ASSESSMENT OF INWARD TRAFFIC NOISE IMPACT AT RESIDENTIAL DEVELOPMENT, WONDERFUL BARN, LEIXLIP, CO. KILDARE

Transcription

1 ASSESSMENT OF INWARD TRAFFIC NOISE IMPACT AT RESIDENTIAL DEVELOPMENT, WONDERFUL BARN, LEIXLIP, CO. KILDARE Technical Report Prepared For Ardstone Capital Ltd. 48 Fitzwilliam Square Dublin Technical Report Prepared By Jennifer Harmon BSc MIOA Our Reference JH/16/9191NR01a Date Of Issue 27 November 2017

2 Document History Document Reference Original Issue Date JH/16/9191NR01 12 December 2016 Revision Level Revision Date Description Sections Affected a 27 November 2017 Site Layout All Record of Approval Details Written by Approved by Signature Name Jennifer Harmon Ronan Murphy Title Senior Acoustic Consultant Senior Acoustic Consultant Date 27 November November 2017 Page 2

3 EXECUTIVE SUMMARY AWN Consulting has been requested by Ardstone Capital Limited to undertake an assessment of the potential road traffic noise intrusion on a proposed residential development at Wonderful Barn, Leixlip Co. Kildare. For the assessment of noise, guidance has been taken from the following documents: Kildare Local Authorities Second Noise Action Plan (July 2013), and; BS 8233:2014 Guidelines for Sound Insulation and Noise Reduction for Buildings. Making reference to the above documents, the following daytime and night time internal noise criteria are proposed: Internal Room Daytime (07:00hrs to 23:00hrs) LAeq (db Re 2 x 10-5 pa ) Night-time (23:00hrs to 07:00hrs) Living Rooms Bedrooms An acoustic model has been developed for the proposed development in order to calculate noise levels across the proposed site, taking into account the site layout plans and road traffic volumes along the M4 Motorway. The predicted noise levels at the external façade of the development buildings have been used to determine the internal noise levels within living room and bedroom spaces, taking account of the proposed building elements (i.e. glazing and walls), the surface area of each and the receiving room volumes. The assessment has determined that the internal noise environment within the development are predicted to be within the recommended criteria adopted from BS 8233:2014 with glazing types offering the following minimum sound insulation performance as follows: Glazing Specification Octave Band Centre Frequency (Hz) Overall k 2k 4k Type Type Rw Figure 7 in this report illustrates the location of the enhanced glazing Type 2 across the development. The assessment has concluded that the insulation capabilities of the development are deemed to be acceptable in order to achieve the target noise levels as outlined in Section 7.7 Planning For Noise Management, set out in Kildare Local Authorities Noise Action Plan and achieve the recommended internal noise levels for residential dwellings set out in BS 8233:2014. Page 3

4 CONTENTS Page Executive Summary Introduction Assessment Criteria Kildare Noise Action Plan (2013) British Standard BS 8233 (2014) WHO Community Noise Summary Site Description Assessment of Site Noise Survey Survey Results Assessment of the Development Site Assessment of the Proposed Development Assessment of Building Sound Insulation Glazing Wall Construction Ventilation Strategy Conclusions 16 Figure 1 Site context and approximate red line boundary 8 Figure 2 Noise Monitoring Position 9 Figure 3 Calculated L den noise levels across development site 11 Figure 4 Calculated L night noise levels across development site 12 Figure 5 Daytime noise levels with proposed development 13 Figure 6 Night-time noise levels with proposed development 14 Appendix A Acoustic Technical Data 17 Page 4

5 1.0 INTRODUCTION AWN Consulting has been requested by Ardstone Capital Limited to undertake an assessment of the potential noise impact associated with the M4 Motorway on a proposed new residential development at Wonderful Barn, Leixlip, Co. Kildare. The noise impact assessment is being carried out in order to ensure a good environment for residential amenity is provided. It is proposed to use guidance from British Standard BS 8233:2014 Guidelines for Sound Insulation and Noise Reduction for Buildings and the World Health Organisation s (WHO) document Guidelines for Community Noise (1999). The assessment methodologies contained within these guidance documents are considered to be current best practice for the assessment of traffic noise on residential developments. This report will include the following: Review of the relevant content of the standards that will be used for the noise assessment; Comment on the expected noise levels across the site, and; Review of mitigation measures that will be considered in relation to the levels of noise incident on the site. Page 5

6 2.0 ASSESSMENT CRITERIA The following section discusses the relevant guidance documents used to set appropriate external and internal noise levels across the site. 2.1 Kildare Noise Action Plan ( ) The Noise Action Plan states the following in terms of the proposed noise control measures to be adopted when considering developments which introduce people to noise: Whilst the control of external levels of environmental noise constitutes one aspect of noise management within planning, and aims to provide benefit to amenity spaces, the control of noise levels within residential properties, and other noise sensitive premises also plays an important role. In the scenario where new noise sensitive premises are introduced to locations already exposed to significant levels of long term environmental noise as set out in the Environmental Noise Regulations, i.e. 70dB L den and 57 db L night, it is considered appropriate to consider aiming to achieve target internal noise levels within noise sensitive rooms, such as living rooms and bedrooms. In the case of new development, or conversions, these targets could be introduced through the use of appropriate planning conditions, and possibly some form of pre-completion testing as used in a number of other EU countries. The choice of targets for internal noise levels could be informed by the WHO Guidelines for Community Noise (2000) and Night Noise Guidelines for Europe (2009) or BS 8233 Given the guidance levels set out within WHO and NNG typically refer to external noise levels, reference has been made to BS 8233 in order to set appropriate internal noise levels within sensitive rooms of the developments. In this instance, reference has been made to the updated 2014 version of the standard. 2.2 British Standard BS 8233 (2014) The standard, BS 8233 (2014) Guidelines for Sound Insulation and Noise Reduction For Buildings, sets out recommended internal noise levels for several different building types from external noise sources such as road traffic noise. The guidance is primarily for use by designers and hence BS 8233 may be used as the basis for an appropriate schedule of noise control measures. The recommended internal noise levels for residential developments are set out below. Activity Location Day 07:00 to 23:00hrs db LAeq,16hour Night 23:00 to 07:00hrs db LAeq,8hour Resting Living room 35 - Dining Dining room/area 40 - Sleeping (daytime resting) Bedroom Table 1 Summary of recommended internal noise levels from BS 8233 The document also notes that where development is considered necessary or desirable, despite external noise levels above WHO guidelines, the internal target levels may be relaxed by up to 5 db and reasonable internal conditions still achieved. Page 6

7 In relation to noise levels in external amenity areas, BS 8233 provides the following guidance: For traditional external areas that are used for amenity space, such as gardens and patios, it is desirable that the external noise level does not exceed 50 db L Aeq,T, with an upper guideline value of 55 db L Aeq,T which would be acceptable in noisier environments. However, it is also recognized that these guideline values are not achievable in all circumstances where development might be desirable. In higher noise areas, such as city centres or urban areas adjoining the strategic transport network, a compromise between elevated noise levels and other factors, such as the convenience of living in these locations or making efficient use of land resources to ensure development needs can be met, might be warranted. In such a situation, development should be designed to achieve the lowest practicable levels in these external amenity spaces, but should not be prohibited 2.3 WHO Community Noise The World Health Organization (WHO) document Guidelines for Community Noise (1999) provides the following design criteria and guidelines in relation to noise: 2.4 Summary The effects of noise in dwellings, typically, are sleep disturbance, annoyance and speech interference. For bedrooms the critical effect is sleep disturbance. Indoor guideline values for bedrooms are 30dB L Aeq for continuous noise and 45dB L Amax for single sound events. Lower noise levels may be disturbing depending on the nature of the noise source. To enable casual conversation indoors during daytime, the sound level of interfering noise should not exceed 35dB L Aeq. In summary, and with consideration of the guidelines outlined in the Kildare Noise Action Plan, WHO Guidelines for Community Noise and BS 8233:2014 it is considered that the following criteria are relevant in the context of the proposed development: 35dB L Aeq,16hour daytime within living / bedrooms; 40dB L Aeq,16hour daytime within dining rooms, and; 30dB L Aeq,8hour night-time within bedrooms. External noise levels in amenity areas should be designed so as to achieve the lowest practicable levels, within reasonable design constraints. Page 7

8 3.0 SITE DESCRIPTION The site is located to the north of the Wonderful Barn, Leixlip Co. Kildare. The site is bound to the south by greenfield lands associated with the Wonderful Barn grounds and the M4 Motorway to beyond. The north, east and west of the site are all bound by existing residential estates. Figure 1 illustrates the site location in the context of the surrounding lands. Figure 1 Site context and approximate red line boundary The proposal includes for a total of 450 properties in a mixture of terrace and semidetached 3 and 4 bedroom dwellings. Page 8

9 4.0 ASSESSMENT OF SITE 4.1 Noise Survey Survey Details An attended noise survey was conducted at the site over a daytime period to obtain a profile of typical noise levels at different locations in close proximity to and away from the M4 to inform the assessment. The survey was conducted between 10:30hrs to 13:30hrs on 25 November 2016 using a Brüel and Kjaer Type 2250 Sound level meter. Noise levels were measured over 15 minute periods at each location. A summary of the acoustic parameters discussed below are included in Appendix A. The three monitoring locations are displayed in Figure 2 below. N3 N2 N1 Figure 2 Noise monitoring positions Survey Results Location N1 The results of the noise measurements made at Location N1 are presented in Table 2 below. Start Time (Hrs) Measured Noise Levels, db re 2 x 10-5 pa LAeq LAFMax LAF10 LAF90 10: : : Average Calculated Lden 65 Table 2 Results of noise survey Location N1 Page 9

10 Noise levels measured at this location were dominated by traffic along the M4 Motorway, traffic along the R404, occasional traffic passing along local access road pedestrian activity and overhead aircraft. Location N2 The results of the noise measurements made at Location N2 are presented in Table 3 below. Start Time (Hrs) Measured Noise Levels, db re 2 x 10-5 pa LAeq LAFMax LAF10 LAF90 11: : : Average Calculated Lden 68 Table 3 Results of noise survey Location N2 Noise levels measured at this location were dominated by traffic along the M4 Motorway, overhead aircraft and occasional pedestrian activity. The results of the noise measurements made at Location N3 are presented in Table 4 below. Start Time (Hrs) Measured Noise Levels, db re 2 x 10-5 pa LAeq LAFMax LAF10 LAF90 10: : : Average Calculated Lden 57 Table 4 Results of noise survey Location N3 Noise levels measured at this location were noted to be influenced by distance M4 traffic, birdsong and overhead aircraft. 4.3 Assessment of The Development Site In order to calculate noise levels across the site, a noise model of the lands was developed. The general methodology and details of the software package used (i.e. Brüel & Kjær Type 7810 Predictor) are presented in Appendix A of this document. The noise model was developed using OS mapping for the extent of the study area and the M4 Motorway alignment, and estimated traffic flow in terms of the Annual Average Daily Traffic (AADT). Traffic data for the M4 was obtained from the NRA s automated traffic counters for the closest automated data counter along this road located between Junction 6 Celbridge and Junction 7 Maynooth. The counted AADT traffic along this route for 2016 is 56,451 (93% coverage) with 5.2% HGV for the year The annual growth factor was calculated as 0.5%. Page 10

11 A modelled flow of 60,000 AADT was used in the model with a road speed of 120km/h. Estimated traffic flows of 5,000 AADT were modelled along the R404 and R449 to the east and west of the development site respectively. The model was calibrated against the noise levels measured at the monitoring locations N1 to N3 and a strong correlation was achieved (within 2dB of measured levels) hence is a good representation of traffic noise levels incident across the site. Based on the model inputs discussed above, noise levels across the development site have been predicted in order to determine the noise impact using the Kildare Noise Action Plan definition of significant noise levels above which mitigation measures may need to be considered. The Action Plan defines these levels as follows: >70dB(A) L den, and; >57dB(A) L night. Figures 3 and 4 present the calculated L den and L night across the site. Figure 3 Calculated Lden noise levels across development site The results indicate that noise levels are in the range of 50 to 66dB L den across the site. Noise levels at all locations across the development site are below the L den threshold value of 70dB. Figure 4 presents the calculated L night across the development site. Page 11

12 Figure 4 Calculated Lnight noise levels across development site The range of noise levels calculated across the site are in the range of <50 to 57dB L night. The most southern parts of the development site are therefore just at the Kildare Noise Action Plan noise threshold level for night-time periods. Page 12

13 6.0 ASSESSMENT OF THE PROPOSED DEVELOPMENT In order to determine the noise levels at the various façades of the proposed development, the computer noise model discussed in Section 5.0 was modified to include the proposed buildings. Receivers were located at the facades of the most exposed buildings at first floor level. The calculated noise levels at these receiver locations will be used to determine the required sound insulation specification of the building envelope to comply with the internal noise levels as recommended is BS8233:2014 discussed previously in Section 2.2. In order to calculate noise levels over the appropriate periods in compliance with this standard, noise levels are calculated over daytime periods, i.e. 07:00 to 23:00hrs and night-time periods, 23:00 to 07:00hrs. The calculated noise levels across the site for the daytime and night-time periods, incorporating the development site are presented in Figures 5 and 6 below. The calculation height for both scenarios is 4m above ground level. Figure 5 Daytime noise levels (db LAeq,16hour) with development in place Page 13

14 Figure 6 Night-time noise levels (db LAeq,8hour) with development in place Specific noise levels have been calculated at the facades of key exposed properties across the development site. Highest external noise levels are calculated at properties facing towards the M4 which do not benefit from screening from the development on-site buildings, noise levels at these facades are calculated in the range of 58 to 66dB L Aeq,16hr. At all other facades, set back from the southern properties, calculated daytime noise levels are below 55dB L Aeq,16hr. The sound insulation requirements of the proposed building facades based on the calculated noise levels are set out in the following section. Page 14

15 7.0 ASSESSMENT OF BUILDING SOUND INSULATION Based on the predicted day and night-time noise levels presented in Section 6, the appropriate sound insulation performance of the building envelope can be specified in order to achieve the appropriate internal noise levels set out in Section Glazing As is the case in most buildings, the glazed elements of the building envelope are typically the weakest element from a sound insulation perspective. On review of the calculated noise levels across the development site over day and night-time periods, two glazing specifications have been determined for the residential properties in order to achieve the recommended internal noise levels for day and night-time periods within living rooms and bedrooms. In this instance, glazing Type 1 offering a minimum sound insulation performance of 33dB R w is deemed suitable for the majority of properties across the development site. A standard thermal double glazed system will typically achieve this level of performance. Type 2 providing an enhanced sound insulation performance of 37dB R w or greater is recommended for properties within higher noise zones. Figure 7 illustrates the recommended location of glazing Type 2 highlighted in red. This predominately relates to bedrooms and living spaces of properties along this line. For all other property facades, glazing Type 1 provides a sufficient level of sound insulation. Glazing Type 2 Figure 7 Areas of Glazing Type 2 Across development site Table 5 below is deemed suitable for the full development in order to achieve an acceptable internal noise environment. Page 15

16 Glazing Specification Octave Band Centre Frequency (Hz) k 2k 4k Overall Rw Type Type Table 5 Sound insulation performance requirements for glazing, SRI (db) Taking account of the external noise levels, the surface area of the glazing and walls, and the relevant receiving room volumes, the calculated internal noise levels are below 35dB L Aeq,16hr for daytime periods and 30dB L Aeq,8hr night-time within bedrooms, the most sensitive rooms of the building. This glazing specification also achieves the internal daytime noise criterion for daytime periods within living rooms of 40dB L Aeq. It is important to note that the acoustic performance specifications detailed herein are minimum requirements which apply to the overall glazing system. In the context of the acoustic performance specification the glazing system is understood to include any and all of the component parts that form part of the glazing element of the façade, i.e. glass, frames, seals, openable elements etc. 7.2 Wall Construction In general all wall constructions, i.e. block work or concrete, offer a high degree of sound insulation, much greater than that offered by the glazing systems set out in Section 7.1. Therefore, noise intrusion via the wall construction will be minimal. The calculated internal noise levels across the building façade have assumed a minimum sound reduction index of 50dB R w for this construction. 7.3 Ventilation The ventilation strategy for the development will be in accordance with Part F of the Building Regulations and will be finalised at the detail design stage. Options which will be considered in order to achieve compliance with background ventilation requirements will be adjustable hit and miss acoustic ventilators or trickle vents built into the façade or window frames respectively. The installed ventilation either through window trickle vents or wall vents should achieve a sound insulation performance equal to or greater than the glazing specification noted in Section 7.1 above. Page 16

17 8.0 CONCLUSIONS Using guidance outlined in the Kildare Noise Action Plan, the development site in question has been assessed in terms of its noise exposure category from road traffic noise. Based on this assessment, the development site has been found to be below the range of noise levels deemed to be significant and where the onset of mitigation measures would typically be considered for noise, i.e. 70dB L den and 57dB L night. In order to comply with Section 7.7 of the Noise Action Plan, guidance contained within BS 8233 has been used to determine a range of suitable internal noise levels for sensitive rooms within the buildings. Calculated noise levels at the external façade of all development buildings have been used to determine the internal noise levels within living room and bedroom spaces, taking account of the proposed standard building elements. The assessment has determined that the internal noise environment within the sensitive areas of the development are predicted to be within the recommended criteria adopted from BS 8233 using a standard double glazing system. The minimum sound insulation performance of the assumed glazing is set out within the body of this report. Page 17

18 A.1 Acoustic Parameters APPENDIX A ACOUSTIC TECHNICAL DATA db Hertz (Hz) L Aeq,T L AF10 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). The unit of sound frequency in cycles per second. 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 L Aeq value is to either the L AF10 or L AF90 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. Refers to those A-weighted noise levels in the top 10 percentile of the sampling interval; it is the level which is exceeded for 10% of the measurement period. It is used to determine the intermittent high noise level features of locally generated noise and usually gives an indicator of the level of road traffic. Measured using the Fast time weighting. L AF90 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 describe a background level. Measured using the Fast time weighting. L AFmax L AFmin The maximum RMS A-weighted sound pressure level occurring within a specified time period. Measured using the Fast time weighting. The minimum RMS A-weighted sound pressure level occurring within a specified time period. Measured using the Fast time weighting. Page 18

19 L den Is the 24 hour noise rating level determined by the averaging of the L day with the L evening plus a 5 db penalty and the L night plus a 10 db penalty. L den is calculated using the following formula: Where: - Lday is the A-weighted long-term average sound level as defined in ISO , determined over all the day periods of a year; - - Levening is the A-weighted long-term average sound level as defined in ISO , determined over all the evening periods of a year and; - - Lnight is the A-weighted long-term average sound level as defined in ISO , determined over all the night periods of a year. A.2 Noise Model Information A computer-based prediction model has been prepared in order to quantify the traffic noise level associated with the M4 Motorway on the proposed development site. Brüel & Kjær Type 7810 Predictor Proprietary noise calculation software was used for the purposes of this impact assessment. The selected software, Brüel & Kjær Type 7810 Predictor, calculates traffic noise levels in accordance with CRTN guidance. Brüel & Kjær Type 7810 Predictor is a proprietary noise calculation package for computing noise levels in the vicinity of noise sources. Predictor predicts 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 sound power or traffic flow and average velocity; 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. Prediction of traffic noise Noise emissions during the operational phase of the project have been modelled using Predictor in accordance with CRTN. The CRTN method of predicting noise from a road scheme consists of the following five elements: divide the road scheme into segments so that the variation of noise within this segment is small; calculate the basic noise level at a reference distance of 10 metres from the nearside carriageway edge for each segment; Page 19

20 assess for each segment the noise level at the reception point taking into account distance attenuation and screening of the source line; correct the noise level at the reception point to take account of site layout features including reflections from buildings and facades, and the size of source segment; combine the contributions from all segments to give the predicted noise level at the receiver location for the whole road scheme. Note that all calculations are performed to one decimal place. Page 20