under: the Resource Management Act 1991

Transcription

1 Before Hearing Commissioners at Christchurch under: the Resource Management Act 1991 in the matter of: applications CRC175507, CRC176030, CRC175508, CRC175509, CRC to reclaim land and construct a wharf in Te Awaparahi Bay, Lyttelton Harbour and in the matter of: Lyttelton Port Company Limited Applicant Statement of evidence of Darran Humpheson (Underwater Acoustics) Dated: 4 September 2017 REFERENCE: JM Appleyard (jo.appleyard@chapmantripp.com) JR Cross (Jessie.cross@chapmantripp.com)

2 1 EVIDENCE OF DARRAN HUMPHESON INTRODUCTION 1 My name is Darran Humpheson. 2 I hold a Bachelor of Science degree with Honours in Applied Physics and a Master of Science degree in Environmental Acoustics. 3 I am an Associate Director of Acoustics at AECOM New Zealand Limited. I am the acoustics team leader of AECOM s Christchurch office. 4 I have been employed in acoustics since 1991, and I have previously held positions as a consultant for international firms Bureau Veritas (Technical Director ), RPS Group plc (Technical Director ) and as a UK Ministry of Defence scientist (Head of the Royal Air Force s Noise and Vibration Division ). 5 I have undertaken underwater noise assessments for a range of projects which have involved piling noise, dredging operations, tidal energy production and the effects of shipping. I have recently presented expert evidence on underwater acoustics for the following projects: 5.1 Trans-Tasman Resources Limited s 2014 and 2017 hearings to extract iron ore from the South Taranaki Bight. 5.2 Chatham Rock Phosphates application to extract mineral deposits from the Chatham Rise I am a member of a number of relevant associations and am a Corporate Member of the UK Institute of Acoustics. I am a New Zealand representative of the International Standards Organisation (ISO) technical committee ISO/TC 43 SC1 Noise. 7 I have been instructed by Lyttelton Port Company Limited (LPC) to prepare an underwater noise assessment for LPC s application for resource consents to reclaim land and construct a wharf at Te Awaparahi Bay in Lyttelton Harbour (Applications). Together, the Applications are to undertake works known as the Te Awaparahi Bay Reclamation Project (Project). 8 My assessment was undertaken in August 2017 after the Applications were lodged. The results of my assessment are reported in my evidence and will be used to inform the potential noise effects on Hector s dolphins. 9 I have knowledge of the Port s operations and the local area.

3 2 SCOPE OF EVIDENCE 10 This evidence is divided into two parts. Part 1 comprises my underwater noise assessment. Part 2 is a response to issues raised in the section 42A report (Officer s Report). 11 My assessment covers the following topics: 11.1 underwater source levels of piling noise; 11.2 noise modelling; 11.3 underwater noise thresholds; and 11.4 underwater sound levels presented as noise contours and sound level reduction with distance from the piling activities. 12 I also respond to the following issues raised in the Officer s Report: 12.1 Performance of acoustic dampening techniques (e.g. bubble curtains and cofferdam) and whether they are practicable and beneficial. 13 In preparing this evidence I have reviewed: 13.1 Te Awaparahi Bay Reclamation Project: Design Information for the Resource Consent Application, Beca, April 2017 Appendix 1 to the Applications; and 13.2 Recommendations for managing the impact of pile driving noise on Hector s dolphins in Lyttelton Harbour, Eva Leunissen and Steve Dawson, Department of Marine Science, University of Otago, Although this is not an Environment Court hearing, I note that in preparing my evidence I have reviewed the code of conduct for expert witnesses contained in part 7 of the Environment Court Practice Note I have complied with it in preparing my evidence. I confirm that the issues addressed in this statement of evidence are within my area of expertise. I have not omitted to consider material facts known to me that might alter or detract from the opinions expressed. PART 1: ASSESSMENT 15 I have calculated underwater sound levels within Lyttelton Harbour for the Te Awaparahi Bay Reclamation Project during the construction of a piled-wharf (750 m x 40 m), which will be constructed in two stages along the southern edge of the 21 ha reclamation area.

4 3 16 I have used dbsea software, which is a commercially available software package for calculating underwater sound levels. I have used dbsea taking into account the following factors: 16.1 Bathymetry data which has been provided by MetOcean Solutions and reflects the bathymetry of Lyttelton Harbour upon completion of the Channel Deepening Project (CDP) which will increase the width and depth of the existing shipping channel Seafloor properties, which have been derived from a number of borehole samples provided by LPC. The seafloor layers (silty sand/clay/silty mud) vary in composition and depth. The sub seafloor conditions have been extended to three layers and take into account the density, speed of sound and various attenuation factors of each layer. Seafloor properties can influence the degree of attenuation and reflection of sound back into the water column Sound speed profile data of the water column has been assumed to be linear as the water depth is relatively shallow. Detailed sound speed profile data is typically relevant for deep water propagation, typically greater than 250 m in depth Currents and tides which affect the propagation of sound. Typically there is only a marginal difference in sound level between static and with tide conditions. A positive tidal flow has been used Temperature, turbidity and salinity data collected from the monitoring stations within inner Lyttelton Harbour as part of the CDP baseline environmental monitoring programme was considered. Summer and winter average profiles have been considered (average of 17 C and 9 C respectively). Within the assessment it was concluded that the effect of temperature on underwater sound transmission is more significant than the effect of suspended sediment within the water column. Accordingly, I have only considered the variation in seasonal temperatures as part of these additional factors. Source data for piling operations 17 Having reviewed the project s design information and having discussed the works with Mr Jared Pettersson of LPC, I have assumed a source sound pressure level (SL) of 193 db re 1µPa at 1m. I have based this SL on a combination of data measured by the

5 4 University of Otago 1 and source level data from larger diameter piling activities which I have reviewed. 18 The frequency content of the piling noise is shown below in Table 1. The dominant levels of noise are around the 250-1,000Hz frequency bands. There is a drop off in the higher frequencies (greater than 32kHz). Table 1 Assumed frequency data of piling Sound Pressure Level db re 1µPa at 1m per octave band centre frequency band (Hz) Overall k 2k 4k 8k 16k 32k 64k The University of Otago report states the average Sound Exposure Level (SEL) source level of a 600mm driven pile is 182 db re 1µPa 2 s at 1m with a maximum recorded SEL of 194 db re 1µPa 2 s at 1m. The SEL is a measure of the noise dose or sound energy exposure of the noise event. It takes into account both the sound energy and duration of the event referenced to a unit period of time (one second). 20 The piling diameter for this project is 900 mm and the expected blow rate of the piling hammer would be between blows per minute. Each blow would last a fraction of a second (resulting in a sound impulse of a maximum of 250 ms). I understand from LPC s contractor that the duty cycle of the piling hammer would likely operate on a 15 minute on and 15 minute off period. During a typical day the total piling duration would only be 4-5 hours, i.e. half of a normal construction day. 21 Piling noise is not continuous as the sound levels would occur as a series of impulses. I have estimated that the actual on-time of the noise would be approximately 10% of a one hour period, i.e. ~5 minutes. The remainder of the time there would be negligible noise being generated by the piling works. Although there is likely to be more than one rig, only one rig would be operational at any one time. 22 When my assumed SL is corrected for a 10% operating period, I have calculated a SEL equivalent of 182 db re 1µPa 2 s at 1m which is similar to that stated in the University of Otago report. Noise Model 23 A 3D model of Lyttelton Harbour has been constructed in the dbsea software, see Figure 1. The bathymetry data reflects the as-built 1 Eva Leunissen and Steve Dawson, Department of Marine Science, University of Otago. Recommendations for managing the impact of pile driving noise on Hector s dolphins in Lyttelton Harbour. 2017

6 5 situation after the CDP. It is understood that the channel will be dredged to approximately half of its finished depth prior to the reclamation project, with the remaining dredging occurring afterwards. By considering the full depth of the channel, I have conducted a worst case assessment. Figure 1 Terrain and Bathymetry Data - dbsea 24 A parabolic equation (PE) has been used to calculate underwater sound levels. Whilst dbsea can use alternative algorithms, I consider the PE calculation is best suited to the local conditions of the harbour and provides a good balance between accuracy and calculation speed. 25 An independent validation of the dbsea PE algorithm for very shallow water conditions has been performed 2. The results of this validation show that the dbsea model will on average result in overpredictions of around 2 db in shallow water. Maximum average differences were found to be around 10 db depending upon the calculation and measurement depth in the water column. 26 I have performed a number of sensitivity calculations using the dbsea software to assess the significance or otherwise of various assumptions. For example, the difference between summer and winter conditions equates to an approximate 2 db increase in sound levels for colder water. Accordingly, all sound levels presented in my evidence are for the winter water conditions. I also considered the 2 Internoise 2016, Towards a noise map model for shallow waters: analysis of propagation losses estimation, D Santos Dominguez et al, Universidad de Vigo - Atlantic

7 6 effects of different bathymetry within the harbour by relying on historic data from NIWA and DOC. The data from MetOcean Solutions I have used in my assessment results in marginally higher underwater sound levels. 27 Not only does dbsea calculate overall sound levels, it also provides details of the frequency spectra. Since the absorption of sound in water is frequency dependent, the dbsea software can be used to determine how the frequency of sound will vary with distance (high frequencies are absorbed more than lower frequencies). For example, the typical absorption in the 500 Hz frequency band is approximately 0.02 db per km whereas for higher frequencies absorption of 1 db or more per km are typical for frequencies greater than 12 khz. At 64 khz the absorption rate is around 20 db per km. At distances of approximately 3 km from the piling, high frequency sound levels are significantly reduced. 28 Water depth has an effect on receiver levels as does the presence of the Cashin Quay Wharf and the surrounding land structures. The propagation of sound in shallow water differs to that of deep water. Figure 2 shows a screenshot from the dbsea model which highlights the spreading of sound levels from the source. The noise contours are the maximum sound pressure levels during a single piling activity. Figure 2 Representation of underwater sound levels 29 A series of receiver locations have been used to determine the sound level reduction with distance. The receiver locations are located on a transect 200 m from the source location and run alongside the channel. The data is based on winter conditions and is

8 7 Table 2 shown in Table 2. I have used this information to compare with the transmission loss contours provided in Figure 4 of the University of Otago report (attached as Appendix A) which are based upon measured conditions within Lyttelton Harbour. My data compares well with the University of Otago data. Distance / metres Receiver SPL db re 1µPa at 1m Sound level reduction with distance ,600 3,200 6, Underwater Noise Thresholds 30 The University of Otago report considers that: 30.1 TTS (Temporary hearing Threshold Shift) will occur at an SEL of 146 db re 1µPa 2 s for 1 hour of exposure of 2,760 strikes 3. This is based on the subject being a trained harbour porpoise exposed to one hour of played-back piling Exposure of a trained harbour porpoise to a play back piling of SEL 133 db re 1µPa 2 s (single strike) began to induce a behavioural response A hearing detection threshold of SEL 75 db re 1µPa 2 s is likely for a trained harbour porpoise. 31 I have used these thresholds in my assessment to derive noise contours and distances at which these sound levels occur. 32 Drawing 1 attached as Appendix B to my evidence shows the extent of the TTS and behavioural response contours. The contours are the maximum sound level across all depths as projected to the surface. 33 Sound levels will vary with depth and I have produced a cross section from the piling activity to Stoddart Point which is approximately 1,480 m away, see Figure 3. This cross-section represents the part of Lyttelton Harbour between the Port and Diamond Harbour which is directly opposite the project s work area. 34 I understand from discussions with the project team, in particular Dr Deanna Clement, that the distances at which the TTS and behavioural sound levels occur are relevant, and whether there is a pathway from the inner harbour area around Quail Island to the 3 The reclamation project will likely generate pulses per minute and will operate for 30 minutes every hour (15 mins on / 15 mins off). This equates to ~1,350 pulses per hour, less than half the number considered in the University of Otago report.

9 8 Heads, such that Hector s dolphins are able to navigate relatively quiet water during piling. 35 The cross section in Figure 3 shows that sound levels will vary with depth. The greater sound levels will occur at the lower depths. The distances shown are the mid-depth point for the TTS and behavioural response contours. Figure 3 Cross-section from piling to Stoddart Point 36 There is an 800 m distance between the calculated TTS contour and Stoddart Point and 230 m distance between the behavioural response contour and Stoddart Point. 37 As already stated the dbsea software is likely to over predict sound levels by around 2 db on average for shallow water conditions. The presented sound levels and distances are in my opinion conservative and in practice may be lower. I have also calculated sound levels for the cooler winter conditions which is likely to result in a further 2 db decrease in sound levels in warmer summer conditions. Supplementary information 38 The US National Oceanic and Atmospheric Administration (NOAA) has published guidance on suitable response thresholds of various

10 9 groupings of marine mammals 4. The dbsea software allows the NOAA weighting to be applied to the low, mid and high frequency hearing range cetaceans. The following dbsea screenshots demonstrate the effects of the NOAA weightings. I understand that Hector s dolphins have a hearing frequency range which spans the NOAA mid to high frequency ranges. The NOAA frequency ranges are: 38.1 Low-frequency cetaceans (hearing range 7 Hz to 35 khz): large, baleen whale species 38.2 Mid-frequency cetaceans (hearing range 150 Hz to 160 khz): dolphin species 38.3 High-frequency cetaceans (hearing range 275 Hz to 160 khz): porpoise species Figure 4 NOAA Low Frequency Cetacean Weighted Sound Pressure Level Contours (SEL) Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (NOAA Technical Memorandum NMFS-OPR-55)

11 10 Figure 5 NOAA Mid Frequency Cetacean Weighted Sound Pressure Level Contours (SEL) Figure 6 NOAA Mid Frequency Cetacean Weighted Sound Pressure Level Contours (SEL) 39 The dbsea software also allows a detection threshold to be applied for certain species. The following plot (Figure 7) shows the hearing threshold detection range for the harbour porpoise. There is no weighting within the dbsea software for Hector s dolphins.

12 11 Figure 7 dbsea harbour porpoise hearing detection threshold contour PART 2: RESPONSE TO SECTION 42A REPORT 40 Dr Simon Childerhouse s report (Appendix 6 of the Officer s Report) considers in paragraph 13 and 26 that acoustic dampening techniques (e.g. bubble curtains and cofferdam) should be investigated and where practicable and beneficial be implemented prior to piling. 41 I consider that there are two options available to reduce the effects of piling activities: 41.1 reduction of noise generated by the source; and 41.2 acoustic barriers to reduce the radiated noise. 42 Noise reduction at the source is typically achieved by the use of alternative piling techniques including reducing the impact hammer energy. If piling hammer energy levels are lowered to the minimum required to overcome the resistive forces of driving the pile in the seafloor then, although the peak noise levels generated are generally lower, the total time required for installation is several times longer. The implication of this is that although the zone of impact is smaller, the disturbance is present for a longer time period. Furthermore, as described in the evidence of Stephen Lee, there are limits to which alternative piling methods can reduce energy, and thus sound levels during construction.

13 12 43 Acoustic barriers can be deployed around the pile to reduce the level of noise which radiates into the surrounding water. The actual barrier can be implemented in a number of ways with varying degrees of noise reduction efficacy. These methods can include bubble curtains, cofferdams and sleeve type methods. 44 A bubble curtain is a layer of air bubbles produced in the water column surrounding the pile which acts to reduce the radiated noise level by introducing a strong impedance mismatch. The air bubbles are typically released from a perforated tube as compressed air is forced through it so that the bubbles ascend to the surface. They can include multiple such tubes around the sound source to provide greater coverage at all depths. 45 Bubble curtains can provide a reduction of the noise levels radiated into the water. One study on the use of air bubble curtains to reduce receiver sound levels for harbour porpoises 5 found that the average attenuation was 13 db SEL. The study site was in the vicinity of Kerteminde harbour, Denmark and the water depth was 3-5 m with a moderate 0.5 m/s tidal current. Another study 6 found that the broadband sound level reduction was 3-5 db for a water depth of 8 m and the researchers hypothesised that the low performance was a result of noise being re-radiated back into the water column from both the barge and also from within the seafloor. In both studies the engineering solutions required to achieve this level of sound level reduction were recognised by the work as logistically challenging, especially in non-still waters. 46 I consider that whilst there may be material benefits for the use of bubble curtains, there are a number of practical limitations which have to be considered, as follows: 46.1 The time required to install the bubble curtain for each pile may lengthen the duration of piling activity as the equipment has to be carefully placed around each pile, typically using divers The dynamic conditions of the Lyttelton Harbour mean there are often rough water conditions (both from shipping activity, waves and tidally induced) therefore the integrity of the bubble curtain will be very difficult to maintain. 5 Lucke et al, The use of an air bubble curtain to reduce the received sound levels for harbor porpoises (Phocoena phocoena), J. Acoust. Soc. Am., Vol. 130, No. 5, Pt. 2, November B. Würsig et al, Development of an air bubble curtain to reduce underwater noise of percussive piling, Marine Environmental Research 49 (2000) 79-93

14 The transmission of some sound energy through the seafloor may also contribute to the received level due to reemergence of the sound back into the water column. 47 I am not aware of any New Zealand projects which have used bubble curtains to reduce underwater sound levels. There is a lack of experience of this technique which may mean that if implemented there would be a significant, and likely costly, period of testing and experimentation which may not prove the method effective. 48 The use of cofferdams can be a very effective solution with negligible impacts to the marine environment once piling starts. A cofferdam is constructed by piling a continuous wall of sheet piles and then dewatering the work area. The limitations of using this noise reduction method are the time and costs required to construct the cofferdam around the work areas and the disruption that may occur by effectively sealing off an entire work site and the initial noise generated by the sheet piling. Alternatively, enclosed coffer dams can be used which are effectively dewatered pile sleeves. 49 A pile sleeve refers to a barrier method that involves coating or wrapping the pile (or a surrounding steel tube) in a material that that has the potential to reduce the transmission of sound into the water. These materials are typically air filled foams with an acoustic impedance different to that of water. At frequencies of 400 Hz and below, where most of the acoustic energy is radiated during piling, the transmission reduction is relatively small, typically less than 5 db. There are a number of commercial pile sleeve solutions being developed, for example by Menck and IHC Merwede. These systems have demonstrated level reductions of db and have been proven as relatively easy to install. However these systems have been primarily developed for large offshore piling operations (i.e. windfarms) in the northern hemisphere which use very different piling gear and drive far less but larger piles. They are not designed for wharf construction where a large number of smaller piles are driven in relatively quick succession. Therefore I consider coffer dams are unlikely to be an appropriate noise mitigation technique for The Project. 50 Dr Childerhouse states at paragraph 26 of his report that: While I am not aware of bubble curtains being used in New Zealand previously, they are frequently used overseas and can reduce noise levels by up to 90%. 51 Given the challenges to installing bubble curtains outlined at paragraph 46 above, in my opinion it would not be possible to achieve noise level reductions anywhere close to 90% for the proposed piling activity.

15 14 CONCLUSION 52 I have undertaken an underwater noise assessment of the piling activities for wharf construction proposed as part of the Te Awaparahi Bay Reclamation Project using dbsea software and the bathymetry, seafloor and water conditions of Lyttelton Harbour. 53 Piling noise will not be continuous. I have estimated that piling noise will only be present for 4-5 hours of a construction day. During that period actual noise emissions will only be generated for approximately 1/10 th of a one hour period, i.e. approximately 5 minutes every hour. 54 The noise modelling has shown that sound levels will vary throughout Lyttelton Harbour and that noise levels will reduce to a level of 146 db SEL 1µPa 2 s at a distance of 600 m and a SEL of 133 db 1µPa 2 s at 1,170 m. A pathway of quieter sound levels of 800 m and 230 m respectively is predicted between Stoddart Point and the TTS and behavioural response noise contours respectively. 55 The use of physical barriers to minimise noise such as bubble curtains and cofferdams have been shown to reduce underwater sound levels by 3-13 db for a well maintained curtain of bubbles. Cofferdams have significantly greater sound level reduction performance (greater than 20 db). There are practical difficulties with both mitigation options which may affect their feasibility, particularly in the Lyttelton Harbour context. Dated: 4 September 2017 Darran Humpheson

16 15 Appendix A Transmission loss contours from University of Otago Report

17 16

18 17 Appendix B TTS and Behavioural Response Contours

19 I Legend Project Area TTS 146dB SELcum re 1µPa²s max at all depths (1hour) 133dB SELcum re 1µPa²s at 1m (1hour) 133dB SELcum re 1µPa²s max at all depths (1hour) 600m Last saved by: POPEM ( ) Last Plotted: never Filename: P:\605X\ \4. Tech work Area\4.99 GIS\06_Working\ _Noise Contours\dBSea limit contours A4.mxd 300m 270m 230m Canterbury Maps Copyright A ECOM New Zea land Limited, This map is confidential and shall only be used for the purposes of this project. The signing of this title block confirms the design and drafting of this proje ct have bee n prepared and checked in accorda nce with the AECOM Qua lity Assurance system ce rtified to AS/NZS ISO 9001:2008. SPATIAL REFERENCE Scale: 1:25, CONSULTANT AECOM New Zealand Limited Level 2, 2 Hazeldean Road, Addington CHRISTCHURCH 8140 tel fax (A4 size) SHEET TITLE 300 Metres Map features depicted in terms of NZTM 2000 projection. MAP NUMBER 1 PROJECT NUMBER Underwater noise contours from piling activities CLIENT Lyttelton Port Company (LPC) PROJECT Te Awaparahi Bay Reclamation Project