turbine noise assessments. The following assessment was therefore carried out in accordance with the Good Practice Guide.

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2. RELEVANT GUIDANCE AND STANDARDS

2.1 Government policy

2.1.1 Planning Policy Wales

The latest overarching planning policy document is Planning Policy Wales, Edition 5, November 2012. In Chapter 12 of this document, which covers infrastructure and services, it is the stated policy of the Welsh Government that the need for wind energy is a key part of meeting its vision for future renewable electricity production as set out in the Energy Policy Statement (2010) and this should be taken into account by decision makers when determining such applications.

The impacts from renewable energy development will vary depending on their type, location and scale. For planning purposes a development of between 50kW and 5MW falls into the ‘sub local authority’ scale for planning purposes.

Specific guidance on renewables is provided in TAN 8: this is discussed in detail below.

2.1.2 TAN 8

This Technical Advice note includes at Annex C, paragraphs 2.14 to 2.16, a description of the noise emitted by wind turbines and how it varies with wind speed. It states that the report The Assessment and Rating of Noise from Wind Farms (ETSU-R-97) describes a framework for the measurement of wind farm noise and gives indicative noise levels calculated to offer a reasonable degree of protection to wind farm neighbours, without placing unreasonable restrictions on wind farm development or adding unduly to the costs and administrative burdens on wind energy developers or planning authorities. The recommendations of the cross-interest Noise Working Group which prepared the report is regarded as relevant guidance on good practice.

TAN 8 Annex C also says (paragraph 2.17) that there is no evidence that ground- transmitted low frequency noise from wind turbines is at a sufficient level to be harmful to human health.

2.2 Guidance now superseded

2.2.1 BS.4142:1997

The usual basis for assessing noise of industrial origin throughout the UK until very recently was BS.4142:1997, which called for a comparison of the ‘new’ noise with the pre-existing LA90. The standard was extensively revised and published in November 2014. The basic premise of the standard has not changed over the years, but there were always problems with its direct application to wind energy developments because the conditions stipulated by the 1997 standard were often difficult to satisfy.

The latest version states at paragraph 1.3(h) that noise sources falling within the scopes of other standards or guidance should not be assessed using BS.4142:2014. ETSU-R-97 and the Institute of Acoustics Good Practice Guide constitute such guidance.

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2.2.2 Renewables Advisory Board and BERR

In October 2007 a report ‘Onshore wind energy planning conditions: Guidance note’ was produced for the Renewables Advisory Board and the Department for Business, Enterprise and Regulatory Reform by TNEI Services Ltd. The purpose of the document was to provide advice on the appropriate types of planning condition relevant to wind energy development. It incorporated information already present within existing planning guidance, provided additional advice regarding the use of planning conditions, and outlined generic conditions for use in wind energy developments. It was aimed at Local Planning Authorities, statutory consultees, objector groups, potential wind applicants and other stakeholders.

As far as noise was concerned, the BERR guidance reproduced the relevant parts of ETSU- R-97, further strengthening the view that the latter was entirely appropriate for this type of development.

2.3 ETSU-R-97

2.3.1 Background noise

Developments of this type in Wales are to be assessed using the DTI Energy Technology Support Unit’s report dating from 1996, ETSU-R-97. The report was published as a result of the deliberations of the Department of Trade and Industry’s wind turbine noise working group, set up to provide guidance to the industry and planning authorities. At the time (in the early 1990s), it was recognised that the application of existing guidance posed difficulties when applied to wind energy developments. A major concern about the application of BS.4142 as it then existed, and the treatment of industrial noise in the environment generally, was that it had always been assumed that the worst case for noise emission propagation from a 24-hour industrial operation would occur at night, in still conditions. This was emphatically not the case for wind turbine noise, because in still wind conditions the turbines would not operate. The working group consisted of wind farm developers, DTI staff, environmental health officers and independent noise consultants. The report remained within the spirit of BS.4142 whilst dealing with the practical difficulties of determining the underlying background noise level and the setting of noise limits in very quiet rural areas. It was originally intended that the guidance would be reviewed after ten years had elapsed: a recently-published review of planning conditions for renewable energy generally (which was prepared for RAB/BERR — see below) has confirmed the continuing validity of the recommendations. It remains Welsh Government policy that wind energy projects should be assessed using ETSU-R- 97 as best practice guidance.

The report describes a framework for the measurement of wind turbine noise and indicates desirable noise levels, so that without placing unreasonable restrictions on wind power developments, neighbouring residential properties can gain protection from excessive noise. A primary objective of the report is to suggest noise limits in a form suitable for adoption as planning conditions. The Noise Working Group that produced the report considered that absolute noise limits regardless of wind speeds are not suited to wind farms in the UK, and that it is more appropriate in the majority of cases to set noise limits relative to background noise. The background noise levels are to be measured over a range of wind speeds so that the impact of turbine noise, which is also wind-speed dependant, can be evaluated.

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One of the most important recommendations in the ETSU-R-97 report is that the statistical index LA90,10min should be used for both the background noise and the wind turbine noise. This allows reliable measurements to be made without them being corrupted by louder, transitory noise events from other sources. The report notes that for the typical wind energy scheme, the LA90,10min is between 1.5 and 2.5 dB lower than the LAeq over the same measurement period. This is worthy of note because for conventional noise measurements in the environment, the LAeq index is generally regarded as the most appropriate descriptor, and it is normal practice to use it when noise limits are being set. In the present assessment, it is assumed that the LA90,10min index is always 2dB lower than the LAeq, as is confirmed by the IOA Good Practice Guide.

A methodology is provided for the measurement of background noise levels under various wind conditions. The report recommends that data should be discarded if they may have been corrupted by extraneous noise sources, such as falling rain or abnormally high flow rates in watercourses (eg after a period of prolonged rain). At all times, the noise levels measured in the environment are to be correlated with wind speed measurements at the site, using a reference height of 10m above ground. There were good reasons for the adoption of the 10m wind speed when the Noise Working Group reported in 1996. It had been suggested that at a height of 10 metres, the true wind speed would be measured on an operational wind farm, because the wind would not have been affected by the rotor wakes of turbines upwind of the mast. This would mean that the same measurement point could be used both before and after the wind farm was built. A potential additional benefit, according to ETSU-R-97, was that the (then) IEA recommended practice, now the IEC 61400-11 standard, used the same standardised wind speed measurement height and thus there may be additional consistency throughout the measurement and assessment procedure.

Because the background noise levels can vary by several decibels at any given wind speed, a curve is to be fitted to the raw data (having first discarded doubtful measurements) in order to determine the typical variation in background noise level with wind speed. The exercise is carried out for ‘quiet’ daytime periods and night-time periods, defined as follows.

Quiet daytime is from 18.00h to 23.00h on weekdays, 13.00h to 23.00h on Saturdays, and all day Sunday. Night-time is between 23.00h and 07.00h daily. All other periods (weekdays and Saturday mornings) are defined as normal daytime, when it would be expected that the ambient noise levels may be somewhat elevated because of human activity, distant road traffic, and natural noise sources. These daytime periods are not used at all in the derivation of ‘prevailing background’ noise curves.

Noise at night is not seen by ETSU-R-97 to be as critical as the ‘quiet’ daytime noise levels. This somewhat counter-intuitive position arises because between the defined hours of 23.00h and 07.00h residents are likely to be asleep, and thus would not be affected by noise out-of-doors. The typical attenuation of sound from outside to inside, taking into account the reduction in level through a partly-open window, means that levels that may be unacceptable during the quiet daytime period are quite acceptable at night. Accordingly, a ‘flat’ night-time limit of 43dB LA90,10min is generally adopted recommended. This is almost always easier to meet than the daytime limit, and it is therefore the daytime limit that effectively controls the location of a wind turbine. The noise levels at any point are directly affected by the distance between that point and the turbine.

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It is important to note that although rather higher noise emissions are apparently permissible at night, the turbine would operate with the same settings 24 hours a day. Diurnal variations in wind shear, however, may affect the noise levels received at a particular location.

No specific method is prescribed for the calculation of wind turbine noise, although there is a basic requirement for turbine sound power level to be determined by the standard test method referenced above. The Acoustics Bulletin article of March 2009 made more specific recommendations, the main point being that the methodology in ISO 9613-2 should be used with certain standard assumptions, and these were confirmed by the more recent Good Practice Guide.

2.3.2 Noise limits

The practice of controlling wind turbine noise by means of noise limits at the nearest noise-sensitive properties is always considered appropriate. Noise limits should be applied to external locations and should apply only to those areas frequently used for relaxation or activities for which a quiet environment is highly desirable. Noise limits should be set relative to the background noise at the nearest noise-sensitive properties. Thus, the limits reflect the variation in both turbine source noise and background noise with wind speed.

According to ETSU-R-97, separate noise limits should apply for daytime and for night- time, because during the night the emphasis should be on preventing sleep disturbance rather than protecting external amenity. Noise from the wind turbine or combination of turbines should be limited to 5dB above background for daytime and night-time, remembering that the background level of each period may be different.

The day-time level of the LA90,10min of the wind turbine noise should normally be limited to an absolute level within the range 35 to 40 dB. Wherever the limit is set, the intention is to offer a reasonable degree of protection to the neighbours of wind turbines without placing unreasonable restrictions on developments. For a single turbine scheme a lower fixed daytime limit of 35dB would normally be considered appropriate. However, there is provision for a simplified assessment method.

At page 66 ETSU-R-97 admits that the setting of noise limits according to the full procedure is a complex process, and although a long background noise survey is entirely appropriate for a wind farm consisting of several turbines, it is recognised that there may be situations in which a simplified methodology is appropriate. The simplified assessment method is described as follows.

“Much of the complexity of the proposed method is necessary because of the variety of background noise environments present in the UK. However, if the developer can demonstrated that noise conditions would be met even if there was no increase in background noise with wind speed until quite high wind speeds, than a simplified approach can be adopted. We are of the opinion that if the noise is limited to an LA90,10min of 35dB up to wind speeds of 10m/s at 10m height then this condition alone would offer sufficient protection of amenity, and background noise surveys would be unnecessary. We feel that, even in sheltered areas when the wind speed exceeds 10m/s on the wind farm site, some additional background noise will be generated which will increase background noise levels at the property. This type of condition may be suitable for single

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turbines or wind farms with very large separation distances between the turbines and the nearest properties.”

The proposed development is a single turbine, which is of a size that was conceivable in the late 1990s at the date ETSU-R-97 was published (as opposed to the multi-megawatt turbines now available). It therefore follows that if compliance with a blanket 35dB noise limit can be demonstrated by calculation, no background noise survey is required.

The noise limit for the permitted single wind turbine at Scoveston Park is specified at condition 6 of the planning permission dated 30 May 2013, which reads:

“The wind turbine noise level measured shall be in accordance with the Department of Trade and Industry Report The Assessment and Rating of Noise from Wind Farms (ETSU-R-97) and, as such, shall not exceed an absolute noise level of 38dB expressed as LA90,10min at any non-financially-involved existing dwelling (including the amenity area of the garden), and 45dB expressed as LA90,10min at any financially involved existing dwelling, up to on-site wind speeds of 10m/s measured at a height of 10 metres”.

The stated reason for the condition is:

“In order to maintain and protect the amenity of nearby residents by the reduction of ambient noise levels to an acceptable level in accordance with the requirements of section 13.13 (Reducing Noise and Light Pollution) of Planning Policy Wales, Edition 7 (July 2014) and Technical Advice Notes (Wales) 11 (October 1997) and to accord with the requirements of policies GN.1 and GN.4 of the Local Development Plan for Pembrokeshire (adopted February 2013).”

An identical condition is suggested for the proposed second wind turbine, with the additional provision that the noise limit should apply cumulatively to both Scoveston Park turbines in accordance with the recommendations in the IOA Good Practice Guide.

The blanket 35dB limit is increased to 45dB in order to all for a greater permissible margin above background where the occupier of the property in question has some financial interest in the project.

2.4 Guidance on the use of ETSU-R-97

2.4.1 Acoustics Bulletin article

After some years of applying the ETSU-R-97 guidance, there was a perceived need to update the guidance in order to keep it relevant to modern large wind turbines. A panel of acoustics practitioners in the field held a number of discussions, the product of which was an agreed procedure published in Acoustics Bulletin in the March/April 2009 issue (volume 34, number 2). This is often referred to as ‘the Acoustics Bulletin article’. In the period between the appearance of that publication and the date of writing the present report, two enhancements or clarifications of ETSU-R-97 in the Agreement have received widespread acceptance among local planning authorities and at Public Inquiries into wind energy applications. The enhancements relate to (i) the issue of site-specific wind shear, and (ii) the assumptions to be made when predicting wind turbine noise at remote locations.

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2.4.2 DECC report

On 6 April 2011 a report by the Hayes McKenzie Partnership was published by the Department of Energy and Climate Change. This report, Analysis of how noise impacts are considered in the determination of wind farm planning applications, was a review commissioned by DECC to look into how noise impacts from wind farms are determined in England, and provide suggestions on the possible need for more detailed guidance. One important conclusion was that there were variations in the interpretation of the ETSU-R-97 methodology, and this could usefully be made more prescriptive.

The authors found that there was no guidance on the subjects of wind shear, excessive amplitude modulation, or the treatment of cumulative noise impact from multiple wind farms. However, they did not find any reason to use guidance other than the original ETSU-R-97, as interpreted and amended by the 2009 Acoustics Bulletin article.

2.4.3 IOA Good Practice Guide (2013)

The Institute of Acoustics’ Good Practice Guide for the Application of ETSU-R-97… (May 2013) and its six supplements (2014) include a number of important recommendations, many of which originally appeared in the Acoustics Bulletin article of March 2009. The guide presents current good practice in the application of the ETSU-R-97 assessment methodology for all wind turbine developments above 50kW, reflecting the original principles within that guidance and the results of research and experience since its 1996 publication. The document was prepared by an Institute of Acoustics working group but further comments were received from the relevant Government Oversight Group at DEFRA and absorbed into the Guide.

As far as the present project is concerned, the Guide is particularly relevant to the consideration of turbine noise emission characteristics (noise input data) and to the comparison of the prediction noise immission levels with a blanket noise limit. Guidance is also provided on the assessment of cumulative noise levels from more than one scheme affecting a given receptor.

Summary points are provided as numbered Summary Boxes (SB): those relevant to the present study are provided below with explanation. Additional supplementary guidance notes were published for consultation in November 2013 for consultation. These expand on some of the aspects considered in the Good Practice Guide, including the conduct of background noise surveys, data analysis, wind shear, and post-completion noise measurements.

SB2 states that the study area should cover at least the area predicted to exceed 35dB LA90 at up to 10m/s wind speed from all existing and proposed turbines. There is no requirement to consider noise levels at wind speeds above 10m/s because the subject turbine reaches its maximum noise output at a lower wind speeds than 10m/s (derived at 10m height), and its wind speed versus noise characteristic reaches a plateau level. This is entirely in step with a blanket noise limit.

SB4 to SB 12 inclusive relate to the conduct of a background noise monitoring campaign. SB13 confirms that the definitions of ‘amenity hours’ and ‘night-time hours’ in ETSU-R- 97 remain applicable. SB14 to SB19 inclusive relate to the analysis of background noise data.

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SB20 deals with the prediction of noise immission levels from wind turbines. In summary, it confirms the recommendations of the Acoustics Bulletin article of March 2009 in respect of the difference between LA90 and LAeq, the adoption of a ground factor G of 0.5, the inclusion of a margin of uncertainty in the turbine noise emissions, together with a statement of its robustness, and the basic parameters for source and receiver heights and atmospheric conditions.

Under Section 7 Other Guidance the IOA Guide covers points including planning conditions, (of which a sample is provided), and states that the evidence in relation to ‘excess’ or ‘other’ amplitude modulation (AM) is still developing. An IOA working group has been formed to consider the issue of defining and measuring AM but at the time of writing, current practice is not to assign a planning condition to deal with AM. It has not proved possible to date to develop a workable and valid form of condition.

Six Supplementary Guidance Notes are referred to in the IOA Good Practice Guide. Four of these were published in July 2014, and the other two in September 2014. They relate to data collection, sound power level data, data processing and filtering, wind shear, post-completion measurements, and offshore wind.

2.5 Planning conditions for existing wind turbines

The existing wind turbines at Castle Pill Farm, having been ‘repowered’ since June 2009 are subject to planning conditions restricting the noise immission levels at neighbouring noise-sensitive locations. The usual ETSU-R-97 related planning conditions would limit daytime noise levels to 35dB or 5dB above background, whichever is the greater.

Regardless of the noise limits that may be appropriate to the single turbine scheme under discussion, the Castle Pill conditions would be applicable to the cumulative case. This would, however, require an assessment of the pre-existing background sound levels.

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3. ASSESSMENT PROCEDURE

3.1 Characteristics of wind turbine noise

Noise from modern wind turbines is typically made up of two contributory elements: a reasonably steady, broad-band noise of aerodynamic origin, which depends on blade tip speed, and a regular, pulsed element resulting from the regular rotation of the blades past a fixed point, often described as ‘amplitude modulation’ (AM). Modern large turbine designs emit noise primarily of aerodynamic origin: mechanical noise from the nacelle, and any tonal content, has been virtually eliminated from the latest designs.

3.2 Turbine sound power data

The turbine proposed is an Enercon E-48 rated at 500kW. This is an upwind type turbine with a three-blade rotor 48m in diameter. The hub height would be 55.6 metres. The OS grid coordinates of the turbine are 192892E, 206801N.

The base data for the wind turbine were taken from the manufacturer’s published noise levels, reproduced in Table 1(a). It is understood that the measurements from which these data were derived were conducted in accordance with the method in BS EN 64100- 11:2003. This method calls for measurements close enough to a single turbine that background noise is insignificant.

This turbine on a 55.6m hub would emit an overall sound power level of 101.5dB(A) at -1 the reference wind speed of 8ms (ie the v10, referenced to a height of 10m). The sound power depends on wind speed, but at speeds below 4ms-1 or above 10ms-1 the noise emissions are often not stated because there are practical difficulties in making measurements. This is not a problem for present purposes because the maximum noise impact of a wind turbine almost invariably occurs between 6 and 8 m/s (standardised 10m wind speed).

The sound power levels assumed for the present assessment are shown in Table 1(a). Spectral information for the candidate turbine type was taken from a noise test report on a similar turbine, adjusted to result in the same overall sound power level, so the same degree of uncertainty was included for both the overall and the spectral noise emissions. The A-weighted octave band spectrum used for predictive work is shown in Table 1(b).

The turbine is assumed to have directional characteristics such that the maximum noise level at a given distance occurs directly downwind of the turbine. The noise contains no tonal noise components which would warrant a tonal penalty as described in ETSU-R-97.

TABLE 1(a): Enercon E-48 500kW: Sound power levels dB for noise predictions

wind speed v10 m/s 4 5 6 7 8 9 10

sound power level LwA dB 94.0 96.0 98.2 99.9 101.5 102.1 102.5

TABLE 1(b): Assumed A-weighted sound power spectrum, dB, at a wind speed of 8m/s Frequency Hz 63 125 250 500 1k 2k 4k 8k Sound power level dB 83.7 89.2 92.8 94.9 96.9 94.2 86.9 80.8

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3.3 Calculation procedure

The method adopted for the prediction of noise from the wind turbine was the ISO 9613- 2:1996 method interpreted in the light of the Institute of Acoustics Good Practice Guide.

The model assumes hemispherical sound radiation with relatively low attenuation by ground effects, because the receptor is in the acoustic far-field of an elevated sound source. Attenuation resulting from ground effects varies with frequency and distance, and the predictions are based on octave band data. The source sound power levels used for calculation purposes take no account of the available noise reduction methods on the candidate turbine, or indeed on similar types, although various modifications may be available.

The Good Practice Guide states that in order to give reliable predictions of the aggregate noise levels at receptor locations, certain assumptions should be made. These represent the worst case for noise immission of each receptor, ie for the condition when the wind blows from the turbine to the reception point. The assumptions are: (a) The turbine is directly upwind of the reception point; (b) The manufacturer’s warranted noise data, or test data including uncertainty, are used as input to the acoustical model;

(c) A ground attenuation factor G = 0.5 for Gs, Gm and Gr (the ground types in the source region, middle region and receiver region as defined by ISO 9613-2) (d) The noise source height is turbine hub height; (e) The receiver height is 4m (corresponding to a first-floor window, but note that this conflicts with ETSU-R-97 recommendations); (f) An air temperature of 10°C and relative humidity of 70%.

In order to calculate the steady noise from the proposed site the effect of the turbine at each receptor location is calculated. ETSU-R-97 suggests that the steady nature of the noise emitted by wind turbines is such that the level difference between LAeq and LA90 is typically 2dB. This has been confirmed by readings from several wind turbines in various types of terrain, and is supported by the Institute of Acoustics Good Practice Guide. A 2dB deduction was therefore made from the warranted sound power level (including uncertainty) to yield the typical LA90 for calculation purposes.

The direction of the wind makes the noise from the turbine effectively directional, since the noise level at a given distance upwind of the turbine will be lower than at the same distance downwind.

3.4 Receptor locations

There are several dwellings within approximately 1km of the proposed wind turbine. Representative OS grid locations and distances from the proposed turbine for the nearest residential properties or for representative properties on housing estates are shown in Table 2 and Figure 1. The locations chosen for noise predictions are typically the nearest point on the curtilage of the property. Upper Scoveston is occupied by the site landowner and therefore has a financial interest in the development.

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TABLE 2: Receptor locations for noise predictions ref. name of location easting, m northing, m distance, m R1 Upper Scoveston 192941 207365 566 R2 Castle Pill Road 191987 207018 931 R3 Road (nearest) 192178 207670 1125 R4 Conway Drive (nearest) 192076 207506 1078 R5 Bigginshill 192727 206019 799 R6 Wayside 192878 206029 772 R7 Scoveston Grove 193572 207093 740 R8 Middle Scoveston 193679 207017 816 R9 Lower Scoveston 193772 206862 882 R10 Southview 193815 206867 925

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4. PREDICTIONS

4.1 Results

The predicted worst-case noise levels for the various receiver locations are presented graphically in Figures 2, 3 and 4, and are summarised to the nearest whole decibel in Table 3. The wind speeds are at a height of 10 metres as previously explained.

The results of comparing the predicted noise immission levels with a ‘flat’ 38dB noise limit, or the 45dB noise limit for financially involved dwellings as appropriate, are shown in Table 4.

TABLE 3: Worst-case turbine noise levels, LA90,10min dB ms-1 4 5 6 7 8 9 10 R1 Upper Scoveston 21 25 30 31 32 32 32 R2 Castle Pill Road 16 20 24 26 27 27 27 R3 Neyland Road 14 18 22 24 25 25 25 R4 Conway Drive 14 19 23 24 25 25 25 R5 Bigginshill 17 22 26 28 28 28 28 R6 Wayside 18 22 26 28 29 29 29 R7 Scoveston Grove 18 23 27 29 29 29 29 R8 Middle Scoveston 17 22 26 28 28 28 28 R9 Lower Scoveston 16 21 25 27 27 27 27 R10 Southview 16 20 24 26 27 27 27

TABLE 4: Noise limit and worst-case headroom under a flat (solus) limit ms-1 4 5 6 7 8 9 10 proposed limit 38 38 38 38 38 38 38 limit (financial interest) 45 45 45 45 45 45 45 R1 Upper Scoveston 24 20 15 14 13 13 13 R2 Castle Pill Road 22 18 14 12 11 11 11 R3 Neyland Road 24 20 16 14 13 13 13 R4 Conway Drive 24 19 15 14 13 13 13 R5 Bigginshill 21 16 12 10 10 10 10 R6 Wayside 20 16 12 10 9 9 9 R7 Scoveston Grove 20 15 11 9 9 9 9 R8 Middle Scoveston 21 16 12 10 10 10 10 R9 Lower Scoveston 22 17 13 11 11 11 11 R10 Southview 22 18 14 12 11 11 11

4.2 Compliance with assumed noise limits

At the nearest non-involved dwellings the noise of the turbine, when the wind direction means it is directly upwind of the receptor, will be below the proposed flat noise limit regardless of wind speed. When the turbine is in a crosswind direction from the receptor the noise immission levels will be 1 to 2 dB lower, and when it is directly downwind they will be 8 to 10 dB lower.

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At Upper Scoveston the higher noise limit of 45dB is applicable, and the turbine will operate well within this limit.

Because of the proximity of the operational Castle Pill Farm wind turbines and other consented turbines, a 38dB flat limit is considered appropriate only for the proposed turbine considered in isolation, since the cumulative effects of the other turbines will determine the effects on amenity and acceptability. This point is considered in Section 0.

4.3 Construction noise

During the construction of the turbine there will be a small amount of additional road traffic in the vicinity of the site, but it would be normal practice for the vehicle routes to be carefully prescribed by the Highways Department in order to minimise disruption and disturbance. The frequency and numbers of such vehicle movements will be insufficient to affect the road traffic noise experienced by local residents. The working hours on site can also be limited by condition if the local planning authority should think it appropriate, and by extension, no deliveries of materials to the site would take place outside these hours.

The construction of a concrete gravity foundation is not a particularly noisy process, and uses familiar construction equipment. The excavation of the cavity for the concrete base takes no more than a few days. Placement of the steel reinforcement is not a noisy process except for the occasional requirement to cut rebar using an angle grinder or similar device. This also requires the presence of an electrical generator on site.

Goods vehicles making deliveries to the site, excavators and other earthmoving equipment, and concrete mixers or pumps have typical sound power levels in the range 102 to 106 dB(A) overall. The nearest significant operations of earthmoving or concreting activities to noise-sensitive property will be more than 700m away. A sound power source of 106dB(A) at this distance would produce a noise level of no more than 41dB(A) before ground attenuation effects are taken into account. This level of construction noise would be regarded as entirely acceptable by BS.5228-1:2009 ‘Code of practice for noise and vibration control from construction and open sites’. It would not be likely to exceed the LOAEL (lowest observable adverse effect level) during the working day, and would be comparable with the familiar noise from the diesel engines in farm machinery.

The predicted increase in total road traffic will be minimal as a result of the additional HGV movements generated during the construction phase. A traffic management plan would normally be implemented to mitigate the effects of construction traffic in the neighbourhood. Any slight negative effects would last only for the few weeks of the proposed construction period.

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5. CUMULATIVE NOISE ASSESSMENT

5.1 Neighbouring operational and consented wind turbines

For the purposes of cumulative noise assessment, the four operational wind turbines at the existing Castle Pill Farm development and the four turbines at Wear Point were all considered. These are detailed in Table 5. The consented single turbine at Scoveston Park (T682) is assumed identical to the second turbine currently proposed.

TABLE 5: Turbines considered in cumulative assessment turbines type easting northing Castle Pill: T1 EWT-54 900kW, 50m hub 192356 207072 T2 EWT-54 900kW, 50m hub 192395 206795 T3 EWT-54 900kW, 50m hub 192402 206174 T4 EWT-54 900kW, 50m hub 192634 206568 Wear Point: T1 Senvion MM82, 70m hub 194161 204521 T2 Senvion MM82, 70m hub 193927 204534 T3 Senvion MM82, 70m hub 193567 204505 T4 Senvion MM82, 70m hub 193287 204629 Scoveston Park: T682 Enercon E-48, 55.6m hub 192941 206972

For calculation purposes the output sound power levels for each turbine type were taken from commercially available literature with due allowance for measurement uncertainty. Where spectral noise emission data were unavailable, a typical spectrum shape for the appropriate class of turbine was used to derive the excess attenuation in the ISO9613-2 calculations. The sound power levels used for prediction purposes, including uncertainty, are shown in Table 6.

TABLE 6: Assumed sound power levels dB for operational turbines Type 4 5 6 7 8 9 10 EWT-54 95.0 98.1 99.4 100.7 102.0 102.0 102.0 Senvion MM82 95.0 101.4 103.4 104.4 105.5 106.5 107.1

5.2 Cumulative noise predictions and limits

As a ‘first pass’ noise prediction, all ten turbines were treated as if they were all part of the same wind farm. The ISO-9613-2 methodology was then applied on the basis that all turbines are simultaneously upwind of each receptor location in turn. This broad-brush approach would indicate if any cumulative noise problem were likely, and if so, a more rigorous appraisal could be conducted.

The results of the cumulative noise predictions at the ten receptor locations used for the present study are shown in Table 7, and graphically in Figures 5, 6 and 7.

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TABLE 7: Worst-case cumulative turbine noise, LA90,10min dB m/s 4 5 6 7 8 9 10 R1 Upper Scoveston 31 34 37 39 40 40 40 R2 Castle Pill Road 33 37 38 39 41 41 41 R3 Neyland Road 28 32 33 35 36 36 36 R4 Conway Drive 30 33 35 36 37 37 37 R5 Bigginshill 33 37 38 39 41 41 41 R6 Wayside 31 35 37 38 39 39 40 R7 Scoveston Grove 27 31 33 35 36 36 36 R8 Middle Scoveston 26 30 33 34 35 35 35 R9 Lower Scoveston 25 29 32 33 34 35 35 R10 Southview 25 29 32 33 34 34 34

It is important to note that it is no longer possible to undertake any background noise surveys at properties in the locality, as the results would be corrupted by noise from operational wind turbines.

At location R1 (Upper Scoveston) the 45dB ‘flat’ limit for financially involved properties is met by all existing and consented turbines cumulatively. At three locations, R2, R5 and R6, the existing 38dB ‘flat’ limit would be exceeded at higher wind speeds: these results are shaded in Table 7. However, higher noise limits are assumed to apply to the existing planning consents. Table 8 shows the increases in noise immission levels at these three locations resulting from the addition of the second Scoveston Park (T682A) turbine to the operational and consented turbines. In all cases the results are no more than a fraction of a decibel greater. The cumulative noise levels at the same three locations, in the absence of the proposed T682A, are illustrated in Figure 8.

TABLE 8: Change in cumulative turbine noise, LA90,10min dB with T682A added ms-1 4 5 6 7 8 9 10 R2 Castle Pill Road 0.1 0.1 0.2 0.2 0.2 0.2 0.2 R5 Bigginshill 0.1 0.1 0.3 0.3 0.3 0.3 0.3 R6 Wayside 0.2 0.2 0.4 0.4 0.4 0.4 0.4

The results suggest that provided the existing noise limits can in the worst cumulative case be met, then the introduction of the new turbine will have no significant effect on amenity.

The noise prediction method assumes that all turbines are simultaneously upwind of every receptor location, which makes it a robust worst-case assessment. Such conditions can never occur in practice, so at least some of the turbines will contribute less to the overall noise immission level at a given receptor.

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6. CONCLUSIONS

Noise from the turbine will remain within a ‘flat’ limit of 38dB, or 45dB for the financially involved property. Because of the operational wind farm in the vicinity, there is no practicable way of undertaking a background noise survey in the usual way as this would inevitably include noise contributions from the existing turbines.

The noise limit in the planning conditions for the existing and consented wind turbines in the vicinity will continue to be met after the addition of the proposed second turbine at Scoveston Park.

Construction activities will be short-lived and noise arising from construction will not adversely affect local residents. It may therefore be concluded that provided construction activity proceeds only during the normal working day, no noise nuisance is expected.

It is proposed that a simplified planning limit is appropriate for the proposed turbine in isolation, and the existing planning limit should also apply to the cumulative case on accordance with the guidance on best practice. A ‘solus’ limit is required because it is likely that the proposed turbine will have an operational life beyond that of the existing and consented turbines. Such a limit will not be detrimental to the amenity of local residents.

It follows that there are no noise grounds for refusing planning permission for the proposed additional wind turbine at Scoveston Park.

Ian F Bennett BSc CEng MIOA 11 February 2015

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Figure 1: Noise prediction locations and proposed wind turbine

Four operational Castle Pill turbines T1, T2, T3, T4 Scoveston Park turbine with planning permission T682 Proposed second Scoveston Park turbine T682A Representative noise receptor locations R1 to R10 inclusive The four operational Wear Point turbines are 1.5km to the south of the map

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