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Shelburne Basin Venture Exploration Drilling Project

Marine Acoustic Monitoring Plan

Project Shelburne Basin Venture Exploration Drilling Project

Document Title Marine Acoustic Monitoring Plan

Document Number EP201601210732

Document Revision 04R

Document Status Issued for Authority Approval (IFAA)

Owner / Author L. Smandych/D. Smart (JASCO Applied Sciences)

Issue Date March 15, 2016

Expiry Date None

Security Classification Unrestricted

Disclosure External via CNSOPB and CEAA

TABLE OF CONTENTS

1. INTRODUCTION ............................................................................................................... 1

2. PROGRAM PURPOSE AND OBJECTIVE ......................................................................... 1

2.1. Predicted Sound Levels ............................................................................................ 2

2.2. Design ...................................................................................................................... 2

2.3. Equipment ................................................................................................................ 4

2.4. Recording Configuration and Field Operations .......................................................... 7

2.5. Analysis and Reporting ............................................................................................. 8

LIST OF FIGURES

Figure 1: Overview of the Program design ................................................................................. 3

Figure 2: Deep water static recorder configuration ..................................................................... 5

Figure 3: Catenary based drifting acoustic recorder ................................................................... 6

Figure 4: Example power spectral density levels and 1/3-octave-band pressure levels plotted

over frequency ........................................................................................................... 9

Figure 5: Sample of a sound source verification regression plot, showing peak SPL, 90% rms

SPL, and SEL versus range* ...................................................................................... 9

LIST OF APPENDICES

Appendix A Shelburne Basin Venture Exploration Drilling Project - Acoustic Monitoring Plan

(October 21, 2015 submission)

Shelburne Marine Acoustic Monitoring Plan

Document # EP201601210732 - 1 - March 15, 2016

Revision 04R Unrestricted

1. INTRODUCTION

In accordance with Condition 3.12.3 of the Decision Statement issued under Section 54 of the

Canadian Environmental Assessment Act, 2012 (CEAA, 2012), to Shell Canada Limited (Shell)

for the Shelburne Basin Venture Exploration Drilling Project (the Project):

The Proponent shall monitor effects on fish and fish habitat, including marine mammals

and sea turtles, to verify the accuracy of the predictions made during the environmental

assessment and to evaluate the effectiveness of mitigation measures identified under

conditions 3.1 to 3.11, including:

3.12.3 Verifying predicted underwater noise levels with field measurements during

the first phase of the drilling program. The proponent shall provide to the Board a

plan on how this will be conducted at least 30 days in advance of drilling and the

monitoring results within 90 days after a well is suspended and/or abandoned.

Shell submitted the Shelburne Venture Exploration Drilling Project: Marine Acoustic Monitoring

Plan (the Plan) to the Canada-Nova Scotia Offshore Petroleum Board (CNSOPB) on October

21, 2015 outlining a program the collect acoustic data to verify the underwater noise levels

(Appendix 1). The Plan was to be implemented by JASCO Applied Sciences (JASCO) during

the first phase of Project drilling activities. An attempt was made to complete the Program

during the drilling of the first well (Cheshire, L-97), however offshore weather conditions and

other operational constraints precluded contractor safety and the safe deployment and retrieval

of the catenary recorder.

Given the constraints imposed by weather conditions on Plan implementation, Shell has been

working with JASCO to modify the Plan in an effort to lower health, safety and environment

(HSE) risk, circumvent potential weather restrictions, and improve the acquisition of quality data

to meet the intent of Condition 3.12.3. The proposed amendment to the Program involves the

addition of a second static recorder. The addition of a second moored recorder may provide

improved data that can be safely acquired in a wider range of weather conditions and during

shorter windows of drilling activity. This option offers a higher probability of gathering good

quality acoustic data with less overall risk. The catenary recorder will be used should there be

an opportunity to align drilling activity with a favorable weather window (break in weather and/or

less than Beaufort Scale, Sea State 2).

2. PROGRAM PURPOSE AND OBJECTIVE

Shell will implement the Plan during the first phase of the drilling program (i.e., the two well

drilling program which commenced in Q4 2015). The primary objective of this Plan is to describe

how underwater sound levels from a mobile offshore drilling unit (MODU) predicted in the 2014




Project Environmental Impact Statement (EIS), will be verified with field measurements. The

predicted sound levels in the EIS were based on existing Environmental Assessment (EA)

reports, Strategic EAs, monitoring programs and scientific literature. For this proposed

program, field measurements will be verified based upon the sound generated by the Project

MODU, the Stena IceMax.

2.1. Predicted Sound Levels

The MODU will generate and release three main sources of underwater sound:

vessel operation sounds (mechanical and vibration);

thruster cavitation from the dynamic positioning (DP) systems; and

direct drilling sound from the drill string and drill bit.

During drilling, it is expected that all sources of sound will be emitted continuously (non-

impulsive). Sound Pressure Levels (SPLs) emitted from the operating MODU are likely to range

between 130 and 190 dB re 1uPa @ 1 m. All criteria (noise thresholds that may elicit impact on

fish, turtles, and marine mammals), are found in Section 7 of the EIS (http://www.ceaa-

acee.gc.ca/050/document-eng.cfm?document=101799).

Sound level (SL) measurements will provide reference source levels of the drilling vessel and

equipment used during drilling. Whereas the source levels applied in the EIS relied primarily on

estimated source levels derived from existing literature, the actual sound levels that will be

introduced into the underwater environment during drilling will be recorded and measured and

will be compared to those applied in the EIS.

The purpose of taking field (underwater) sound level recordings will be:

1. to measure the drilling sound levels at orientations to the MODU and characterize the

sound levels associated with drilling activities;

2. to analyze acquired data and verify the drilling sound data used in the EIS; and

3. to deliver the results in a final report.

2.2. Design

This Acoustic Monitoring Program will use two static recorders and a single drifting catenary

recorder, if weather and sea state conditions permit (Figure 1). The static recorders will be

deployed upon arrival in the Project area and will record continuously for approximately three (3)

days (Program duration). One recorder will be positioned along the beam of the MODU, and the

other along the stem-stern line of the MODU. It is anticipated that the sounds from the dynamic

positioning system thrusters will have a directional component that can be measured by having

http://www.ceaa-acee.gc.ca/050/document-eng.cfm?document=101799





the recorders oriented at 0 and 90 degrees relative to the vessel. Both static recorders will be

deployed approximately 2000 m from the MODU.The continuous recordings will provide an

assessment of the variability in the sound levels from the MODU over its daily operating cycle

and in different sea states. The static recorders will also document the sound levels near the

seabed, which would be the levels encountered by deep diving odontocetes that are known to

be in the area. The static recorder sound levels will be back-propagated to determine the source

level of the MODU as a function of frequency. Conductivity-temperature-depth (CTD) data will

be collected as an input to the propagation loss modeling for the back propagation.

Figure 1: Overview of the Program design

Attempts will be made to have the drifting recorder collect data at multiple ranges from the

MODU at a depth of 100 m. Because the recorder drifts, the measurements will be relatively

short, on the order of 15 minutes each. The drifts will be arranged so that the recorder’s closest

points of approach (CPA) to the MODU will range between 600 m and 4000 m (4 km) The

sound levels from these drifts will be analyzed to determine the source level of the MODU.




2.3. Equipment

The static recorders will be deployed approximately 2000 m from the MODU. The hydrophone

will be located approximately 25 m above the seabed (Figure 2). Each recorder will be left to

record continuously until completion of the Program (approximately three days). The static

recorders will be weighted to the seafloor by six (6) stacked 20 kg Olympic plates (40 cm

diameter). Upon completion of the monitoring, the release mechanism on the mooring will be

triggered from the surface allowing the recorder to disconnect from the anchor weight and rise

to the surface for retrieval. The anchor weights will remain on the sea floor.




Figure 2: Deep water static recorder configuration




The catenary mooring will be a drifting recording instrument that will be deployed over the side a

vessel used to support the Program. The mooring consists of a surface float and an ‘S’ shaped

catenary mooring that isolates the hydrophone from surface motion (Figure 3). The surface float

includes a visual flasher, radar reflector, and Iridium GPS beacon to track its location. Iridium

messages will be available to Shell representatives ashore, as well as on the MODU so that no

interference occurs with operations. The GPS logs will be used to infer the range of the

hydrophones from the project activities during the range-versus-received level analysis.

The catenary mooring acts as a spring to isolate vertical motion of the surface float from the

hydrophones. When properly designed and tuned for the sea state and the mass of the

recorders all of the surface motion is absorbed by the sinking section of the ‘S’ leaving the

floating section and hydrophone undisturbed. The mooring team will simulate and physically

tune the mooring to ensure the hydrophones remain isolated from the surface in all sea states

over which operations are expected to occur.

Figure 3: Catenary based drifting acoustic recorder




The AMAR at the base of the drifting system is fitted with a Star Oddi depth sensor that is used to confirm the correct functioning of the catenary line and settled depth of the hydrophones.

2.4. Recording Configuration and Field Operations

Both static and catenary recorders will sample at a rate of 128 000 samples per second (128

ksps) using a JASCO AMAR recorder and a GeoSpectrum M14 hydrophone. The M14 is a

specially designed hydrophone that provides calibrated sound levels from below 2 Hz to above

20 kHz. The combined response of the M14 and AMAR will return all of the data necessary to

perform a complete analysis of all radiated sound from the drilling activity.

The ability to perform the measurements will depend on weather conditions and sea state. Good

weather conditions are required to safely handle, deploy and retrieve the two static systems and

catenary recorder, however unlike the catenary system, which requires a sea state of

approximately 2 m, the static recorders are easier to deploy and may be deployed in higher sea

states (up to Sea State 5). The deployment of the static recorders may be completed in a

higher seas state because the overall mooring is less complex (reduce fouling risk) as

compared to the catenary mooring, therefore requiring less time to deploy. Each static recorder

will require a shorter favorable weather window of approximately two hours to deploy and two

hours for retrieval. Other advantages of the static recorders include:

once the mooring is in place on the sea floor, the recorders are not impacted by surface

conditions and can be left to record continuously through all sea states. The quality of

measurements may therefore be improved;

the moorings can be left on the sea floor and retrieved at the end of three days

(recorders have a recording capacity of five days). This may provide more opportunity to

capture favourable weather windows;

the depth of recorder is approximately 25 m off the seabed, therefore more favourable

for capturing drilling noise measurements;

data will be recorded continuously therefore there is more opportunity to align with the

Project drilling schedule to capture drilling noise. Unlike the catenary system, periods of

continuous drilling are not required because the static moorings will record all activity

over the three days operation period. Sounds can then be sourced/confirmed post field

via the MODU operations logs and be back-propagated to determine the source level of

the MODU as a function of frequency; and

depth of recorder is advantageous for documenting the sound levels near the seabed,

which would be encountered by deep diving odontocetes in the area.

If the MODU is fully operational with a sea state of approximately 2, it may be possible to perform the required drift measurements within approximately 30 to 45 minutes at each ranges (between 600 m and 4 km CPA). For each MODU machinery state to be measured JASCO will:




Test and calibrate the recorders, hydrophones, and Iridium beacon;

Deploy the mooring approximately 4 km downwind from the MODU, then move the deployment vessel at least 1 km from the recorder and minimize the sounds (engine noise) produced by the vessel;

After approximately 15 minutes, return to the mooring and use a boat hook to grab the 20 m tether line. Secure this line to the vessel side. Verify from the deployment and retrieval GPS locations that the mooring is drifting downwind and is not being taken towards the MODU by a water current. During the transit, download the data from the AMAR and verify that the MODU sounds are being recorded above the sounds from the deployment vessel and any surface motion induced noise; and

Slowly tow the mooring to another location(s) downwind of the MODU and repeat the measurements.

2.5. Analysis and Reporting

On completion of the field measurement phase, the data will be downloaded from the AMAR

recorders and the full data set will be processed to determine the per-second peak, rms SPL,

SEL and 1/3-octave-band rms SPLs. The MODU operations logs will be reviewed to select

periods with different machinery states for analysis. The data from the static recorders will be

back-propagated to determine the source spectrum (Figure 4) of the MODU in each machinery

state, as well as the source level variability. Since the recorders will be located within

approximately 2000 m of water, simple spherical spreading is expected to be accurate for the

back propagation, however, acoustic propagation models using the locally measured sound

speed profile will also be used in case there is significant refraction in the environment.

Summary of the data from the static recorders will also be provided that include percentile

exceedance levels, decade band levels and histograms, and long term spectral averages of the

received sound levels.




Figure 4: Example power spectral density levels and 1/3-octave-band pressure levels

plotted over frequency

For the catenary recorder, for the time periods where the deployment vessel was idling far from the recorder the peak rms SPL and SEL levels will be plotted versus range to the MODU, and then a regression applied to the data to determine the source levels and spreading loss (Figure 5).

Figure 5: Sample of a sound source verification regression plot, showing peak SPL,

90% rms SPL, and SEL versus range*

*Solid line is best fit of the empirical function to Lp90 values. Dashed line is the best-fit shifted to exceed

90% of the Lp90 values (90th percentile fit). The equations show the effective source level (in this case

213.4 dB) and the spreading loss (16.4 log (R)) in the environment.




Verification and comparison of the analyzed drilling sound levels will be made with those

predicted in the EIS for the Project. Shell will submit a Final Acoustic Monitoring Report to the

CNSOPB within 90 days after the well is suspended and/or abandoned.

Appendix A: Shelburne Basin Venture Exploration Drilling Project - Acoustic Monitoring Plan (October

21, 2015 submission)

Shell Canada Energy 400 - 4th Avenue S.W.

P.O. Box 100, Station M

Calgary, Alberta T2P 2H5

Internet www.shell.ca

October 21, 2015

Eric Theriault

Advisor, Environmental Affairs

Canada-Nova Scotia Offshore Petroleum Board

1791 Barrington Street, 6th Floor, TD Centre

Halifax, NS, B3J 3K9

RE: Shell Shelburne Venture Exploration Drilling Project

CEAA Condition 3.12.3; Marine Acoustic Monitoring Plan

On June 15, 2015, Shell Canada Limited (Shell) received the Decision Statement Issued under

Section 54 of the Canadian Environmental Assessment Act, 2012 for the Shelburne Basin

Venture Exploration Drilling Project (the Project). CEAA Condition 3.12.3 states:

The Proponent shall monitor effects on fish and fish habitat, including marine mammals and

sea turtles, to verify the accuracy of the predictions made during the environmental



3.12.3 verifying predicted underwater noise levels with field measurements during the first

phase of the drilling program. The proponent shall provide to the Board a plan on how this

will be conducted at least 30 days in advance of drilling and the monitoring results within 90

days after a well is suspended and/or abandoned.

In compliance with CEAA Condition 3.12.3, Shell submitted a draft Shelburne Venture

Exploration Drilling Project: Marine Acoustic Monitoring Plan (the Plan) to the Canada-Nova

Scotia Offshore Petroleum Board (CNSOPB) on September 17, 2015. Shell has since

contracted JASCO Applied Sciences (JASCO) to complete the acoustic monitoring

program for the Project. Based upon their experience and expertise, the Plan has been

updated (please see attached). The implementation of the Plan will occur during the drilling

of the first Project well (Cheshire).

As part of the acoustic monitoring, Shell proposes to use one (1) static recorder that will be

deployed 2000m from the MODU and left in place for approximately 3 days. The recorder

will be weighted to the seafloor by six (6) stacked 20kg Olympic plates (40cm diameter).

Upon completion of the monitoring, the release mechanism on the mooring will be triggered

http://www.shell.ca/

Shelburne Acoustic Monitoring Plan October 21, 2015

2

from the surface allowing the recorder to disconnect from the anchor weight and rise to the

surface for retrieval. The anchor weight will remain on the sea floor.

Residual environmental effects of the deployment of the recorder are predicted to be not

significant. There are no Special Areas located within 2km of the proposed well location. The

deployment of the recorder to the sea floor could result in mortality of sessile benthic fauna

and infauna directly under the anchor weight, however given the size of the weight (40cm

diameter) disturbance, if any, will be minimal. Entanglement in the rigging between the

weights and the top of the mooring is likely not to occur given the short duration the mooring

will be in place. Although the stainless steel weights will remain on the sea floor, it is

anticipated that they will likely be colonized by epifauna over time and will not result in

significant adverse environmental effects on the benthos.

Sincerely,

Lara Smandych

Senior Environmental Planner

Shell Canada Limited


3

Shelburne Venture Exploration Drilling Project: Marine Acoustic Monitoring Plan

I. Introduction

In accordance with Condition 3.12.3 of the Decision Statement issued under Section 54 of

the Canadian Environmental Assessment Act, 2012, to Shell Canada Limited (Shell) for the

Shelburne Basin Venture Exploration Drilling Project (the Project):

The Proponent shall monitor effects on fish and fish habitat, including marine mammals and

sea turtles, to verify the accuracy of the predictions made during the environmental



3.12.3 verifying predicted underwater noise levels with field measurements during the

first phase of the drilling program. The proponent shall provide to the Board a plan on

how this will be conducted at least 30 days in advance of drilling and the monitoring

results within 90 days after a well is suspended and/or abandoned.

Shell prepared a draft Shelburne Venture Exploration Drilling Project Marine Acoustic

Monitoring Plan to be implemented during the first phase of Project drilling activities. This Plan

was submitted to the Canada-Nova Scotia Offshore Petroleum Board (CNSOPB) on

September 17, 2015, approximately 30 days in advance of the commencement of drilling in

compliance with the CEAA condition. Below is the amended plan that will be executed by

JASCO Applied Sciences (JASCO), based out of Dartmouth, Nova Scotia.

II. Program Purpose and Objective

Shell will implement an acoustic monitoring program during the first phase of the drilling

program (i.e. the two well drilling program commencing Q4 2015). First Phase is understood

as the time period post spud and approximately mid-way through the 130 day drilling

schedule of the first well. At this time, field work would likely commence late Q4 2015 or early

Q1 2016.

The primary objective of this Plan is to describe how underwater sound levels from a mobile

offshore drilling unit (MODU) predicted in the 2014 Project Environmental Impact Statement

(EIS) will be verified with field measurements. The predicted sound levels in the EIS were

based on past Environmental Assessment (EA) reports, Strategic EAs, monitoring programs

and scientific literature. For this proposed program, field measurements will be verified based

upon the sound generated by the Project MODU, the Stena IceMax.


4

Predicted Sound Levels:

The MODU will generate and release three main sources of underwater sound:

Vessel operation sounds (mechanic and vibration);

Thruster cavitation from the dynamic positioning (DP) systems; and

Direct drilling sound from the drill string and drill bit.

During drilling, it is expected that all sources of sound will be emitted continuously (non-

impulse). Sound Pressure Levels (SPLs) emitted from the operating MODU are likely to range

between 130-190 dB re 1uPa @ 1m. All criteria (noise thresholds that may elicit impact on

fish, turtles, and marine mammals), are found in Section 7 of the EIS (http://www.ceaa-

acee.gc.ca/050/document-eng.cfm?document=101799).

Sound level (SL) measurements will provide reference source levels of the drilling vessel and

equipment used during drilling. Whereas the source levels applied in the EIS relied primarily

on estimated source levels derived from existing literature, the actual sound levels that will

be introduced into the underwater environment during drilling will be recorded and

measured and will be compared to those applied in the EIS.

The purpose of taking field (underwater) sound level recordings will be:

1. To measure the drilling sound levels at different distances and depths from the MODU

and characterize the sound levels associated with drilling activities.

2. To analyze acquired data and verify the drilling sound data used in the EIS.

3. To deliver the results in a final report.

Design:

The acoustic monitoring will use two components: a single drifting catenary recorder and a

single static recorder (Figure 1). The drifting recorder will collect data at multiple ranges from

the MODU at a depth of 100 m. Because the recorder drifts, the measurements will be

relatively short, on the order of 15 minutes each. The drifts will be arranged so that the

recorder’s closest points of approach (CPA) to the MODU are approximately 600, 1000, 2000,

5000, and 10000 m.

Time and weather permitting the drifts at each range will be repeated multiple times to

measure different operating states of the MODU and / or provide a larger statistical sample

in the normal operating condition. The sound levels from these drifts will be analyzed to

determine the source level of the MODU.

The static recorder will document the sound levels near the seabed, which can be

encountered by deep diving odontocetes. This recorder will record continuously for

approximately three (3) days which will provide an assessment of the variability in the sound

levels from the MODU over its daily operating cycle and different sea states.




5

Figure 1: Overview of the program design

Equipment:

The catenary mooring will be a drifting recording instrument that will be deployed over the

side the chartered vessel used to support the acoustic measurement program. The mooring

consists of a surface float and an ‘S’ shaped catenary mooring that isolates the hydrophone

from surface motion (Figure 2). The surface float includes a visual flasher, radar reflector, and

Iridium GPS beacon to track its location. Iridium messages will be available to Shell

representatives ashore, as well as on the MODU so that no interference occurs with

operations. The GPS logs will be used to infer the range of the hydrophones from the project

activities during the range-vs-received level analysis.

The catenary mooring acts as a spring to isolate vertical motion of the surface float from the

hydrophones. When properly designed and tuned for the sea state and the mass of the

recorders all of the surface motion is absorbed by the sinking section of the ‘S’ leaving the

floating section and hydrophone undisturbed. The mooring team will simulate and physically

tune the mooring to ensure the hydrophones remain isolated from the surface in all sea

states over which operations are expected to occur.


6

Figure 2: Catenary based drifting acoustic recorder

The AMAR at the base of the drifting system is fitted with a Star Oddi depth sensor that is

used to confirm the correct functioning of the catenary line and settled depth of the

hydrophones.

The static recorder will be deployed on arrival in the project area approximately 2000m from

the MODU. The hydrophone will be located approximately 25 m above the seabed (Figure

3). It will be left to record continuously until completion of the catenary recorder program

(approximately 3 days).

The static recorder will be weighted to the seafloor by six (6) stacked 20kg Olympic plates

(40cm diameter). Upon completion of the monitoring, the release mechanism on the

mooring will be triggered from the surface allowing the recorder to disconnect from the

anchor weight and rise to the surface for retrieval. The anchor weight will remain on the sea

floor.


7

Figure 3: Deep water static recorder configuration


8

Recording Configuration and Field Operations:

Both recorders will sample at a rate of 64 000 samples per second (64 ksps) using a JASCO

AMAR recorder and a GeoSpectrum M14 hydrophone. The M14 is a specially designed

hydrophone that provides calibrated sound levels from below 2 Hz to above 20 kHz. The

combined response of the M14 and AMAR will return all of the data necessary to perform a

complete analysis of all radiated sound from the drilling activity.

The time required to perform the measurements will depend on weather conditions and

operations at the MODU. If the MODU is fully operational and weather conditions are good,

it may be possible to perform all of the required drift measurements within a single day. For

each sound source to be measured, it will take approximately 30 to 45 minutes to collect

data at each of the five ranges (600, 1000, 2000, 5000 and 10000 m CPAs). For each MODU

machinery state to be measured JASCO will:

- Test and calibrate the recorders, hydrophones, and Iridium beacon;

- Deploy the mooring approximately 10 km downwind from the MODU, then move the

deployment vessel at least 1 km from the recorders and minimize the sounds (engine

noise) produced by the vessel;

- After approximately15 minutes, return to the mooring and use a boat hook to grab the

20 m tether line. Secure this line to the vessel side. Verify from the deployment and

retrieval GPS locations that the mooring is drifting downwind and is not being taken

towards the MODU by water currents. During the transit, download the data from the

AMAR and verify that the MODU sounds are being recorded above the sounds from

the deployment vessel and any surface motion induced noise;

- Slowly tow the mooring to a location 5 km downwind of the MODU. Move off at least 1

km and idle the vessel for 15 minutes;

- Return to the mooring, and tow it to a location 2 km downwind of the MODU and

repeat the measurements;

- Return to the mooring, and tow it to a location 1 km downwind of the MODU and

repeat the measurements;

- Return to the mooring, and tow it to a location 600 m downwind of the MODU, repeat

the measurements; and

- Time and weather conditions permitting repeat these measurements across wind or

downwind from the MODU.

Note that measurements will be made from the 10 km downwind range progressively closer

to the MODU, and the drift dynamics will be analyzed between drifts. The acoustics team will

ensure that there is no chance that the catenary mooring or acoustic support vessel will

enter inside the 500 m exclusion zone.

Each set of drift measurements will take 4 to 6 hours to complete. Shell anticipates that it will

not be possible to measure the operational sounds from the rig without the DP system on,

however it may be possible to measure with and without the drill operating. Three days of

measurements are allocated, which may provide at least two sets of drift measurements,

with and without the drill operating.


9

Conductivity-temperature-depth (CTD) casts will be performed each day. The CTD data

may be necessary to help interpret any anomalous propagation results from the

measurements.

Analysis and Reporting:

On completion of the field measurement phase, the data will be downloaded from the

AMAR recorders and processed to determine the per-second peak, rms SPL, SEL and 1/3-

octave-band rms SPLs. For the time periods where the deployment vessel was idling far from

the recorder the peak rms SPL and SEL levels will be plotted versus range to the MODU, and

then a regression applied to the data to determine the source levels and spreading loss

(Figure 4). The 1/3-octave-band data will also be plotted as a function of range to

determine the source spectrum of the drill and MODU operations (Figure 5). A summary of

the data from the static recorder will be provided that include percentile exceedance

levels, decade band levels and histograms, and long term spectral average results.

Figure 4: Sample of a sound source verification regression plot, showing peak SPL, 90% rms SPL, and SEL versus range. Solid line is best fit of the empirical function to Lp90 values. Dashed line is the best-fit shifted to exceed 90% of the Lp90 values (90th percentile fit). The equations show the effective source level (in this case 213.4 dB) and the

spreading loss (16.4 log (R)) in the environment


10

Figure 5: Example power spectral density levels and 1/3-octave-band pressure levels plotted over frequency

Verification and comparison of the analyzed drilling sound levels will be made with those

predicted in the EIS for the Project. Shell will submit a final acoustic monitoring report to the

CNSOPB within 90 days after the well is suspended and/or abandoned.

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