10.0 noise and vibration 10.1 introductionbs 5228-1:2009+a1:2014 sets out guidance on permissible...

NOISE & VIBRATION AWN Consulting Limited _____________________________________________________________________________________________________

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PROJECT CRAG DATA CENTRE Chapter 10,

10.0 NOISE AND VIBRATION

10.1 INTRODUCTION This section assesses the likely noise and vibration impacts arising from the proposed development in the context of current relevant standards and guidance and identifies any requirements or possibilities for mitigation. The facility is herein referenced to as the subject site. The chapter and assessment has been completed having regard to the guidance outlined in the Environmental Protection Agency’s Guidelines on the information to be contained in Environmental Impact Assessment Reports (Draft, September 2017) and Advice Notes for Preparing Environmental Impact Statements (Draft, September 2015). In the first instance, it is beneficial to provide an outline of the fundamentals of Noise and Vibration against which the more technical elements of the section can be put into context. In addition, a Glossary of Acoustic Terminology has been prepared and included in Appendix 10-1 for reference.

10.1.1 Fundamentals of Noise A sound wave travelling through the air is a regular disturbance of the atmospheric pressure. These pressure fluctuations are detected by the human ear, producing the sensation of hearing. In order to take account of the vast range of pressure levels that can be detected by the ear, it is convenient to measure sound in terms of a logarithmic ratio of sound pressures. These values are expressed as Sound Pressure Levels in decibels (dB). The audible range of sounds expressed in terms of Sound Pressure Levels is 0 dB (nominally, the threshold of hearing) to 120 dB (for the threshold of pain). In general, a subjective impression of doubling of loudness corresponds to a tenfold increase in sound energy which conveniently equates to a 10 dB increase in Sound Pressure Level. It should be noted that a doubling in sound energy (such as may be caused by a doubling of traffic flows) increases the Sound Pressure Level by 3 dB. The frequency of sound is the rate at which a sound wave oscillates, and is expressed in Hertz (Hz). The sensitivity of the human ear to different frequencies in the audible range is not uniform. For example, hearing sensitivity decreases markedly as frequency falls below 250 Hz. In order to rank the Sound Pressure Level of various noise sources, the measured level has to be adjusted to give comparatively more weight to the frequencies that are readily detected by the human ear. Several weighting mechanisms have been proposed but the ‘A-weighting’ system has been found to provide one of the best correlations with perceived loudness. Sound Pressure Level’s measured using ‘A weighting’ are expressed in terms of dBA. An indication of the level of some common sounds on the dBA scale is presented in Figure 10.1, which shows a quiet bedroom at around 35 dBA, a nearby noisy Heavy Goods Vehicle at 7 m at 90 dBA and a pneumatic drill at 7 m at about 100 dBA.

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Figure 10.1 Typical Common Sounds on the dBA Scale (Environmental Protection Agency)

10.1.2 Fundamentals of Vibration

Vibration standards come in two varieties: those dealing with human comfort and those dealing with cosmetic or structural damage to buildings. In both instances, it is appropriate to consider the magnitude of vibration in terms of Peak Particle Velocity. Peak Particle Velocity is defined in BS 5228-2:2009+A1:2014 Code of Practice for Noise and Vibration Control on Construction and Open Sites – Vibration as the:

‘Instantaneous maximum velocity reached by a vibrating element as it oscillates about its rest position.’

The unit of measurement of Peak Particle Velocity is most commonly millimetres per second, mm/s. However, when dealing with human perception to vibration and the tolerances of sensitive equipment the unit of measurement of micrometres per second, µm/s, may be used. It is also important to take account of the frequency at which the vibration occurs, which similar to sound is expressed in Hertz (Hz). Buildings are sensitive to vibration at very low frequencies, i.e. less than 10 Hz, and are more resistant to vibration at higher frequencies, i.e. above 50 Hz. It is acknowledged, however, that humans are sensitive to vibration stimuli at much lower magnitudes than those likely to cause damage to buildings. Vibration typically becomes perceptible at around 150 to 300 µm/s PPV and may become disturbing or annoying at higher magnitudes. However, higher levels of vibration are typically tolerated for single events or events of short term duration, particularly during construction Projects and when the origin of vibration is known.

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10.2 METHODOLOGY In assessing the noise and vibration impacts the following methodology will be adopted:

• Characterise the receiving environment through a series of baseline surveys;

• Determine appropriate criteria for evaluating the significance of noise and vibration impacts through reference to local guidance documents and international best practice, where applicable;

• Calculate the potential noise impacts using industry standardised calculation methods;

• Assess the calculated levels against the adopted criteria;

• Specify mitigation measures to reduce the noise and vibration impacts; and,

• Present the residual predicted impact of the proposed development including with mitigation measures in place.

10.2.1 Assessment Criteria – Construction Phase 10.2.1.1 Noise

There is no published statutory Irish guidance relating to the maximum permissible noise level that may be generated during the construction phase of a project. Reference is therefore made to British Standard BS 5228-1:2009+A1:2014 Code of Practice for Noise and Vibration Control On Construction and Open Sites - Noise for the control of construction noise impacts. The approach in this standard calls for the designation of a noise sensitive receptor into a specific category (A, B or C) based on existing ambient noise levels in the absence of construction noise. This then sets a threshold noise value that, if exceeded at this location, indicates a significant noise impact is associated with the construction activities. BS 5228-1:2009+A1:2014 sets out guidance on permissible noise levels relative to the existing noise environment. Table 10.1 sets out the values which, when exceeded, signify a significant effect at the facades of residential receptors.

Assessment category and threshold value period (LAeq) Threshold value, in decibels (dB)

Category A1 Category B2 Category C3

Daytime (07:00 – 19:00) and Saturdays (07:00 – 13:00)

65 70 75

Night-time (23:00 to 07:00hrs) 45 50 55

Evenings and weekends4 55 60 65

Table 10.1 Example Threshold of Significant Effect at Dwellings

For the appropriate periods (i.e. daytime) the ambient noise level is determined and rounded to the nearest 5 dB. Baseline monitoring carried out as part of this assessment (Section 10.3) would indicate that the categories detailed in Table 10.2 are appropriate in terms of the nearest noise sensitive receptors being considered in this instance.

1 threshold values to use when ambient noise levels (when rounded to the nearest 5 dB) are less than

these values. 2 threshold values to use when ambient noise levels (when rounded to the nearest 5 dB) are the same as

category A values. 3 threshold values to use when ambient noise levels (when rounded to the nearest 5 dB) are higher than

category A values. 4 19:00 – 23:00 weekdays, 13:00 – 23:00 Saturdays and 07:00 – 23:00 Sundays.

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Period as defined in BS 5228-1:2009+A1:20145 Rounded

Baseline Noise Level LAeq (dB)

Category Suggested Limit

Daytime (07:00 – 19:00) and Saturdays (07:00 – 13:00)

65 B 70

Evening (19:00 to 23:00hrs) 65 C 65

Night time (23:00 to 07:00hrs) 55 C 55

Table 10.2 Rounded Baseline Noise Levels and Associated Categories

If the construction noise exceeds the appropriate category value, then a significant effect is deemed to occur.

10.2.1.2 Vibration Vibration standards are generally split into two categories, those dealing with human comfort and those dealing with cosmetic or structural damage to buildings. In both instances, in terms of construction vibration, it is appropriate to consider the magnitude of vibration in terms of Peak Particle Velocity (PPV). Human Comfort It is acknowledged that humans are particularly sensitive to vibration stimuli and that any perception of vibration may lead to concern. In the case of road traffic, vibration is perceptible at around 0.5 mm/s and may become disturbing or annoying at higher magnitudes. However, higher levels of vibration are typically tolerated for single events or events of short duration. For example, rock breaking and piling, two of the primary sources of vibration during construction, are typically tolerated at vibration levels up to 12 mm/s and 5 mm/s respectively (BS 5228-2:2009+A1:2014). This guidance is applicable to the daytime only; it is unreasonable to expect people to be tolerant of such activities during the night. Cosmetic Damage It is noted that in the absence of specific guidance relevant to the nature of development proposed, guidance for acceptable vibration within buildings during the construction phase of a development is provided in the following documents:

• British Standard BS 7385-2:1993 Evaluation and Measurement for Vibration in Buildings - Guide to Damage Levels from Ground Borne Vibration (BS7385-2:1993); and,

• British Standard BS 5228-2:2009+A1:2014 Code of Practice for Noise and Vibration Control on Construction and Open Sites – Vibration (BS5228-2:2009+A1:2014)

BS 7385-2:1993 states that there should typically be no cosmetic damage if transient vibration does not exceed 15 mm/s at low frequencies rising to 20 mm/s at 15 Hz and 50 mm/s at 40 Hz and above. These guidelines relate to relatively modern buildings and should be reduced to 50% or less for more critical buildings that may be prone to dynamic magnification due to resonance (tall lightweight structures). BS5228-2:2009+A1:2014 recommends that, for soundly constructed residential property and similar structures that are generally in good repair, a threshold for minor

5 Not proposed construction hours

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or cosmetic (i.e. non-structural) damage should be taken as a peak component particle velocity (in frequency range of predominant pulse) of 15 mm/s at 4 Hz increasing to 20 mm/s at 15 Hz and 50 mm/s at 40 Hz and above. Below these values minor damage is unlikely. Where continuous vibration is such as to give rise to dynamic magnification due to resonance, the guide values may need to be reduced by up to 50%. BS5228-2:2009+A1:2014 also comments that important buildings which are difficult to repair might require special consideration on a case by case basis. Table 10.3 presents the vibration criteria to be adopted during construction at nearby soundly constructed residential properties and similar structures that are generally in good repair. These limit values have been selected to avoid cosmetic (i.e. non-structural) damage. Please note that the potential for vibration induced damage is greater at lower frequencies of vibration. Therefore, the limit values proposed are related to the frequency range of the vibration. To put this into context most building damage from man-made sources (construction, traffic etc.) occurs in the frequency range of 1 Hz to 150 Hz.

Allowable vibration (in terms of peak particle velocity) at the closest part of sensitive property to the source of vibration, at a frequency of

Less than 10 Hz 10 to 50 Hz 50 to 100 Hz (and above)

15 mm/s 20 mm/s 50 mm/s

Table 10.3 Allowable vibration during construction phase for soundly constructed buildings

Underground Services Consideration should also be given to the potential for vibration induced damage to underground services nearby. Generally underground structures are less susceptible to damage due to vibration. Notwithstanding this, BS 5228-2:2009+A1:2014 recommends that in the absence of specific criteria from the statutory undertakers the following criteria should be applied to underground services:

• Maximum Peak Particle Velocity for intermittent or transient vibrations – 30 mm/s; and,

• Maximum Peak Particle Velocity for continuous vibrations – 15 mm/s These criteria should be reduced by 30% in the case where dilapidated brick sewers are encountered.

10.2.2 Assessment Criteria – Operational Phase 10.2.2.1 Noise

The South Dublin County Council Development Plan outlines the following objectives in in respect of noise: IE7 Objective 1 To implement the provisions of EU and National legislation on

air, light and noise control and other relevant legislative requirements, as appropriate, in conjunction with all relevant stakeholders.

IE7 Objective 3 To implement the relevant spatial planning recommendations

and actions of the Dublin Agglomeration Environmental Noise Action Plan 2013 - 2018.

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The most relevant objective to the proposed development is the implementation Dublin Agglomeration Environmental Noise Action Plan (NAP, 2013 – 2018). The Noise Action Plan (NAP) states the following thresholds be applied when considering developments which introduce people to noise:

“Undesirable high sound levels are defined areas with a night time level greater than 55 decibels and a daytime level greater than 70 decibels”

Section 9.2.3 of the NAP sets out the following in respect of the potential treatment of noise at the planning stage:

“To require developers to produce a sound impact assessment and mitigation plans, where necessary, for any new development where the Planning Authority considers that any new development will impact negatively on pre-existing environmental sound levels within their Council area”

In this context, it is considered that the following impact assessment is commensurate with such a requirement. Further to this, it is necessary to discuss criteria against which the potential noise impact of the proposed development can be assessed. Reference is therefore made to the Environmental Protection Agency (EPA) Guidance Note for Noise: Licence Applications, Surveys and Assessments in Relation to Scheduled Activities (NG4, 2014). This document essentially consolidates previous guidance issued by the Agency and outlines methodologies for the derivation of appropriate noise criteria dependent on prevailing levels of noise in the absence of a development. An important caveat that is stated in the document under the section Applicability of this Document:

“Note that the guidance within this document relates to the assessment and measurement of noise in relation to Agency scheduled activities only.”

It is noted that whilst the facility is licenced by the Agency, this is only in respect of emissions to atmosphere. In the absence of local guidance however, and considering the nature of the proposed development, the guidelines outlined in NG4 are considered to be highly relevant in this instance. In terms of operational noise, NG4 outlines the following limits in respect of facilities not located in an area with low background noise levels:

Daytime (07:00 to 19:00 hrs)

Evening (19:00 to 23:00 hrs)

Night-time (23:00 to 07:00 hrs)

55 dB LArT,15mins 50 dB LArT,15mins 45 dB LAeq,15mins

Table 10.4 Proposed Operational Noise Criteria

Due to the continuous nature of operations associated with proposed development, the night time limit is deemed to be most relevant and has been referenced as the design goal for operational noise. Section 4.4.1 of NG4 also contains the following comments in relation to emergency plant items:

“In some instances, licensed sites will have certain items of emergency equipment (e.g. standby generators) that will only operate in urgent situations

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(e.g. grid power failure). Depending upon the context, it may be deemed permissible for such items of equipment to give rise to exceedances in the noise criteria/limits during limited testing and emergency operation only. If such equipment is in regular use for any purposes other than intermittent testing, it is subject to the standard limit values for the site”.

In terms of emergency operation of generators on site (i.e. during an electricity grid failure) the following noise design goal is deemed to be applicable at the nearest noise sensitive receptors:

Emergency Situation 55dB LAeq,15min General comment in relation to noise at common boundaries with adjacent sites will be presented in the relevant sections of this document. These criteria have been derived from relevant local and national guidance as outlined previously.

10.2.2.2 Vibration

No significant sources of vibration are expected to arise during the operational phase of the development. Operational vibration has therefore not been addressed further in this chapter.

10.3 RECEIVING ENVIRONMENT

10.3.1 Baseline Noise Survey An environmental noise survey was conducted in order to quantify the existing noise environment. The survey was conducted in general accordance with ISO 1996-2:2017 Acoustics - Description, Measurement and Assessment of Environmental Noise -Determination of Sound Pressure Levels. Specific details are set out below.

10.3.1.1 Measurement Locations Noise measurements were conducted at two positions on the site boundary that are reflective of noise levels at the nearest noise sensitive receptors. Details for the particular locations are outlined below. Location USL01 Located on the eastern boundary of the site adjacent to the M50

motorway. This location is considered to be representative of noise levels arising at noise sensitive receptors located to the east of the M50.

Location USL02 Located on the southern boundary of the site adjacent to canal.

This location is considered to be representative of noise levels arising at the nearest noise sensitive receptors located south of the New Nangor Road.

In order to inform the current application a further series of noise monitoring surveys were undertaken in order to consider the wider area. Details for the particular locations are outlined below. Location S01 Located to the North of the M50 Motorway adjacent to the

western façade of the Yeats Way apartment complex.

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Location S02 Located to the south of the canal on the New Nangor Road adjacent to the northern façade of the Aras Na Cluaine apartment complex, Clondalkin.

Location S03 Located to the south west of the canal adjacent to No. 29

Mayfield Park6.

Figure 10.2 Baseline Noise Survey Locations

10.3.1.2 Survey Periods

Noise measurements were conducted at Locations S01 to S03 over the following periods:

• Daytime - 12:52 hrs 15:04 hrs on Friday, February 9th 2018;

• Evening – 22:00 hrs to 23:00 hrs on Wednesday, February 14th 2018; and,

• Night-time - 23:47 hrs on Monday, February 19th to 01:20 hrs on Tuesday, February 20th 2018.

The measurements periods were selected in order to provide a typical snapshot of the existing noise climate, with the primary purpose being to ensure that the proposed noise criteria associated with the development are commensurate with the prevailing environment. Unattended surveying was completed at USL01 and USL02 over the following periods:

• USL01 - 17:34 hrs on Wednesday, January 31st 2018 to 15:23 hrs on Friday, February 9th; and,

• USL02 - 17:50 hrs on Wednesday, January 31st 2018 to 15:35 hrs on Friday, February 9th.

6 It is noted that due to ongoing construction works to the east of Mayfield Park, this location was selected

to ensure that construction noise did not influence the measured levels.

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10.3.1.3 Personnel and Instrumentation Survey Locations S01 to S03 Noise measurements were conducted using a NTi Audio XL-2 TA Precision Sound Level meter. The measurement apparatus was check calibrated both before and after each survey using a Brüel & Kjær Type 4231 Sound Level Meter Calibrator. Survey Locations USL01 and USL02 Noise measurements were conducted using Rion NL-52 Precision Sound Level meters. The measurement apparatus was check calibrated both before and after each survey using a Brüel & Kjær Type 4231 Sound Level Meter Calibrator.

10.3.1.4 Procedure Measurements were conducted at Locations S01 to S05 on a cyclical basis. Sample periods for the noise measurements were nominally 10 to 15 minutes during all survey periods. The results were noted onto a Survey Record Sheet immediately following each sample, and were also saved to the instrument memory for later analysis where appropriate. Survey personnel noted all primary noise sources contributing to noise build-up. Measurements were conducted at Locations USL01 and USL02 on a continuous basis. Sample periods for the noise measurements were nominally 5 minutes during all survey periods.

10.3.1.5 Weather The weather during the daytime survey period was dry with temperatures of 5 °C and winds of 2 to 4 m/s. The weather during the evening survey periods was dry with temperatures of 2 to 3 °C and winds not exceeding 3 m/s. The weather during the evening survey periods was dry with temperatures of 3 to 4 °C and winds not exceeding 2 m/s.

10.3.1.6 Measurement Parameters The noise survey results are presented in terms of the following parameters: LAeq is the equivalent continuous sound level. It is a type of average and is

used to describe a fluctuating noise in terms of a single noise level over the sample period.

LA90 is the sound level that is exceeded for 90% of the sample period. It is typically used as a descriptor for background noise.

The “A” suffix denotes the fact that the sound levels have been “A-weighted” in order to account for the non-linear nature of human hearing. All sound levels in this report are expressed in terms of decibels (dB) relative to 2x10-5 Pa.

10.3.2 Results and Discussion The survey results of the baseline survey are summarised in Table 10.5 to Table 10.9.

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10.3.2.1 Survey Location USL01 The survey results for location USL01 have been presented in Table 10.5.

Date

Sound Pressure Level (dB re 2x10-5 Pa)

Day (07:00 to 19:00hrs)

Evening (19:00 to 23:00hrs)

Night (23:00 to 07:00hrs)

LAeq LA90 LAeq LA90 LAeq LA90

31 Jan 2018 61 58 61 59 58 54

1 Feb 2018 65 63 63 60 59 52

2 Feb 2018 63 60 60 57 59 53

3 Feb 2018 65 62 63 60 57 52

4 Feb 2018 66 63 63 61 58 53

5 Feb 2018 66 64 62 58 60 53

6 Feb 2018 66 64 62 58 58 50

7 Feb 2018 63 60 61 58 58 51

8 Feb 2018 63 60 60 57 58 51

9 Feb 2018 63 61 - - 58 52

Average 64 62 62 59 58 52

Max 66 64 63 61 60 54

Min 61 58 60 57 57 50

Table 10.5 Survey Results – USL01

Road traffic noise from the M50 was the dominant noise source during the survey.

10.3.2.2 Survey Location USL02 The survey results for location USL02 have been presented in Table 10.6.

Date

Sound Pressure Level (dB re 2x10-5 Pa)

Day (07:00 to 19:00hrs)

Evening (19:00 to 23:00hrs)

Night (23:00 to 07:00hrs)

LAeq LA90 LAeq LA90 LAeq LA90

31 Jan 2018 61 56 60 56 57 51

1 Feb 2018 63 60 61 57 57 50

2 Feb 2018 61 57 58 54 57 50

3 Feb 2018 63 59 61 58 56 49

4 Feb 2018 63 59 61 57 57 52

5 Feb 2018 63 60 59 54 57 50

6 Feb 2018 64 61 60 55 56 47

7 Feb 2018 62 57 59 54 56 49

8 Feb 2018 61 57 59 53 56 47

9 Feb 2018 61 57 - - 56 49

Average 62 58 60 55 56 49

Max 64 61 61 58 57 52

Min 61 56 58 53 56 47

Table 10.6 Survey Results – USL02

Road traffic noise from the M50 was the dominant noise source during the survey.

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10.3.2.3 Survey Location S01

Period Survey Time Sound Pressure Level (dB re 2x10-5 Pa)

LAeq LA90

Day 12:52 - 13:07 71 70

14:26 - 14:41 70 69

Evening 22:04 - 22:19 67 63

Night 23:47 - 23:57 64 61

00:52 - 01:02 63 59

Table 10.7 Survey Results – Survey Location S01

During the daytime survey period, the dominant intermittent noise source influencing the ambient noise level was road traffic noise from the M50. Measured ambient noise levels fell in the range of 70 to 71 dB LAeq whilst background noise levels fell in the range of 69 to 70 dB LA90. During the evening survey period, the dominant intermittent noise source influencing the ambient noise level was road traffic noise from the M50. Some localised activity within the car park also influenced the measurement. Measured ambient noise levels fell in the range of 67 dB LAeq whilst background noise levels fell in the range of 63 dB LA90. During the night survey period, the dominant intermittent noise source influencing the ambient noise level was road traffic noise from the M50. Measured ambient noise levels fell in the range of 63 to 64 dB LAeq whilst background noise levels fell in the range of 59 to 16 dB LA90.



LAeq LA90

Day 13:21 - 13:36 73 65

13:36 - 13:51 74 66

Evening 22:26 - 22:41 66 55

Night 00:07 - 00:17 68 53

00:17 - 00:27 68 52


During the daytime survey period, the dominant intermittent noise source influencing the ambient noise level was road traffic noise from the R134 (New Nangor Road). Measured ambient noise levels fell in the range of 73 to 74 dB LAeq whilst background noise levels fell in the range of 65 to 66 dB LA90. During the evening survey period, the dominant intermittent noise source influencing the ambient noise level was road traffic noise from the R134 (New Nangor Road). Measured ambient noise levels fell in the range of 66 dB LAeq whilst background noise levels fell in the range of 55 dB LA90. During the night survey period, the dominant intermittent noise source influencing the ambient noise level was road traffic noise from the R134 (New Nangor Road). Measured ambient noise levels fell in the range of 68 dB LAeq whilst background noise levels fell in the range of 52 to 53 dB LA90.

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LAeq LA90

Day 14:02 - 14:17 62 57

14:49 - 15:04 62 57

Evening 22:46 - 23:01 57 46

Night 00:34 - 00:44 54 47

01:10 - 01:20 55 47


During the daytime survey period, the dominant intermittent noise source influencing the ambient noise level was road traffic noise from the R134 (New Nangor Road). Measured ambient noise levels fell in the range of 62 dB LAeq whilst background noise levels fell in the range of 57 dB LA90. During the evening survey period, the dominant intermittent noise source influencing the ambient noise level was road traffic noise from the R134 (New Nangor Road). Measured ambient noise levels fell in the range of 57 dB LAeq whilst background noise levels fell in the range of 46 dB LA90. During the night survey period, the dominant intermittent noise source influencing the ambient noise level was road traffic noise from the R134 (New Nangor Road). Measured ambient noise levels fell in the range of 54 to 55 dB LAeq whilst background noise levels fell in the range of 46 dB LA90.

10.4 CHARACTERISTICS OF THE DEVELOPMENT When considering a development of this nature, the potential noise and vibration impact on the surroundings must be considered for each of two distinct stages:

• Construction phase; and,

• Operational phase. As stated, the construction phase will involve extensive excavation over the development site as well as the construction of buildings over a phased construction period. The primary sources of outward noise in the operational context are deemed to be long term in duration and will involve, 1) Building services noise; and, 2) Emergency site operations. These issues are discussed in detailed in the following sections.

10.5 POTENTIAL IMPACTS OF THE DEVELOPMENT 10.5.1 Nearest Noise Sensitive Receptors

Figure 10.3 highlights the nearest noise sensitive receptors located adjacent the proposed development. The receptors comprise residential dwellings including houses and apartments.

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Figure 10.3 Nearest Noise Sensitive Receptors

10.5.2 Construction Phase

10.5.2.1 Noise

It is predicted that the construction programme will create typical construction activity related noise onsite. During the construction phase of the proposed development, a variety of items of plant will be in use, such as rock breakers, excavators, lifting equipment, dumper trucks, compressors and generators. Due to the nature of daytime activities undertaken on a construction site of this nature, there is potential for generation of significant levels of noise. The flow of vehicular traffic to and from a construction site is also a potential source of relatively high noise levels. The potential for vibration at neighbouring sensitive locations during construction is typically limited to excavation works and lorry movements on uneven road surfaces. Due to the fact that the construction programme has been established in outline form only, it is difficult to calculate the actual magnitude of noise emissions to the local environment. However, it is possible to predict typical noise levels using guidance set out in BS 5228-1:2009+A1:2014. Table 10.10 outlines typical plant items and associated noise levels that are anticipated for various phases of the construction programme.

Phase Item of Plant (BS 5228-1:2009+A1:2014 Ref.) Construction Noise Level

at 10m Distance (dB LAeq(1hour))

Site Preparation

Pneumatic Breaker (D2.2) 81

Rock Breaker (C9.12) 85

Wheeled Loader Lorry (D3 1) 75

Tracked Semi-Mobile Crusher (C9.14) 90

Track Excavator (C2 22) 72

Dozer (C2.13) 78

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Phase Item of Plant (BS 5228-1:2009+A1:2014 Ref.) Construction Noise Level

at 10m Distance (dB LAeq(1hour))

Dump Truck (C4.2) 78

Foundations

Large Rotary Bored Piling Rig – Cast In-Situ (C3.14) 83

Tracked Excavator (C3.24) 74

Concrete Pump (C3.25) 78

Compressor (D7 6) 77

Poker Vibrator (C4 33) 78

Steel Erection

Tower Crane (C4.48) 76

Sarens SCG 120 Crane 86

Articulated lorry (C11.10) 77

General Construction

Hand tools 81

Pneumatic Circular Saw (D7.79) 75

Internal fit – out 70

Landscaping

Dozer (C2.13) 78

Dump Truck (C4.2) 78

Surfacing (D8.25) 68

Table 10.10 Typical Noise Levels Associated with Construction Plant Items

For the purposes of the assessment we have assumed that standard good practice measures for the control of noise from construction sites will be implemented. Table 10.11 presents the predicted daytime noise levels from an indicative construction period on site. Note construction noise sources are assumed to be running 66% of the time. The predictions have been prepared to the nearest residential noise sensitive receptor to the site which is the Aras Na Cluaine apartment complex situated some 180 metres to the south of the site.

Location Phase

Predicted Construction Noise

Level LAeq,12hour (dB)

Daytime Construction Noise

Criteria LAeq,12hour (dB)

Complies?

R03

Aras Na Cluaine

apartment complex

Site Preparation 61

70 Weekdays / 65 Saturdays

Foundations 55

Steel Erection 56

General Construction 51

Landscaping 50

Table 10.11 Review of Potential Daytime Construction Noise Impact

The predicted external construction noise levels are within the relevant noise criteria over the construction phase. There are no items of plant that would be expected to give rise to noise levels that would be considered out of the ordinary or in exceedance of the levels outlined. The impact on the noise environment due to construction activities will be transient in nature

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and mitigation measures will be implemented to minimise the impact of construction activities on the noise environment.

10.5.2.2 Vibration Due to the proximity of sensitive locations to site works however, there is little likelihood of structural or even cosmetic damage to existing neighbouring dwellings as a result of vibration.

10.5.3 Operational Phase

10.5.3.1 Noise During the operational phase, the primary source of noise is expected to arise from building service plant which will be required to service data centre. All of these plant items generate noise to some degree and as such have potential to give rise to negative impacts. The nature of plant operation will be relatively consistent once the facility is operational, and can therefore be regarded as potentially medium to long term in duration, depending on the expected life of the facility. The only variation to this being in the case of elevated ambient air temperatures (which requires cooling plant to operate at higher capacity) and emergency operations (whereby emergency generators may be required to operate at any stage), these scenarios have been discussed further in the following sections. The scenario modelled as part of this assessment has been based on a peak summer temperature of 18° C (wet bulb) which would be envisaged to occur approximately 4 no. days per annum on average. As such, the assessment outlines a worst case outlook in terms of operational noise generation. It must be noted that reference to wet bulb temperature is a specific evaporative cooling parameter and does not equate to ambient air temperatures. In addition, while these temperatures would occur during the daytime period, the following assessment is presented on the basis of comparison with the night time noise limits. More typical night time plant operations would therefore be expected to generate significantly lower noise levels than those presented in the following sections.

Routine Operations The predicted noise levels associated with routine operations have been presented in Table 10.12.

Receptor Height (m)

Predicted Operational Noise Levels (dB LAeq,T) - Routine Operations

Predicted Noise Level

Design Goal Achieves Design

Goal

R01 4.5 36 45

R02 14 42 45

R03 14 43 45

R04 14 42 45

R05 4.5 39 45

R06 4.5 38 45

R07 4.5 37 45

R08 16.5 36 45

Table 10.12 Predicted Operational Noise Levels - Routine Operations

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Figure 10.4 Predicted Noise Levels - Routine Operations (dB LAeq,T at 4m height)

The results confirm that noise levels associated with typical worst operation of the facility comply with the adopted design goal. Emergency Operations In the event of a failure in electricity supply from the Energy Centre, standby generators will operate in order to maintain the sites operations. During such circumstances it is appropriate to adopt a criterion of 55 dB LAeq,T. The predicted noise levels associated with emergency operations have been presented in Table 10.12.

Receptor Height (m)

Predicted Operational Noise Levels (dB LAeq,T) - Emergency and Generator Testing

Predicted Noise Level

Design Goal Achieves Design

Goal

R01 4.5 41 55

R02 14 48 55

R03 14 49 55

R04 14 48 55

R05 4.5 45 55

R06 4.5 45 55

R07 4.5 44 55

R08 16.5 54 55

Table 10.13 Predicted Operational Noise Levels - Emergency and Generator Testing

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Figure 10.5 Predicted Noise Levels - Emergency and Generator Testing (dB LAeq,T at 4m height)

Modelling of this scenario has shown that in conjunction with worst case operations, additional noise generated by emergency operations shall also comply with the prescribed limit. Summary The scenario presented represented as part of this assessment outlines a worst-case outlook on noise generation from the site. The predicted noise levels and associated noise contours confirm that the site specific levels comply with the day, evening and night time criteria adopted for this assessment. In terms of emergency operations, it has been confirmed that the operations will remain within the adopted criterion of 55dB LAeq,T.

10.6 DO NOTHING SCENARIO The Do-Nothing scenario includes either 1) No development occurs and the site remains unused with existing unused buildings and infrastructure remaining in place, or 2) development of the site in accordance with the previously approved data centre and associated energy centre. In the first scenario, noise and vibration at the site will remain as per the baseline and will change in accordance with trends within the wider area (including new developments in the industrial estate, changes in road traffic noise, etc). If the site is developed as per the approved application, the impacts on noise and vibration will be as described in the Environmental Impact Statement for that development.

10.7 REMEDIAL AND MITIGATION MEASURES In order to sufficiently ameliorate the likely noise impact, a schedule of noise control measures has been formulated for both construction and operational phases associated with the proposed development.

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10.7.1.1 Noise With regard to construction activities, reference is made to BS 5228-1:2009+A1:2014, which offers detailed guidance on the control of noise and vibration from demolition and construction activities. Various mitigation measures will be considered and applied during the construction of the proposed development. Specific examples of such measures include:

• Limiting the hours during which site activities likely to create high levels of noise or vibration are permitted;

• Establishing channels of communication between the contractor/developer, Local Authority and residents;

• Appointing a site representative responsible for matters relating to noise and vibration;

• Monitoring levels of noise and/or vibration during critical periods and at sensitive locations; and,

• All site access roads will be kept even so as to mitigate the potential for vibration from lorries.

Furthermore, it is envisaged that a variety of practicable noise control measures will be employed. These may include:

• Selection of plant with low inherent potential for generation of noise and/ or vibration;

• Erection of barriers as necessary around items such as generators or high duty compressors; and,

• Situate any noisy plant as far away from sensitive properties as permitted by site constraints and the use of vibration isolated support structures where necessary.

10.7.1.2 Vibration

Vibration arising from construction activities at the nearest receptors shall be limited to the values set out in Table 10.3. It should be noted that these limits are not absolute, but provide guidance as to magnitudes of vibration that are very unlikely to cause cosmetic damage. Magnitudes of vibration slightly greater than those in the table are normally unlikely to cause cosmetic damage, but construction work creating such magnitudes should proceed with caution. Where there is existing damage these limits may need to be reduced by up to 50%.

10.7.2 Operational Phase

10.7.2.1 Noise A full appraisal of potential noise impacts will be undertaken at the detailed design stage. The results of this appraisal will be submitted to South Dublin County Council for review prior to commencement.

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In addition to the specification of “low noise” equipment, the detailed design will also consider following mitigation measures, and incorporate into the design where necessary:

• Acoustic louvres to all naturally ventilated façades including, but not limited to, generator plant rooms, chiller plant rooms and boiler plant rooms;

• Attenuators to be installed to gas engine air intake ducts;

• “Hospital” grade silencers to be incorporated to all gas engine and generator exhausts;

• Acoustic rated doors on all relevant plant room access points; and,

• Specification of appropriate building elements within the energy centre, specifically the enclosure of the gas engine plant rooms will require external blockwork walls as well as a high performance ceiling and roof build up.

It is envisaged that adoption of the measures outlined above will ensure that level of noise emissions from the site will remain in line with the relevant day, evening and night criteria going forward.

10.7.2.2 Vibration No mitigation will be required in respect of operational vibration.

10.8 PREDICTED IMPACTS OF THE DEVELOPMENT

10.8.1 Construction Phase During the construction phase of the project, it is expected that activities will generate elevated noise levels in the vicinity of the nearest noise sensitive receptors. It is noted that once appropriate mitigation measures are adopted, that the level of noise will fall within limits typically set for the indication of potentially significant impacts. As such the impacts arising during the construction phase can be regarded as slight to moderate negative over a temporary to short term duration.

10.8.2 Operational Phase During the operational phase, mechanical plant items required to service and power the data centre will generate increased levels of noise in the vicinity of the nearest noise sensitive receptors. Proprietary noise control measures will be employed in order to ensure that noise emissions from plant do not exceed the adopted criterion at the façade of any nearby noise sensitive receptors. The resultant noise impact will therefore be insignificant over a long term duration.

10.9 CUMULATIVE IMPACT


As the predicted impacts to the environment are slight in the short term and insignificant in the long term, the cumulative impacts from simultaneous construction of the proposed development and any external developments in the immediate vicinity

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of the site are deemed short-term and slight with appropriate mitigation measures in place.

10.9.2 Operational Phase For the operational phase of the proposed development, the cumulative impact is deemed to be insignificant.

10.10 RESIDUAL IMPACTS

10.10.1 Construction Phase In so far as the mitigation measures are applied in full, the level of residual noise generated from the proposed development during the construction phase would be expected to fall within the appropriate limits.

10.10.2 Operational Phase In so far as the mitigation measures are applied in full, the level of residual noise generated from the proposed development during the operational phase would be expected to fall within the appropriate limits.

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APPENDIX 10.1 GLOSSARY OF ACOUSTIC TERMINOLOGY

Ambient Noise The totally encompassing sound in a given situation at a given

time, usually composed of sound from many sources, near and far.

Background Noise The steady existing noise level present without contribution from

any intermittent sources. The A-weighted sound pressure level of the residual noise at the assessment position that is exceeded for 90 per cent of a given time interval, T (LAF90,T).

Broadband Sounds that contain energy distributed across a wide range of

frequencies. dB Decibel - The scale in which sound pressure level is expressed. It

is defined as 20 times the logarithm of the ratio between the RMS pressure of the sound field and the reference pressure of 20 micro-pascals (20 μPa).

dB LpA An ‘A-weighted decibel’ - a measure of the overall noise level of

sound across the audible frequency range (20 Hz – 20 kHz) with A-frequency weighting (i.e. ‘A’–weighting) to compensate for the varying sensitivity of the human ear to sound at different frequencies.

LAeq,T This is the equivalent continuous sound level. It is a type of

average and is used to describe a fluctuating noise in terms of a single noise level over the sample period (T).The closer the LAeq value is to either the LAF10 or LAF90 value indicates the relative impact of the intermittent sources and their contribution. The relative spread between the values determines the impact of intermittent sources such as traffic on the background. As standard it is measured using the fast time weighting constant of 125 ms.

LAFN The A-weighted noise level exceeded for N% of the sampling

interval. Measured using the “Fast” time weighting. LAF90 Refers to those A-weighted noise levels in the lower 90 percentile

of the sampling interval; it is the level which is exceeded for 90% of the measurement period. It will therefore exclude the intermittent features of traffic and is used to estimate a background level. Measured using the “Fast” time weighting.

Noise Any sound, that has the potential to cause disturbance, discomfort

or psychological stress to a person exposed to it, or any sound that could cause actual physiological harm to a person exposed to it, or physical damage to any structure exposed to it, is known as noise.

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APPENDIX 10.1 (Cont.) GLOSSARY OF ACOUSTIC TERMINOLOGY

Noise Sensitive Receptor Any dwelling house, hotel or hostel, health building, educational

establishment, place of worship or entertainment, or any other facility or other area of high amenity which for its proper enjoyment requires the absence of noise at nuisance levels.

Octave Band A frequency interval, the upper limit of which is twice that of the

lower limit. For example, the 1,000 Hz octave band contains acoustical energy between 707 Hz and 1,414 Hz. The centre frequencies used for the designation of octave bands are defined in ISO and ANSI standards.

Sound Pressure Level The sound pressure level at a point is defined as:

0

20P

PLogLp dB

Tonal Sounds which cover a range of only a few Hz which contains a

clearly audible tone i.e. distinguishable, discrete or continuous noise (whine, hiss, screech, or hum etc.) are referred to as being ‘tonal’.

1/3 Octave Analysis Frequency analysis of sound such that the frequency spectrum is

subdivided into bands of one–third of an octave each.

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APPENDIX 10.2 NOISE MODELLING DETAILS

10.2.1 Noise Model

A 3D computer-based prediction model has been prepared in order to quantify the noise level associated with the proposed development. This section discusses the methodology behind the noise modelling process.

10.2.2 Brüel & Kjær Type 7810 Predictor Proprietary noise calculation software has been used for the purposes of this modelling exercise. The selected software, Brüel & Kjær Type 7810 Predictor, calculates noise levels in accordance with ISO 9613-2:1996 Acoustics – Attenuation of Sound During Propagation Outdoors - General Method of Calculation. Brüel & Kjær Type 7810 Predictor is a proprietary noise calculation package for computing noise levels in the vicinity of noise sources. Predictor calculates noise levels in different ways depending on the selected prediction standard. In general, however, the resultant noise level is calculated taking into account a range of factors affecting the propagation of sound, including:

• the magnitude of the noise source in terms of A weighted sound power levels (LWA);

• the distance between the source and receiver;

• the presence of obstacles such as screens or barriers in the propagation path;

• the presence of reflecting surfaces;

• the hardness of the ground between the source and receiver;

• Attenuation due to atmospheric absorption; and

• Meteorological effects such as wind gradient, temperature gradient and humidity (these have significant impact at distances greater than approximately 400m).

10.2.3 Brief Description of ISO9613-2: 1996

ISO9613-2:1996 calculates the noise level based on each of the factors discussed previously. However, the effect of meteorological conditions is significantly simplified by calculating the average downwind sound pressure level, LAT(DW), for the following conditions:

• wind direction at an angle of ±45° to the direction connecting the centre of the dominant sound source and the centre of the specified receiver region with the wind blowing from source to receiver, and;

• wind speed between approximately 1ms-1 and 5ms-1, measured at a height of 3m to 11m above the ground.

The equations and calculations also hold for average propagation under a well-developed moderate ground based temperature inversion, such as commonly occurs on clear calm nights.

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APPENDIX 10.2 NOISE MODELLING DETAILS (Continued)

The basic formula for calculating LAT(DW) from any point source at any receiver location is given by:

LfT(DW) = LW + Dc – A Eqn. A Where: LfT(DW) is an octave band centre frequency component of LAT(DW) in dB relative

to 2x10-5 Pa; LW is the octave band sound power of the point source; Dc is the directivity correction for the point source; A is the octave band attenuation that occurs during propagation, namely

attenuation due to geometric divergence, atmospheric absorption, ground effect, barriers and miscellaneous other effects.

The estimated accuracy associated with this methodology is shown in Table A1 below:

Height,h* Distance, d†

0 < d < 100m 100m < d < 1,000m

0<h<5m ±3dB ±3dB

5m<h<30m ±1dB ±3dB

Table A1 Estimated Accuracy for Broadband Noise of LAT(DW)

* h is the mean height of the source and receiver. † d is the mean distance between the source and receiver. N.B. These estimates have been made from situations where there are no

effects due to reflections or attenuation due to screening.

10.2.4 Input Data and Assumptions The noise model has been constructed using data from various source as follows: Site Layout The general site layout has been obtained from the drawings

forwarded by Kavanagh + Tuite architects. Local Area The location of noise sensitive locations obtained from Ordinance

Survey Ireland (OSI) provided by CSEA. Heights Onsite building heights have not been obtained from elevations

provided by Kavanagh + Tuite architects. Contours Site ground contours/heights have been obtained from site drawings

forwarded by CSEA. The final critical aspect of the noise model development is the inclusion of the various plant noise sources. Details are presented in the following section.

10.2.5 Source Sound Power Data Each noise source was input as sound power in octave bands. The sound power of each source was measured in accordance with BS EN ISO 3740:2001 Acoustics. Determination of Sound Power Levels of Noise Sources – Guidelines for the use of Basic Standards and BS EN ISO 3746:2010 Acoustics - Determination Of Sound

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Power Levels and Sound Energy Levels of Noise Sources using Sound Pressure — Survey Method using an Enveloping Measurement Surface over a Reflecting Plane. This standard involves the measurement of sound pressure at a set of points on an enveloping surface around the source, and applying a correction to the measured level to obtain the sound power of the source. Where direct noise measurement were not possible, noise data has been input into the model based on plant manufacturers’ technical data and/or empirical formulae. Predictor accepts sound power levels in octave bands from 31.5 Hz to 8 kHz. Figure A2 presents a 3D render of the developed site noise model. The red areas/points indicated on the figure illustrate noise sources incorporated into the noise model.

Figure A2 3D view of model

10.2.6 Modelling Calculation Parameters

Prediction calculations for plant noise have been conducted in accordance with ISO 9613-2:1996 Acoustics - Attenuation of Sound During Propagation Outdoors - General Method of Calculation. Ground attenuation factors of 0.5 have been assumed. No metrological corrections were assumed for the calculations. The atmospheric attenuation outlined in Table A2 has been assumed for all calculations.

Temp (ºC) % Humidity

Octave Band Centre Frequencies (Hz)

63 125 250 500 1k 2k 4k 8k

10 70 0.11 0.38 1.02 1.97 3.57 8.76 28.72 103.21

Table A2 Atmospheric Attenuation Assumed for Noise Calculations (dB per km)

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10.0 noise and vibration 10.1 introductionbs 5228-1:2009+a1:2014 sets out guidance on permissible...

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