Appendix K - BC Hydro - Transmission

Environmental Assessment Certificate Application – May 2006 

Vancouver Island Transmission Reinforcement Project 

Appendix K 

 

 

 

 

 

 

 

 

 

 

Atmospheric and Underwater Acoustics Assessment Report 

JASCO Research Ltd. 2006. Vancouver Island Transmission Reinforcement Project: 

Atmospheric and Underwater Acoustics Assessment Report.prepared for British 

Columbia Transmission Corporation 49 pp.

BRITISH COLUMBIA TRANSMISSION CORPORATION 

VANCOUVER ISLAND TRANSMISSION REINFORCEMENT PROJECT 

Atmospheric and Underwater Acoustics Assessment Report 

Prepared by: 

Melanie Austin 

Alex MacGillivray 

Roberto Racca 

David Hannay 

Holly Sneddon 

March 14, 2006

Prepared by: 

Suite #2101 – 4464 Markham Street 

Victoria, BC V8Z 7X8 

Phone: +1.250.483.3300 

Facsimile: +1.250.483.3301 

Email: info@jasco.com 

Web: www.jasco.com 

SUBMITTED TO: 

Attention: Ward Prystay 

Jacques Whitford Limited 

5 th Floor – 4370 Dominion Street 

Burnaby, BC V5G 4L7

JASCO Research Ltd BCTC VITR Project 2006-03-14 

Table of Contents 

Chapter 1 - Atmospheric Noise Assessment ............................................................................... 6 

1. Introduction............................................................................................................................... 6 

2. Existing Conditions................................................................................................................... 6 

2.1. Regulatory Background – Local Noise Bylaws ................................................................... 6 

2.1.1. Corporation of Delta ............................................................................................................. 6 

2.1.2. Capital Regional District - Salt Spring Island....................................................................... 6 

2.1.3. Capital Regional District – Galiano Island ........................................................................... 7 

2.1.4. Municipality of North Cowichan.......................................................................................... 7 

2.1.5. City of Duncan...................................................................................................................... 7 

2.1.6. Commercial Vessel Noise Policies ....................................................................................... 7 

2.2. Existing Noise Environment – Communities Near Overhead Lines and Inland 

Terminals....................................................................................................................................... 8 

2.2.1. Methodology......................................................................................................................... 8 

2.2.2. Details of Measurements at Locations.................................................................................. 8 

2.2.3. Noise Survey Results .......................................................................................................... 10 

2.3. Existing Noise Environment – Communities Near Cable Terminals and Submarine 

Cable Landfalls ........................................................................................................................... 10 

3. Potential Effects – Construction and Operation of Project Facilities................................ 11 

3.1. Methodology ......................................................................................................................... 11 

3.2. Construction Noise............................................................................................................... 11 

3.3. Operation Noise.................................................................................................................... 15 

4. Potential Effects - Corona ...................................................................................................... 18 

5. Potential Effects – Cable Terminal Hydraulic Pump Operation ....................................... 19 

5.1. Nile Creek Shore Terminal Facility ................................................................................... 19 

5.2. Oil-filled Cable System........................................................................................................ 20 

5.3. Hydraulic Pumps ................................................................................................................. 21 

5.4. Vacuum Pumps .................................................................................................................... 21 

5.5. Acoustic Measurements....................................................................................................... 22 

5.5.1. Indoor Measurements.......................................................................................................... 23 

5.5.2. Outdoor Measurements....................................................................................................... 24 

6. Potential Effects – Removal, Construction and Operation of Submarine Cables and 

Cable Terminals.......................................................................................................................... 28 

7. Potential Effects – Cable-laying and Cable-removal Vessels.............................................. 28 

8. Conclusion ............................................................................................................................... 30 

9. References Cited...................................................................................................................... 32 

3


Chapter 2: Underwater Noise Assessment ............................................................................... 33 

1. Introduction............................................................................................................................. 33 

2. Baseline measurements........................................................................................................... 33 

2.1. Methodology ......................................................................................................................... 33 

2.2. Trincomali Channel measurements ................................................................................... 35 

2.3. Strait of Georgia measurements ......................................................................................... 35 

3. Construction and operation noise.......................................................................................... 37 

3.1. Cable construction noise...................................................................................................... 37 

3.2. Cable operation noise .......................................................................................................... 38 

4. Noise Modelling....................................................................................................................... 39 

4.1. Methodology ......................................................................................................................... 39 

4.2. Construction Noise Modelling Results............................................................................... 42 

4.2.1. Cable ship............................................................................................................................ 42 

4.2.2. Small workboat ................................................................................................................... 42 

5. Conclusion ............................................................................................................................... 48 

6. References Cited...................................................................................................................... 49 

4


Preface 

This report contains JASCO Research Ltd’s assessment of the baseline atmospheric and 

underwater noise environments near the Vancouver Island Transmission Reinforcement (VITR) 

Project facilities and transmission line Right of Way (ROW) that are part of the proposed 

replacement and upgrade of BCTC’s existing 138 kV overhead line and submarine cable 

transmission interconnection system from the Arnott Substation in Delta, B.C., to the Vancouver 

Island Terminal in North Cowichan, B.C. The report outlines the changes in noise level that can 

be expected during the construction work and in the subsequent operation of the systems. Topics 

and areas of study directly correspond to those sections on noise found in the VITR Draft Terms 

of Reference (May 2005). 

This report is organized into two separate sections; the first section addresses the atmospheric 

noise assessment and the second section addresses underwater noise issues. The two sections 

include separate background information, methods, results and conclusions. 

The atmospheric section provides the following information specifically for communities and 

environments near the proposed VITR Project facilities and ROW: (i) relevant local noise 

bylaws, (ii) an assessment of existing noise conditions in communities near overhead lines, 

inland terminals, cable terminals and submarine cable landfalls, and (iii) a discussion of potential 

effects of construction and operation of project facilities, corona, hydraulic pump operation, 

removal, construction and operation of submarine cables and cable terminals, and cable laying 

and cable removal vessels on baseline noise levels. 

The underwater section presents results of field measurements performed in Trincomali Channel 

and the Strait of Georgia. The final part of this report provides a review of the existing noise 

conditions along the transmission line route, and discusses potential effects of cable construction 

and operation on the baseline noise levels. 

5

JASCO Research Ltd BCTC VITR Project - Atmospheric 2006-03-14 

Chapter 1 - Atmospheric Noise Assessment 

1. Introduction 

This chapter provides an assessment of the baseline atmospheric (in-air or audible) noise 

environment in communities near the VITR facilities and transmission line Right of Way (ROW) 

that are part of the proposed reinforcement, and of the changes in noise level that can be 

expected during the construction work and in the subsequent operation of the system. In the 

sections that follow, the results of acoustic measurements performed at a number of locations are 

presented in the context of local regulations for allowable levels of anthropogenic noise. 

Numerical modelling of sound propagation is then used to forecast the potential increase in noise 

due to activities including the construction and operation of additional facilities, removal and 

laying of submarine cables, excavation for underground cable or overhead line poles, and 

helicopter assisted installation of new tower components. The potential for increased audible 

noise from hydraulic pumps associated with the cable terminals and from the operation of 

transmission lines under atmospheric conditions including rain or fog, mostly due to corona 

discharge, is also discussed. 

2. Existing Conditions 

2.1. Regulatory Background – Local Noise Bylaws 

Atmospheric noise from construction and other anthropogenic activities in the urban areas within 

the vicinity of the ROW is regulated locally through the municipal bylaws discussed in this 

section. 

2.1.1. Corporation of Delta 

Noise Control Bylaw No. 1906 – This bylaw regulates noise and sound and states that the 

generation of noise from machinery or construction activities is restricted as follows: from 

Monday to Friday not before 7:00 am nor after 7:00 pm; on Saturday not before 9:00 am nor 

after 5:00 pm; Sunday not at all. 

2.1.2. Capital Regional District - Salt Spring Island 

Bylaw 2047 “Noise Suppression Bylaw (Salt Spring Island) No. 1, 1992, Amendment Bylaw 

NO. 1, 2004” – This bylaw provides for the abatement and control of disturbing noise in the 

electoral area of Salt Spring Island in the Capital Regional District. It states that within the 

electoral area “No person shall make, cause to be made, or continue to make any noise or sound 

in the Electoral Area which creates a noise that disturbs or tends to disturb the quiet, peace, rest, 

enjoyment, comfort or convenience of the neighbourhood or of persons at or near the source of 

such noise or sound.” Disturbing noise levels are not quantified. 

The bylaw forbids any person from loading/unloading any truck, wagon, or motor vehicle in or 

upon any public or private place or premises, and from constructing or using constructing 

equipment before 7:00 am and after sunset or 7:00 pm (whichever is latest) unless the hours of 

6


operation must be determined by factors such as tides, ferry schedules, weather conditions, or 

fire hazards in forests. 

2.1.3. Capital Regional District – Galiano Island 

Noise bylaws for the Southern Gulf Islands fall under the jurisdiction of the Capital Region 

District. At this time there are no Noise Bylaws that are specific to Galiano Island. The Galiano 

Island Community Plan does not specifically detail noise regulations but it does state, “Noise 

abatement techniques are encouraged” in Light Industrial areas. 

2.1.4. Municipality of North Cowichan 

Bylaw No. 2857 “Noise Bylaw 1995” – A bylaw to provide for noise control to “regulate or 

prohibit the making or causing of noises or sounds in or on a highway or elsewhere in the 

municipality which disturb, or tend to disturb, the quiet, rest, enjoyment, comfort, or 

convenience of the neighbourhood, or of persons in the vicinity, or which Council believes are 

objectionable”. 

The bylaw forbids the “erecting, demolishing, altering, or repairing of any buildings or structure, 

or the excavation of any land, street, highway, or lane prior to 7:00 am or after 8:00 pm on 

Monday to Saturday, inclusive, or prior to 9:00 am or after 6:00 pm on Sundays in such a manner 

as to disturb the quiet, peace, rest, enjoyment, comfort, or convenience of any person or persons 

in the neighbourhood or vicinity”. 

2.1.5. City of Duncan 

Bylaw No. 1423 “Noise Control Bylaw, 1984” – A bylaw to regulate or prohibit the making or 

causing of noises or sounds in or on a highway or elsewhere in the municipality which disturb, or 

tend to disturb, the quiet, peace, rest, enjoyment, comfort, or convenience of the neighbourhood, 

or of persons in the vicinity, or which in the opinion of the Council are objectionable or liable to 

disturb the quiet, peace, rest, enjoyment, comfort, or convenience of individuals or the public, 

and may make different regulations or prohibitions for different areas of the municipality. 

Construction hours are defined between 07:00 hours and 22:00 hours. Outside of these hours, 

and on Sundays, it is prohibited to construct, erect, reconstruct, alter, repair or demolish any 

building, structure or thing or excavate or fill in land in any manner which disturbs the quiet, 

peace, rest, enjoyment, comfort or convenience of the neighbourhood or of persons in the 

vicinity, except by written permission of the City Administrator. 

2.1.6. Commercial Vessel Noise Policies 

Currently, there are no Canadian standards that restrict audible noise from marine vessels in 

regards to community impacts. The Canada Labour Code Part II and the Marine Occupational 

Safety and Health (MOSH) regulations address noise from the health and safety perspective of 

the vessel crews. Environmental noise from commercial vessels is addressed through municipal 

bylaws, the harbour authority “Operation Regulations” (different for each port under the Canada 

Marine Act – J. Baumann personal communication, 07-Oct-05), and other onshore bodies 

responsible for regulating noise (M. Chaumont personal communication, 19-Oct-05). 

7


2.2. Existing Noise Environment – Communities Near Overhead Lines 

and Inland Terminals 

2.2.1. Methodology 

Baseline noise levels were measured at representative locations in each community within the 

project area. Noise levels were recorded using a sound level meter with a pre-amplifier and ½” 

Free Field condenser microphone (Larson Davis Models 824, PRM 902, and 2541 respectively). 

Measurement sites were located near residences that lie in close proximity to the transmission 

line Right of Way (ROW). Locations were chosen that characterized the average noise levels in 

each community, that were easily and safely accessible and that provided secure places to leave 

recording equipment for prolonged recording periods. The baseline measurement locations are 

outlined in Table 1. 

Table 1 Baseline noise measurement locations. 

Community Description 

Tsawwassen 543 Tralee Cres., residential neighbourhood along ROW 

Galiano Island 70 Montague Park Rd, Montague Harbour community 

Salt Spring Island Intersection of Long Harbour Rd and Upper Ganges Rd, rural residential area 

North Cowichan Intersection of Bayview Pl and Bayview Dr, rural residential area 

Duncan 

7056 Bell McKinnon Rd, residence adjacent to VIT property 

Measurements at the Tsawwassen, North Cowichan, and Duncan locations consisted of 24-hour 

recordings. Measurements at the Gulf Island locations (Salt Spring and Galiano Island) were 

limited to 18 hours since the measurement opportunities were restricted by ferry schedules. 

Hourly average energy equivalent levels (L eq ) were logged and are summarized further down. 

Typical factors contributing to the overall noise environment included street traffic, air traffic, 

household and yard noises (radios, lawnmowers, chainsaws etc), dogs barking, and natural noises 

such as rustling leaves, crickets, and birds chirping. 

2.2.2. Details of Measurements at Locations 

Tsawwassen 

The transmission line ROW passes through densely populated residential areas, parks, and 

school grounds within the community of Tsawwassen. Baseline measurements were recorded on 

a quiet residential street in front of a residence at 543 Tralee Cres. The centerline of the ROW 

passes through the backyards of the houses along the Northwest side of the street in this area at a 

range of approximately 50m from theses residences. The recording duration lasted 24 hours at 

this location. 

Montague Harbour, Galiano Island 

The overhead transmission line ROW passes between the Taylor Bay Terminal and Montague 

Harbour across Galiano Island. The ROW passes mainly through rural and forested areas. There 

are only a few residences within approximately 70 m of the ROW. Baseline measurements were 

recorded on the property of 70 Montague Park Rd, in the community near Montague Harbor. 

This location was chosen since it represents the section of the ROW across Galiano Island with 

the most sensitive receptors nearby, including the Montague Harbour Marine Park and 

8


Campground, the Marina, several residences and Bed and Breakfast locations. The measurement 

site was located approximately 475m from the location on the ROW where the lines cross 

Montague Harbour over to Parker Island. The recording duration was 18 hours at this location, 

from 12:45pm until 6:45am the following morning. 

Salt Spring Island 

The overhead transmission line ROW crosses Salt Spring Island through rural/residential areas 

and through remote and forested locations. Residences and farms define the sensitive receptors 

along the section of the ROW where baseline measurements were taken. Measurements were 

made at a location, on the eastern side of Salt Spring Island that was directly adjacent to the 

transmission line, at the intersection of Long Harbour Rd and Upper Ganges Rd. The 

microphone was located approximately 25m from the nearest transmission line and 

approximately 35m from the nearest of the steel lattice structures which support the transmission 

lines. Measurements were recorded for 11 hours at this location. Residences, farms and 

businesses are located in this area. 

North Cowichan 

Baseline measurements for the North Cowichan district were recorded in the community of 

Maple Bay at the intersection of Bayview Place and Bayview Dr. This is a very quiet, rural, 

residential area. This location was approximately 575m from the ROW. This area is very hilly 

and rugged. Measurements were taken for a 24-hour period at this location. 

Duncan 

Baseline measurements along the section of the transmission line ROW near to the community of 

Duncan were recorded in front of the residence that is located adjacent to the BCTC Vancouver 

Island Terminal property. This is a rural residential area along a moderately busy street. 

Measurements were taken for a 24-hour period at this location. The nearest sensitive receptors 

along this portion of the ROW are residences. 

9


2.2.3. Noise Survey Results 

Hourly interval summary data were averaged over the recording period and are presented in the 

following table. The hourly L eq statistics represent the equivalent level of a constant sound 

source that would emit the same acoustic energy over a one-hour period as the actual, timevarying 

sound. The table presents the average, maximum, and minimum hourly-L eq values that 

were recorded at each location. Also provided in the table are the maximum and minimum 

sound pressure levels (SPL) observed during the recording period and a selection of average L n 

percentiles, that is the L eq levels that were exceeded ‘n’ percent of the time in the one hour 

intervals. All levels are presented in dBA. 

Table 2: Baseline noise measurement results in A-weighted decibels (dBA). Averaged over 

duration of recording (Rec Len). 

Location Rec Len Avg Max Min Max Min Avg Avg Avg Avg 

(Hours) L eq L eq L eq SPL SPL L 5 L 15 L 50 L 90 

Tsawwassen 24 52 60 34 75 31 56 47 38 35 

Montague 18 32 44 20 23 53 35 32 28 25 

Salt Spring 14 55 63 33 78 28 60 53 42 32 

N Cowichan 24 45 57 37 63 34 47 43 39 36 

Duncan 24 58 64 46 81 42 62 54 47 43 

2.3. Existing Noise Environment – Communities Near Cable Terminals 

and Submarine Cable Landfalls 

The communities in the vicinity of the cable terminals and the nearshore areas of the submarine 

cables include the English Bluff area of Tsawwassen and the communities near Maracaibo on 

Salt Spring Island and near Taylor Bay on Galiano Island. The English Bluff community is a 

residential area with ambient noise sources comprising moderate street traffic, overhead planes 

and common environmental sounds from household animals and birds. The Maracaibo and 

Taylor Bay communities are rural areas with very little traffic and relatively quiet ambient noise 

levels, contributing noise sources being primarily non-anthropogenic. 

The baseline noise level in the community near the English Bluff terminal would be comparable 

to the background ambient noise levels measured at Tralee Cres. in Tsawwassen as described in 

section 2.2.2. The measurements provided in Section 2.2.3 that were taken near Montague 

Harbour on Galiano Island are representative of the baseline noise levels that could be expected 

in the communities near the Taylor Bay terminal and near the Maracaibo terminal. Based on 

those measurements and knowledge of the community environments (urban residential for 

English Bluff; rural for Maracaibo and Taylor Bay) the following reasonable estimates of the 

background noise environments in the communities near the terminal sites are provided: 

Location 

Estimated Average Hourly L eq Values (dBA) 

English Bluff 50-55 

Maracaibo 35-40 

Taylor Bay 30-35 

10


3. Potential Effects – Construction and Operation of Project Facilities 

3.1. Methodology 

Sound propagation modelling of several representative construction scenarios was performed to 

evaluate the extent of the areas that could potentially be affected by these construction activities. 

An atmospheric noise propagation model developed at JASCO Research Ltd was used to 

determine the transmission loss characteristics in each of the representative communities. The 

model is based on the Parabolic Equation numerical solution method and provides very accurate 

computation of frequency dependent transmission loss accounting for diffraction, air turbulence 

and ground interaction. The model takes into account features such as topography and ground 

cover, and environmental factors such as wind speed, temperature and humidity. The frequency 

resolved transmission loss values generated by the model are applied to third-octave band 

acoustic source levels to provide received levels as a function of directional distance from the 

noise source. Where a source is composed of multiple discrete components whose noise levels 

are individually measured, as may be the case for a large transmission line substation, the 

received levels for each component are modelled independently and added. The results of the 

model are summed across frequency bands (with appropriate weighting) to give broadband noise 

level contours that map the geographic extent of the noise under consideration. By 

superimposing these contours in a GIS framework on chart layers showing dwellings or 

communities, the interaction between noise and population can be assessed. For the purpose of 

this study, to provide realistic average propagation conditions, the atmospheric conditions were 

assumed to be windless and with a vertical profile of temperature and humidity typical of a clear 

autumn day. 

3.2. Construction Noise 

Construction activities associated with the transmission line upgrade will be a source of 

increased audible noise in the project area communities; this noise, however, will be temporary 

and short term. The significance of the construction noise relative to the ambient background 

levels will be dependent upon the specific construction activities and the community baseline 

environments that are discussed in Section 2.2.2. The construction activities considered in this 

assessment include: removal of the existing support structures and lines, installation of new 

support structures and lines, and trenching / backfilling in the community of Tsawwassen to put 

the new line underground. 

Most construction noise associated with the project should be limited to daytime hours by 

Municipal Bylaws. Daytime construction may generate noise levels that exceed the ambient 

levels in the surrounding communities and has the potential to cause disturbance by, for example, 

hindering verbal communication at comfortable voice levels. An environmental assessment for 

the Deltaport Third Berth Project (Vancouver Port Authority, 2005) indicates that maximum 

daytime levels in residential areas of 65 dBA are acceptable to meet Health and Welfare Canada 

recommendations that noise levels in interior rooms be limited to 45 dBA, given that modern 

homes with doors and windows shut attenuate noise by approximately 20 dBA. 65 dBA is also 

supported by the guidelines of the World Health Organization for community noise (WHO, 

1999) as a maximum background level to allow vocal communication. Thus, 65 dBA was 

chosen as the criterion level for noise contour mapping of construction noise. While the noise 

11


outside of this contour may exceed the ambient baseline levels in a given community, this 

contour is intended to indicate the extent of possible disturbance. 

Noise level contours are presented in 5 dB increments, to a minimum contour level of 65 dBA. 

The results are intended to represent reasonable worst-case levels and are based on conservative 

assumptions about the maximum noise that could arise from a particular construction activity. In 

actual practice these levels will only be generated during operation of the noisiest of the 

construction equipment, and are not expected to be continuous or long lasting. 

In the community of Tsawwassen the major sources of noise involved in the construction stage 

of the project will be the removal of the existing H-frame structures and the trenching required 

for placing the new cables underground. Modelling was performed to predict the spread of 

sound from these activities in a residential area of Tsawwassen; baseline measurements in this 

community indicated an average hourly L eq value of 52 dBA. The equipment involved in this 

process could include backhoes, cranes, dump trucks, excavators, front-end loaders etc. To 

predict a representative noise spread from these activities, a model was run using aggregate 

third-octave band source levels for an excavator and a moveable crane obtained from a database 

of predicted noise levels on construction sites (Hepworth Acoustics Ltd, 2004). The model 

results are presented in Figure 1 as A-weighted, broadband sound level contours. The source 

position is at the centre of the near-circular inner contours. Terrain relief features cause 

deviations of the contour shapes from concentric circles. The minimum level to which the noise 

contours are plotted is 65 dBA. In this scenario, the maximum distance from the source to which 

noise levels of 65 dBA propagate is 335 m. 

Figure 1: Atmospheric model results for construction noise at a representative location in Tsawwassen. Contours 

indicate A-weighted, broadband sound pressure levels in decibels relative to the standard acoustic reference pressure 

in air of 20 µPa. The source consists of the combined noise from a moveable crane and an excavator, modelled at a 

height of 2m. The solid black lines indicate the transmission line ROW. 

Construction activities on Salt Spring Island will involve the removal of the existing steel lattice 

support structures and lines, the placement of new support structures and stringing of the new 

line. There will be some areas in remote locations that will require the use of helicopters for pole 

maneuvering, but it is anticipated that the major source of audible noise nearest to residences 

along this segment of the transmission line will be from equipment such as cranes, augers, 

backhoes, front end loaders, jackhammers, and tampers. For modelling purposes, source levels 

12


from measurements of moveable cranes and excavators (Hepworth Acoustics Ltd, 2004) were 

used to model the noise footprint in a representative residential area along the transmission line. 

Based on ambient noise measurements the average hourly L eq value in this area is 55 dBA. The 

model results are presented in Figure 2. The construction noise attenuates to a level of 65 dBA 

within approximately 185 m range from the source. Only a few residences are located within 

this range. 

Figure 2: Atmospheric model results for construction noise on Salt Spring Island. Contours indicate A-weighted, 

broadband sound pressure levels in decibels relative to the standard acoustic reference pressure in air of 20 µPa. The 

source consists of the combined noise from a crane and an excavator, modelled at a height of 2m. Solid black lines 

indicate the transmission line ROW and black squares indicate hydro towers, residences and other buildings. 

The major noise source associated with the construction phase of the project on Galiano Island 

will be the helicopter operations that are planned for the removal and replacement of the top 

sections of the existing steel lattice support structures along the transmission line. For modelling 

purposes it was assumed that a Sikorsky S-64 SkyCrane helicopter (or equivalent) would be used 

for this task at most locations on Galiano Island. Third-octave band source level data were 

obtained from the literature (True and Hickey, 1977) for the SkyCrane. The model was run at the 

location where the existing steel lattice structure will be extended to greater height to support the 

new high voltage line crossing over Montague Harbour. Based on ambient noise measurements 

the average hourly L eq level in this area is 32 dBA. The towers are approximately 41m tall at this 

location and thus the source height was modelled at a height of 45m above the ground. 

The model results, presented as sound level contours in 5 dBA increments, are presented in 

Figure 3. This noise footprint clearly shows the enhanced propagation of sound over water as 

compared to the propagation over land. Due to this effect the helicopter noise may reach 

residences along the Northeast shoreline of Salt Spring Island (9-10 km away) at levels between 

65 and 75 dBA. Inland on Galiano Island however, the helicopter noise drops to a level of 

65 dBA at a maximum range of 3 km. 

13


Figure 3: Atmospheric model results for construction noise on Galiano Island. Contours indicate A-weighted, 

broadband sound pressure levels in decibels relative to the standard acoustic reference pressure in air of 20 µPa. The 

source is a Sikorsky S-64 SkyCrane helicopter, modelled at a height of 45m. Solid black lines indicate the 

transmission line ROW and black squares indicate residences and other buildings. 

In the North Cowichan district the transmission line ROW mainly crosses forested and 

agricultural land. The ROW passes in the vicinity of a few farms and residences, particularly in 

the area near Maple Bay. The measured ambient noise level in this community has an average 

hourly L eq value of 45 dBA. The terrain in the communities near Maple Bay is very rugged and 

hilly. It is anticipated that the line replacement activities in this area will involve the use of 

helicopters and that this will be the major source of audible noise during the construction phase 

of this project in this community. For modelling purposes the third-octave band source levels of 

a Sikorsky SkyCrane helicopter were modelled in this community with a source height of 25m - 

the existing steel lattice support structures have an average height of 22 m. The sound attenuates 

rapidly due to terrain relief as it propagates over land, but it can be seen to propagate to further 

distances where it crosses Maple Bay. Sound levels between 65 and 75 dBA may propagate to 

the Western side of Salt Spring Island; along this shoreline, however, there are very few 

residences. 

14


15


nearest residences. Furthermore, the sound levels at the perimeter of the substation property, 

after the addition of the new transformer, are also below the typical limits used in the power 

transmission industry of 55 dBA at the substation property line in a residential zone (IEEE Std 

1127-1998). 

Figure 5: Atmospheric model results for operation of transformers at the Vancouver Island Terminal site. Contours 


in air of 20 µPa. The blue contours indicate existing noise levels emanating from the site and red contours indicate 

noise levels after the addition of the phase shifting transformer. Solid black lines indicate the transmission line ROW 

and black squares indicate residences and other buildings. 

A 230kV, 75 MVA shunt reactor will be added at the Taylor Bay Terminal on Galiano Island. 

Again a ‘before and after’ modelling approach was taken to predict any possible increase in 

audible noise at this location. There is an existing transformer at the Taylor Bay site, which was 

modelled to show the existing noise levels in the surrounding area. The model was then run 

again with increased source level to account for the addition of the shunt reactor. It is anticipated 

that the shunt reactor will have a broadband source level of approximately 70 dBA. This level 

will be lower if a sound enclosure is installed; however, the ‘worst case’ scenario was modelled 

for this assessment. The spectral distribution of the noise was assumed to be similar to that from 

the reactors that were measured at the VIT location. The model results indicate that the sound 

field will not increase appreciably due to the addition of the shunt reactor and that the increase in 

sound level at the location of the nearest residence to the substation property will be negligible. 

The minimum sound contour level presented is 35 dBA. The ambient noise level in this 

community is 32 dBA (based on the average hourly L eq value measured in baseline acoustic 

study). Since human beings cannot perceive a decibel difference of 3 dB, it is assumed that the 

noise from the substation has reached ambient levels at the location of the nearest residence to 

the substation property. 

16


Figure 6: Atmospheric model results for operation of transformers at the Taylor Bay Terminal site. Contours 


in air of 20 µPa. The blue contours indicate existing noise levels emanating from the site and red contours indicate 

noise levels after the addition of the shunt reactor. Solid black lines indicate the transmission line ROW and black 

squares indicate residences and other buildings. 

17


4. Potential Effects - Corona 

Corona is the term used to describe the localized ionization of air particles in regions of high 

electric field strength at discrete points along a transmission line. Particles like dust and water 

droplets on the line can enhance this effect and corona noise is often associated with rainy and 

foggy weather conditions. Corona can generate broadband (1Hz – 20kHz) audible noise that is 

characterized by a crackling or hissing sound. Corona performance can be accurately modelled 

and audible noise levels can be predicted at the design stage of the transmission line, based on 

the conductor properties and the line voltage. Typically noise is not a major cause for concern 

for lines that are less than 345 kV. A study of a compact 230 kV line indicates L 50 audible noise 

levels of approximately 45 dBA at 15m in stable rain conditions (Chartier et al, 1994). A second 

study observed median L 50 levels of 44 dBA at the edge of the ROW of a 230 kV line (BPA, 

2003). Thus, corona noise is not expected to significantly affect the ambient levels in the 

communities along the transmission line. 

Digitally superimposed 

UVC picture of corona: 

Voltage: 150 kV 

Findings: Intense corona on 

porcelain insulator 

Source: 

http://www.daycor.com/trans 

mission.html 

18


5. Potential Effects – Cable Terminal Hydraulic Pump Operation 

Hydraulic pumps will be added at the cable terminal stations where transitions from sub-sea to 

overhead cabling occurs, namely at the English Bluff terminal in Tsawwassen, at the Taylor Bay 

terminal on Galiano Island and at the Maracaibo terminal on Salt Spring Island. These pumps 

are required to maintain the pressure inside the sub-sea cables. The pumps operate intermittently 

and are generally housed inside structures to dampen the noise emanating from them. 

An acoustics field measurement program was made December 9, 2005 at BCTC’s Nile Creek 

Shore Terminal station on Vancouver Island. The purpose of the Nile Creek acoustics program 

was to measure acoustic source levels of the hydraulic pumps and vacuum pumps operated at the 

station. 

Sound levels were in fact measured inside and outside the pump building with the hydraulic and 

vacuum pumps running and with the hydraulic pumps stopped. The pump noise emission levels 

at the Nile Creek terminal are expected to be representative of pump noise produced at the 

Tsawwassen, Taylor Bay (Galiano Island), and Maracaibo (Salt Spring Island) shore terminal 

stations. The measurements obtained during this field study and presented in this report are ideal 

for noise level modelling at those locations. 

5.1. Nile Creek Shore Terminal Facility 

The Nile Creek Shore terminal serves as the point of transition from underwater/underground 

cable to overhead transmission lines for two 500 kV transmission circuits. Six underwater cables 

(three per circuit) arrive at shore buried in the seabed. The cables run underground for about 

200m between the shoreline and the station, where they emerge from the ground through 

concrete pedestals supporting vertical insulator stacks as shown in Figure 7. The feed conductors 

exit the top of the vertical insulator stacks and connect to bar and rail systems that lead 

horizontally under the overhead transmission lines and then connect with the overhead lines as 

shown in Figure 8. 

19


Figure 7: Underground cables emerge 

through concrete base and stack of 

insulators. 

Figure 8: Bar and rail system connects conductors to the overhead 

transmission lines. 

5.2. Oil-filled Cable System 

The underwater cables have inner and outer conductors separated by an oil-impregnated 

laminate-paper insulator. The inner conductor carries the transmission line current, while the 

grounded outer conductor serves primarily as a protective jacket. Pressurized oil is supplied to 

the entire length of cable through a conduit on the cable axis. Figure 9 presents a photo of the 

cable’s cross section showing its inner and outer conductors, insulating layers and the axial oil 

conduit. 

Resistive heating from increased electrical load can cause the cable temperature to rise and this 

leads to expansion of the contained oil. When oil expansion occurs the excess oil must be stored 

so it can be reinserted when the temperature decreases. The excess oil is stored in two large tanks 

housed in a storage and pump building at the Nile Creek terminal (see Figure 10). The tanks also 

serve as a reservoir to replace any additional oil lost through leakage. 

20


Figure 9: Cross section of the underwater cable. The 

hollow center is the conduit for insulating oil. 

Figure 10: One of two large oil tanks housed in the 

pump building at the Nile Creek shore terminal. 

5.3. Hydraulic Pumps 

Hydraulic pumps, located beside the storage tanks, maintain the oil pressure in the cables in the 

normal operating range 155-165 psi. A separate pump is used for each of the cables, so a total of 

six pumps plus two backup pumps are housed in the pump building at the Nile Creek terminal. 

The specifications for these pumps are given below: 

Hydraulic Pump specifications 

• Brand: H.K. Porter Company Inc. 

• Model: P215J frame 

• Horsepower: 3 HP at 1140 RPM 

• 3-phase 220V electric motor drive 

A photo of the hydraulic pumps beneath the storage tank is given in Figure 11. An automatic 

pressure monitoring system in the pump building starts the pumps when pressure falls below a 

preset threshold in any cable. The pumps at the Nile Creek terminal are turned on for a fixed 

duration of 90-minutes when pressure in the corresponding cable falls below 155 psi. A 2-minute 

equalizing period occurs immediately after the 90-minute cycle and pressure is rechecked after 

this. If the pressure is still low then the pump is turned on for another 90 minutes. The condition 

of consecutive 90-minute cycles is indicative of a leak, and this does not occur under normal 

circumstances. Typically only a single pump operates at any one time, but occasionally two and 

even three may be in simultaneous operation. 

5.4. Vacuum Pumps 

Each of the two oil storage tanks is supported by a vacuum pump that runs continuously to 

remove water vapour over the oil that could adversely affect its insulating properties. Each tank 

also has one identical backup pump. Figure 12 presents a photograph of one of the vacuum 

pumps. 

21


Figure 11: Hydraulic Pumps 

Figure 12: Vacuum Pump 

The vacuum pump nameplate provided the following specifications: 

Vacuum Pump specifications 

• Brand: Kinney Pumps 

• Model: KC-8 

• 3-phase 220V, ½ HP GE electric motor 

5.5. Acoustic Measurements 

The field program was performed to measure the noise emission levels of the hydraulic and 

vacuum pumps. Because the pumps were housed inside the tank building, noise levels outside 

the building were lowered by the sound-insulating properties of the building’s walls and ceiling. 

We consequently made separate measurements inside and outside of the building, with and 

without the hydraulic pump in operation. During each measurement a Larson Davis System 824 

Type-1 Logging Sound Level Meter (SLM) monitored and logged Flat-weighted and A-weighted 

sound levels on the slow time integration (1-second) setting. Simultaneously digital recordings of 

broadband flat-weighted acoustic pressure were made on a Marantz PMD690 digital recorder at 

48kHz sample rate with 16-bit samples. Calibrations of both the SLM and digital recorder were 

performed in the field using a Larson Davis CAL200 calibrator. A photo of the SLM and digital 

recorder apparatus is given in Figure 13. 

22


Figure 13: Sound level meter and digital recorder deployment for 

outdoor measurements of hydraulic and vacuum pump noise. 

5.5.1. Indoor Measurements 

Measurements of unshielded pump source levels were made by placing the microphone of the 

SLM accurately at 100 cm from the vacuum pump and 130 cm from the hydraulic pump during 

their respective measurements. The foam wind ball of the SLM was removed for these 

measurements. The data from the indoor recordings are presented in spectrogram format (sound 

intensity versus frequency and time) in Figure 14 for the hydraulic pump and Figure 15 for the 

vacuum pump on the same intensity scale. 

Figure 14: Spectrogram of 4 minutes recording of the 

hydraulic pump made at 130 cm distance. 

Figure 15: Spectrogram of 1 minute recording of the 

vacuum pump made at 100 cm distance. 

The near-field measurements of both the hydraulic and vacuum pumps showed that acoustic 

energy was generated at many discrete frequencies under 2 kHz. This is typical of rotational 

pump equipment. The hydraulic pump contained strong tonal energy up to 1700 Hz, while the 

quieter vacuum pump produced most energy below 800 Hz. 

23


One-third octave band source levels for the unshielded pumps were computed from the close 

distance recordings and these are presented in Table 3. The band levels are also plotted in Figure 

16 for the hydraulic pump and Figure 17 for the vacuum pump. 

Unweighted (flat) band levels for the Hydraulic Pump were observed to peak at 85.4 dB(F) re 

20µPa at 1m in the 1250 Hz band. In contrast the vacuum pump source levels peaked lower in 

frequency and level, in the 315 Hz band at 75.3 dB(F). 

Figure 16: 1/3-octave source levels of Hydraulic pump 

inside building (unshielded). 

Figure 17: 1/3-octave source levels of Vacuum 

pump inside building (unshielded). 

Broadband levels between 10 Hz and 20 kHz for the Hydraulic Pump were 90.7 dB(F) and 90.3 

dB(A) re 1m. The corresponding source levels for the Vacuum pump were 80.9 dB(F) and 76.6 

dB(A) re 1m. The small difference between flat and A-weighted levels for the hydraulic pumps 

occurs because the majority of the pump’s energy is between 500 Hz and 2 kHz where A- 

network weights are relatively small. 

5.5.2. Outdoor Measurements 

The placement of the pumps inside the building provided acoustic shielding that reduced the 

sound levels emitted outdoors. Separate measurements were therefore carried out outside the 

building at 17m from the building wall, which was 25m from the hydraulic pump locations 

inside. 

The outdoor measurements were influenced by constant low frequency (less than 200 Hz) hum, 

likely from inductive forces on the transmission line equipment, and by high frequency (above 2 

kHz) electrical ionization noise near insulators. Furthermore the station was located 

approximately 140m from Highway 19 and intermittent vehicle traffic produced broadband noise 

that dominated noise originating from the terminal facility. The field acoustician could not 

audibly detect noise from the vacuum pump alone above the interfering external noise sources. 

However the hydraulic pump was generally quite audible. 

We were able to extract sections of the noise recordings during periods with no vehicles passing 

and these were used to quantify pump noise emissions outside the pump building. Figure 18 and 

24


Figure 19 show spectrograms for sections of the outdoor measurements with no vehicle traffic 

for the cases of the hydraulic pump stopped and running. 

Figure 18: Spectrogram of 1 minute recording 17m from 

the pump building with only the vacuum pump 

operating. 

Figure 19: Spectrogram of 1 minute recording 17m 

from the pump building with both the vacuum and 

hydraulic pumps running. 

The outdoor measurement with vacuum pump running showed frequency lines at 100 Hz, 120 

Hz, 360 Hz and 480 Hz, but none of these appear to correlate with lines from the corresponding 

indoor source level measurement. Consequently these lines are attributed to noise produced by 

the nearby transmission line components and not the vacuum pump. On the other hand, hydraulic 

pump noise tones were measured outside at 540 Hz, 570 Hz, 830 Hz, 1105 Hz, 1380 Hz and 

1680 Hz. The strongest line was at 1380 Hz line as apparent in Figure 19. One-third octave band 

levels were computed from the outdoor measurements, and the levels in the bands between 500 

Hz and 1250 Hz were scaled back to the source position, 25 m away, using a spherical spreading 

correction factor. The outdoors third-octave band source levels of the hydraulic pump are given 

in Table 4. Broadband source levels were also computed using only the bands containing spectral 

lines that correspond with the indoor pump measurements. The omitted bands likely were 

dominated by noise from other sources. The broadband outdoors source levels for the hydraulic 

pumps were 74.5 dB(F) re 1m and 74.3 dB(A) re 1m. These levels are 15 dB less than the 

unshielded source levels, and this emphasizes the importance of housing the pumps in soundinsulating 

enclosures. 

25


Table 3: 1/3-Octave and broadband levels for the hydraulic and vacuum pumps, computed from measurements 

performed inside the pump building at close range. 

Hydraulic Pump Source Level 

Measurement 

Vacuum Pump Source Level 

Measurement 

Wave file name: C:\Documents and 

88.4 88.1 90.7 90.3 80.9 76.6 80.9 76.6 

Settings\dave\My Documents\Projects\BCTC 

2005\Nile Creek Shore Station\Nile Creek 

Recorder files\MZ000005_in hydr\MZ000005.WAV 

Number of channels: 1 




Recorder files\MZ000001_in vac 

pump\MZ000001.WAV 

Sample rate: 48000 


Bits per sample: 16 


Number of samples: 11583488 


Duration (min:sec): 0004:01 


SL range correction: 1.30000m 


Start time for analysis: 0 seconds 


Stop time for analysis: 241 seconds 



Frequency dB(F) dB(A) SL(F) SL(A) Frequency dB(F) dB(A) SL(F) SL(A) 

--------------------------------------------- --------------------------------------------- 

10.0 56.6 -16.0 58.9 -13.7 

10.0 47.2 -25.4 47.2 -25.4 

12.5 54.9 -10.6 57.2 -8.3 

12.5 42.7 -22.8 42.7 -22.8 

16.0 50.1 -8.7 52.4 -6.4 

16.0 47.0 -11.8 47.0 -11.8 

20.0 53.0 2.6 55.3 4.9 

20.0 42.3 -8.1 42.3 -8.1 

25.0 52.3 7.6 54.6 9.9 

25.0 49.8 5.1 49.8 5.1 

31.5 58.8 19.4 61.0 21.6 

31.5 54.1 14.7 54.1 14.7 

40.0 61.9 27.3 64.2 29.6 

40.0 53.4 18.8 53.4 18.8 

50.0 64.4 34.2 66.7 36.5 

50.0 70.2 40.0 70.2 40.0 

63.0 50.0 23.8 52.3 26.1 

63.0 53.7 27.5 53.7 27.5 

80.0 57.1 34.6 59.4 36.9 

80.0 56.7 34.2 56.7 34.2 

100.0 54.0 34.9 56.3 37.2 100.0 56.2 37.1 56.2 37.1 

125.0 67.1 51.0 69.4 53.3 125.0 58.4 42.3 58.4 42.3 

160.0 66.5 53.1 68.8 55.4 160.0 66.8 53.4 66.8 53.4 

200.0 69.6 58.7 71.9 61.0 200.0 67.4 56.5 67.4 56.5 

250.0 76.5 67.9 78.8 70.2 250.0 71.7 63.1 71.7 63.1 

315.0 70.9 64.3 73.1 66.5 315.0 75.3 68.7 75.3 68.7 

400.0 75.3 70.5 77.6 72.8 400.0 71.3 66.5 71.3 66.5 

500.0 76.9 73.7 79.2 76.0 500.0 67.9 64.7 67.9 64.7 

630.0 76.6 74.7 78.9 77.0 630.0 69.7 67.8 69.7 67.8 

800.0 74.9 74.1 77.2 76.4 800.0 68.6 67.8 68.6 67.8 

1000.0 73.5 73.5 75.8 75.8 1000.0 66.6 66.6 66.6 66.6 

1250.0 83.1 83.7 85.4 86.0 1250.0 68.1 68.7 68.1 68.7 

1600.0 80.0 81.0 82.2 83.2 1600.0 60.7 61.7 60.7 61.7 

2000.0 74.3 75.5 76.6 77.8 2000.0 57.1 58.3 57.1 58.3 

2500.0 74.6 75.9 76.9 78.2 2500.0 55.4 56.7 55.4 56.7 

3150.0 72.1 73.3 74.4 75.6 3150.0 54.8 56.0 54.8 56.0 

4000.0 73.9 74.9 76.2 77.2 4000.0 54.2 55.2 54.2 55.2 

5000.0 71.7 72.2 73.9 74.4 5000.0 53.6 54.1 53.6 54.1 

6300.0 68.3 68.2 70.6 70.5 6300.0 54.4 54.3 54.4 54.3 

8000.0 66.7 65.6 69.0 67.9 8000.0 54.6 53.5 54.6 53.5 

10000.0 62.7 60.2 65.0 62.5 10000.0 51.1 48.6 51.1 48.6 

12500.0 57.4 53.1 59.7 55.4 12500.0 49.4 45.1 49.4 45.1 

16000.0 53.3 46.7 55.5 48.9 16000.0 48.7 42.1 48.7 42.1 

20000.0 51.2 41.9 53.5 44.2 20000.0 48.6 39.3 48.6 39.3 

Broadband levels 


26


Table 4: 1/3-Octave and broadband levels for the ambient noise and outdoor hydraulic pump noise levels. 

Measurements were performed outside the pump building. 

Ambient Measurement Outside 

(Vacuum Pump was running) 

Hydraulic Pump Outside 


66.2 46.9 67.5 47.4 74.5 74.3 



Recorder files\MZ000003_out ambient 

ball\MZ000003.WAV 





Recorder files\MZ000004_out hydr 

ball\MZ000004.WAV 















Frequency dB(F) dB(A) 

Frequency dB(F) dB(A) SL(F) SL(A) 

--------------------------- 

--------------------------------------------- 

10.0 57.8 -14.8 

10.0 59.3 -13.3 

12.5 57.8 -7.7 

12.5 59.3 -6.2 

16.0 56.9 -1.9 

16.0 59.3 0.5 

20.0 57.7 7.3 

20.0 59.2 8.8 

25.0 59.9 15.2 

25.0 60.8 16.1 

31.5 56.1 16.7 

31.5 56.8 17.4 

40.0 50.7 16.1 

40.0 53.2 18.6 

50.0 50.8 20.6 

50.0 51.6 21.4 

63.0 44.0 17.8 

63.0 46.2 20.0 

80.0 45.0 22.5 

80.0 47.9 25.4 

100.0 51.2 32.1 

100.0 47.4 28.3 

125.0 47.4 31.3 

125.0 45.1 29.0 

160.0 37.4 24.0 

160.0 36.9 23.5 

200.0 39.3 28.4 

200.0 37.0 26.1 

250.0 33.0 24.4 

250.0 30.2 21.6 

315.0 30.5 23.9 

315.0 29.4 22.8 

400.0 30.6 25.8 

400.0 33.7 28.9 

500.0 32.3 29.1 

500.0 34.2 31.0 62.1 58.9 

630.0 33.7 31.8 

630.0 38.6 36.7 66.5 64.6 

800.0 36.4 35.6 

800.0 40.5 39.7 68.4 67.6 

1000.0 37.1 37.1 

1000.0 39.4 39.4 67.4 67.4 

1250.0 39.6 40.2 

1250.0 40.2 40.8 68.1 68.7 

1600.0 38.6 39.6 

1600.0 37.4 38.4 65.4 66.4 

2000.0 36.6 37.8 

2000.0 34.6 35.8 

2500.0 33.6 34.9 

2500.0 31.5 32.8 

3150.0 31.3 32.5 

3150.0 28.4 29.6 

4000.0 27.0 28.0 

4000.0 26.1 27.1 

5000.0 25.6 26.1 

5000.0 25.8 26.3 

6300.0 26.3 26.2 

6300.0 26.4 26.3 

8000.0 25.7 24.6 

8000.0 25.8 24.7 

10000.0 25.6 23.1 

10000.0 25.8 23.3 

12500.0 25.4 21.1 

12500.0 25.8 21.5 

16000.0 24.5 17.9 

16000.0 24.6 18.0 

20000.0 24.5 15.2 

20000.0 24.3 15.0 



27


6. Potential Effects – Removal, Construction and Operation of 

Submarine Cables and Cable Terminals 

It is not anticipated that the on-shore and near-shore construction activities associated with the 

removal and installation of the submarine cables will cause a significant increase in audible noise 

relative to ambient background noise in the communities along the shoreline. Very near to 

shore, shallow draft workboats and diver-operated jetting equipment will be used for cable 

handling and burial into the sediment. These boats and equipment are not known to generate high 

levels of audible atmospheric noise relative to the observed ambient background noise levels in 

the communities along the transmission line ROW. The construction activities that are expected 

to take place at the cable terminal stations (e.g. installation of new sun shades on cable 

chaseways, modifications to existing chaseways etc) are likewise not expected to generate 

excessive noise levels as only light construction equipment will be involved. Furthermore, these 

activities will be temporary and of short duration. There will be no air-borne audible noise 

associated with operation of the submarine cables. It is not expected that the cable terminals will 

generate an increase in audible noise, relative to ambient background noise levels, during the 

operation of the transmission line due to the lack of noise generating equipment at the cable 

terminals. The only expected noise sources at the cable terminals could include the hydraulic 

pumps (discussed above) and potential corona discharges. As discussed in Section 4, corona 

noise at the terminals is not expected to generate disturbing noise levels relative to ambient 

background noise levels. 

7. Potential Effects – Cable-laying and Cable-removal Vessels 

The underwater section of the transmission line will require the use of specialized marine vessels 

for cable-removal and cable-laying. The vessels will operate in water depths as shallow as 5m 

and they may approach to within about a hundred meters of the shoreline depending on the local 

bathymetry and coastal profile. Airborne noise from the operation of these vessels (mostly from 

winches and other deck mounted equipment) will propagate significantly to the shoreline near 

the cable terminal stations only while the vessels are at the nearest point of their approach. This 

vessel noise will be temporary and of short duration. The exact specifications of the vessels that 

will be used for cable laying and removal, and their maneuvering plans, are not known at this 

time. 

Modeling was performed to determine the disturbance potential of these activities for residences 

along the shoreline, near to the anticipated closest point of approach of the cable vessels. A 

distance from shore of 100 metres beyond the 5-m bathymetry line, along the cable route, was 

used for the nominal vessel location. Making the reasonable generalization that the airborne 

noise generated by the cable vessels will be equally distributed in the frequency bands between 

200Hz and 1kHz, JASCO’s atmospheric noise model was run to determine the A-weighted, 

broadband level of surface ship noise that will generate sound levels of, at most, 65 dBA at the 

location of the nearest residences along the shoreline. The 65 dBA limit was chosen to be a 

reasonable level to limit potential disturbance as discussed in Section 3.2. Model results are 

shown in the following plots for the communities near the Taylor Bay and Maracaibo terminals. 

The results at the Maracaibo terminal clearly demonstrate the attenuation of the sound as it 

reaches the shore due to terrain relief. 

28


To maintain sound levels at the residences along the shoreline near Taylor Cove below 65 dBA, 

the broadband source level of airborne ship noise would have to be below 98 dBA. Because 

there are not many dwellings in the immediate nearshore area at Maracaibo, a higher ship source 

level of 117 dBA would be acceptable to keep sound levels at the residences this region at or 

below 65 dBA. 

Figure 20: Atmospheric model results for cable laying/removal vessel noise near Taylor Bay. Contours indicate A- 

weighted, broadband sound pressure levels in decibels relative to the standard acoustic reference pressure in air of 

20 µPa. Solid black lines indicate the transmission line ROW and black squares indicate residences and other 

buildings. 

29


Figure 21: Atmospheric model results for cable laying/removal vessel noise near Maracaibo. Contours indicate A- 

weighted, broadband sound pressure levels in decibels relative to the standard acoustic reference pressure in air of 

20 µPa. Solid black lines indicate the transmission line ROW and black squares indicate residences and other 

buildings. 

8. Conclusion 

Ambient atmospheric noise levels were measured at a number of representative locations in 

communities near overhead transmission line right of ways and distribution terminals. From 

these, based on similarities of demographics and infrastructure, ambient noise levels were 

estimated for communities near submarine cable landfalls and terminals. Maximum measured 

hourly levels ranged from 44 dBA at the more rural locations to 64 dBA near urban centres and 

thoroughfares. Identifiable sources of noise included street traffic, air traffic, household and yard 

noises (radios, lawnmowers, chainsaws etc), dogs barking and - at quieter locations and times - 

natural noises such as rustling leaves, crickets, and birds chirping. 

Advanced numerical modelling of acoustic propagation in air was used to generate reliable 

estimates of noise footprints both from planned construction activities at representative sites or 

from the future operation of additional components in existing infrastructures. For ground based 

construction activities such as trench excavation and removal or installation of poles the 

maximum radius for sound attenuation to a criterion level of 65 dBA (generally considered as 

unobtrusive background noise) was found to vary between 200 and 350 m depending on the site. 

For tower modification activities involving operation of helicopters down to altitudes of 25 to 45 

m above ground – depending on the type of tower – the ranges to 65 dBA can be much longer 

especially if propagation takes place over water. Thus a SkyCrane helicopter hovering over a 

tower near Montague Harbour on Galiano Island may cause noise levels of 65 dBA as far away 

as the north-eastern shoreline of Salt Spring Island at nearly 10 km, but at no more than 3 km 

inland from the source. The same operation at 25 m altitude above ground in a hilltop area near 

30


Maple Bay, North Cowichan would project noise above 65 dBA to ranges from less than 2 km to 

more than 6 km in a complex footprint determined by the rugged terrain relief. The model based 

estimation of the incremental change in long-term noise levels near existing infrastructures due 

to their upgrading showed the footprints to remain essentially unvaried from the current status. 

Numerical modelling also enabled the “inverse” estimation of the maximum tolerable source 

level (the nominal noise level that would be measured adjacent to the source) from cable laying 

and removal vessels operating near shore if received levels of no more than 65 dBA were to be 

maintained at the nearest dwellings. In the case of the Taylor Bay area, where houses are located 

close to the cable landfall, a vessel noise source level in air as low as 98 dBA would have to be 

ensured to allow shore approach to 100 m outside of the 5m bathymetry line. In the Maracaibo 

area, that has sparser distribution of houses in the vicinity of the landfall and a more noise 

blocking topography, a source level of 117 dBA would be acceptable for vessel approach to the 

same distance from shore. 

The potential for noise disturbance arising from other construction and operational sources such 

as modification of chaseways at cable terminals, operation of workboats and jetting equipment in 

shallow water, hydraulic pumps at cable terminals and corona discharge at overhead lines 

insulators was assessed on the basis of existing knowledge or comparison to similar activities 

elsewhere. None of these were judged to be significant sources of annoyance to neighbouring 

population. 

31


9. References Cited 

Bonneville Power Administration. 2003. Kangley-Echo Lake Transmission Line Project 

Supplemental Draft Environmental Impact Statement. January. 

http://www.efw.bpa.gov/environmental_services/Document_Library/Kangley- 

Echo_Lake/SDEISSummary011403.pdf 

Chartier, V.L., D.E. Blair, M.D. Easley and R.T. Raczkowski. 1995. Corona Performance of a 

Compact 230-kV Line. IEEE Transactions on Power Delivery 10 (1): 410-420. 

IEEE Standard 1127-1998. 1998. IEEE Guide for the Design, Construction and Operation of 

Electric Power Substations for Community Acceptance and Environmental Compatibility. IEEE: 

USA. 

Hepworth Acoustics Ltd. 2004. Update of Noise Database for Prediction of Noise on 

Construction and Open Sites. Prepared for the Department for Environment, Food and Rural 

Affairs, UK. 

True, H.C., and E.J. Rickley. 1977. Noise Characteristics of Eight Helicopters. U.S. Department 

of Transportation Report No. FAA-RD-77-94. 

Vancouver Port Authority. 2005. Environmental Assessment Application for the Deltaport Third 

Berth Project. January. 

http://www.portvancouver.com/container_expansion/deltaport/index.html 

World Health Organization (WHO). 1999. Guidelines for Community Noise. Edited by: B. 

Berglund , T. Lindvall, and D. H. Schwela. 

32

JASCO Research Ltd BCTC VITR Project - Underwater 2006-03-14 

Chapter 2: Underwater Noise Assessment 

1. Introduction 

Construction activities associated with installation of BCTC’s new 230 kV HVAC system 

between the Lower Mainland and Vancouver Island will generate underwater noise in 

Trincomali Channel and the Strait of Georgia that may harass nearby marine wildlife. Existing 

commercial and recreational vessel traffic already produces anthropogenic (man made) noise in 

both of these water bodies. This background noise may mask and therefore lower the importance 

of the new construction-related noise. A measurement study to quantify existing noise levels has 

been performed to determine the relative importance of construction noise in the work areas. A 

separate modelling study has been performed to predict noise levels caused by construction 

activities associated with cable installations. The results of these analyses can be used to 

determine the number of animals potentially impacted by construction of the new HVAC system. 

The three primary components of this underwater noise study are outlined below: 

1. Measurements of background underwater noise levels were made in both 

Trincomali Channel and the Strait of Georgia using a seabed mounted autonomous 

acoustic recorder. Broadband and spectral analyses of these measurements were 

carried out. 

2. The types of equipment that generate highest levels of underwater noise were 

identified for construction activities and for operation of the new submarine cables. 

Noise emission levels (source levels) for these sources were determined from 

measurements made on similar types of equipment. 

3. Noise levels in the vicinity of construction locations and near cable routes have 

been modelled for submarine cable construction activities in both Trincomali Channel 

and the Strait of Georgia. 

2. Baseline measurements 


In order to determine background levels from existing traffic in Trincomali Channel and the 

Strait of Georgia, recordings of underwater ambient noise were performed near planned cable 

installation sites using a bottom mounted autonomous recorder system. Baseline background 

noise levels were measured in both Trincomali Channel and the Strait of Georgia on two separate 

dates, at the two recording locations shown in Figure 1. At each location, a visual log of vessel 

traffic past the recording site was taken from a shore-based observation post during daylight 

hours. 

The autonomous acoustic recorder system, shown schematically in Figure 2, employed a single 

calibrated Reson TC4032 hydrophone connected to a Marantz PMD660 digital audio recorder. 

Approximately 12 hours of acoustic data were recorded at each site at 44.1 kHz sampling rate 

33


with 16-bits resolution. The acoustic recorder was moored at the seabed with concrete weights. 

Following each deployment an acoustic release system triggered from the surface detached the 

weights from the recorder, allowing the system to return to the surface for retrieval. The 

autonomous recorder was deployed and retrieved from a small survey launch operated by 

Coastal Geosciences Ltd of Victoria BC. 

Figure 1: Map showing dates and locations of ambient noise recordings in Trincomali Channel and the Strait of 

Georgia. 

t o f l oat s 

pr essur e 

case 

hydr ophone 

di gi t al 

r ecor der 

12: 00 

bat t er i es 

t o anchor 

Figure 2: Diagram of autonomous acoustic recorder system used for making acoustic measurements in Trincomali 

Channel and the Strait of Georgia. 

34


Following retrieval of the autonomous recorder, acoustic waveform data were downloaded onto 

a PC for subsequent analysis. The recorded signals were processed to determine hourly 

equivalent sound pressure level (hourly L eq ) and mean 1/3-octave band levels for daytime and 

nighttime intervals. Processed ambient noise data for both Trincomali Channel and the Strait of 

Georgia are presented in the following sections. 

2.2. Trincomali Channel measurements 

Underwater ambient noise levels were measured in Trincomali Channel on Wednesday 17 

August 2005 from 11:00 hours to 23:00 hours. Figure 3(a) shows hourly averaged sound 

pressure levels in Trincomali Channel over the recording duration. Data prior to 14:00 hours are 

not presented due to noise contamination in the recording system caused by strong tidal currents 

from 11:00 to 14:00 hours. Figure 3(b) shows mean 1/3-octave band sound pressure levels for 

daytime (14:00 to 19:00) and nighttime (19:00 to 23:00) hours. Vessel traffic through 

Trincomali Channel decreased significantly at night, resulting in a large difference between 

measured daytime and nighttime background levels. During the daytime (before 19:00 hours), 

broadband hourly averaged sound levels varied from 107 dB to 123 dB, whereas during the 

nightime (after 19:00 hours), broadband hourly averaged sound levels varied from 87 dB to 97 

dB. The mean difference between daytime and nighttime broadband levels was 22 dB in 

Trincomali Channel. The frequency distribution of noise in Trincomali Channel was such that 

ambient levels were greater at mid to high frequencies (above 100 Hz), with the loudest levels 

observed in the 500 Hz 1/3-octave band. 

By comparing recordings with observation logs, the majority of noise sources were identified as 

pleasure boats and fishing boats transiting through Trincomali Channel. Although no ferry 

routes pass through the channel, noise from BC Ferries ships travelling through nearby Active 

Pass also contributed to background levels at the recording site. Other noise sources that were 

recorded during the observation period were airplanes flying between Victoria and Vancouver 

and a solitary tug towing a log-boom. The 21 dB difference between measured daytime and 

nightime ambient levels, and the concentration of noise at higher frequencies, was consistent 

with observation that the majority of vessel traffic in Trincomali Channel was composed of small 

to mid-size recreational boats. 

2.3. Strait of Georgia measurements 

Underwater background noise levels were measured in the Strait of Georgia on Thursday, 1 

September 2005 from 11:00 to 23:00 hours. Figure 4(a) shows hourly averaged sound pressure 

levels in the Strait of Georgia over the recording duration. Figure 4(b) shows mean 1/3-octave 

band sound pressure levels for daytime (11:00 to 19:00) and nighttime (19:00 to 23:00) hours. 

Measured daytime and nighttime background levels in the Strait of Georgia were approximately 

the same; the mean difference between mean daytime and nighttime broadband levels was only 1 

dB. The frequency distribution of noise in the Strait of Georgia was such that ambient levels 

were greater at low frequencies (below 100 Hz), with the loudest levels observed in the 80 Hz 

1/3-octave band. 

35


Figure 3: Trincomali Channel baseline noise level measurements, from Wednesday 17 August 2005. (a) Hourly 

equivalent sound pressure level (i.e., 1-hour averaged SPL) versus time. (b) Mean daytime and nighttime 1/3-octave 

band levels versus frequency. 

Figure 4: Strait of Georgia baseline noise level measurements, from Thursday 1 September 2005. (a) Hourly 

equivalent sound pressure level (i.e., 1-hour averaged SPL) versus time. (b) Mean daytime and nighttime 1/3-octave 

band levels versus frequency. 

36


By comparing recordings with observation logs, the primary noise sources in the Strait of 

Georgia acoustic data were identified as commercial shipping (e.g., bulk carriers, container ships 

and barge tugs) and ferries heading to and from Tsawwassen terminal. The Strait of Georgia is 

the primary route for ships traveling to and from the Port of Vancouver, a facility that operates 

on a 24-hour basis. The negligible difference between daytime and nighttime noise levels and 

the concentration of noise at low frequencies was consistent with the observation that the 

majority of vessel traffic in the Strait of Georgia was composed of large commercial ships. 

3. Construction and operation noise 

3.1. Cable construction noise 

Removal and installation of existing submarine transmission cables through Trincomali Channel 

and the Strait of Georgia will be carried out by a dedicated cable lay ship, except for short 

segments in the intertidal zone and in shallow waters where a large vessel cannot operate. In 

very shallow water small workboats will be used to pull the cables ashore. Diver operated air 

lifting or water jetting equipment will be used to bury the submarine cables in the intertidal zone 

and in water less than 3 metres deep. 

The primary source of underwater noise during the removal and installation operations is 

expected to be the cable laying ship. Shallow water workboats are also expected to generate a 

limited amount of noise during the shore pull operations. Trenching noise will not be a factor 

during the cable laying since the transmission cables will not be buried below the seabed in deep 

water. A literature review has found no published measurements of underwater noise from diver 

operated air lifting and water jetting equipment; however, small, diver operated dredging 

equipment in shallow water is not expected to radiate significant amounts of underwater noise. 

Two cable-lay ships have been identified as possible candidates for the removal and installation 

phases of the project: the C/S Bourbon Skagerrak, operated by Nexans Norway AS and the C/S 

Giulio Verne operated by Pirelli Cables. Both vessels are dynamic positioning cable lay ships 

that utilize a tethered ROV at the seabed for touchdown monitoring. Dynamic positioning (DP) 

uses a ship’s thrusters to accurately maintain position to fine tolerances; DP systems are 

employed by many different kinds of construction vessels, including cable ships. While dynamic 

positioning is active, thrusters are the primary source of noise radiated from a ship; thruster noise 

is therefore expected to dominate the radiated noise field during the cable removal and cable 

installation operations. 

37


3.2. Cable operation noise 

The new 230 kV submarine cables are expected to produce 120 Hz tonal vibration noise in the 

water, since Coulomb forces between the conductors will cause the high voltage AC lines to 

vibrate at twice the frequency of the current (Zabar, 1992). The precise noise levels that would 

be generated by the new 230 kV cables cannot be predicted since their electro-acoustic transfer 

characteristics are unknown. However, low level tonal noise from the existing 138 kV 

transmission lines was measured in Trincomali Channel during a very quiet period of recording: 

the sound pressure level at a distance of approximately 100 metres from one of the cables was 

just under 80 dB re µPa (see Figure 5). Thus, assuming cylindrical spreading of sound (which is 

the appropriate spreading law for a line source) the source level of the existing submarine cables 

is approximately 100 dB re µPa@1m. The new 230 kV submarine cables will be operating at a 

higher voltage than the existing lines so that, for a comparable electrical power demand, they 

will carry proportionately less current. Thus, the 120 Hz vibration in the new cables is expected 

to be lower in amplitude because the Coulomb forces that cause the vibration are proportional to 

the transmission line current (Zabar, 1992). On the basis of reasonable assumptions, therefore, 

the acoustic source level of the new submarine cables will not be higher than that of the existing 

cables. 

The only other source of noise associated with the operation of the submarine cables is the shore 

terminals. The shore terminals operate in air and are not expected to introduce detectable levels 

of noise into the underwater environment since the acoustic coupling between air and water is 

poor for an inshore based noise source. 

Figure 5: Spectrum of 120 Hz tonal noise versus frequency recorded ~100 metres from existing 138 kV submarine 

cables. 

38


4. Noise Modelling 


Propagation of noise from submarine cable construction activities in Trincomali Channel and the 

Strait of Georgia has been modelled using JASCO Research Ltd’s Marine Operations Noise 

Model (MONM). MONM computes acoustic propagation for arbitrary 3-D, range-varying 

acoustic environments via a wide-angled parabolic equation (PE) solution to the acoustic wave 

equation. The parabolic equation code in MONM is based on the U.S. Naval Research 

Laboratory’s Range-dependent Acoustic Model (RAM), which has been extensively 

benchmarked for accuracy and is widely employed in the underwater acoustics community 

(Collins, 1993). MONM computes acoustic fields in 3-D by modelling transmission loss along 

evenly spaced radial traverses covering a 360º swath from the source (so-called N×2-D 

modelling). MONM makes use of several types of environmental data including bathymetry, 

sound speed profiles and geoacoustic profiles. The spatial sampling of the acoustic environment 

along model traverses was on a 50 m range step. Frequency dependence of the sound 

propagation characteristics was treated by computing acoustic transmission loss at the center 

frequencies of all 1/3-octave bands between 10 Hz and 2 kHz. Received sound pressure level in 

each band was computed by applying frequency-dependent transmission losses to the 

corresponding 1/3-octave band source levels. This approach has been validated against 

experimental data and has proven to be highly accurate for predicting noise levels in vicinity of 

industrial operations (Hannay and Racca, 2005). 

Bathymetry data for Trincomali Channel and the Strait of Georgia were obtained from the 

Canadian Hydrographic Service Environmental Dataset for Southern Vancouver Island. 

Latitude/longitude point bathymetry data were converted to UTM (zone 10) coordinates and 

interpolated onto a regular x/y grid at 200 metres resolution. Figure 6 shows a map rendering of 

the resulting bathymetry grid that was used for the acoustic propagation modelling. 

Historical temperature/salinity profiles for the Strait of Georgia were analyzed to derive a 

representative sound speed profile for the months of August and September. The DFO Institute 

of Ocean Sciences (Patricia Bay) Ocean Sciences division provided approximately 200 

temperature/salinity casts for the period from 2000 to 2004, on which the analysis was based. 

Temperature/salinity data were converted to sound speed in seawater (Coppens, 1981) and then 

decomposed in terms of a set of derived variables using the statistical technique of principal 

component analysis (PCA) (Davis, 1976). A single representative sound speed profile for the 

Strait of Georgia, shown in Figure 7, was then computed from the principal value decomposition 

using the most frequently occurring values for the derived variables. 

Geoacoustic properties for the seabed in the Strait of Georgia and Trincomali Channel were 

derived from published sedimentary geology for the Strait of Georgia (Barrie & Hill, 2004). For 

the acoustic modelling, the ocean-bottom was assumed to consist of a thick layer of Holocene 

river sediments over a basement of sedimentary rock. The geoacoustic properties of these 

materials, including compressional speed (c p ), density (ρ), shear speed (c s ) and attenuation (α p , 

α s ) were estimated based on typical values from the literature (Hamilton, 1980). Table 1 shows 

the resulting geoacoustic profiles used by MONM for the acoustic modelling. 

39


Representative acoustic source levels for a cable ship were required in order to model the noise 

field generated by the cable removal and installation operations. A review of the available 

literature found no published source levels for a cable ship. The most representative among the 

available source measurements were 1/3-octave band source levels for a dynamic positioning 

rock dumping vessel, the Pompei (Hannay et al. 2004). The Pompei’s dynamic positioning 

source levels were therefore used as an analogue for a cable ship’s source level. Acoustic source 

levels for cable laying and cable removal were assumed to be the same, since the operation of 

ship’s thrusters would be similar during both operations. Figure 8 shows the nominal 1/3-octave 

band source levels for the dynamic positioning cable lay vessel that were used for the acoustic 

modelling. The nominal broadband acoustic source level for the cable ship was 177.0 dB re 

µPa@1m. 

To model shore pull operations in shallow water, 1/3-octave band acoustic source levels for a 9- 

metre workboat, the Yamaha FC-26 (Hannay et al. 2004), were used as a representative 

analogue. Figure 8 shows the nominal 1/3-octave band source levels for the small workboat that 

were used for the acoustic modelling. The nominal broadband acoustic source level for the small 

workboat was 156.9 dB re µPa@1m. 

Figure 6: Contour plot of Southern Vancouver Island bathymetry grid used by MONM for acoustic propagation 

modelling. 

Table 1: Seabed geoacoustic parameters used for the acoustic modelling in the Strait of Georgia and Trincomali 

Channel. 

Material Depth (m) c p (m/s) ρ (g/cc) c s (m/s) α p (dB/λ) α s (dB/λ) 

Sediments 0 1.511 1.488 0.151 0.111 2.599 

Sediments 40 1.563 1.488 0.156 0.292 2.688 

Basement 40 2.100 2.095 0.210 0.292 2.688 

Basement 500 2.606 2.211 0.261 0.292 2.688 

40


Figure 7: Plot of sound speed versus depth derived from historical temperature/salinity data from the Strait of 

Georgia. 

Figure 8: Plot of nominal 1/3-octave band source levels versus frequency for a dynamic positioning cable-lay vessel 

and a small workboat. 

41


4.2. Construction Noise Modelling Results 

4.2.1. Cable ship 

Noise propagation from a cable ship performing cable lay and removal activities was modelled at 

several locations in the Strait of Georgia and Trincomali Channel along the projected cable route. 

The modelling sites for cable lay and removal activities included three locations in the Strait of 

Georgia and one location in Trincomali Channel. The source positions for these sites are the 

central points of the concentric noise level contours (isopleths) presented in Figure 9 through 

Figure 12. The acoustic source was positioned along the planned cable route in all cases. Noise 

level contours in 5 dB increments are shown for a receiver at 50 metres depth, or at the seabottom 

where the water is shallower than 50 metres. Noise levels are unweighted, broadband 

sound pressure levels expressed in decibels referenced to 1 µPa. 

Table 2 lists the 95% range to the 130 dB, 120 dB and 110 dB noise level contours for the cable 

lay and removal scenarios. The 95% range is defined as the distance from the source that 

encompasses 95% of a particular noise contour area and provides a reasonable estimate of the 

typical distance from the source at which this noise level will be encountered. The ranges given 

in Table 2 are useful for estimating the number of marine animals that may be affected by noise 

from submarine cable construction activities. For example, playback studies in the wild have 

observed that Gray Whales exposed to continuous noise levels in excess of 120 dB exhibited 

50% probability of avoidance (Malme et al. 1988). 

4.2.2. Small workboat 

Representative noise propagation from a small workboat performing shore pull operations was 

modelled at a single shallow water location on Roberts Bank, as shown in Figure 13. The 

acoustic source representing this vessel was positioned along the cable route at the 3-metre 

isobath. As with the cable ship, unweighted, broadband noise level contours are shown in 5 dB 

increments for 50 metres receiver depth (or at the sea-bottom). This source was considerably 

quieter than the cable ship: the 95% range to the 110 dB contour was only 110 metres. Thus, 

small workboat activities are not expected to be an important consideration with regards to the 

effects of construction noise on marine wildlife. 

Table 2: Listing of 95% ranges to the 130 dB, 120 dB and 110 dB (re µPa) noise level contours for the cable lay and 

removal modelling scenarios (cf., Figures 9–12). 

Source Location 

95% Range (km) 

130 dB 120 dB 110 dB 

Cable ship Strait of Georgia (Loc 1) 0.35 2.32 14.78 



Cable ship Trincomali Channel 0.26 3.36 6.51 

Mean 0.38 3.03 13.95 

42


Figure 9: Underwater noise level contours for a cable ship performing cable lay/cable removal in the Strait of 

Georgia. Acoustic source is located approximately 5.4 km from Taylor Bay terminal along the planned cable route. 

Noise levels are shown for a receiver at 50 metres depth (or at the sea-bottom where the water is shallower). Noise 

levels are unweighted, broadband sound pressure levels given in decibels referenced to 1 µPa. 

43



Georgia. Acoustic source is located in mid-channel along the planned cable route. Noise levels are shown for a 

receiver at 50 metres depth (or at the sea-bottom where the water is shallower). Noise levels are unweighted, 

broadband sound pressure levels given in decibels referenced to1 µPa. 

44



Georgia. Acoustic source is located approximately 5.6 km from English Bluff terminal along the planned cable 

route. Noise levels are shown for a receiver at 50 metres depth (or at the sea-bottom where the water is shallower). 

Noise levels are unweighted, broadband sound pressure levels given in decibels referenced to 1 µPa. 

45


Figure 12: Underwater noise level contours for a cable ship performing cable lay/cable removal in Trincomali 

Channel. Acoustic source is located in mid-channel along the planned cable route. Noise levels are shown for a 

receiver at 50 metres depth (or at the sea-bottom where the water is shallower). Noise levels are unweighted, 

broadband sound pressure levels given in decibels referenced to 1 µPa. 

46


Figure 13: Underwater noise level contours for a small workboat performing cable pull on Roberts Bank. Acoustic 

source is located along the cable route at the 3 metre isobath approximately 1.3 km from English Bluff terminal. 

Noise levels are shown for a receiver at 50 metres depth (or at the sea-bottom where the water is shallower). Noise 

levels are unweighted, broadband sound pressure levels given in decibels referenced to 1 µPa. 

47


5. Conclusion 

Underwater ambient noise levels were measured near planned cable installation sites in both 

Trincomali Channel and the Strait of Georgia. Analysis of the acoustic data confirmed that 

ambient levels at both locations were dominated by noise from surface vessels. The character of 

the noise field was observed to be quite different at the two locations due to the different kinds of 

vessels utilizing the two channels; traffic in the Strait of Georgia was mainly composed of 

commercial shipping and ferries, whereas traffic through Trincomali Channel consisted mostly 

of small to mid-sized pleasure boats. Average daytime and nighttime ambient levels in 

Trincomali Channel were 115 dB and 93 dB, respectively, whereas average daytime and 

nighttime ambient levels in the Strait of Georgia were 114 dB and 113 dB, respectively. The 

large difference between daytime and nighttime levels in Trincomali Channel was due to the 

sharp decrease in the amount of vessel traffic passing through the channel at night. Nighttime 

ambient levels remained high in the Strait of Georgia due to a constant rate of shipping traffic to 

and from the Port of Vancouver. Ambient levels in Trincomali Channel were greater at mid to 

high frequencies, above 100 Hz, whereas ambient levels in the Strait of Georgia were greater at 

low frequencies, below 100 Hz. The frequency distribution of noise was consistent with the 

primary types of vessel traffic utilizing the two water bodies: pleasure boats in Trincomali 

Channel and large commercial shipping in the Strait of Georgia. 

The dynamic positioning cable lay vessel was identified as the primary source of noise from 

submarine cable removal and installation activities. Underwater noise propagation from a cable 

lay vessel was modelled at several locations in both Trincomali Channel and the Strait of 

Georgia: average 95% ranges from the cable ship to the 130 dB, 120 dB and 110 dB noise level 

contours were 0.38 km, 3.03 km and 13.95 km, respectively. In addition, noise propagation from 

a single workboat was modelled on Roberts Bank: the 95% range from the workboat to all noise 

level contours >110 dB was less than 110 metres. Underwater noise generated by the 

construction vessels will be similar to that of other ships and boats (e.g., pleasure boats, fishing 

vessels, tugs and container ships) already operating in these areas. It was also estimated that 120 

Hz tonal acoustic noise from operation of the new 230 kV submarine cables will not be 

substantially higher than that of the existing cables, which at about 100 dB re 1µPa source level 

is not cause for environmental concern. 

48


6. References Cited 

Barrie, J.V. and P.R. Hill. 2004. Holocene faulting on a tectonic margin: Georgia Basin, British 

Columbia, Canada. Geo-Marine Letters 24: 86-96. 

Collins, M.D. 1993. A split-step Pade solution for the parabolic equation method. Journal of the 

Acoustical Society of America. 93: 1736–1742. 

Coppens, A.B. 1981. Simple equations for the speed of sound in Neptunian waters. Journal of 

the Acoustical Society of America. 69: 862-863. 

Davis, R.E. 1976. Predictability of sea surface temperature and sea level pressure anomalies over 

the North Pacific Ocean. Journal of Physical Oceanography 6: 249-266. 

Hamilton, E. 1980. Geoacoustic modeling of the sea floor. Journal of the Acoustical Society of 

America 68: 1313-1340. 

Hannay, D., A. MacGillivray, M. Laurinolli and R. Racca. 2004. Source Level Measurements 

from 2004 Acoustics Program. Prepared by JASCO Research Ltd. for Sakhalin Energy 

Investment Company. 

Hannay, D. and R. Racca. 2005. Acoustic Model Validation. Prepared by JASCO Research Ltd. 

for Sakhalin Energy Investment Company. Document # 0000-S-90-04-P-7058-00. 

Malme, C.I., B. Würsig, J.E. Bird and P. Tyack. 1988. Observations of feeding gray whale 

responses to controlled industrial noise exposure. pp. 55-73. In: W.M. Sackinger, M.O. Jefferies, 

J.L. Imm and S.D. Treacy (eds.) Vol. 2. Port and Ocean Engineering under Arctic Conditions. 

University of Alaska, Fairbanks, AK. 111pp. 

Zabar, Z., L. Birenbaum, B.R. Cheo, P.N. Joshi and A. Spagnolo. 1992. A detector to identify a 

de-energized feeder among a group of live ones. IEEE Transactions on Power Delivery. 7: 1820- 

1824. 

49

Appendix K - BC Hydro - Transmission

Create successful ePaper yourself

Delete template?

Save as template?