Technical Assistance Consultant’s Report€¦ · Bhagalpur is acclaimed all over the world for...

Technical Assistance Consultant’s Report

This consultant’s report does not necessarily reflect the views of ADB or the Government concerned, and ADB and the Government cannot be held liable for its contents. (For project preparatory technical assistance: All the views expressed herein may not be incorporated into the proposed project’s design.

Project Number: 7106 August 2011

India: Preparing the Bihar Urban Development Project—Underwater Noise Impacts on Ganges River Dolphin

Prepared by:

GHK Consulting Limited, UKG, in association with STUP Consultants P. Ltd., IND, and

Castalia Strategic Advisors, USA

For Urban Development and Housing Department, Government of Bihar

Bihar Urban Development Investment Program (BUDIP)

(ADB TA 7106-IND)

Appendix 2 to Subproject Appraisal Report

ENVIRONMENTAL IMPACT ASSESSMENT Supplementary Report

on

Underwater noise impacts on Ganges River Dolphin

Bhagalpur Water Supply (Tranche 1)

FINAL

GHK, UK in association with

Castalia

STUP Consultants

Urban Development &

Housing Department

Government of Bihar

Asian Development Bank (ADB)

AUGUST 2011

Report on Underwater noise impacts on Ganges River Dolphin 1

CONTENTS

1. Introduction................................................................................................................. 2 2. Objectives................................................................................................................... 2 3. Selection of Specialized Agency…………………………………………………………..2 4. Scope of Work ............................................................................................................ 3 5. Project Area ................................................................................................................ 3 6. Data Used in the Study and Preparation of the Report .............................................. 4

7. Report ........................................................................................................................ 4

8. Acknowledgement………………………………………………………………………...…4


1. Introduction

The Government of Bihar (GoB) under Bihar Urban Development Investment Program (BUDP) intends to develop the basic infrastructure of major towns of the state and requested the Asian Development Bank (ADB) for financial assistance. The ADB to assess feasibility of such financial assistance appointed GHK Consulting Limited, UKG for a technical assistance (TA) in preparing urban sector roadmap of Bihar and investment plan for 4 (four) major towns namely Gaya, Bhagalpur, Muzaffarpur and Darbhanga in the subsectors of Water supply, sewerage, drainage and solid waste management. In the process of the study, due to uncertainty in adequate and economical water source, investment proposal for Gaya has been kept in lesser priority while the other 3 (three) towns stood under active consideration to access ADB‟s financial assistance under multi-tranche financing facility (MFF). In the first tranche it is proposed to take up the water supply subproject for Bhagalpur town. The subproject1 is designed with surface water source of river Ganga flowing along northern boundary of the town. It is proposed to abstract water from the river through a pair of intake wells sunk in the river bed at about 100 meter inside from the bank.

The river abutting the entire northern boundary of Bhagalpur lies within the Vikramshila

Gangetic Dolphin Sanctuary stretching over 25 km upstream to 25 km downstream of the town. This 50 km stretch of the river is designated since 1991 as the protected area for the endangered Gangetic dolphins by the Government of India. To ensure the protection of this endangered species the subproject is environmentally categorized as „A‟ and accordingly the TA Consultants conducted an Environmental Impact Assessment (EIA)2 as part of the investment program.

Subsequent to the submission of the EIA Report, the ADB desired the TA Consultants

to further conduct a study on the underwater noise impacts on dolphin community in river Ganges to strengthen the EIA Report and take necessary mitigation measures in case of any significant risk involved in the water abstraction proposition.

The study was accordingly conducted and the report is submitted herewith as a

supplementary report to the original EIA Report3.

2. Objectives

To conduct a comprehensive study on underwater noise impacts on the gangetic dolphins emerging out of operation of heavy duty pumps proposed to be installed in the river for abstracting water for water supply to the Bhagalpur town and propose appropriate mitigation measures in case of any significant risk to the dolphin community.

3. Selection of Specialized Agency

The work among various other exercises required to develop an underwater noise propagation model to characterise the spread of noise throughout the river environment and establish likely zones of noise impact. The TA Consultants initially enquired with various institutions and professionals to avail such services within the national resources. Without however having sufficiently positive response from the national expertise, with the approval of ADB the TA

1 GHK: Subproject Appraisal Report Bhagalpur Water Supply (Tranche 1) Final, May 2011.

2 GHK: Appendix 2 to Subproject Appraisal Report, Environmental Impact Assessment Bhagalpur Water Supply

(Tranche 1) Final, July 2011. 3 2 GHK: Appendix 2 to Subproject Appraisal Report, Environmental Impact Assessment Bhagalpur Water Supply

(Tranche 1) Final, July 2011.


Consultants approached for such services internationally. AECOM Australia Pty Ltd. Australia was selected on the basis of lowest quoted price, after approval of ADB.

4. Scope of Work The scope of work as detailed by the Bank was broadly to study the underwater noise impacts on Gangetic Dolphins arising of operation of vertical turbine pumps in a pair of intake wells proposed to be installed in the river for abstraction of water for Bhagalpur town and identifying reasonable and practical mitigation measures for safety of the dolphins. The study among other exercises included:

(a) Study of existing conditions of the ambient underwater noise environment; (b) Developing an underwater noise propagation model to characterise the spread of

noise throughout the river environment; (c) Predicting underwater noise levels to noise exposure criteria and establishing likely

zones of noise impact; and (d) Preparation and submission of Report

5. Project Area

Bhagalpur town is a Municipal Corporation in the state of Bihar, India. It is one of the oldest districts of Bihar located in the southern region and situated in the planes of the Ganga basin at about 25 metre above Mean Sea Level. It is the third largest city of Bihar. It covers an area of 2569.50 sq km and lies between 25º07' - 25º30' N Latitude and between 86º37' - 87º30' E Longitude. It is the administrative headquarters of the Bhagalpur District. Bhagalpur is acclaimed all over the world for its silk products and it is known in India as the “Silk City” famous for its Tussar Silk and Tussar Saree.

The proposed intake site is located at Barari Ghat at the foot of Vikramshila bridge, near Bhagalpur, geographical position of which is 25º16‟07.8” N, 87º01‟41.4”

N

Map of Bhagalpur Town (Not To Scale)

Intake Wells

http://en.wikipedia.org/wiki/Bihar

http://en.wikipedia.org/wiki/India

http://en.wikipedia.org/wiki/Ganges

http://en.wikipedia.org/wiki/Bihar


6. Data Used in the Study and Preparation of the Report

Following data/reports prepared by the TA Consultants were used by the specialized agency in conducting the study and preparing the report:

(i) Subproject Appraisal Report of Bhagalpur Water Supply Subproject; (ii) Bathymetric Survey Report of the location of Intake Wells; (iii) Geotechnical Investigation Report of the location of Intake Wells; (iv) Hydrology Report of the river with particular reference to the location of Intake

Wells; (v) Biodiversity Report in respect to Impact on Aquatic Biodiversity of River Ganga in

and around Bhagalpur for construction of Intake structure at Bhagalpur. In addition the specialized agency has referred to various relevant publications as listed in the list of References of its report.

7. Report

The Report prepared by the specialized agency, M/s AECOM Australia Pty Ltd. on the subject study is annexed and Attachment 1.

8. Acknowledgement

The Consultants wish to acknowledge with thanks and appreciation the cooperation of the Asian Development Bank in providing guidance in conducting the study.

Attachment1



AECOM

Bihar Urban Development Investment Program


14 October 2011



Prepared for

Asian Development Bank

Prepared by

AECOM Australia Pty Ltd

Level 28, 91 King William Street, Adelaide SA 5000, Australia

T +61 8 7100 6400 F +61 8 7100 6499 www.aecom.com

ABN 20 093 846 925

14 October 2011

60223695

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© AECOM Australia Pty Ltd (AECOM). All rights reserved.

AECOM has prepared this document for the sole use of the Client and for a specific purpose, each as expressly stated in the document. No other

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14 October 2011

Quality Information

Document Underwater noise impacts on Ganges River Dolphin

Ref 60223695

Date 14 October 2011

Prepared by Dr Dick Petersen

Reviewed by Darren Jurevicius

Revision History

Revision Revision

Date Details

Authorised

Name/Position Signature

A 23-Sep-2011 Draft report Dr Dick Petersen

Acoustic Engineer

0 10-Oct-2011 Final issue Dr Dick Petersen

Acoustic Engineer

1 14-Oct-2011 Addressed comments Dr Dick Petersen

Acoustic Engineer

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14 October 2011

Table of Contents

Glossary 5 Executive Summary 6 1.0 Introduction 7 2.0 Principles of underwater acoustics 8

2.1 Nature of underwater sound 8 2.2 Underwater noise descriptors 8

3.0 Description of existing conditions 9 4.0 Effects of noise on river dolphins 10

4.1 Sound production and communication 10 4.2 Hearing sensitivity 10 4.3 Effects of noise 11 4.4 Zones of noise impact 13

5.0 Pump noise assessment 14 5.1 Intake well and pump configuration 14 5.2 Pump source level characterisation 15 5.3 Radiated source level into Ganges River 16 5.4 Underwater noise propagation modelling 17 5.5 Zones of noise impacts 20

6.0 Management and mitigation measures 22 7.0 Conclusion 23 References 24

Appendix A A Underwater noise contour map A

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Glossary

dB Unit for unweighted or linear noise levels

Hz The rate at which the water or air particles oscillate backward and forward determines its

frequency given in cycles per second or Hertz (Hz).

Peak level Maximum sound pressure over the measurement period expressed in dB re 1 µPa. The peak

level is commonly used for impulsive sources.

SEL Sound energy over the measurement period expressed in dB re 1 μPa2s. The SEL is commonly

used for impulsive underwater noise sources such as impact pile driving because it allows a

comparison of the energy contained in impulsive signals of different duration and peak levels. The

measurement period for impulsive signals is usually defined as the time period containing 90% of

the sound energy (2007).

SL The intensity of underwater noise sources is compared by their source level (SL) expressed in dB

re 1 µPa at 1 m for SPLs and dB re 1 μPa2s at 1 m for SELs. The source level is defined as the

sound pressure (or energy) level that would be measured at 1 m from an ideal point source

radiating the same amount of sound as the actual source being measured.

SPL Sound pressure averaged over the measurement period expressed in dB re 1 µPa. Continuous

sources such as vibro-piling and dredging are commonly characterised in terms of an SPL.

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Executive Summary

The Bhagalpur Water Supply Subproject of the Bihar Urban Development Investment Program includes the

construction and operation of two intake wells within the Vikramshila Gangetic Dolphin Sanctuary (VGDS) in the

Ganges River. The intake wells contain vertical turbine pumps which will generate underwater noise.

This noise may adversely affect the endangered Ganges River Dolphins which relies on sound for sensing of its

environment. AECOM Australia Pty Ltd was engaged by the Asian Development Bank to assess the impacts of

underwater noise radiating from the intake wells on the Ganges River Dolphins.

The hearing sensitivity of the Ganges River Dolphin has not been studied. Based on the hearing sensitivity of

other river dolphins, their hearing is thought to be most sensitive between 20 and 80 kHz which overlaps with the

dominant frequency range of their echolocation signals. Hearing thresholds are likely to be 50 to 60 dB re 1 µPa

at the most sensitive frequencies and reduce significantly at lower frequencies.

The risk of hearing damage is expected to be negligible as predictions indicated that it occurs only within a few

metres from the intake wells after a full day of noise exposure. The dolphins are likely to avoid the immediate

vicinity of the wells such that hearing damage is unlikely to occur.

Noise radiating from the intake wells is not expected to significantly interfere with the echolocation ability of the

Ganges River Dolphin as their echolocation clicks have dominant energy around 65 kHz, which is well above the

dominant frequency range of the pump noise. Communication signals are more likely to be masked by the pump

noise but only within a few tens of metres from the intake wells. The risk of significantly impacting on the dolphin’s

communication and echolocation abilities is therefore low.

Significant and sustained avoidance behaviour is predicted to occur up 40 m from the intake wells. The expected

avoidance reaction will mitigate the risk of hearing damage.

Biologically important behaviours, such as breeding, feeding and resting, may potentially be affected up to 575 m

from the intake wells. The associated risk depends on the biological significance of the noise-affected area.

However, considering the size of the VGDS relative to the noise-affected area, it is likely that suitable and

sufficient habitat is available elsewhere. The risk of noise significantly impacting on the Ganges River Dolphin is

therefore likely to be low.

Management and mitigation measures that could be implemented to minimise the underwater pump noise include

using low-speed pumps, properly balancing rotating equipment, replacing worn, loose or unbalanced parts of the

pump and motor assembly, and implementation of a condition monitoring program.

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1. Introduction

The Bihar Urban Development Investment Program (BUDIP) aims to optimise social and economic development

in four premier towns of Bihar, India. Bhagalpur is one of these towns and improvement of the water supply in this

town is proposed as a first subproject under BUDIP. The Asian Development Bank (ADB) funds the BUDIP and

requires the consideration of environmental issues in all aspects of its operations.

The water supply subproject includes the construction and operation of two intake wells within the Vikramshila

Gangetic Dolphin Sanctuary (VGDS) in the Ganges River. The intake wells each contain two operating vertical

turbine pumps which will generate underwater noise. This noise may adversely affect the endangered Ganges

River Dolphins which relies on sound for sensing of its environment.

AECOM Australia Pty Ltd was engaged by the ADB to assess the impacts of underwater noise radiating from the

intake wells on the Ganges River Dolphins. The process adopted to assess the impacts is summarised below

(with reference to the relevant report sections):

- Section 1: Provide an overview of the project.

- Section 2: Introduce the basic terminology and principles of underwater acoustics.

- Section 3: Describe the existing conditions of the ambient underwater noise environment.

- Section 4: Investigate the hearing and use of sound by the Ganges River Dolphin, establish the potential

effects of noise, and determine suitable noise exposure criteria for assessment of these effects.

- Section 5: Develop an underwater noise propagation model to characterise the spread of noise throughout

the river environment. Compare predicted underwater noise levels to noise exposure criteria and establish

likely zones of noise impact.

- Section 6: Identify reasonable and practical management and mitigation procedures.

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2. Principles of underwater acoustics

2.1 Nature of underwater sound

Underwater sound is an acoustic pressure wave that travels through water and occurs as a backward and forward

motion of the water particles driven by a vibrating source. The magnitude of the water particle motion determines

the intensity of the sound. The rate at which the water particles oscillate backward and forward determines its

frequency given in cycles per second or Hertz (Hz).

Sound travels about four-and-a-half times faster in water than in air. Absorption of sound at frequencies where

man-made noise generally has most energy is much smaller in water than in air. As a result, man-made noise is

typically audible over much greater ranges underwater than in air. Most sources of noise generate acoustic

energy over a broad range of frequencies. Screeching or whistling noises are composed mainly of high frequency

sounds while rumbles or booms are composed mainly of low frequency sounds.

Sounds are usually characterised according to whether they are continuous or impulsive in character. Continuous

sounds occur without pauses and examples include ship traffic, pumps and the ambient noise environment.

Impulsive sounds are of short duration and occur singly, irregularly, or as part of a repeating pattern. Blasting

represents a single impulsive event whereas the periodic impacts from a pile driving rig results in a patterned

impulsive sequence. Impulsive signals typically sound like bangs and generally include a broad range of

frequencies.

Sound pressures are measured underwater with a hydrophone. The international standard unit of sound pressure

is the Pascal (Pa). Sound pressures encountered underwater range from levels just detectable by the mammal

ear (hundreds of µPa) to much greater levels causing hearing damage (billions of Pa). Because this range is so

enormous, sound pressure is normally described in terms of a sound pressure level (SPL) with units of decibel

(dB) referenced to a standard pressure of 1 µPa.

2.2 Underwater noise descriptors

Underwater noise descriptors commonly used for presenting source, measured or received underwater noise

levels include the following:

- Sound pressure level (SPL) – Sound pressure averaged over the measurement period expressed in dB re 1

µPa. Continuous sources such as vibro-piling and dredging are commonly characterised in terms of an SPL.

- Sound exposure level (SEL) – Sound energy over the measurement period expressed in dB re 1 μPa2s. The

SEL is commonly used for impulsive sources such as impact pile driving because it allows a comparison of

the energy contained in impulsive signals of different duration and peak levels. The measurement period for

impulsive signals is usually defined as the time period containing 90% of the sound energy.

- Peak level – Highest sound pressure over the measurement period expressed in dB re 1 µPa. The peak

level is commonly used for impulsive sources.

- Source level – The intensity of underwater noise sources is compared by their source level (SL) expressed

in dB re 1 µPa at 1 m. The source level is defined as the sound pressure, exposure or peak level that would

be measured at 1 m from an ideal point source radiating the same amount of sound as the actual source

being measured.

SPLs and SELs can be presented either as overall levels or as frequency dependent spectral or third-octave band

levels indicating the frequency content of a source. Overall SPLs and SELs present the total average noise and

energy level, respectively, within a given frequency bandwidth – usually the band that contains most of the

energy. Spectral density levels are expressed in units of dB re 1 μPa2/Hz and provide a greater frequency

resolution than third-octave band levels, which are expressed in units of dB re 1 µPa.

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3. Description of existing conditions

The level and frequency characteristics of the ambient noise environment are two factors that control how far

away a given noise source can be detected (Richardson et al., 1995). In general, noise is only detectable if it is of

a higher level than the ambient noise environment at similar frequencies. A lower ambient noise environment

results in audible noise out to greater ranges before diminishing below the background noise level. The potential

zone in which the pump noise radiating from the intake wells is detectable thus depends on the level and type of

ambient noise in the river area surrounding the site.

The main sources of ambient noise in the river area surrounding the intake wells include motorised country boats

used by fishermen, wind-dependent noise, biological noise from other marine species, precipitation noise, and

thermal noise (Richardson et al., 1995). The character and levels of the ambient noise environment is the oceans

have been studied extensively, and generalised ambient ocean noise spectra are available (Wenz, 1962). Studies

into the ambient noise environment within rivers are sparse.

A study into the ambient noise environment in the Danube River concluded that noise levels were typically above

110 dB re 1 µPa peaking at 135 dB re 1 µPa, with dominant energy occurring above 1 kHz (Wysocki et al., 2007).

Peak ambient noise levels ranging between 114 to 159 dB re 1 µPa were recorded within the Yakima River,

Richland, WA, US (WSDOT 2004). Ambient noise levels measured at locations in the St Lawrence River,

Quebec, Canada, ranged between 90–110 dB re 1 µPa during the quietest periods (Jasco Research, 2006).

Based on the above discussions, it is expected that ambient noise levels around the intake wells range between

90 and 120 dB re 1 µPa, mainly depending on weather conditions and the number of motorised boats within 2 to 3

km from the intake wells.

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4. Effects of noise on river dolphins

4.1 Sound production and communication

The Ganges River Dolphin is part of the superfamily Platanistoida which also includes the Amazon River, Chinese

River, Indus River and La Plata Dolphins. The Ganges River Dolphin does not have a crystalline eye lens,

rendering it effectively blind (Herald et al., 1969), and lives in an environment in which vision is not the primary

sense because light does not penetrate far beneath the river surface. As such, the Ganges River Dolphin relies

primarily on sound as its sense for communication and awareness of its environment.

Communication generally has a variety of functions including mother/calf cohesion, group cohesion, individual

recognition and danger avoidance. Dolphins typically communicate with whistles, clicks and squeals at

frequencies ranging from 1 to 20 kHz and most energy typically occurring around 10 kHz. The acoustic properties

of the Ganges River Dolphin’s communication signals have not been studied. Other river dolphin species are

known to produce whistles, clicks and squeals. The Amazon River Dolphin produces squeals and whistles

between 1 and 12 kHz with dominant frequency around 2 kHz (Richardson et al., 1995). The Chinese River

Dolphin produces whistles between 3 and 18 kHz with dominant energy around 6 kHz (Wang et al., 2006). The

Indus River Dolphin produces clicks in the frequency range of 1 to 16 kHz and whistles between 5 and 48 kHz

(Collado & Wartzok, 2007).

Dolphins produce echolocation signals to determine the physical features of their surroundings. Echolocation

signals consist of a train of short clicks with most energy at high frequencies above 20 kHz. The Ganges River

Dolphin’s clicks are about 40 µs long with an inter-click interval of 10-100 ms and dominant energy around 65 kHz

(Sugimatsu et al., 2011).

4.2 Hearing sensitivity

The hearing sensitivity of dolphins generally varies with frequency. Audiograms are therefore used to represent a

dolphin’s sensitivity to sounds of different frequencies. An audiogram of a species relates the absolute threshold

of hearing (in dB re 1 µPa) of that species to frequency. A species is most sensitive to sounds at frequencies

where its absolute threshold of hearing is lowest. As an example, humans are most sensitive to sounds between

2-4 kHz where the absolute threshold is lowest.

The hearing sensitivity of the Ganges River Dolphin has not been investigated. Audiograms for the Chinese and

Amazon River Dolphins are included in Figure 1 (Nedwell et al., 2004). These species have most sensitive

hearing between 20 and 80 kHz which overlaps with the dominant frequency range of their echolocation signals.

Hearing thresholds are 50 to 60 dB re 1 µPa at the most sensitive frequencies and reduce significantly at lower

frequencies. Hearing sensitivity at frequencies below 1 kHz, where man-made noise typically has most energy, is

quiet poor with hearing thresholds expected to be greater than 100 dB re µPa.

Figure 1 – Audiograms for the Chinese and Amazon River Dolphins (Nedwell et al., 2004)

http://en.wikipedia.org/wiki/Lens_(vision)

http://en.wikipedia.org/wiki/Blindness

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Southall et al. (2007) assigned cetacean species to one of three functional hearing groups—low, mid and high-

frequency cetaceans—based on their hearing characteristics. The superfamily of river dolphins is included in the

high-frequency cetacean group which has an estimated auditory bandwidth of 200 Hz to 180 kHz. The group-

specific frequency weighting (M-weighting) illustrated in Figure 2 is applied to this group to account for the fact

that they do not hear equally well at all frequencies within their functional hearing range, as indicated by the

audiograms in Figure 1.

Figure 2 – M-weighting function for the high-frequency cetacean functional hearing group (Southall et al. 2007)

M-weighting of noise levels de-emphasizes frequencies that are near the lower and upper frequency end of the

estimated hearing range, where noise levels have to be higher to result in the same auditory effect (Southall et al.

2007). M-weighting is similar in intent to C-weighting commonly used when assessing the impact of high-

amplitude sounds on humans.

4.3 Effects of noise

Potential impacts of noise on dolphins include mortality, hearing damage, masking of communication and other

biologically important sounds, and behavioural responses (Richardson et al. 1995). Mortality only occurs in the

immediate vicinity of very high energy noise sources, such as blasting, and is unlikely to occur for the considered

pump noise.

4.3.1 Behavioural response

Behavioural responses to noise include changes in vocalisation, resting, diving and breathing patterns, changes in

mother-infant spatial relationships, and avoidance of the noise source (Richardson et al., 1995).

Southall et al. (2007) conducted a review of numerous studies into behavioural disturbance in high-frequency

cetaceans from continuous man-made noise. Most of these studies concerned the effects on harbor porpoise. A

ranking of behavioural response severity was adopted to emphasise that not all behavioural responses are

equally significant. Behavioural changes may be relative minor and/or brief, have the potential to affect important

behaviours such as foraging, breeding and resting, or are likely to affect these vital behaviours.

The review by Southall et al. (2007) concluded that harbor porpoise display behavioural response at very low

noise exposures of SPL 90 to 120 dB re 1 µPa, at least for initial exposures. It is noted that for the majority of

observations, the behavioural changes to levels below 120 dB re 1 µPa were relatively minor or brief. Significant

and sustained avoidance behaviour was recorded when noise levels exceeded 140 dB re 1 µPa. Habituation to

sound was noted in some but not all studies.

The United States (US) National Oceanic and Atmospheric Administration (NOAA) adopts interim noise exposure

criteria for assessing behavioural disruption and injury in cetaceans from underwater noise. An exposure criterion

of SPL 120 dB re 1 µPa is conservatively adopted for behavioural disruption (NOAA 2011).

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Whether the harbor porpoise data reviewed by Southall et al. (2007) can be extended to the Ganges River

Dolphin is unknown. However, combining the conclusions of their review and the conservative interim criterion

adopted by NOAA, it is assumed as a precautionary measure that noise levels above SPL 120 dB re 1 µPa may

cause behavioural disturbance.

A study into the habitat use and distribution of the Ganges River Dolphin in the VGDS concluded that the number

of motorised boats and boat noise were not significantly correlated with dolphin encounter rates (Kelkar, 2008).

Small boats equipped with outboard engines can produce source levels in the order of 160 dB re 1 µPa at 1 m, or

received levels of over 120 dB re 1 µPa at 1 m up to 500 m. Although the study results suggest that boat noise is

not displacing dolphins, it is not conclusively showing that such noise levels do not impact on their behaviour.

4.3.2 Masking

Masking of biologically important sounds may interfere with communication and social interaction and cause

changes in behaviour as well. The zone of masking impact will be highly variable and depends on many factors

including the distance between the listener and sources of the signal and masking noise, the level of the signal

and masking noise, and the propagation of noise from the signal and masking source to the listener (Richardson

et al., 1995).

It is important to note that masking of communication and echolocation signals naturally occurs by the ambient

noise environment. Man-made noise causes additional masking of a signal only when it is of a higher level than

the ambient environment within the species’ critical hearing bandwidth at the signal’s dominant frequencies

(Richardson et al., 1995). The critical bandwidth for dolphins is typically assumed to be one-third octave band

wide (Richardson et al., 1995).

Echolocation clicks produced by the Ganges River Dolphin have dominant energy around 65 kHz (Sugimatsu et

al., 2011). This is well above the dominant frequency range of most man-made noise, including pump noise.

Masking of echolocation signals is therefore not a significant issue for most man-made sources (Richardson et al.,

1995). In other words, the pump noise is not expected to significantly interfere with the echolocation ability of the

Ganges River Dolphin.

The Ganges River Dolphin is likely to produce communication signals, such as whistles, squeals or clicks, based

on communication signals produced by other river dolphins. These signals generally have energy at much lower

frequencies than the echolocation clicks, i.e. as low as 1-6 kHz. Communication signals are therefore more likely

masked by man-made noise than echolocation clicks.

4.3.3 Hearing damage

When the dolphin’s auditory system is exposed to a high level of sound for a specific duration, the sensory hair

cells begin to fatigue and do not immediately return to their normal shape (NRC 2005). This causes a reduction in

the hearing sensitivity, or an increase in hearing threshold. If the noise exposure is below some critical sound

energy level, the hair cells will eventually return to their normal shape. This effect is called a temporary threshold

shift (TTS) as the hearing loss is temporary. If the noise exposure exceeds the critical sound energy level, the hair

cells become permanently damaged and the effect is called permanent threshold shift (PTS).

Noise exposure criteria for marine mammals were recommended by a group of experts based on a review of

available data (Southall et al. 2007). An M-weighted exposure criterion of SEL 215 dB(M) re 1 µPa2s is

recommended for PTS from continuous noise. This is based on a TTS-onset level of SEL 195 dB(M) re 1 µPa2s

measured in mid-frequency cetaceans, and adding 20 dB to estimate PTS on-set (Southall et al. 2007).

The United States (US) National Oceanic and Atmospheric Administration (NOAA) adopts interim noise exposure

criteria for assessing injury in cetaceans from underwater noise. An injury criterion of SPL 180 dB re 1 µPa is

adopted for PTS conservatively based on available data for TTS (NOAA 2011).

4.3.4 Noise exposure criteria

Table 1 summarises the noise exposure criteria adopted for assessing hearing damage (PTS or TTS) and

behavioural effects on the Ganges River Dolphin from pump noise. The noise exposure criteria are based on the

review presented by Southall et al. (2007) and the current interim criteria adopted by the NOAA (2011), which

were discussed above.

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Table 1 – Noise exposure criteria for physiological (PTS and TTS) and behavioural impacts from impact piling on cetaceans

Impact Noise exposure criteria

Permanent threshold shift SEL 215 dB(M) re 1µPa2s

Temporary threshold shift SEL 195 dB(M) re 1µPa2s

Behavioural response SPL 120 dB re 1 µPa

4.4 Zones of noise impact

Given the source noise characteristics, a model that predicts the propagation of sound away from the source, and

noise exposure criteria, the radii within which impacts are expected to occur can be predicted. The resulting radii

define zones of noise impact around the noise source which are illustrated in Figure 3. The following zones of

noise impact can be defined (Richardson et al. 1995):

- Zone of audibility – Area within which Ganges River Dolphin might hear the pump noise but not show any

significant behavioural or physiological response. The size of the zone of audibility is highly dependent on

the ambient noise environment.

- Zone of responsiveness – Area within which the Ganges River Dolphin might react behaviourally to the

pump noise. This zone is smaller than the zone of audibility as dolphins usually do not show significant

behavioural responses to noises that are faint but audible.

- Zone of hearing injury – Area closest to the intake well where the pump noise levels may be high enough to

cause temporary or permanent threshold shift after prolonged exposure.

The zones of impact predict the how far away the pump noise is expected to have an impact on the Ganges River

Dolphin, either behaviourally or physiologically. This information should be used in conjunction with information on

the biological significance of the noise-affected area to assess the risk of significantly affecting the Ganges River

Dolphins.

Figure 3 – Zones of audibility, responsiveness and hearing injury (TTS or PTS) around a noise source

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5. Pump noise assessment

5.1 Intake well and pump configuration

Two intake wells with internal diameters of 9 m will be used for pumping in water from the Ganges River. A

schematic diagram illustrating the concept design for the intake well is included in Figure 4. The circular wall of

the well will be constructed from approximately 1.2 m thick reinforced concrete and the bottom will be plugged

with concrete as well. The wall will contain four top and four bottom gates for water inlet with approximate

dimensions of 1 x 1 m. The bottom four gates are closed when the water level is above the top four gates such

that a maximum of four of gates will be open to the river at any one time.

Figure 4 – Schematic diagram of intake well and pump configuration

The well will contain two working and one stand-by vertical turbine pumps each extracting 1650 m3/hr at 36 m

head and equally spaced. The pump assembly is submerged by about 10 m at low water level and 21 m at high

water level. There will be a minimum 1 m clearance between the pump bowl and well floor.

The pump motor will be located in a motor room located on top of the intake well. The motor and pump will be

connected by a stainless steel shaft. The motor room walls will be constructed of 250 mm thick brick or concrete

and a solid floor will be installed. The shaft will hang through holes in the floor. The motors are likely to have a

power rating of around 200-300 kW and running speed of 1470 rpm or 24.5 Hz, based on product data for WPIL

pumps provided to us by GHK on 11 August 2011.

The motor is expected to produce noise levels of approximately 85 dB(A) at 1.9 m. Vibrations at the pump bowl

assembly will be limited to a peak to peak displacement level of 50 µm.

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5.2 Pump source level characterisation

5.2.1 Noise generation process

The noise generation process can be divided into three parts: generation of vibratory energy by rotating parts of

the motor and pump assembly or turbulent flow; transmission of this vibratory energy to radiating surfaces in

contact with the water including the pump column pipe, concrete well wall and impeller blades; and radiation of

sound into the water from the vibrating surfaces (Ross, 1987).

Noise radiated from vibrating surfaces within the intake wells will predominantly be transferred to the river via the

eight gates that let water into the well. Noise transfer via the concrete walls is predicted to be negligible in

comparison due to the 1.2 m thickness. Vibrations in the concrete walls are also expected to be small in

comparison to the pump assembly such that structure-borne noise radiated from the concrete walls is predicted to

be negligible. In other words, we predict that most of the noise radiated into the river originates from the pump

assembly surfaces located within the wells and is transferred to the river via the gates.

Air-borne noise radiated from the motor is not expected to be a significant issue because the noise will be largely

contained within the motor room. Moreover, the air-water surface is highly reflective and most of the air-borne

from the motor room would not be transmitted into the water. Any noise that is transmitted will be negligible in

comparison to the intake well internal noise radiating from the gates.

5.2.2 Upper limit estimate for source level

An initial estimate of the source level radiating from the intake well can be made by using the concept of acoustic

conversion efficiency which is defined as the ratio of the radiated sound power to the mechanical power of the

source. The acoustic conversion efficiency is the product of the conversion efficiencies for the three parts of the

noise-production process (Ross, 1987). Conversion efficiencies as low as 10-8

are common for sources in water

while values as high as 10-4

to 10-2

are often found for sounds radiated into the air (Ross, 1987).

The power rating of the pump motors is expected to be in the order of 300 kW. Based on typical acoustic

conversion efficiencies of 10-5

to 10-8

, the radiated sound power is expected to range between 3 mW and 3 W. A

point source radiating this sound power would produce a source level of 145 to 175 dB re 1 µPa at 1 m. In other

words, the noise radiating from the well into the Ganges River is expected to be limited to 175 dB re 1 µPa at 1 m.

5.2.3 Measurements of cooling water intake pump noise

Underwater noise levels radiating from a cooling water intake pump well were previously conducted by AECOM at

the AGL Torrens Island Power Station (TIPS), South Australia. The power station pumps in seawater using eight

310 kW pumps running at 495 rpm and each pumping at a rate of 1000 m3/hr. Two of the eight pumps were in

operation during the measurements. Measurements were taken at a distance of approximately 330 m from the

pumps at a depth of about 6-7 m. Figure 5 illustrates the measured pump noise levels.

Figure 5 – Measured underwater noise level at a range of 330 m from Torrens Island Power Station pumps, South Australia

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Strong tonal components at harmonics related to the running speed and blade-pass frequency (BPF) of the pump

were observed. The tonal component at the fundamental frequency of 8.25 Hz is not clearly visible due to

relatively high self-noise levels at low frequencies which occurred due to the strong current that passed the

hydrophone. These self-noise problems are generally difficult to overcome when measuring underwater noise

levels below 20 Hz (Richardson et al. 1995).

Figure 5 shows that sound pressure levels at the observed tones below 150 Hz range between 90 dB and 100 dB

re 1 µPa. A broadband noise level of 116 dB 1 µPa was measured between 20 Hz and 1 kHz where pump noise

is expected to have dominant energy. This relates to a source level of 166 dB re 1 µPa at 1 m for the radiated

pump noise from the intake well (assuming spherical spreading), i.e. 163 dB re 1 µPa at 1 m for each pump. Note

that this level is well below the upper limit estimate provided in Section 5.2.2 for pumps of similar size.

5.2.4 Modelled source level for pumps

Based on the above discussions, a conservative estimate for the source level of one vertical turbine pump is

175 dB re 1 µPa at 1 m. The pumps are likely to operate at running speeds of 1470 rpm based on product data for

WPIL pumps provided to us by GHK on 11 August 2011. Pump noise is therefore expected to contain tonal

components at the fundamental frequency of 24.5 Hz and associated harmonics.

The modelled one-third octave band source levels for one pump are illustrated in Figure 6. The pump noise is

modelled to have dominant energy below 200 Hz where tonal components related to the running speed are

expected to occur. The M-weighted overall source level is SPL 167 dB(M) re 1 µPa at 1 m, which is 8 dB lower

than the unweighted source level. This difference occurs because the M-weighting function de-emphasises the

noise levels below 200 Hz which are outside the estimated hearing range of the Ganges River Dolphin.

Figure 6 – Modelled one-third octave band unweighted and M-weighted source levels for pump noise

5.3 Radiated source level into Ganges River

The intake wells are expected to behave as reverberant chambers because the water-air interface and concrete

walls and floors are all highly reflective. The sound pressure at a location in the intake wells is therefore the

summation of the sound travelling directly from the pumps (direct field) and the sound travelling along paths

emanating from the pumps arriving after multiple reflections (reverberant field).

Reverberant chamber theory (Jones & Hoefs, 1996) was used to predict the noise levels at the well-side of the

water inlet gates. The noise intensity (W/m2) at these locations was then calculated from these noise levels and

multiplied by the gate area to arrive at sound power levels at the well-side of the gates. The sound power radiating

into the river was conservatively assumed to be the same as the 1.2 m long gates through the concrete walls are

not expected to provide significant noise reduction. The predicted sound power radiating into the river from the

gates was converted to an equivalent source level.

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A source level of 164 dB re 1 µPa at 1 m is predicted for the noise radiating from one intake well with two pumps

operational. This assumes a predicted source level of 175 dB re 1 µPa at 1 m for each of the two pumps. The

modelled one-third octave band radiated source levels for one intake well are included in Figure 7. These source

levels are used in the underwater noise propagation model presented in the next section.

Figure 7 – Modelled one-third octave band unweighted and M-weighted source levels for noise radiated into Ganges River

5.4 Underwater noise propagation modelling

5.4.1 Source-path-receiver model

Underwater noise propagation models predict the sound transmission loss between a source and receiver. Given

the source level (SL) of the considered noise source, the predicted transmission loss (TL) is used to predict the

sound pressure level (SPL) at the receiver location as SPL = SL – TL. The source-path-receiver model illustrated

in Figure 8 presents the basic principles of underwater noise propagation modelling (Richardson et al., 1995).

Figure 8 – Source-path-receiver model for sound transmission loss modelling

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5.4.2 Noise transmission loss modelling

The underwater noise propagation model RAMGeo1 was used to predict the spreading of pump noise radiating

from the intake wells throughout the marine environment. The implementation of the RAMGeo model included in

the AcTUP v2.2l acoustic toolbox developed at Curtin University’s Centre for Marine Science & Technology,

Australia, was used in the underwater noise calculations. Bathymetry data and river bed geo-acoustic properties

were included in the modelling.

A bathymetric survey was conducted around the locations of the two intake wells. The survey covered an area

about 140 m towards the river from the water edge and about 70 m from the water edge towards the bank. The

width covers about 90 m in the water front and about 120 m on the bank (GHK Consulting, 2011). Bathymetric

data was not obtained for the areas of interest for long-distance underwater noise propagation, i.e. upstream,

downstream and across the river. The exact location of the intake wells will be determined during the detailed

engineering stage as this requires a detailed hydrological model analysis. For the preliminary stage, the location

may be assumed to be about 100 m from the water edge towards the river. The depth of water at this location was

approximately 10 m during the bathymetric survey and can be up to 20 m during high tide. The bathymetry profile

included in the modelling therefore assumed a depth of 20 m at the intake well location gradually decreasing to a

constant depth of 30 m at distances beyond 200 m upstream, downstream and across the river. This is expected

to result in conservative predictions as noise propagation is less efficient the shallower the water.

A geotechnical investigation was conducted at the proposed locations of the intake wells (GHK Consulting, 2011).

Two bore holes were sunk to a depth of 30 m below the river bed. Analysis of the bore hole samples indicated the

presence of two layers generally consisting of a mixture of silt and clay. The first layer mainly consists of silt

extending to a depth of 25 m. The second layer mainly consists of clay extending from 25 m to the measurements

depth. Based on this data, the riverbed was modelled as a 25 m thick layer of silt overlaying a 25 m thick layer of

clay, with a sound attenuating layer of bedrock included below the clay. The geo-acoustic properties of the layers

included in the model are presented in Table 2 (Jensen et al., 1994).

Table 2 – Modelled geo-acoustic properties of river bed (Jensen et al., 1994)

Geo-acoustic property Riverbed layer

Silt Clay Bedrock

Depth (m) 0–25 25–50 > 50

Compressional wave speed (m/s) 1575 1500 2800

Sheer wave speed (m/s) 0–210 50 550

Compressional wave absorption (dB/) 1.0 0.2 30

Shear wave absorption (dB/) 1.5 1.0 30

Density (kg/m3) 1980–2080 2080 2400

The transmission loss was computed versus depth out to range of 10 km at the one-third octave band frequencies

between 16 Hz to 4 kHz. Graphs illustrating the predicted transmission loss versus depth and range from the

source at each of the one-third octave band frequencies are included in Appendix A. The minimum (i.e. worst-

case) transmission loss at each range step was calculated with the results presented in Figure 9.

The results in Figure 9 indicate that noise levels at frequencies of 250 Hz and above are predicted to reduce at a

rate of 15log10R. Noise propagation is less sufficient at lower frequencies due to the shallow depth of the river.

Note that the modelled pump source noise levels have significant energy at these lower frequencies.

1 Range-dependent Acoustic Model (RAM) developed at the US Naval Research Laboratory by Mike Collins.

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Figure 9 – Transmission loss modelling results illustrating the reduction in noise level (dB) with range from the intake wells at the modelled one-third octave band frequencies

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5.4.3 Underwater noise prediction results

An underwater noise contour map illustrating the propagation of noise throughout the river area surrounding the

intake wells is included in Appendix A. The contour map shows the highest noise level along water depth.

Figure 10 present the predicted overall SPL radiated from the intake wells versus range and depth. The dash-

dotted line indicates the modelled bathymetry profile. The results were calculated from the one-third octave band

source level estimate (Figure 7) and transmission loss predictions (Figure 9).

Figure 10 – Predicted SPL radiated from intake wells versus range and depth

Figures 12 and 13 present the predicted overall SPL and daily SEL radiated from the intake wells versus range,

respectively. The results show the maximum level along depth at each range step. The two intake wells are

located at the same location in the calculations which is a reasonable assumption when considering long-distance

propagation, i.e. when the distance from the two wells is much larger than the distance between the wells (30 m).

5.5 Zones of noise impacts

Underwater noise levels over SPL 120 dB re 1 µPa may potentially affect important behaviours such as foraging,

breeding and resting. Significant and sustained avoidance behaviour is expected when underwater noise levels

exceed 140 dB re 1 µPa. Comparing these threshold levels to the noise predictions in Figure 11 indicates that

biologically important behaviours may potentially be affected up to 575 m from the intake wells while sustained

avoidance behaviour is predicted to occur up 40 m.

Hearing damage is expected to occur when exposure levels exceed SEL 195 dB(M) re 1 µPa2s for temporary

damage (TTS) and 215 dB(M) re 1 µPa2s for permanent damage (PTS). Comparing these threshold levels to the

noise predictions in Figure 12 indicates that PTS is highly unlikely to occur while TTS could occur within 6 m but

only after 24 hours of exposure. Because dolphins are expected to avoid the immediate vicinity of the intake wells,

it is believed unlikely that TTS will occur.

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Figure 11 – Predicted SPL radiated from intake wells versus range compared to the behavioural response threshold of 120 dB re 1 µPa

Figure 12 – Predicted daily SEL radiated from intake wells versus range compared to the TTS on-set threshold of 195 dB(M) re 1 µPa2s

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6. Management and mitigation measures

Management and mitigation measures that could be implemented where reasonable and practical to further

minimise the risk to noise impacts upon the Ganges River Dolphin include the following:

- Use low-speed pumps: Reducing the running speed of the pumps generally reduces noise emissions and

shifts dominant noise energy towards lower frequencies where hearing of the Ganges River Dolphin is less

sensitive.

- Properly balance rotating equipment: Ensure rotating parts of the pump and motor assembly are properly

balanced. This minimises structural vibrations that may radiate off surfaces as underwater noise.

- Replace worn, loose or unbalanced parts of the pump and motor assembly: Worn, loose or unbalanced parts

may generate excessive structural vibrations that may radiate off surfaces as underwater noise.

- Condition monitoring: Implement a condition monitoring plan to ensure excessive vibrations in the motor and

pump assembly are detected and resolved.

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7. Conclusion

The potential impacts on the Ganges River Dolphin of underwater noise associated with operation of the intake

wells for the Bhagalpur Water Supply Subproject of the BUDIP was assessed.

The risk of hearing damage was identified as negligible as predictions indicated that it occurs only within a few

metres from the intake wells after a full day of noise exposure. The dolphins are likely to avoid the immediate

vicinity of the wells such that hearing damage is unlikely to occur.

Noise radiating from the intake wells is not expected to significantly interfere with the echolocation ability of the

Ganges River Dolphin as their echolocation clicks have dominant energy around 65 kHz which is well above the

dominant frequency range of the pump noise. Communication signals are more likely to be masked by the pump

noise but only within a few tens of metres from the intake wells. The risk of significantly impacting on the dolphin’s

communication and echolocation abilities is therefore low.

Significant and sustained avoidance behaviour is predicted to occur up 40 m from the intake wells. The expected

avoidance reaction will further mitigate the risk of hearing damage.

Biologically important behaviours, such as breeding, feeding and resting, may potentially be affected up to 575 m

from the intake wells. The associated risk depends on the biological significance of the noise-affected area.

However, considering the size of the VGDS relative to the noise-affected area, it is likely that suitable and

sufficient habitat is available elsewhere. The risk of noise significantly impacting on the Ganges River Dolphin is

therefore likely to be low.

Management and mitigation measures that could be implemented to minimise the underwater pump noise include

using low-speed pumps, properly balancing rotating equipment, replacing worn, loose or unbalanced parts of the

pump and motor assembly, and implementation of a condition monitoring program.

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References

Collado, L. J., & Wartzok, D. (2007). The freshwater dolphin Inia geoffrensis geoffrensis produces high frequency

whistles. Journal of the Acoustical Society of America , 121 (2), 1203-1212.

GHK Consulting. (2011). BUDIP Bathymetric Survey Report, Bhagalpur Water Supply (Tranche 1).

GHK Consulting. (2011). BUDIP Geotechnical Investigation, Bhagalpur Water Supply (Tranche 1).

Herald et al. (1969). Blind River Dolphin: First Side-Swimming Cetacean. Science , 166, 1408-1410.

Jasco Research. (2006). Cacouna Energy LNG Terminal: Assessment of Underwater Noise Impacts. Montreal,

QC, Canada.

Jensen et al. (1994). Computational Ocean Acoustics. Woodbury, NY: AIP Press.

Jones, A. D., & Hoefs, S. A. (1996). Acoustical Properties of the MOD Salisbury Test Tank and Techniques for

Measurements. Department of Defence . Melbourne 3001 Victoria: DSTO Aeronautical and Maritime Research

Laboratory.

Kelkar, N. (2008). Patterns of habitat use and distribution of Ganges river dolphins Platanista gangetica gangetica

in a human-domintaed riverscape in Bihar, India. Master Thesis, Manipal University, Centre for Wildlife Studies,

Bangalore.

Nedwell et al. (2004). Fish and Marine Mammal Audiograms: A summary of available information. Subacoustech

Report 534R0214.

National Oceanic and Atmospheric Administration (NOAA 2011). Interim Sound Threshold Guidance for Marine

Mammals. http://www.nwr.noaa.gov/Marine-Mammals/MM-sound-thrshld.cfm.

NRC. (2005). Marine Mammal Populations and Ocean Noise - Determining When Noise Causes Biologically

Significant Effects. National Research Council, National Academies Press.

Richardson et al. (1995). Marine Mammals and Noise. San Diego: Academic Press.

Ross, D. (1987). Mechanics of Underwater Noise. Los Altos, California: Peninsula Publishing.

Southall et al. (2007). Marine Mammal Noise Exposure Criteria: Initial Scientific Recommendations. Aquatic

Mammals, 33(4).

Sugimatsu et al. (2011). Annual Behavioral Changes of the Ganges River Dolphins (Platanista gangetica) Based

on the Three Long-Term Monitoring Seasons using 6-Hydrophone Array System. IEEE Symposium on and 2011

Workshop on Scientific Use of Submarine Cables and Related Technologies, (pp. 1-7). Tokyo.

Wang et al. (2006). Estimated detection distance of a baiji's (Chinese river dolphin, Lipotes vexillifer) whistles

using a passive acoustic survey method. Journal of the Acoustical Society of America , 120 (3), 1361-1365.

Washington State Department of Transportation. (2004). Underwater sound levels associated with construction of

the SR 240 Bridge on the Yakima River at Richland. Office of Air Quality and Noise, Seattle, WA.

Wenz, G. M. (1962). Acoustic ambient noise in the ocean: Spectra and sources. Journal of the Acoustical Society

of America , 34 (12), 1936-1956.

Wysocki et al. (2007). Diversity in ambient noise in European freshwater habitats: Noise levels, spectral profiles,

and impact on fishes. Journal of the Acoustical Society of America , 121 (5), 2559-2566.

http://www.nwr.noaa.gov/Marine-Mammals/MM-sound-thrshld.cfm

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Appendix A

Underwater noise contour map

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PROJECT ID

LAST MODIFIEDCREATED BY

60223695TRE/CDP10/10/2011

SOUND PRESSURE LEVEL (dB)

<105105-110110-115115-120

120-125125-130130-135135-140

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Underwater noise impacts on Ganges River DolphinBhagalpur Water Supply (Tranche 1)Bihar Urban Development Investment Program A1

FigureASIAN DEVELOPMENT BANK

BHAGALPUR WATER SUPPLY (TRANCHE 1)UNDERWATER NOISE CONTOUR MAP

115110

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