ITV CORONATION STREET PRODUCTION FACILITY, TRAFFORD WHARF ROAD ASSESSMENT OF POTENTIAL NOISE & VIBRATION IMPACT OF PROPOSED METROLINK LINE

Transcription

1 ITV CORONATION STREET PRODUCTION FACILITY, TRAFFORD WHARF ROAD ASSESSMENT OF POTENTIAL NOISE & VIBRATION IMPACT OF PROPOSED METROLINK LINE On behalf of: ITV plc

2 Report No v1 October 2014 ITV CORONATION STREET PRODUCTION FACILITY, TRAFFORD WHARF ROAD ASSESSMENT OF POTENTIAL NOISE & VIBRATION IMPACT OF PROPOSED METROLINK LINE Report prepared by: Hepworth Acoustics Ltd 21 Little Peter Street Manchester M15 4PS On behalf of: ITV plc Report prepared by: Donald Quinn BSc MIOA Technical Director Report checked by: Peter Hepworth BSc FIOA Managing Director

3 CONTENTS PAGE 1.0 INTRODUCTION AND DESCRIPTION OF PROPOSALS NOISE AND VIBRATION MEASUREMENTS POTENTIAL CONSTRUCTION NOISE LEVELS ASSESSMENT OF NOISE AND VIBRATION IMPACT SUMMARY 14 FIGURE 1 TfGM PROPOSED METROLINK TRAFFORD PARK LINE ROUTE MAP FIGURE 2: ITV TWR SITE, WITH ROUTE OF PROPOSED METROLINK PLOT 1 TYPICAL TRAM PASS-BY PLOT 2 TRAM RAIL SQUEAL PLOT 3 TRAM HORN PLOT 4 WORST CASE CONSTRUCTION PHASE NOISE Appendix I Noise Units and Indices

4 1.0 INTRODUCTION AND DESCRIPTION OF PROPOSALS 1.1 Hepworth Acoustics has been commissioned by ITV to assess the potential noise and vibration impact associated with the construction phase and operational phase of a proposed Metrolink tram line upon activities at their Trafford Wharf Road site. 1.2 We understand that the proposals for the Trafford Park line are at an early stage, but that they include a two way tram line to pass the ITV site east - west along Trafford Wharf Road, turning to the south along Warren Bruce Road. Proposals also include a tram stop outside the Imperial War Museum North on Trafford Wharf Road just to the east of the ITV site. Figure 1 shows a proposed route plan. Figure 2 also shows the layout of the ITV site. 1.3 Coronation Street filming takes place on the purpose built outdoor lot and within studio buildings located at the Trafford Wharf Road site. These filming activities require stringent acoustic criteria and the design of the site incorporates comprehensive sound insulation and noise control measures designed to control the impact of noise from existing sources in the area. 1.4 The construction phase and the operational phase of the proposed Metrolink line, and the associated stop outside the Imperial War Museum, have the potential to significantly increase, and most crucially change the character of, the existing ambient noise climate around the site. As such, the proposed Metrolink line has the potential to result in significant disruption to outdoor and indoor filming. Also, elevated levels of groundborne vibration may impact on sensitive camera equipment and be reradiated as noise within studio buildings 1.5 Our assessment has included the following: A review of the computer noise model of the ITV site prepared during the planning phase of the development. A series of tram source noise measurements including typical pass-bys on an appropriate section of existing Metrolink line, tram horns and rail squeal associated with trams turning tight bends on the line; Tel: Page 1 of 22

5 Vibration measurements associated with tram pass-bys on an appropriate section of existing Metrolink line; Adopting typical source noise levels for likely Metrolink line construction operations; Computerised modelling of likely Metrolink construction and operational noise levels; Assessing the potential noise and vibration impact on filming activities of the construction and operational phases of the Metrolink line. 1.6 Noise levels referred to in the text of this report have been rounded to the nearest decibel, as fractions of decibels are imperceptible. A description of noise units and noise characteristics is provided in Appendix I. Tel: Page 2 of 22

6 2.0 NOISE AND VIBRATION MEASUREMENTS Noise & Vibration Measurements of Tram Pass-bys 2.1 Noise and groundborne vibration measurements were carried out for a series of tram pass-bys on an existing section of Metrolink line considered to be similar to that which would be installed along Trafford Wharf Road. 2.2 Noise and vibration measurements were taken on Eccles New Road (the A57) which is a long straight road where trams share the carriageway with other vehicles in the same way that could be expected along Trafford Wharf Road. The measurements were taken at a distance of approximately 5m from the nearside (west-bound) track. 2.3 Tram pass-by noise measurements were taken using a B&K 2260 Type 1 sound analyser (serial no ) which was calibrated before and after the measurements with no variance noted. The sound analyser was mounted onto a tripod at a height of approximately 1.4 metres above ground in free-field conditions. The weather conditions during the survey were dry, cool and overcast with occasional light winds (<4m/s). 2.4 The noise measurements were taken in terms of octave band L max and SEL values and are summarised as follows: Table 1: Summary of tram pass-by noise levels at 5m from nearside track (db) Description Octave band centre frequency (Hz) k 2k 4k 8k A Average tram pass-by SEL Highest Lmax Table 1 shows that both SEL and L max noise levels are dominated by the influence of noise in the 1 khz octave band. Tel: Page 3 of 22

7 2.6 Vibration measurements were taken using a Profound tri-axial Vibration Monitoring system (serial no ). The transducer was located on the pavement at the same location as the sound analyser, orientated such that the x-axis was parallel to the tram tracks and the y-axis was perpendicular to the tram tracks. Measurements were taken in terms of 1 min PPV (peak particle velocity) periods over the course of an hour. The results are shown in Chart 1 below: Chart 1: Measured tram pass-by vibration (PPV) levels (mm/s) 2.7 Vibration levels from tram pass-bys were typically below 1 mm/s, although the highest measured peak velocity was 1.2 mm/s measured at 11:07. Tel: Page 4 of 22

8 Noise Measurements of Transient Noise from Trams 2.8 A series of noise measurements were also taken of other transient noise associated with Metrolink trams. These measurements, which were taken at various locations around Manchester city centre, included noise from the squeal of tram wheels against the tracks when turning tight bends, and noise from tram horns. 2.9 The highest measured noise levels from each of these sources is shown in Table 2: Table 2: Summary of highest measured L max transient noise levels from trams, corrected to a distance of 10 m (db) Description Octave band centre frequency (Hz) k 2k 4k 8k A Tram wheel noise at tight bends Tram horns Table 2 shows that for tram wheel noise at bends, the measured noise levels in the 2 khz and 4 khz octave bands are much higher than at other frequencies. A similar situation exists for the noise for tram horns in the 500 Hz octave band. This indicates noise with a very tonal character compared to broadband noise. It is this specific tonal character of noise, along with its transient nature, that makes it potentially disruptive to ITV filming activities. Tel: Page 5 of 22

9 3.0 POTENTIAL CONSTRUCTION NOISE LEVELS 3.1 At this early stage, it is not clear what specific construction activities and operations would be necessary to construct the proposed Metrolink line. However, by reference to appropriate technical guidance documents, we have adopted a series of source noise levels for typical operations and activities that could be expected as part of the construction phase. 3.2 BS5228-1:2009+A1:2014 Code of practice for noise and vibration control on construction and open sites Part 1: Noise, provides the latest guidance on the assessment and control of noise from construction sites. Annex C of the standard provides details of source noise levels for typical construction site activities. For the purposes of this assessment, we have adopted the following source noise levels to represent the potential noise emissions associated with the construction phase of the proposed Metrolink line. This is not an exhaustive list, and it is possible that noisier equipment could be used during the construction phase. However we consider this represents a conservative estimate of likely noise levels: Table 3: Adopted construction activity noise levels at a distance of 10m (db) Description BS5228 table ref. Octave band centre frequency (Hz) k 2k 4k 8k A Wheeled excavator C Hand held circular saw C Breaker mounted on wheeled backhoe C Please note that the source noise data provided in BS5228 for the equipment set out above is in terms of average L eq noise levels and no corresponding peaks of noise are given. Therefore, for the purposes of this assessment, the source L eq values have been increased by 5 db to represent a conservative estimate of the corresponding L max noise levels during use of the equipment. 3.4 At this stage, it is not possible to determine vibration levels associated with the construction phase of the proposed Metrolink line. However, we consider that due to the requirement to Tel: Page 6 of 22

10 remove the existing road surface, excavate and relocate any existing services and install new foundations and rails etc. there are likely to be numerous activities that may require the use of heavy equipment and percussive tools. Tel: Page 7 of 22

11 4.0 ASSESSMENT OF NOISE AND VIBRATION IMPACT Potential Vibration Impact 4.1 We consider that it is the magnitude of regular transient peaks of vibration, rather than the number of peaks or average vibration levels that must be considered when determining the potential disruption to ITV operations. 4.2 The vibration levels (in terms of PPV) measured from tram pass-bys on an existing section of Metrolink line similar to that anticipated on Trafford Wharf Road were up to 1.2mm/s at a distance of 5m from the nearside track. This is the same level of vibration that was measured at a distance of 5m from the kerbside of Trafford Wharf Road during the passage of HGVs as part of our initial noise and vibration measurements at the Trafford Wharf Road site. 4.3 Measured peaks of vibration from tram pass-bys were no higher than the vibration levels associated with HGV pass-bys at a similar measurement distance from the edge of Trafford Wharf Road. On the basis that vibration from existing HGV traffic on Trafford Wharf Road does not cause any vibration impact on ITV operations, there is no reason to believe that the passage of trams past the site will result in any significant vibration impact, as long as the mounting of the Metrolink lines is similar to that used on the existing line at Eccles New Road (where vibration levels were monitored). 4.4 However, because it is likely to involve numerous activities that will require heavy equipment and percussive tools, we consider that the construction phase of the Metrolink line has the potential to result in groundborne vibration impact on ITV activities. The precise likelihood and extent of vibration impact can only be determined when more information is available. Tel: Page 8 of 22

12 Potential Noise Impact 4.5 Trams flows on the line are anticipated to be no more than one every 6 minutes in each direction, which equates a total hourly two-way flow of 20 trams (or one every three minutes). As such, on the ITV site average noise levels from tram pass-bys over a one hour period (i.e. the L Aeq,1hour noise level) will be fairly low. However, the noise from trams and associated construction phase activities will be a series of regular transient noise events that have the potential to be audible on the outdoor lot and possibly within studios, resulting in disruption of filming. Our assessment has therefore focussed on the potential transient peaks of noise in terms of L max noise levels. 4.6 For the purposes of this assessment, we have adopted the following criteria: To control noise impact on the outdoor lot, we consider that transient peaks of noise from new intrusive noise sources (in terms of octave band L max) should be controlled to be at least 10 db below existing average noise levels (in terms of octave band L eq). The internal noise criterion for the studio buildings is NR20 for average noise and peaks of noise. Therefore, in order to control noise impact on the studios, transient peaks of noise from new intrusive noise sources must be controlled to be below NR20 inside the studios. 4.7 Measurements of the existing average ambient noise levels on the outdoor lot were taken during the day on a weekday in December 2013 as part of the acoustic commissioning tests on the completed development. Outdoor Lot 4.8 In order to determine the potential noise impact of the construction and operational phases of the proposed Metrolink line on the outdoor lot, we have updated the computerised noise model that we constructed using the CadnaA noise modelling software during the planning stage of the ITV site. The CadnaA software enables a 3-dimensional computer model to be created as a basis for Tel: Page 9 of 22

13 calculating noise propagation across the site. The noise model takes account of the noise propagation terms within ISO9613: Acoustics Attenuation of sound during propagation outdoors, including distance attenuation, ground absorption, screening and atmospheric absorption. In order to represent a conservative estimate of the likely resulting transient peaks of noise, the influence of reflections has been excluded and only direct noise has been considered. 4.9 The model includes the m brick wall along the Trafford Wharf Road boundary of the site and all scenic backdrops and other buildings that provide screening of existing noise sources on the outdoor lot Using the noise model along with the adopted source noise levels for trams and for construction phase activities, we have calculated likely resulting noise levels on the outdoor lot We have prepared noise contour plots for a number of scenarios to determine the potential noise impact of the Metrolink line on the outdoor lot. These scenarios are as follows: Transient peak noise levels from a typical tram pass-by on a straight section of Metrolink line; Transient peak noise levels from use of a tram horn; Transient peak noise levels from tram rail squeal at the bend in the line where it turns from Trafford Wharf Road onto Warren Bruce Road; Worst-case transient peak noise level from construction phase activities For the rail squeal scenario, we have located the noise source at the junction of Trafford Wharf Road and Warren Bruce Road Whilst noise from the other scenarios could be expected to occur at any location along the route of the line, for the purposes of this assessment and the worst-case location for each could vary, Tel: Page 10 of 22

14 we used a single location slightly further to the east on Trafford Wharf Road for the noise modelling Figures 3, 4 and 5 show the contour plots and Table 4 summarises the findings of the noise modelling for the outdoor lot: Table 4: Description Summary of noise modelling results for outdoor lot (db) Octave band centre frequency (Hz) k 2k 4k 8k A Existing measured L eq on outdoor lot Adopted criterion (L max) Calculated worst-case Metrolink Lmax noise levels Typical tram pass-by Calculated tram rail squeal Calculated tram horn Construction phase operations Comparison of calculated Lmax noise level and criterion Typical tram pass-by Calculated tram rail squeal Calculated tram horn Construction phase operations Table 4 shows that under all scenarios, the calculated L max noise levels in at least one octave band is above the adopted criterion. For a typical tram pass-by, there is only a marginal exceedence of 2 db at 4 khz. However, for all other scenarios, the calculated L max levels are at least 10 db above the adopted criterion in at least one octave band. For these scenarios, transient peaks of noise will potentially be clearly audible on the outdoor lot The calculated noise levels at 2 khz and 4 khz from rail squeal, and at 4 khz during construction activities are at least 24 db above the adopted criterion. Such noise levels will be very clearly Tel: Page 11 of 22

15 audible on the outdoor lot. Given that transient peaks from rail squeal could occur every 3 6 minutes, we consider that such noise levels could have a serious impact on filming activities at ITV. Studios 4.17 In order to determine the potential impact of noise break-in to the studio buildings, we have carried out some simple calculations of likely resulting L max noise levels inside studios. As a worst case, the calculations have assumed that the transient noise events take place on Trafford Wharf Road just to the east of the ITV site where there is a clear line of sight of the eastern elevation of Studios 3 and The calculations have taken into account distance attenuation to the nearest point of Studio 4 and a simple allowance for the sound reduction index of the studio building envelope. The calculations are summarised as follows: Table 5: Description Summary of noise modelling results for outdoor lot (db) Octave band centre frequency (Hz) k 2k 4k 8k NR Calculated Metrolink Lmax noise levels outside Studio 4 Typical tram pass-by Calculated tram rail squeal Calculated tram horn Construction phase operations Sound reduction index of studio external wall SRI of studio wall Calculated resulting Lmax inside studio Typical tram pass-by Calculated tram rail squeal Tel: Page 12 of 22

16 Calculated tram horn Construction phase operations Table 5 shows that although resulting peaks of noise within the studio will be fairly low, L max levels from tram horns and from rail squeal will be at or marginally above the studio acoustic criterion of NR20. As such, we consider that there is the potential for peaks of noise associated with the Metrolink line could have the potential to disrupt filming activities within the most exposed studios. Based upon the construction phase noise sources we have adopted for this assessment, our calculations show that peaks of noise will be within the studios acoustic criterion. However, if noisier activities or equipment are necessary, then there is the potential for disruption from the construction phase too. Metrolink Passenger Information PA Announcements 4.20 It has not been possible to obtain source noise levels of passenger information PA system announcements. However, given the potential proximity of the proposed Imperial War Museum stop, we consider that the level and character of noise associated with PA system announcements has the potential to disrupt filming activities on the ITV site. Tel: Page 13 of 22

17 5.0 SUMMARY 5.1 Hepworth Acoustics was commissioned by ITV to assess the potential noise and vibration impact associated with the construction phase and operational phase of a proposed Metrolink tram line upon activities at their Trafford Wharf Road site. 5.2 The assessment has included measurements of appropriate source noise and vibration levels for tram movements on the existing Metrolink network, adopting appropriate source noise levels for construction phase activities and reviewing the computer noise model of the site that was prepared at the planning stage of the ITV site. 5.3 The tram vibration measurements have indicated that there is unlikely to be any significant vibration impact on the ITV site associated with the operational phase of the Metrolink line as long as the mounting of the Metrolink line is similar to that used at Eccles New Road. However, because it is likely to require the use of percussive plant, it is possible that vibration impact may occur during the construction phase of the line. 5.4 Using the computer noise model with the measured tram source noise levels and adopted construction phase source noise levels, it has been shown that there is the potential for noise to have a serious impact on filming activities on the outdoor lot. 5.5 Peaks of noise inside the most exposed studio, whilst fairly low in absolute terms, also have the potential to disrupt filming due to the very stringent acoustic criterion for studios. 5.6 We therefore conclude that both the construction and operational phases of the proposed Metrolink line has the potential to have a detrimental effect on ITV filming activities. Tel: Page 14 of 22

18 FIGURE 1 TfGM PROPOSED METROLINK TRAFFORD PARK LINE ROUTE MAP Key: Figure 1: TfGM Proposed Metrolink Trafford Park Line Route Map ITV site location Title: Project: Tel: Page 15 of 22

19 FIGURE 2: ITV TWR SITE, WITH ROUTE OF PROPOSED METROLINK Key: Not to scale Outdoor lot Studio buildings - Proposed route of Metrolink line Figure 2: ITV TWR Site, with route of proposed Metrolink Title: Project: Tel: Page 16 of 22

20 Key: Calculated LAmax noise levels (db) PLOT 1 TYPICAL TRAM PASS-BY Plot 1: Typical Tram Pass-by Title: Project: Tel: Page 17 of 22

21 Key: Calculated LAmax noise levels (db) PLOT 2 TRAM RAIL SQUEAL Plot 2: Tram Rail Squeal Title: Project: Tel: Page 18 of 22

22 PLOT 3 TRAM HORN Key: Calculated LAmax noise levels (db) Title: Plot 3: Tram Horn Project: Tel: Page 19 of 22

23 Key: PLOT 4 WORST CASE CONSTRUCTION PHASE NOISE Calculated LAmax noise levels (db) Plot 4: Worst-case construction phase noise Title: Project: Tel: Page 20 of 22

24 Appendix I Noise Units and Indices a) Sound Pressure Level and the decibel (db) A sound wave is a small fluctuation of atmospheric pressure. The human ear responds to these variations in pressure, producing the sensation of hearing. The ear can detect a very wide range of pressure variations. In order to cope with this wide range of pressure variations, a logarithmic scale is used to convert the values into manageable numbers. Although it might seem unusual to use a logarithmic scale to measure a physical phenomenon, it has been found that human hearing also responds to sound in an approximately logarithmic fashion. The db (decibel) is the logarithmic unit used to describe sound (or noise) levels. The usual range of sound pressure levels is from 0 db (threshold of hearing) to 120 db (threshold of pain). b) Frequency and hertz (Hz) As well as the loudness of a sound, the frequency content of a sound is also very important. Frequency is a measure of the rate of fluctuation of a sound wave. The unit used is cycles per second, or hertz (Hz). Sometimes large frequency values are written as kilohertz (khz), where 1 khz = 1000 Hz. Young people with normal hearing can hear frequencies in the range 20 Hz to 20,000 Hz. However, the upper frequency limit gradually reduces as a person gets older. c) Glossary of Terms When a noise level is constant and does not fluctuate, it can be described adequately by measuring the db level. However, when the noise level varies with time, the measured db level will vary as well. In this case it is therefore not possible to represent the noise climate with a simple db value. In order to describe noise where the level is continuously varying, a number of other indices can be used. The index used in this report is described below together with a glossary of terms. Tel: Page 21 of 22

25 L Aeq This is the A weighted 'equivalent continuous noise level' which is an average of the total sound energy measured over a specified time period. In other words, L Aeq is the level of a continuous noise which has the same total (A weighted) energy as the real fluctuating noise, measured over the same time period. It is increasingly being used as the preferred parameter for all forms of environmental noise. L Amax This is the maximum A weighted noise level that was recorded during the monitoring period. Tel: Page 22 of 22