Smithwick2016_KitimatArmPiezometerDeploymentHIRES

Piezometer Deployment Strategy for
Marine Slope Stability Research in
Kitimat Fjord, British Columbia
By: Brendan Smithwick
Bachelors of Science Honours Report
The School of Earth and Ocean Sciences, The University of Victoria
Supervisors:
Dr. Gwyn Lintern, Natural Resources Canada
Dr. Lucinda Leonard, The University of Victoria
Submitted April 2016

B.Smithwick: EOS Honours Thesis
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Abstract:
Natural Resources Canada (NRCan) is assessing the slope stability hazards in
Kitimat Arm glacial fjord, BC, that may put ongoing and future developments at risk.
In 1975 a submarine slope failure in Kitimat Arm generated a tsunami which,
damaged infrastructure. Pore pressure in marine sediments affects slope stability;
thus measurements of in situ pore pressure using piezometers will be a critical
input to the Kitimat Arm hazard assessment. The goal of this project is to identify
the best location for piezometer deployments and plan instrumentation logistics for
the May 2016 Pacific Geoscience Centre expedition.
Five locations have been evaluated for the potential of undrained conditions, which
are targets for piezometer deployment. These locations host uniquely different
features, including slump morphology, a potential failure block, a biogenic gassy
escarpment, deltaic sediment with potential artesian pressure, and an area of
historically high river flow.
A strategy for deployment of the piezometers has been selected called the controlled
gravity deployment. This involves the instrument being lowered through the water
column at a controlled velocity. When it impacts the seabed it will penetrate to a
chosen penetration depth under a 2 tonne driving weight.
Six piezometers are available for deployment on the May 2016 expedition, three of
which are planned to be cabled to shore for future data transmission to the Sidney,
British Columbia office of the Geological Survey of Canada and three of which are
planned to collect data autonomously for about one year.

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Acknowledgments:
I would like to thank my supervisors Gwyn Lintern and Lucinda Leonard for the
opportunity to work on this exciting project. Along with this I would like to thank
Cooper Stacey, Dan Perera, Rob Kung, Peter Neelands, Greg Middleton, and the
Pacific Geoscience Centre staff for the help and advice they gave me during this
project and for their future efforts in completing this hazard assessment. It has been
a privilege to gain access and work with an incredible data set that has taken years
of collection effort by Natural Resources Canada.
I would also like to thank my EOS colleges at the University of Victoria department
for all the interesting conversations that have helped me understand this exciting
field of study as well as the SEOS staff.

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Table of Contents
Abstract:.......................................................................................................................................2
Acknowledgments:...................................................................................................................3
List of Figures.............................................................................................................................5
1 Introduction:...........................................................................................................................7
2 Background:............................................................................................................................9
2.1 Kitimat Arm study area:............................................................................................................9
2.2 Seafloor Morphology:.............................................................................................................. 10
2.3 Geotechnical Parameters Affecting Slope Stability...................................................... 12
2.3.1 Factor of Safety:................................................................................................................................12
2.3.2 Pore Pressure Effect on Slope Stability:..................................................................................14
2.3.3 Undrained vs Drained Sediment Conditions (targets for deployment):...................15
2.3.4 Ebbing Tides and Excess Pore Pressure:................................................................................15
2.3.5 Sediment Loading and Excess Pore Pressure: .....................................................................15
2.3.6 Artesian Flows and Pore Pressure:...........................................................................................16
2.3.7 Stratigraphy that Facilitates Excessive Pore Pressure:....................................................16
3 Methods:................................................................................................................................ 16
3.1 Multibeam Sonar Bathymetry.............................................................................................. 16
3.2 Seismic Reflection Subsurface Imaging:........................................................................... 17
3.3 Free Fall Cone Penetrometer (FFCPT) for Sediment Physical Properties:.......... 18
3.3.1 Overview of FFCPT..........................................................................................................................18
3.3.2 Dynamic Penetration Resistance Calculation: .....................................................................20
3.3.3 Piezometer Dynamic Penetration Calculation:....................................................................21
3.3.4 Sediment Classification based on Physical Properties from FFCPT:..........................23
3.4 Grab Samples for Sediment Composition:....................................................................... 24
3.5 Marine Sediment Cores:......................................................................................................... 27
3.6 Instrumentation: ...................................................................................................................... 27
3.6.1 Overview: ............................................................................................................................................27
3.6.2 Test Deployment of Piezometers:.............................................................................................28
3.6.3 Controlled Gravity Deployment (CGD):..................................................................................29
4 Results: Prospective Deployment Locations:........................................................... 30
4.1 Overview:..................................................................................................................................... 30
4.2 Moon Bay (Areas 1 & 2):...................................................................................................................30
4.3 Kitimat Arm West (Area 3):.............................................................................................................40
4.4 Delta Front West (Area 4):...............................................................................................................45
4.5 Delta Front East (Area 5): ................................................................................................................49
5 Results: Instrumentation Specifications: .................................................................. 50
5.1 Instrumentation specification overview: ........................................................................ 50
5.2 Constraints List ......................................................................................................................... 51
5.3 Geotech piezometer constraints:........................................................................................ 51
5.3.1 Battery and Memory Capacity....................................................................................................51
5.3.2 The Piezometer Test Deployment Memory Capacity Issue Addressed.....................52
5.3.3 Cabled Deployment Constraints................................................................................................53
5.3.4 Sampling Rate During Deployment..........................................................................................53
5.4 Deployment fabrication:........................................................................................................ 54

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5.4.1 Controlled Gravity Deployment (CGD)....................................................................................54
5.4.2 Sea Bed Penetration Resistance.................................................................................................55
5.4.3 Deployment Velocity of Controlled Gravity Deployment................................................55
5.4.4 Mud Plate Size ...................................................................................................................................56
5.4.5 Accelerometer for Measuring Dynamic Penetration Resistance During
Deployment ...................................................................................................................................................58
5.4.6 Pressure Sensor for Measuring Depth During Deployment...........................................59
5.4.7 Mechanical Components of the Controlled Gravity Deployment (Figure 31) ........60
5.5 Parts required ........................................................................................................................... 61
5.6 Assembly plan............................................................................................................................ 61
5.6.1 Cable Splice to Connector:............................................................................................................61
5.6.2 Coupling Cable with Prawn Line................................................................................................61
5.6.3 Pipe Fitting: ........................................................................................................................................62
5.6.4 Onboard:..............................................................................................................................................62
5.6.5 Programming:....................................................................................................................................62
5.6.6 Deployment:.......................................................................................................................................62
5.7 Calibration .................................................................................................................................. 63
5.8 Instrumentation Conclusion: ............................................................................................... 63
6 Discussion and Conclusion: ............................................................................................ 64
6.1 Discussion of Prospective Deployment Locations........................................................ 64
6.2 Other Considerations of the CGD ........................................................................................ 66
6.3 Data Collection Discussion.................................................................................................... 67
6.4 Future Piezometer Deployment Discussion ................................................................... 67
6.5 Conclusion................................................................................................................................... 68
References:............................................................................................................................... 69
Appendix.1 Parts List ........................................................................................................... 71
List of Figures
Figure Description Pg.#
Figure 1 Slide deposits of historic slope failures in Kitimat Arm 7
Figure 2 Kitimat Arm Study Area 11
Figure 3 Simplified free body diagram of forces acting on a package of sediment on a failure plane. 12
Figure 4 Multibeam bathymetry signal array 17
Figure 5 ODMI Brookes Ocean Free Fall Cone Penetrometer (FFCPT) 19
Figure 6 Robertson soil classification scheme derived from FFCPT data 23
Figure 7 National Resource Canada 2015 grab sample locations in Kitimat Arm 25
Figure 8 Environment Canada Grab samples collected in 2015 26
Figure 9 Piezometer test deployment during the 2015004PGC expedition using ROPOS remotely
operated vehicle
28
Figure 10 Location of test deployment piezometer 27

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Figure 11 Multibeam bathymetry of Moon Bay 31
Figure 12 Multibeam bathymetry and seismic reflections of Moon Bay South 33
Figure 13 Cabled piezometer deployment at Moon Bay South 34
Figure 14 Slope map of Moon Bay South 35
Figure 15 Multibeam bathymetry of Moon Bay North 37
Figure 16 Autonomous piezometer deployment at Moon Bay North 38
Figure 17 Work required to penetrate the piezometer to 4 m depth in Moon Bay North 39
Figure 18 Multibeam bathymetry and seismic reflections of Kitimat Arm West 41
Figure 19 Sediment thickness map and seismic at Kitimat Arm West 42
Figure 20 Cabled piezometer at Kitimat Arm West 43
Figure 21 Kitimat Arm West Slope map 44
Figure 22 Multibeam bathymetry, pore pressure salinity and sediment penetration resistance at
Delta Front West
46
Figure 23 Seismic at Delta Front West 47
Figure 24 FFCPT 92 reveals undrained conditions ~0.35 m into the seabed. 48
Figure 25 Multibeam bathymetry and seismic at Delta Front East 49
Figure 26 Conceptual diagram of the CGD strategy. 56
Figure 27 Force balance during deployment impact with seabed 56
Figure 28 Free fall cone penetrometer dynamic penetration resistance averaged over the top 10 cm
of the seabed
57
Figure 29 The maximum deceleration experienced by free fall cone penetrometer. 58
Figure 30 Using the pressure sensor to determine penetration depth of the piezometer 59
Figure 31 Mechanical components diagram of piezometer deployment 60

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1 Introduction:
An investigation of marine slope stability on the west coast is being completed by
Natural Resources Canada (NRCan). It is NRCan that is responsible for ensuring
public safety from geohazards, such as slope stability. Significant infrastructure
proposals in the region have motivated this study. The piezometer deployment
strategy outlined in this report will contribute to this larger project.
The Kitimat Arm fjord will be the focal point of this report. Some of the
infrastructure developments in Kitimat Arm fjord include Canada LNG, Kitimat LNG,
Douglas channel LNG and Rio Tinto Alcan modernization.
It is important to
understand the slope
stability within any fjord
system. Slope failures can
result in fatalities and in
destruction of
infrastructure. The Kitimat
Arm fjord is not exempt
from this hazard. In 1975
two to three tsunamis up to
8 metres high were created
from slope failures at the
delta front of the
fjord (Brown, 1979). The failures occurred 53 minutes after low tide. Along with the
tsunamis, a barge-loading site at Moon bay was totally destroyed and the seaward
half of the old Alcan Wharf head was carried away (Brown, 1979). Other slides
occurred in 1971 and 1974 (Figure 1).
Figure 1 Slide deposits of historic slope failures in Kitimat Arm
(Johns et al. 1984)

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Slope stability can be quantified by analytically calculating the factor of safety. Pore
pressure is a critical variable within this calculation (Bishop & Morgenstern, 1960).
Thus in order to properly assess the risk of submarine landslide in the Kitimat arm
it is necessary to measure pore pressure by probing the sediment. Piezometers have
been used for this successfully offshore Norway at the Ormen Lange Gas Field
(Strout & Tjelta, 2005). Strout & Tjelta (2005) have released piezometer
deployment recommendations that will be considered in the scope of this report.
The purpose of this project is to devise a strategy for the deployment of piezometers
in Kitimat Arm. The main goals to be achieved are:
1. To determine a practical way to deploy the piezometers
2. To use geoscience tools to locate ideal deployment sites with probable
positive excess pore pressure
3. To address shortcomings that may require further survey techniques.
Section 2 will discuss the Kitimat Arm study area and geotechnical parameters
important to slope stability. In section 3 the methods used to determine prospective
deployment locations of the piezometers will be described. Section 4 will describe
the prospective deployment locations determined from the methods. Section 5 will
go through the instrument specifications and deployment strategy. Section 6 will
contain a general discussion on the project.

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2 Background:
2.1 Kitimat Arm study area:
Kitimat Arm is a glacial fjord running through the Kitimat Ranges ~ 650 km
northwest of Vancouver on the North Coast of BC (Figure 2). Kitimat Arm is a glacial
fjord running between the ~3000 m high peaks of the Kitimat Ranges. The Kitimat
ranges, part of the Coast Crystalline belt, are primarily composed of massive granitic
rocks (Bornhold, 1983). The Kitimat Arm is one of many long straight valleys
trending north-northeast in this region of British Columbia Canada. The valley was
extensively modified during the Pleistocene by glaciation and fluvial erosion and
deposition.
It has been suggested that by Duffel and Souther (1964) that the Kitimat valley is the
surface expression of a major fault. New seismic and multibeam evidence found by
Conway et. al (2012) supports this.
The Kitimat Arm has typical fjord morphology with steep bedrock walls and a
smooth sediment-floored basin. Three basins exist in the Douglas-Kitimat fjord
system separated by sills. The basin has general depths of 200-220m. The basin of
interest for the deployment is the Kitimat Arm Basin because this is the location of
infrastructure development.
Sediment stratigraphic units within the Kitimat Arm basin include the following
(Bornhold, 1983):
• Till
• Glacio-marine
• Stratified sands and sandy muds
• Acoustically transparent muds
• Sandy muds with occasional sand layers
• Hummocky slumped sediments on delta front

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Extensive sedimentation occurred during de-glaciation ~13100 – 11000 years BP
(before 1950). Large volumes of acoustically transparent grey mud, as seen in
seismic section, with occasional drop stones, were deposited during glacial out
washing. The basin floor and fjord walls are covered with this sediment. Isostatic
rebound has situated these muds above present sea level on coastal slopes
(Bornhold, 1983).
The deltaic sedimentation near Kitimat Arm began about 9000 – 9500 years BP.
This sediment includes deposited hemiepelagic sediment, landslides, debris and
turbidity flow deposits. In general deltaic sands and silts prograde over the silty-clay
glacio marine muds (Bornhold, 1983).
2.2 Seafloor Morphology:
Morphologies of interest include for this study retrogressive slide scars, head
scarps, slide debris, submarine fans, submarine channels and pockmarks. These are
all morphologies that identify a slope stability event or forcing.

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Figure 2 Kitimat Arm Study Area: Piezometer Prospective Deployment Locations are shown as
numbered polygons on map. Seafloor bathymetry mapped with Multibeam Sonar.

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2.3 Geotechnical Parameters Affecting Slope Stability
2.3.1 Factor of Safety:
The Factor of Safety (FS) is an analytical indicator of the stability of a slope. It is an
important parameter in areas at risk of slope failure. It will be defined here to
outline the importance of static pore pressure in its definition. This description is
simplified to express the importance of the concept but is not intended to be a
critical variable in this report. The simplest definition of FS is the shear strength on
a failure plain divided by the shear stress (Figure 3 & (Equation 1):
‫ܵܨ‬ ൌ
݄ܵ݁ܽ‫݄ݐ݃݊݁ݎݐܵ ݎ‬
݄ܵ݁ܽ‫ݏݏ݁ݎݐܵ ݎ‬
(Equation 1) (Das, 2011)
It can be seen that if the shear strength is less than the shear stress, the factor of
safety will be less than one and the
slope will fail. If the shear strength is
larger than the shear stress, the factor
of safety will be greater than one and
the slope will be stable. The larger the
factor of safety is compared to one, the
more stable the slope will be. A factor of
safety greater than 1.3 is usually
considered acceptably safe during
construction on a slope (Das, 2011).
The shear strength of sediment is represented with the following equation (Das,
2011):
߬௙ ൌ ܿ′ ൅ ߪ′tan ሺ߮ሻ (Equation 2)
Where:
Figure 3 Simplified free body diagram of forces
acting on a package of sediment on a failure plane.

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• ߬௙= shear strength (or shear stress at failure)
• ܿ′= cohesion of the sediment (empirically measured)
• ߪ′= effective normal stress acting on the friction plane
• ߮= effective stress angle of internal friction
The ߪ′tan ሺ߮ሻ term is essentially the friction component of the shear strength. This is
dependent on effective normal stress ߪ′ (Das, 2011). The sediment pore pressure
works against the normal stress. Marine sediments are saturated with seawater so
the slope is considered submerged and the submerged unit weight of marine
sediment (ߛ′) is used in the following equation for effective stress (Chowdhury et. al,
2009):
ߪᇱ
ൌ ߪ௧ − ‫ݑ‬௘
(Equation 3)
‫ݑ‬௘ ൌ ‫ݑ‬ − ‫ݑ‬௦
(Equation 4) (see 2.3.2)
ߪ௧ ൌ ݄ߛ′ (Equation 5)
ߪᇱ
ൌ ݄ߛᇱ
− ሺ‫ݑ‬ − ‫ݑ‬௦ሻ (Equation 6)
Where:
• ߪ′= effective normal stress acting on the friction plane
• ߪ௧= total normal stress acting on the friction plane
• ‫=ݑ‬ total pore pressure (a measurable quantity)
• ‫ݑ‬௘= excess pore pressure
• ‫ݑ‬௦= hydrostatic pore pressure
• ݄= depth below the sea bed
• ߛᇱ
ൌ ߛ௦௘ௗ − ߛ௪= submerged unit weight of marine sediment
• ߛ௦௘ௗ= unit weight of water saturated marine sediment
• ߛ௪= unit weight of sea water
Shear stress can be simply considered as the gravitational stress of the overburden
sediments on a failure plane (Das, 2011).

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߬௦ ൌ ߛᇱ
‫ߚ ݊݅ݏݖ‬ (Equation 7)
Where:
• ߬௦= shear stress on a failure plane
• ‫ݖ‬ = depth to failure plane
• ߚ= slope angle
2.3.2 Pore Pressure Effect on Slope Stability:
As explained previously slope stability is affected by pore pressure. In the marine
environment the slope is submerged. If pore pressure is greater than the hydrostatic
pressure the slope may be unstable. This follows(Equation 4):
‫ݑ‬௘ ൌ ‫ݑ‬ − ‫ݑ‬௦
(Equation 4)
Where: ‫ݑ‬௘ is excess pore pressure; ‫ ݑ‬is sediment pore pressure; ‫ݑ‬௦ is hydrostatic
pressure (Equation 8):
‫ݑ‬௦ ൌ ߩ௪݄݃ (Equation 8)
Where ߩ௪=density of water, ݃= acceleration due to gravity, and ݄ = height of water
column overburden.
When ‫ݑ‬ > ‫ݑ‬௦ instability can occur because excess pore pressure lowers shear
strength.
Factors that contribute to increased pore pressure are: (1) artesian pressure (pore
pressure induced by fresh ground water flow into marine slope); this will cause a
decrease in salinity; (2) ebbing tides; (3) prevention of fluid drainage during rapid
sedimentation.

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2.3.3 Undrained vs Drained Sediment Conditions (targets for deployment):
Drained sediment condition: In drained sediments sufficient permeability allows
pore fluid to escape a decreasing volume of pore space due to consolidation. This
escape of pore fluid results in an absence of excess pore pressure (Duncan & Wright,
2014).
Undrained sediment condition: Insufficient permeability does not allow water to
enter or escape the sediment quickly. Changing loads result in increased pore
pressure. Sediment that is undrained cannot release pore water to accommodate a
reduction in pore space like in the drained sediment condition. A positive effective
pore pressure is the result of this situation (Duncan & Wright, 2014).
Any sediment can be in a drained or undrained condition. Clays are more likely to be
found in an undrained condition due to their low permeability. Sands are more
likely to occur in a drained condition due to their high permeability.
Because positive effective pore pressures occur in undrained sediments and positive
effective pore pressure leads to a lowered factor of safety, sediments that are
deemed likely to be in an undrained condition represent good targets for
piezometer deployment.
2.3.4 Ebbing Tides and Excess Pore Pressure:
During low tide the hydrostatic pressure at the seabed is reduced. If the sediments
are undrained they cannot keep up with this reduction in pressure. The pore
pressure is maintained at a higher pressure than hydrostatic. This results in positive
excess pore pressure. This reduces the factor of safety by decreasing the normal
force. The slope is now at increased risk of slope failure.
Identifying excess pore pressure in situ as a function of tide pressure changes is
target of piezometer deployment.
2.3.5 Sediment Loading and Excess Pore Pressure:
Stable geologic formations are permeable enough to allow pore fluids to escape
during sedimentation and equilibrate to normal hydrostatic pressure. In situations

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where the sedimentation rate is high, fluid circulation may become restricted. Some
of the overburden becomes supported by pore pressure. Consolidation is retarded
and the sediment remains under consolidated (Sultan et al, 2004).
The factor of safety can be lowered in two ways in this case (Das, 2011):
1. Loading of sediment increases the shear stress on the slope
2. Trapped pore fluid responds to this condition by increasing pore pressure.
This lowers the shear strength of the sediment
Anthropogenic sediment loading may have been a factor in the 1975 Kitimat slope
failure. Wharf construction began one year before the slide (Brown, 1979).
2.3.6 Artesian Flows and Pore Pressure:
Ground water entering the fjord wall with hydrostatic head can become pressurized
if trapped in fine-grained sediments. Morrison (1984) refers to a borehole at Moon
Bay containing fresh water above mean tide pressure.
2.3.7 Stratigraphy that Facilitates Excessive Pore Pressure:
Permeable sediments confined by low permeability sediments can confine pressure
by acting as a fluid conduit. Morrison (1984) refers to bore holes at the Alcan Wharf
that had slight artesian pressures within strata of this type. He also refers to a test
hole at Emsley Cove in which a 15 metres above mean tide pressure was measured
in gravel overlying bedrock capped with fine grained marine sediments.
3 Methods:
3.1 Multibeam Sonar Bathymetry
Multibeam or “swath” bathymetry is sonar collected with multiple transducers.
Conventional echo sounding emits a single sound wave from the bottom of a ship;
using the delay time for the return signal and the speed of sound in water, the
seafloor depth below the ship can be determined. Multibeam uses the same
principle but utilizes an array of signals in a fan to capture depth measurements

17
from a cone around the ship (Figure 4). Multibeam data of the Kitimat Arm and the
Douglas Channel collected by the Canadian Hydrological Survey in 2010 is utilized
in this report.
Multibeam data were compiled
in QGIS. Two-dimensional
depth profiles were taken from
the three-dimensional fabrics
composed within the
multibeam data. The data were
used for determining the
geomorphological condition of
the seabed and hydrostatic
gradients. Three-dimensional
fabrics were plotted with
Matlab to create
comprehensive views of the
seafloor topography.
3.2 Seismic Reflection Subsurface Imaging:
Multibeam methods provide an effective way to determine sea floor topography but do
not allow us visual access to the sub surface. Huntec Seismic data from the 2013007PGC
expedition and chirp 3.5 kHz seismic reflections collected during the 2015002PGC and
2013007PGC expeditions were used to determine potential fluid conduits and gassy
sediments in the subsurface. Fluid conduits are targets for the piezometer deployment
because pore pressure measured within these structures reveals subsurface process
parameters key to understanding the slope stability. Gas can also increase effective pore
pressure. The Geologic Survey of Canada Atlantic Seismic toolkit was used to process
the seismic images.
Figure 4 Multibeam bathymetry signal array (Image from:
NERC-BAS, 2015)

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3.3 Free Fall Cone Penetrometer (FFCPT) for Sediment Physical Properties:
3.3.1 Overview of FFCPT
The Geological Survey of Canada deployed an ODMI Brooke Ocean Free Fall Cone
Penetrometer (FFCPT) during the 2015002PGC expedition in various locations
around the Kitimat Arm. The deployment of this instrument has similarities to
piezometer deployment; therefore the information collected during the FFCPT’s
deployment can be utilized for the piezometer deployment. The instrument is a 1.8
m long 88 mm diameter rod tipped with a 60° cone (Figure 5). The instrument
weighs 60.0 kg in air and 49.7 kg in water.
The instrument free falls through the water column, then impacts the seabed
penetrating the subsurface. During penetration a physical properties profile is
collected during penetration by the sensors and electronic module components
within the instrument. The instrument is equipped with three accelerometers for
measuring the dynamics of the instrument, and a porous ring containing a piezo-
electric sensor to measure dynamic pore pressure. It also includes a pressure sensor
on its back end open to the water column for depth measurements along with an
optical sensor used to indicate the penetration of the seabed (ODMIBrookeOcean,
2009).

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The physical properties data collected by this instrument serves two purposes in the
deployment of the piezometer system in Kitimat Arm. The physical properties
acquired with this instrument can be used:
1. To classify the sediment type using the Robertson Classification Scheme
(Robertson, 1990)
2. To define soil characteristic deployment parameters for the piezometer
deployment
The free fall penetrometer will be used to estimate the sediment physical properties
the piezometer will encounter when it is deployed. Parameters of importance
include:
• Dynamic Penetration Resistance (DPR): Will be used to estimate the drop
height and weight of instrument deployment to determine
o Free fall velocity
o Impact force
Figure 5 ODMI Brookes Ocean Free Fall Cone Penetrometer (FFCPT) example deployment on left
and instrument components on right (ODMIBrookeOcean, 2009)

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• Dynamic Pore Pressure (DPP): Will be referenced to ensure that the
piezometric sensor will not exceed its specified maximum pressure rating.
The rating on the selected GEOTech PVT piezometer is 150 mH2O (see
section 5.2.3.1).
3.3.2 Dynamic Penetration Resistance Calculation:
FFCPT view, the software provided with the Brooke FFCPT uses raw accelerometer
data, the geometry and mass of the instrument to calculate dynamic penetration
resistance of the seabed (ODMIBrookeOcean, 2009).
DPR as a function of depth (ܳௗሺ‫ݖ‬ሻ ሺ݇ܲܽሻ) is calculated with the following force
balance (Equation 9):
ܳௗሺ‫ݖ‬ሻ ൌ ሺ‫ܨ‬ூሺ‫ݖ‬ሻ ൅ ‫ܨ‬௚ − ‫ܨ‬஻ − ‫ܨ‬஽ሺ‫ݒ‬ሻሻ/ሺ‫ܣ‬ ∗ 1000ሻ
ൌ ‫ܨ‬௦ሺ‫ݖ‬ሻ/ሺ‫ܣ‬ ∗ 1000ሻ
(Equation 9)
Where:
• ܳௗሺ‫ݖ‬ሻ= Dynamic penetration resistance with dependence of depth below sea bed
(z)
• ‫ܨ‬௦ሺ‫ݖ‬ሻ= Sediment resistive force of penetration (N)
• ‫ܨ‬ூሺ‫ݖ‬ሻ= Impact force (N)
• ‫ܨ‬௚= Weight of the instrument (N)
• ‫ܨ‬஻= Buoyant force on the instrument (N)
• ‫ܨ‬஽= Drag on the instrument dependent on velocity (‫ݒ‬ሺ
௠
௦
ሻ) (N)
• A = Cross-sectional area of the instrument (݉ଶ
)
A profile of the dynamic penetration resistance with depth is created by fcptView.
This method was used for soil property definition. The profile can also be manually

21
calculated from the raw acceleration values. The manual method was used in the
piezometer deployment parameter definition to simplify the calculation.
3.3.3 Piezometer Dynamic Penetration Calculation:
Using unit cancelation the force that the GEOtech Piezometer will encounter when
penetrating the seabed can be estimated by multiplying the piezometers cross
sectional area by the dynamic penetration resistance (ܳௗሺ‫ݖ‬ሻ) (Equation 10):
‫ܨ‬ ൌ ܳௗሺ‫ݖ‬ሻ ∙ ‫ܣ‬ (Equation 10)
Where:
• A = cross-sectional area of the instrument (݉ଶ
)
Further we can determine the work required for the piezometer to penetrate to a
particular depth by integrating the force over that depth (Equation 11):
W=‫׬‬ ‫ܨ‬ሺ‫ݖ‬ሻ݀‫ݖ‬
௭೎
଴
ൌ ‫ܣ‬ ‫׬‬ ܳௗሺ‫ݖ‬ሻ݀‫ݖ‬
௭೎
଴
(Equation 11)
Where
• W= work required to penetrate the piezometer to a depth of ‫ݖ‬௖ (J)
ܳௗሺ‫ݖ‬ሻ as a function can be approximated by fitting a curve or line through the
calculated dynamic penetration resistance depth profile from the FFCPT data. This
enables estimation the resistive force to depths greater than those measured by the
FFCPT. It should be noted that DPR in nature does not definitively vary with depth.
The variability of sediment type plays a significant role in the DPR.
The line fit accuracy can be verified by comparing the integral of the actual DPR
function and the line fit over the measured depth. Because ܳௗሺ‫ݖ‬ሻ is a discrete vector
of elements, a trapezoidal numerical integration is used (Equation 12):

22
‫ܣ‬ න ܳௗሺ‫ݖ‬ሻ݀‫ݖ‬
௭೎
଴
ൌ ‫ܣ‬ ෍൫‫ݖ‬ሺ݊ሻ − ‫ݖ‬ሺ݊ − 1ሻ൯ ∙
ܳௗ൫‫ݖ‬ሺ݊ሻ൯ ൅ ܳௗ൫‫ݖ‬ሺ݊ − 1ሻ൯
2
ேିଵ
௡ୀଶ
≈ ‫ܣ‬ න ܳ௙௜௧ሺ‫ݖ‬ሻ݀‫ݖ‬
௭೎
଴

(Equation 12)
Kinetic energy of the piezometer free falling and gravitational potential energy are
required to perform this work. Water drag is also combined in this work to simplify
the solution. The estimated velocity required can be calculated with (Equation 13:
ܹ ൌ ‫ܧ‬௞ ൅ ‫ܧ‬௉ − ‫ܧ‬஻ ൌ
1
2
݉‫ݒ‬ଶ
൅ ݉݃‫ݖ‬௦ − ݉௪݃‫ݖ‬௦
(Equation 13)
Where:
• ‫ܧ‬௞ = Kinetic energy required to perform the penetration work (J)
• ‫ܧ‬௉ = Gravitational potential energy required to perform the penetration work (J)
• ‫ܧ‬஻ ൌ Buoyant energy resisting the penetration work (J)
• ݉ ൌ Mass of the piezometer deployment (kg)
• ݉௪ ൌMass of sea water displaced by the instrument (kg)
• ‫ݒ‬ ൌ Velocity that the piezometer head impacts the sea bed (
௠
௦మ)
• ‫ݖ‬௦ ൌ Depth of penetration (m)
Note that the buoyant force of the instrument works against the penetration work.
Therefore the mass in (Equation 13 is the mass of the instrument deployment in
seawater.
(Equation 13 can be rearranged to solve for the mass of the instrument required to
penetrate to a selected depth (‫ݖ‬௦) (Equation 14)

23
݉ ൌ ሺܹ − ݉௪݃‫ݖ‬௦ ሻ/ሺ
1
2
݉‫ݒ‬ଶ
൅ ݉݃‫ݖ‬௦ሻ
(Equation 14)
One problem that arises here is that ݉௪ is an instrument property. The assumption
will be made that mass can be added without significantly increasing the volume. To
define the volume of the instrument (Equation 15) will be used.
݉௪ ൌ ܸூߩ௦௪ (Equation 15)
Where:
• ܸூ= Volume of the instrument deployment (݉ଷ
)
• ߩ௦௪= Density of seawater (ߩ௦௪ ൌ 1029݇݃/݉ଷ
)
3.3.4 Sediment Classification based on Physical
Properties from FFCPT:
Sediment behaviour type is derived using the
dynamic penetration resistance and dynamic
pore pressure measured with the FFCPT. The
ODMI Brooke Ocean software package that
comes with the FFCPT utilizes the Robertson
classification scheme to accomplish this
(ODMIBrookeOcean, 2009)(Figure 6).
Robertson (1990) describes that soils that fall
in categories 1 – 4 are generally penetrated in
an undrained condition. These types are
described as:
Figure 6 Robertson soil classification scheme
derived from FFCPT data. Qn is the normalized
dynamic penetration resistance.
7
6
5

24
1. Sensitive fine grained
2. Organic Sediments: wood waste and peats
3. Clays: clay to silty clay
4. Silt Mixtures: clayey silt to silty clay
5. Sand Mixtures: silty sand to sandy silt
6. Sands: clean sands to silty sands
7. Gravelly sand to sand
Generally the sediment behaviour type overestimates the sand composition using
the ODMI Brookes institute FFCPT; this observation is based on comparison with
sediment core grain size distribution.
3.4 Grab Samples for Sediment Composition:
Grab samples are taken from the top layer of the marine sediment, collected with a
large scoop. The Shipek grab sampler was used to collect the samples collected by
the NRCan during the 2015002PGC and the 2015003PGC expeditions (Figure 7).
Grab samples are tested for salinity right after collection. Grab samples were also
collected by Environment Canada in early 2015 (Figure 8).These samples were
tested for salinity at the Pacific Geoscience Centre. Low salinity may indicate a
potential artesian flow, which is one cause of positive effective pore pressure. A low
salinity measurement on a grab sample may indicate fresh water seepage through
the fjord wall. As described in the background section, this fresh water seepage may
have an artesian pressure associated with it. Because this artesian pressure is a
contributor to the effective pore pressure, locations of fresh water seepage are
targets for piezometer measurement.

25
Figure 7 Left: 2015002PGC expedition grab sample station locations; Right: 2015003PGC cruise grab
sample station locations
An anomaly of low salinity was recognized at grab sample STN110 on the
2015002PGC expedition. This low salinity anomaly was verified in the 2015003PGC
expedition during resampling at grab sample STN11 (see section 4 Delta front west).

26
Salinity Measurements:
Grab samples collected by NRCan and by Environment Canada were tested for
salinity with the following procedure.
Procedure:
1. The sample was inspected
for quality, for example
has it oxidized? Is it dry?
2. The sample was
homogenized. This
involves mixing the
sample to homogenize
chemistry.
3. Centrifuge tube was filled
with the sample and
sealed.
4. A batch of 16 samples was
made and put in the
centrifuge for ~20 min at
~4000 rpm
5. The sample will have
separated into liquid and
solid components after being centrifuged. Water was extracted off the top of
the sample using a pipette.
6. 3-4 drops of the sample were placed on a refractometer and the apparent
salinity was measured.
7. The remaining water from the sample was extracted using a pipette into a
glass jar for storage at 4 degrees Celsius.
Figure 8 Environment Canada Grab samples collected in
2015

27
3.5 Marine Sediment Cores:
Marine sediment cores were collected by NRCan during the 2015002PGC and
2015003PGC expeditions using a piston coring method. Piston coring uses weight to
drive tubing into the sea floor. The depth at which the core penetrates the sea floor
depends on the height above the seafloor that you allow the piston to drop from and
the penetration strength of the marine floor. Cores can be logged with depth to
determine sediment stratigraphic structure and composition.
3.6 Instrumentation:
3.6.1 Overview:
The main objective of this thesis is to find the optimal location within the Kitimat
Arm to probe the marine sediment pore pressure using piezometers. Two
autonomous piezometers were deployed on the NRCan September 2015004PGC
expedition (Figure 9). The setup and strategy for this test deployment was
performed at the end of the author’s 2015 summer work term at NRCan. The future
deployment will rely on the strategy outlined in this report (see section 5).
Figure 9 Location of test deployment piezometer. These were deployed September 2015 and are
scheduled for recovery May 2016.

28
3.6.2 Test Deployment of Piezometers:
Figure 10 Piezometer test deployment during the 2015004PGC expedition using ROPOS remotely
operated vehicle
3.6.2.1 Deployment:
Deployment of two piezometers was accomplished aboard the CCGS John. P. Tully
on the 2015004PGC expedition using the ROPOS ROV (remotely operated
vehicle)(Figure 10). The deployment timeline is outlined below:
1. On September.8 2015 three piezometers were programmed as shown in
Table 1 below:
Piezometer ID Measurement Period (min) Pressure Measurement at IOS
Hanger (cBar)
7463 30 9960-9983
7462 30 10260-10283
7459 15 10111-10104
Table 1 Test deployment piezometers programmed on Sept.8 2015, for 2015004PGC cruise
deployment
2. The ship reached the deployment location on September 28 2015.
3. The piezometers’ ceramics were saturated with distilled water on the boat to
ensure that no air bubbles affected the pressure measurements of the
piezometers. It was noted that Piezometer 1 lost some of its water saturation
before entering the sea.
4. ROPOS carried the assembled piezometers to the sea bottom (coordinates in
NAD83 UTM zone 9)(Figure 9):

29
a. Piezometer 1: 520092.221E 5981731.559N at depth = 103 m
b. Piezometer 2: 522444.462E 5982149.540N at depth = 53 m
5. Piezometers were slowly pushed into the marine mud by ROPOS’s
mechanical arm at an attempted velocity of 2 cm/s. They were pushed ~1m
into the mud. Two of the three piezometers were deployed.
6. 100 m buoyant prawn line was attached to the I-bolts on the piezometers.
weighted every 10m by lead weights. This line will be used in the recovery of
the piezometers by dragging for the line.
3.6.2.2 Recovery:
Recovery of the test deployment is scheduled for the May 2016 expedition. Recovery
will be accomplished by dragging an anchor to snag the deployed prawn line.
3.6.3 Controlled Gravity Deployment (CGD):
The monetary expense of using the ROPOS ROV is significant. Also it was noted that
during the test piezometer deployment, the ROV lost grip on one of the piezometers
and was unable to penetrate to its planned depth into the seabed. These problems
have been addressed by using the deployment strategy used by NRCan for a similar
instrument on the Fraser Delta (Lintern et. al, 2002). The design of this method was
created by Thomas and Sills (1990) at the University of Oxford. This method will be
adapted for the Kitimat piezometer deployment and will be referred to as the
Controlled Gravity Deployment in this report (CGD). The CGD will work similar to
the FFCPT and piston sediment coring methods by allowing gravity to perform the
work required to penetrate the seabed with the instrument. The difference will be
that rather than allowing the instrument to free fall, it will be lowered at a
controlled velocity. Mechanical elements developed for the instrument deployed on
the Fraser Delta by Ocean Networks Canada and a 2 tonne torpedo used in piston
sediment coring will be utilized in this adapted design. A special adapter for the
piezometer to connect to these parts is being fabricated, as outlined in this report
(see section 5.4.1 for more details).

30
4 Results: Prospective Deployment Locations:
4.1 Overview:
Using the methods described in section 3, prospective deployment locations for the
piezometers were evaluated. The following section will give a description of each
location along with recommendations for deployment of piezometers. Other survey
recommendations will also be given for each location.
4.2 Moon Bay (Areas 1 & 2):
4.2.1 Location Overview:
Moon Bay is the location of the 1975 slope failure documented by Brown (1979).
The slide scar and debris can be seen in Figure 11, as well as a slump feature to the
south that was defined in AMEC’s 2011 report (AMEC, 2011). As can be seen in
Figure 11 there is a steep sidewall north of the slump. The timing of the event that
created this feature is unknown. It must have formed after the 1975 slide because it
is crosscut by 1975-slide debris. It is possible that the unstable slope conditions that
resulted in the failures north of the slump could also occur at the slump. Pore
pressure measurements on the slump sediments, are required to determine the
stability of this feature. A residual block of sediment (blue polygon, in Figure 11)
north of the 1975 slide scar, did not fail during the 1975 event. Section 4.2.3 will
describe how an autonomous piezometer can evaluate this feature.

31
Figure 11 (a) Multibeam bathymetry of Moon Bay (vertical exaggeration 1.6x). Contour interval: 3.4 m
(b) Bathymetry repeat showing Moon Bay, the location of the 1975 slide (red polygon) and other
features. A slump feature is identified by the yellow polygon. A sidewall cross cut by 1975 slide debris
exists north of the slump. Another possible failure exists to the north of the 1975 slide scar. Inset map
shows location of Moon Bay within Kitimat Arm.

32
4.2.2 Moon Bay South (Area 1):
Description:
Moon Bay south is a subsection of Moon Bay. The feature of interest here is the
slump outlined in Figure 11b. The composition of the sediment was identified in
core 25 as massive bioturbated silty clay mud. Subsurface expressions of the slump
can be seen clearly in Huntech seismic line 28 and 3.5 kHz chirp seismic line 43,
which transect the slump (Figure 12c and Figure 12d). A contact extends from the
failure section underneath the slump morphology. Deformation can also be seen at
the edge of the slump trough that permeates through the stratum. It is possible that
the slump could fail along the contact, where a measurable excess pore pressure
may occur. The seismic sections are at locations where ~ 10 metres of sediment
overlies the contact. It is not practical to penetrate the piezometer to the contact at
this location but looking at 3.5 kHz chirp seismic line 13 it can be seen that the
slumping sediment stratum seems to thin out upslope (Figure 12b).
Recommendations:
A deployment in this location has the benefit of being close enough to shore to allow
for piezometers to be cabled to a communication station on shore. A maximum cable
length of 364 metres will be required for this deployment, which is within the
equipment constraints (see section 5.2.3) (Figure 13). This setup can supply real
time data from the piezometer over a wireless data network.
Piezometer deployment can be made where the slumping sediment package thins
out to ~ 5 metres. Here a 24 m hydraulic gradient can be set up between two
piezometers (P2 and P3). Setting up a known gradient will have some advantages. It
will create a value of comparison for the two piezometers measurements. It will also
capture the down slope hydraulic flow gradient that exists between the instruments
(Figure 13).

33
Figure12(a)MultibeambathymetryMoonBaySouth(verticalexaggeration1.6x).Contourinterval:3.9m.InsetmapshowsMoonBaySouth’s
locationinKitimatArm.(b)to(d)SeismiclinesprocessedwithTheGeologicalSurveyofCanadaAtlanticSeismictoolkit.(b)Seismicline13
showingsedimentabovethecontactthinupslope.Core25ismassivebioturbatedsiltyclaymudandFFCPT52measuredhomogeneousphysical
properties.(c)and(d)Seismicsections43and28showcontactextendingunderslumpedsedimentfromthefailedsection.

34
Figure 13 (a) A Cable and communication station map of a 3-piezometer array. The contours represent
depth (m). (b) Seismic section 13 shows the penetration of the piezometers and the expected hydrostatic
gradient of ~24 m. (c) Sediment thickness map from the AMEC (2011) report with recommended
piezometer placements shown as blue dots.

35
A potential concern is whether or not the piezometers may penetrate through the
sediment to bedrock. The AMEC (2012) report has supplied predicted sediment
thickness maps derived from their seismic survey. All piezometers within this array
should be deployed to 4 metres penetration at a predicted sediment thickness of 5 –
10 metres to avoid impact of piezometers with bedrock (Figure 13).
Another concern during deployment is the slope at which the instruments can be
practically deployed. The recommended piezometer array has P2 deployed at a
slope angle of 22°. If this angle is determined to be too steep for deployment by the
ship captain, then the slope map in Figure 14 can be used to shift the array to a
location of lower slope angle.
Figure 14 Slope map of Moon Bay South. Slope contours are in degrees and vectors are pointing down
slope. P1 is at a slope angle of 18°; P2 is at a slope angle of 22°; P3 is at a slope angle of 17°.

36
4.2.3 Moon Bay North (Area 2):
Description:
Moon Bay North is where the 1975 slide occurred (Figure 15a and Brown, 1979).
A strain line can be seen running down a possible failure block. It is highlighted in
Figure 15a and Figure 15b. Free Fall Cone Penetrometer (FFCPT) data were
processed using the Robertson classification scheme. FFCPT 87 and 82 show
potentially undrained sediments at about a metre depth Figure 15c. It's possible
that this layer runs under the possible failure block. A profile taken across the
FFCPT profile shows how the failure plane may run under the sediment block
(Figure 15d).
Dynamic penetration resistance from free fall cone penetrometer data has been
mapped to determine where the sediment is soft (Figure 16b). Maximum
penetration will occur in soft sediments. It can also be noted that penetration
resistance is relatively high in the slide scar. The sediments here are probably
exposed consolidated sediments.
Recommendations:
A sediment core should be taken to determine the composition of the slide scar and
the over burden. Piezometers should target this layer. It is recommended that an
autonomous piezometer be deployed in soft sediments to the east of the potential
failure at a depth of 3 - 4 metres. The profile in Figure 16c illustrates the piezometer
penetration. A 4 metre penetration can be accomplished with a deployment velocity
of 0.2 m/s and a driving mass of 80kg. These parameters have been determined by
the method described in section 3.3.3, which uses the FFCPT data (Figure 17).

37
Figure15(a)MultibeambathymetryofMoonBayNorth(verticalexaggerationof1.6x).Contourinterval:3.6m.Rednumbersrepresentexpedition
stationsIDs.GreenrectanglesareFFCPTstations.Theredrectangleistestpiezometerdeployment1andtheyellowrectangleisgrabsample11.Red
rectangleindicateslocationofthemultibeamsectionin(b).(b)MultibeambathymetryofapossiblefailureatMoonBayNorth(verticalexaggeration
of12.5x).Contourinterval:3.6m.(c)AcorrelationofFFCPTstationstransectingpossiblefailure.Apossibleundrainedlayerhasbeenrevealedin
FFCPT82and87.(d)Abathymetricprofilederivedfromthemultibeamdataillustratinghowtheundrainedlayermayextendunderthepossible
failure.

38
Figure 16 (a) Multibeam bathymetry map showing proposed autonomous deployment within sediment
block north of Moon Bay. (b) Dynamic penetration contours derived from free fall cone penetrometer
data collected during the 2015002PGC expedition. Consolidated sediment has been exposed on the 1975
slide scar. (c) Soft sediments east of the potential failure are ideal for a 4 metre penetration piezometer
deployment. 4 metre penetration will reach the assumed undrained sediment layer.

39
Figure 17 Work required to penetrate the piezometer to depth calculated using method described in
section 3.3.3. (a) Using FFCPT 80 data (thick black line) we can extrapolate deeper work requirements
with a linear fit (thin black line). A 4 m depth will require ~ 1.4J of work. (b) Using FFCPT 83 data (thick
black line) we can extrapolate deeper work requirements with a linear fit (thin black line). A 4 m depth
will require ~ 1.4J of work which is the same as FFCPT 80
It is not practical to deploy a cabled piezometer in this location because a cable
length of 1000 m would be required. This is greater than the maximum transmission
distance of the piezometer, which is 400 m. The slope gradient here is less than 10
degrees and is not a concern to deployment.
A test deployment piezometer is deployed in the slide scar and is scheduled for
recovery in May 2016.

40
4.3 Kitimat Arm West (Area 3):
Description:
The bathymetry of Kitimat Arm West is shown in Figure 18, along with
seismic lines across the area. At the north end of Kitimat Arm West there is apparent
landslide debris. A sediment package drapes over buried bedrock south of this slide
creating an escarpment. Seismic line 42 (Figure 18c), shows an apparent contact
between sediment and what could be bedrock. Biogenic gas may also be present.
Three seismic lines reveal that there is complex structure beneath the sediment.
Bornhold (2010) made similar observations on a seismic section running parallel to
shore (Figure 19b). He interpreted one of the peaks to be biogenic gas. AMEC (2011)
created a sediment thickness map from these interpretations.
Huntech seismic line 28 is the only place that the reflector can be definitively
interpreted as bedrock Figure 18e. A definitive spherical scattering pattern can be
viewed at this contact. Also bedding apparent within the sediment package drapes
over the bedrock contact.
An interesting 'pock mark' like feature exists at the south end of Kitimat Arm West.
This may indicate fluid flow or biogenic gas. Up slope from this within the sediment
apron a relatively high amplitude reflector with little lateral extent is revealed in
Seismic line 42 (Figure 18c) as well as Bornholds (2010) seismic line (Figure 19b).
Bornhold has interpreted this as biogenic gas but it could be pressurized fluid.
Recommendations for Piezometer deployment:
Seismic data reveal two potential biogenic gas accumulations (Figure 18):
1. Located between two peaks ~ 10 m into the sediment.
2. Up slope from the ‘Pockmark’ within a sediment apron
Piezometer deployment in either of these spots may be of academic interest. An
autonomous piezometer deployed within the escarpment sediment may be of
geohazard interest because of its proximity and relationship with the large slide
scar.

41
Figure18(a)MultibeambathymetryofKitimatArmWest(verticalexaggerationof1.6x).Contourinterval:4.4m.(b)Bathymetryrepeat
showingslidefeaturesandsedimentzonesofpotentialbiogenicgasbuildup.(c)Seismicline42revealspotentialbiogenicgasinsubsurface
andbedrockstructure(d)Seismicline43revealssimilarsubsurfacefeaturesasline42butinterpretationsarehardertomakeduetoapoor
resolutionimage.(e)Seismicline28revealsaclearcontactbetweensedimentandbedrock.

42
Figure 19 (a) Sediment thickness map from AMEC (2011). The piezometer array (P1-P3) has been
mapped to show the expected sediment thicknesses that will be encountered during deployment.
Sediment thicknesses: P1 = 35 to 40 m; P2 = 30 to 35 m; P3 = 10 to 15 m. (b) Seismic profile parallel to
shore through Kitimat Arm West (Bornhold, 2010). Bornhold did not provide an exact navigation profile
for this seismic line but his description roughly places it as shown in (a). A thick sediment sequence
containing biogenic gas is revealed.

43
Figure 20 (a) Kitimat Arm West bathymetry with red rectangle showing the location of the cable layout
map (c). Also three recommended piezometer sites have been mapped (P1-P3). Depths of piezometer
placements are: P1 = 40 m; P2 = 55 m; P3 = 42 m. (b) Seismic section 42 illustrates how piezometers P2
and P3 will penetrate the sediment to ~ 3 m. (c) A cable layout map for Kitimat Arm West. Contour
interval: 5 m.

44
This location is also a prospect for a cabled deployment. It is close enough to the
shore as to be accessible by cable transmission (Figure 20c). The sediment filled
trough has gas at ~ 10 m depth within the sediment so it cannot be practically
reached by a piezometer and it is not revealed to be located any shallower in any of
the data. Therefore it is recommended as a secondary option to the Moon Bay South
cabled deployment (section 4.2.2). A piezometer array has been mapped in Figure
20. Two piezometers (P1 and P2) are placed within the sediment trough with an
expected hydrostatic gradient of ~16 m. The trough can be seen clearly in Figure 21
where the slope vectors converge. Another piezometer (P3) is placed in the ~15
metre package of sediment over the escarpment (Figure 20b).
Figure 21 Kitimat Arm West Slope map. Slope contours are in degrees and vectors are pointing
downslope. P1 is at a slope angle of 9°; P2 is at a slope angle of 8°; P3 is at a slope angle of 15°. P1 and P2
are placed in sediment trough. Converging slope vectors indicate this trough.

45
4.4 Delta Front West (Area 4):
Description:
The bathymetry of Delta Front West is shown in Figure 22a. The blue
polygon shows the location of what Bornhold (2010) described to be 2 - 3 m soft
sediment underlain by course-grained highly reflective deltaic sediment that is
challenging to penetrate with seismic reflection surveying (Figure 22b). An example
of this can be seen in NRCan seismic line 43 (Figure 23). Also this sediment core
109, which is composed of homogenous sandy mud, did not penetrate deeper than
2.2 metres in this location. This may indicate resistance as the core approached the
coarse deltaic sediment. For comparison Core 108 of similar composition
penetrated 4.4 metres in a zone above the eastern sidewall that has apparent
penetration resistances higher than core 109’s location (top 1 metres penetration
resistance of sediment as determined by FFCPT)(Figure 22d). Coarser sediments
will have greater permeability than the fine-grain sediments on the surface. This
greater permeability will facilitate fluid flow. A sand and gravel aquifer exists to the
north that could act as a source of fresh water flow (Figure 22a inset map). This
aquifer location was retrieved from the BC Ministry of Environment data base for
this report (retrieved from: https://catalogue.data.gov.bc.ca/dataset/ground-water-
aquifers, Sept,2015).
Grab sample 110 taken during the 2015002PGC cruise recordedrelatively
low salinity. Grab sample 12 taken during the 2015003PGC cruise confirmed this
low salinity (Figure 22c). It is possible that artesian flow is seeping through the
delta front here and there is excess pore pressure. Grab sample 12 was taken at the
edge of the southern end sidewall. From seismic line 43 it is clear that this is where
the reflective sediments become exposed (Figure 23b). This would support the
theory that fresh water is moving through coarse-grained permeable sediments and
being released at an exposure point of course-grain deltaic sediment to the seabed.
It is less definitive as to why a fresh water signature was measured at grab sample
110. Grab sample 110 is more proximal to FFCPT 92, which measured undrained
conditions possibly caused by artesian pressure (Figure 24).

46
Figure22(a)MultibeambathymetryofDeltaFrontWest(verticalexageration1.6x).Contourinterval:2.1-2.5m.(b)Bathymetryrepeatshowing
sectionof2-3msoftsediment(bluepolygon);lowsalinitygrabsamplelocations;FFCPTindicatingundrainedconditions;Areaofhighpenetration
resistance(yellowpolygon).(c)SalinitycontourmapofKitimatArm.(d)PenetrationresistancecontoursatDeltaFrontWest.Contoursofsalinity
andpenetrationresistanceinterpolatedfromgrabsampleandFFCPTdatarespectivelyusingaweightedaverageinverselyporportionaltodistance

47
Figure 23 (a) Map of Delta Front West showing seismic line 43’s profile. Low salinity grab sample 12 also
shown. (b) 3.5 kHz seismic line 43 reveals a 2-3 m soft sediment layer overlying highly reflective
sediment. Low salinity grab 12 is position where this reflective sediment is exposed to the seabed.

48
Environment Canada grab samples were determined to be contaminated by
leakage and evaporation. Salinity measurements taken were disregarded in this
report.
Recommendations:
An autonomous piezometer would be
able to penetrate the soft sediment layer
2 metres and get close to the apparent
coarse grained deltaic sediments. To
minimize risk of damage to the
instrument it is recommended that the
autonomous piezometer be deployed
between core 109 and FFCPT92 where
sediment physical property conditions
are known to be soft.
Along with this it would be
beneficial to measure salinity with depth in a sediment core. The grab samples only
collect ~0.6 m at most of sediment. If the apparent deltaic sediment is acting as a
fresh water fluid conduit, the salinity in the pore water of the sediment core should
increase towards the highly reflective contact. For consistency it is recommended
that the core be taken near one of the low salinity grab samples. This will have the
benefit of verifying that the grab sample method can provide valuable results when
attempting to find fresh water flow through a delta front.
Figure 24 2015002PGC expedition FFCPT 92
revealed undrained conditions ~0.35 m into the
seabed.

49
4.5 Delta Front East (Area 5):
Delta Front East was where the 1974 slide occurred (Figure 25a and Johns et al.
1984). AMEC (2011) suggested the slide might have been triggered by heavy river
discharge along with anthropogenic channelization of the river that induced
significant undercutting erosion of part of the eastern sidewall slope. The sidewall
slope morphology is outlined in seismic line 43(Figure 25b). There is a possible 16
m unit of sediment that may have been involved in the 1974 slide. Sediment core 21
is sandy-silt to sandy-clay. Test deployment piezometer 2 is deployed here Figure
25a and is scheduled for recovery May 2016.
Figure 25 (a) Multibeam bathymetry of Delta Front East (vertical exageration 1.6x). Contour ~2.6 m. (b)
3.5 kHz sesmic line showing ~16 m sediment package associated with the 1974 slide.

50
5 Results: Instrumentation Specifications:
5.1 Instrumentation specification overview:
Six Geotech piezometers will be deployed on the May 2016 Pacific
Geoscience Centre expedition. Two were deployed in September 2015 and will be
recovered and re-deployed on the May 2016 expedition. Three piezometers will be
deployed autonomously and three will be deployed and cabled to shore.
The Geotech piezometers have constraints that need to be understood for a
successful deployment. The deployment package, cable and instruments are
designed for deployments no deeper than 150 metres below sea level. The limited
memory capacity of 1700 loggings will constrain the maximum autonomous
deployment time to 1.16 years (see section 5.2.1).
The test deployments were mistakenly set to a logging interval that results in
a memory capacity of only 35.42 days. When the Geotech piezometers run out of
memory they begin logging over the oldest loggings. Because of this, the collected
data on the test deployments must be extracted as soon as they are recovered or
data may be lost (see section 5.3.2)
The constraints to cabled deployment will be as follows. Transmission
distances should be no longer than 400 metres. The Pacific Geoscience Center has
1500 metres of cable in its possession, so 400 metres of cable for of the three cabled
piezometer is possible (see section 5.3.3).
The mechanical parts required for deployment are explicitly listed within
this report (see: Appendix 1). These parts should be acquired as soon as possible.
An accelerometer has been selected to accompany the deployment to
measure deceleration during seabed penetration. These measurements can be used
to estimate of the seabed’s dynamic penetration resistance (see section 5.4.5)
A pressure sensor can be mounted to the CGD sleeve to measure the water
depth of the deployment. It can also be used to measure the penetration depth of the
piezometer into the seabed. The RBR Ltd. XR-420 CTD (conductivity-temperature-
depth sensor) can measure up to 250 m water depth so it will be sufficient for this
operation (see section 5.4.6)

51
The following sections of this report outline the justification for the
parameters of the piezometer deployment.
5.2 Constraints List
1. Piezometer battery life: 100000 logs
2. Piezometer memory: 1700 logs
3. Autonomous deployment time: maximum of 1.16 yrs, at a 6-hour piezometer
logging interval
4. Deployment depth: maximum of 150 metres depth below sea level
5. Cable length: maximum of 400 metres
6. Recommended deployment velocity: 0.2 metres/second
7. Deceleration maximum: 16.98 g
8. Mud plate dimensions: minimum of 0.63 m x 0.63 m
5.3 Geotech piezometer constraints:
5.3.1 Battery and Memory Capacity
The Geotech piezometer deployment periods are limited by their battery and
memory capacity (Table 2). For example a logging interval of 309 min (5.15 hours)
will result in the piezometer running out of memory in 1 year and result in the
battery running out in 59 yrs. The memory capacity is the main constraint of the
instrument.

52
Table 2. Geotech Battery and Memory capacity. The time until memory runs out is calculated by
multiplying the memory capacity by the logging interval. The time until battery runs out is calculated by
multiplying the battery capacity by the logging interval. Capacity specifications are sourced from
Geotech Website (Geotech, 2015). These specifications have been confirmed with Martin Carlson at
Geotech (personal communication, Feb 12. 2016). A 6-hour logging interval (red highlight) is
recommended as the minimum.
Battery
Capacity (loggings)
Memory Capacity
(loggings)
100000 1700
Instrument
specs
Logging
Interval (min)
Interval
(hrs)
Time until
memory runs
out (days)
Time until
battery runs out
(days)
Min interval 1.00 0.02 1.18 69.44
15.00 0.25 17.71 1041.67
30.00 0.50 35.42 2083.33
144.00 2.40 170.00 10000.00
309.18 5.15 365.00 21470.59
360 6 425 25000
Max interval 1440.00 24.00 1700.00 100000.00
In addition to the limitation in memory capacity it should be noted that when
the memory runs out, the instrument will begin to overwrite the oldest loggings.
Therefore autonomous deployments will need to be collected before the memory
runs out or risk losing the deployment loggings of the piezometer. This has been
confirmed with Martin Carlson at Geotech (personal communication, Feb 12. 2016).
What is the minimum acceptable logging interval? Because the tide signal
contributes to pore pressure, this signal should be captured in measurement so it
can be properly processed. The Nyquist-Shannon theorem should be applied here
(Nyquist, 1928).
The Kitimat Arm tide cycle is diurnal, with a period of ~12 hours. Nyquist’s theory
states that the logging interval will need to be half the period in order to capture this
signal. Therefore the logging interval will need to be 6 hours or less. A 6 hour
logging interval will provide 1.16 years of memory capacity
5.3.2 The Piezometer Test Deployment Memory Capacity Issue Addressed
Unfortunately due to user error the test deployments have been set to a
logging interval of 30 min. This will only provide a memory capacity of 35 days. The

53
instrument recovery in May 2016 will find that these piezometers have retained
only the previous month of loggings.
Because the piezometer overwrites older loggings when it runs out of
memory it will be critical to extract the data from the piezometers as soon as they
are recovered or risk losing deployment data.
5.3.3 Cabled Deployment Constraints
5.3.3.1 Cable transmission distance
The Ölflex cables used with the Geotech piezometers are confirmed to
transmit data up to 500 metres (Martin Carlson, Geotech, personal communication,
Feb 5 2016). This was confirmed in a deployment offshore Norway, using unspliced
cable.
A 250-metre spool of cable has been supplied with each of the 6 Geotech
piezometers. Therefore 1500 metres of cable is available for the deployment.
3 piezometers will be cabled so 500 metres of cable will be available for each
piezometer. Because the cable will be spliced, transmission will need to be tested on
the 500-meter length of cable in the lab. It may be found that 400 metres of
transmission is all the piezometers are capable of.
5.3.3.2 Other cable specifications
The piezometers and cable should be deployed to no more than 150 metres
water depth (Martin Carlson, Geotech, personal communication, Feb 12 2015). The
breaking force of the Ölflex cable has been calculated from its tensile strength of
2300 psi to be 117 lbs (Lapp Group, 2015). The low tensile strength of the cable
means that it will need to be reinforced with prawn line. The prawn line will also be
used to recover the piezometers.
5.3.4 Sampling Rate During Deployment
During deployment of cabled piezometers, a dynamic pore pressure profile
can be taken of the piezometer penetration. This will require direct connection from

54
the piezometer to a computer for logging. The ‘SCAN’ command can be sent to the
piezometer to output a string of the following form every 0.8 seconds:
• S , M , P , T , U [CR][LF]
Where: S is the serial number of the piezometer; M is the mode (0= Not logging;
1=logging); P is the absolute pressure in pascals, multiplied by 10; T is the absolute
temperature in celsius times 10; U is the battery voltage multipled by 10 (Geotech,
2015). A serial terminal can be used to record these strings during deployment.
5.4 Deployment fabrication:
5.4.1 Controlled Gravity Deployment (CGD)
Figure 26 Conceptual diagram of the CGD strategy.
Controlled gravity deployment (CGD) will be used to deploy the piezometers
in Kitimat Arm. The technique works as displayed in Figure 26. The deployment and
sleeve are coupled together before deployment. The sleeve is attached by wire to
the winch on the ship. The deployment weight is supported on the sleeve by rotating
wings through slots on the sleeve.
1. At time 1 the CGD is lowered through the water column at a constant velocity
(v(t)). The wings support the deployment weight with normal force (Fn).
2. At time 2 the tip of the deployment contacts the seabed. This puts an upward
force (FSed) on the deployment. The force FSed overcomes Fn meaning that

55
the weight of deployment is relieved from the wings. The wings fold into the
deployment under their own weight through slots on the sleeve.
3. At time 3 the deployment has penetrated the seabed to the mud plate. The
CGD is stationary at this point. The wings have folded completely into the
deployment.
4. At time 4 the winch wire back to the ship hoists the sleeve. The wings no
longer obstruct the removal of the sleeve so the deployment is left on the
seabed.
5.4.2 Sea Bed Penetration Resistance
The deceleration of the instrument as it penetrates the seabed will be
proportional to the penetration resistance of the seabed. Free fall cone
penetrometer (FFCPT) data can be used to approximate the penetration resistance
that will be encountered in an area (see section 3.3.3). The piezometer will need to
overcome the penetration resistance in order to penetrate the seabed to a chosen
depth.
5.4.3 Deployment Velocity of Controlled Gravity Deployment
The winch selected for the CGD deployment has the ability to regulate
rotational velocity. Velocities of 0.2 m/s will be attempted. For cabled piezometers a
slower deployment velocity will result in a higher dynamic pore pressure depth
resolution. As stated in section 1.4 the sample period during deployment is 0.8 s
(5.3.4). A deployment velocity of 0.2 m/s will give a measurement of dynamic pore
pressure every 0.16 m during sea floor penetration (Table 3).

56
Table 3. Depth resolution of dynamic pore pressure profile based on deployment velocity. Depth
resolution equals deployment velocity multiplied by the logging rate of 0.8 loggings per second.
Deceleration has not been accounted for in this calculation.
Deployment Velocity (m/s) Depth Resolution (m) Loggings per Meter (loggings/m)
0.1 0.08 12
0.2 0.16 6
0.3 0.24 4
0.4 0.32 3
0.5 0.4 2
0.6 0.48 2
0.7 0.56 1
1 0.8 1
5.4.4 Mud Plate Size
Figure 27 Force balance during deployment impact with seabed. FG is the force of gravity; FS is the
penetration resistance of the seabed; FB is the buoyant force; FD is the force of drag.
The deployed instrument should penetrate no deeper then the mud plate of
the instrument. Consider a driving mass of ~2000 kg which is the weight of the lead
filled torpedo that is used by NRCan for piston coring. The area of the mud plate (A)
will be calculated from the force balance during penetration (Figure 27). ܳௗሺ‫ݖ‬ሻ is
the penetration resistance at a depth below the seabed (z). The units of ܳௗሺ‫ݖ‬ሻ are
kPa. Assume ‫ݏ݅ ܩܨ‬ ≫ ‫.ܦܨ & ܤܨ‬
It is also assumed that penetration resistance against the piezometer is
significantly smaller then the mud plate area. This is a good approximation because

57
the cross sectional area of the piezometer is significantly smaller than the mud plate.
Therefore piezometer penetration resistance can be ignored.
Newton’s second law:
ܳௗሺ‫ݖ‬ሻ ൌ ሺ݉ܽ ൅ ‫ܨ‬௚ሻ/ሺ‫ܣ‬ ∗ 1000ሻ ൌ ‫ܨ‬௦ሺ‫ݖ‬ሻ/ሺ‫ܣ‬ ∗ 1000ሻ (Equation 16)
To stop the deployment at the mud plate the sediments penetration must be greater
than the gravitational force:
ܳௗሺ‫ݖ‬ሻ ∗ ‫ܣ‬ ∗ 1000 > ‫ܨ‬௚
(Equation 17)
Therefore the area of the mud plate can by calculated be rearranging Equation 17:
‫ܣ‬ > ‫ܨ‬௚/ሺܳௗሺ‫ݖ‬ሻ ∗ 1000ሻ (Equation 18)
ܳௗሺ‫ݖ‬ሻ may be the average or minimum dynamic penetration over 10 cm, calculated
from the 2015PGC002 free fall cone penetrometer data (Figure 28). In other words,
the mud plate should not penetrate the seabed more than 10 cm.
Figure 28 Free fall cone penetrometer dynamic penetration resistance averaged over the top 10 cm of
the seabed. The mud plate can be calculated by considering the minimum and average dynamic
penetration resistances for all the samples.
From Equation 18 the mud plate area required for the minimum and average
dynamic penetration resistances can be calculated (Table 4). A square piece of

58
plywood with dimensions 0.63 m x 0.63 m or a circle mud plate of 0.45 m diameter
would be large enough to stop the 2 tonne penetration.
Table 4. Mud plate geometry calculated using dynamic penetration data measured with free fall cone
penetrometer and Equation 1.
Minimum Resistance (50 kPa) Average Resistance (125 kPa)
Area of mud plate
(m^2) 0.39 0.16
Circular mud plate
diameter (m) 0.71 0.45
Square mud plate
side length (m) 0.63 0.40
5.4.5 Accelerometer for Measuring Dynamic Penetration Resistance During
Deployment
Dynamic penetration resistance can be measured during the piezometer
deployment by mounting it to the sleeve. The maximum g experienced by the free
fall cone penetrometer during the 2015002PGC expedition was 16.98 g so an
accelerometer with at least 0-17g is needed (Figure 29).
Figure 29 The maximum deceleration experienced by free fall cone penetrometer.
The accelerometer needs to internally log data and it needs to be put inside a
pressure canister. The Micro DAQ 3-Axis Shock, Pressure, Humidity and
Temperature Data Logger meets these specifications ($799 USD). Purchase can be
made at: https://www.microdaq.com/madgetech-shock-pressure-humidity-
temperature-data-logger.php (accessed Feb.28 2015). The -50 to 50 g version has
an appropriate range. The uncertainty is +-1.0 g. The dimensions of the

59
accelerometer are 8.9 cm x 11.2 cm x 2.6 cm. A pressure canister of inner
dimensions 12 cm length, and 10 cm diameter will be needed to house this
instrument. The Mag tech software and USB package will be required for
programming this device ($119 USD), available from:
https://www.microdaq.com/madgetech-ifc200-software-interface-kit.php
(accessed Feb.28 2015).
5.4.6 Pressure Sensor for Measuring Depth During Deployment
A pressure sensor will be mounted
to the sleeve for recording depth during
deployment (Figure 30). The pressure
sensor can also verify the penetration of
the piezometer by adding a depth-offset
equal to the distance from the pressure
sensor to the tip of the piezometer. The
RBR Ltd. XR-420 CTD can measure up to
250 m water depth so it will be sufficient
for this operation. ASL Environmental
leases this instrument for $30 a day with a
set up cost of $200 (Rates retrieved from:
http://www.aslenv.com/Leasingrates.ht
ml, accessed Feb, 2015)
Figure 30 Using the pressure sensor to
determine penetration depth of the
piezometer. A depth offset is added to the
measured depth.
Pressure

60
5.4.7 Mechanical Components of the Controlled Gravity Deployment (Figure 31)
Figure 31 Mechanical components diagram. P1 is the sleeve/deployment coupling; P2 is a Subconn Male
to Female connector junction; P3 is a cable splice; P4 is a steel butt weld flange; P5 is a plywood mud
plate; P6 is a steel nipple; P7 is the Geotech piezometer assembly. (NOT TO SCALE)
• P1: The slip sleeve/deployment coupling (P1) mechanism is being drafted in
solid works. Six will need to be fabricated for the six deployments.
• P2: Subconn male to female connector junction. This will make deployment
more efficient because the cable spool can be connected to the piezometer
quickly before deployment.
• P3: Cable splice
• P4: This part is a 1” schedule 40, 316 stainless steel butt weld flange. It will
need to be welded to P6.
• P5: Plywood mud plate. Plywood will be used because it will rot out during
deployment making the instrument easier to recover. The plywood will be a
square 0.63 m x 0.63 m as determined in section 5.4.4. The mud plate will be
bolted to P4.
• P6: Steel nipple of length 1 to 3 metres. The pipe specifications are 1”
schedule 40, 316 stainless steel nipple. The instrument cable will be threaded
through this steel pipe. This steel pipe will be threaded into the piezometer
(P7).
• P7: Geotech Piezometer.

61
Parts List:
Table 5. Parts list for six piezometers, three to be cabled and three to be autonomous (For full details see
Appendix 1).
Part Description Number of parts
needed
P1 Sleeve/deployment coupling mechanism 6
P2-M Subconn Micro Circular series -2 or 3 Male 6
P2-F Subconn Micro Circular series -2 or 3 Female 3
P2-F-dummy Subconn Micro Circular series -2 or 3 Female dummy 3
P3 3-4 ft Vinyl tubing. 6 X Epoxy. 1
P4 1” schedule 40, 316 stainless steel butt weld flange 6
P5 4’ x 8’ ¾’ thick plywood sheet 1
P6 – 2 m (6 ft) 1” schedule 40, 316 stainless steel nipple 6 ft length 2
P6 – 3 m (10 ft) 1” schedule 40, 316 stainless steel nipple 6 ft length 1
5.5 Parts required
• See Appendix 1
5.6 Assembly plan
5.6.1 Cable Splice to Connector:
1. A short length of vinyl tubing will be cut and the wire will be threaded through it.
2. The conducting wires will be soldered and taped.
3. The vinyl tubing will then be slid to encapsulate the splice and taped into
position at one end.
4. The vinyl tubing will be filled with epoxy. This will seal the splice watertight.
5. The cable leading from piezometer and a male subconn connector will be striped
to expose conductors.
6. A short length of vinyl tubing will be cut and the wire will be threaded through it.
7. The conducting wires will be soldered and taped.
8. The vinyl tubing will then be slid to encapsulate the splice and taped into
position at one end.
9. The vinyl tubing will be filled with epoxy. This will seal the splice watertight.
5.6.2 Coupling Cable with Prawn Line
1. 500 metres of cable will be put on a single spool
2. 500 metres of prawn line will be put on a second spool
3. The cable and prawn line will be unspooled evenly and taped every 3metres
4. The pared cable and prawn line will be rolled onto an empty spool
5. This will be done for 3 lengths of 500 metres

62
5.6.3 Pipe Fitting:
1. The butt weld flange will be welded to the steel nipple
2. The Ölflex cable connected to piezometer will be threaded through a 1” steel
nipple
3. The steel nipple will be threaded to piezometer
4. Piezometer will be set aside for deployment
5.6.4 Onboard:
1. The prepared deployment will be bolted into the sleeve/deployment coupling
2. The instrument will be plugged into the 500 metre length of cable coupled with
prawn line
5.6.5 Programming:
1. Piezometer cable will be connected to the Geotech piezometer USB interface and
expedition computer
2. The Geotech piezometer will be used to set the date, time and sampling interval
for the piezometer. Logging will than be initiated.
3. For autonomous piezometers this is all that is necessary
4. For cabled piezometers, a terminal software (such as putty) will be used to
monitor the deployment. The ASCI output should be printed into a .txt file
5.6.6 Deployment:
Autonomous:
A CGD will deploy the instrument.
Cabled
1. The cable will be unspooled and a figure of 8 wrapping will be made on the
speed boat
2. The speedboat will drive to shore with the cable end that is monitoring the
piezometer. The cable will be allowed to sink to the sea bed
3. A CGD will deploy the instrument. The data will be collected during this
deployment.
4. The cable will be moored at shore

63
5.7 Calibration
It has been noted that the piezometers can drift over time. In fact, they have already
drifted since their manufactured calibration (Table 6).
Table 6 Piezometer measurements at sealevel (Pacific Geoscience Centre Sidney, BC). Errors calculated
using the expected pressure (Environment Canada YYJ weather station: March.30 2016)
Date Time Piezometer
Measured
pressure
(kPa)
Standard
deviation
(kPa) Location
Expected
(Victoria
Airport) (kPa)
Error
(kPa)
expected
error (kPa)
30-03-2016 8:30 7133 104.16 office 101.9 2.26 0
30-03-2016 11:19 7133 104.27 0.0206 office 102 2.27 0
30-03-2016 8:30 7461 103.49 0.0864 office 101.9 1.59 -0.2943
30-03-2016 11:29 7461 103.5 0.0706 office 102 1.5 -0.2943
30-03-2016 10:40 7460 103.53 0.0807 hanger 102 1.53 -0.2943
30-03-2016 10:44 7464 103.17 0.0813 hanger 102 1.17 -0.2943
Calibration reports supplied by the manufacturer Geotech produced linear curves
with depth so the drift will be assumed to be constant with depth. Measurements of
the piezometers sea level pressure will be taken before and after deployment. A
linear extrapolation between the initial and final calibration values will be made
over time to determine the amount of drift that has occurred with time.
5.8 Instrumentation Conclusion:
Six piezometers will be deployed on the Pacific Geoscience Centre May 2016
expedition. Three will be deployed cabled to the shore and three will be deployed
autonomously. The piezometers cannot be deployed below 150 metres below sea
level. The length of cable for each piezometer cannot be longer then 400 metres. The
piezometers should be set to a logging interval of a minimum of 6 hours. The logging
interval must be long enough to produce a memory capacity that lasts the entire
deployment period. An accelerometer and pressure sensor will be mounted to the
deployment sleeve for monitoring the deceleration and depth of the deployment
respectively.
Parts are required for the controlled gravity deployment method. These
parts are listed in Appendix.1.

64
6 Discussion and Conclusion:
6.1 Discussion of Prospective Deployment Locations
The methods used in this report have produced evidence for undrained
conditions in at least 4 of 5 evaluated locations that will be valuable targets for
piezometer deployment. It has been demonstrated that the Free Fall Cone
penetrometer is an effective instrument that can effectively be used to survey the
physical properties of the seabed. The FFCPT was also compared with the
piezometer deployment, which will utilize the same physical principals as the
FFCPT. The addition of geotechnical measurements from core sample will be of
great value for verification of the results that have been produced by the free fall
cone penetrometer.
Two cabled deployment plans have been described in section 5. These are
the Moon Bay South cabled deployment and Kitimat Arm West cabled deployment.
Only one of these options is possible with the resources available. The priority
deployment should be the Moon Bay South cabled deployment because penetration
to the required depths is achievable with the current instrument setup. The
maximum data transmission distance of the Geotech piezometer along an unspliced
Ölflex cable is 500 metres. Because splicing will occur it is important that the
transmission capabilities of the piezometers are tested in the lab. The three
remaining autonomous piezometers should be distributed between the other three
areas, those being Moon Bay North, Kitimat Arm West and Delta Front West.
This report does not lay out the logistical plan for the set up of the
communication station required to transmit the cabled piezometer data back to the
Sidney, British Columbia office. This will be a project for the following year after the
scheduled May 2016 deployments.

65
Two sections of Moon Bay have been looked at due to this location’s
historical relevance to slope stability in the Kitimat Arm. The association of
anthropogenic changes (AMEC, 2011) on the slope in Moon Bay makes it an
excellent case study for mitigating potential human induced slides in the fjord. More
information about the subsurface here is required to pin point the exact set of
circumstances that resulted in failure.
A large package of sediment on a steep escarpment exists at Kitimat Arm
West. Probing this sediment with piezometers at the north end may give insight into
the conditions that caused the north end slope failure. At Kitimat Arm West the pock
mark feature stands out. This feature’s association to biogenic gas by Bornhold
(2010) is interesting. It may also be a result of fluid flow. The bedrock geology
seams to play an important role in this sedimentological feature. Future studies of
the bedrock geology here may help support fault line discoveries that Conway et. al
(2012) made about the Kitimat Arm and Douglas Channel.
The low salinity values produced at Delta Front West are anomalous even
when compared with grab samples across the delta front. This suggests that the
aquifer mapped by the BC Ministry of Environment has fluid pathways to this
particular part of the delta. The BC government used water well data associated
with this particular aquifer to define the current extent sand-gravel aquifer. It will
be of value in the future to collect terrestrial bore hole data so that a higher
resolution ground water map can be made. The assumptions made about artesian
flow within this report were based on statements by Morrison (1984) who referred
to borehole data from the Alcan wharf construction. These were not obtained for
this report and may be lost. Therefore at this point there is no direct evidence for
artesian flow into the delta front or fjord walls of Kitimat Arm.
Delta Front West is also unique to the delta front in the fact that it has under
gone anthropogenic alteration such as dredging and fill of the deltaic sediment

66
(AMEC, 2011). This probably has had a significant effect on the fluid dynamics
within this section of the delta front.
The contamination of Environment Canada grab samples can be used as an
example of how difficult it can be to measure in situ properties of the seabed. For
pore pressure salinity specifically, salinity measurements of pore pressure must be
done before the sample has been exposed to the atmosphere for long periods of time
allowing water to evaporate and produce anomalously high salinity values. It would
be interesting to experiment with in situ resistivity measurements for the purpose
of salinity measurements with depth. An instrument of this type has been designed
by Rosenburger et al. (1998) although it was used to determine sediment behaviour
type in deep waters as opposed to fresh water seepage through sediment in fjord
basins. Future work developing an instrument that uses a free fall deployment
method to penetrate the seabed with a resistivity sensor could provide high-
resolution maps of fresh water seepage into fjord systems.
6.2 Other Considerations of the CGD
The execution of the controlled gravity deployment will require the assembly
procedures to be complete. Some potential failures to deployment include:
1. Piezometer cable becoming tangled with the winch wire
2. Cable detachment from logging computer
3. Pressures exceeding rating on instrument due to high penetration velocity
4. Impact of instrument with bedrock
5. Improper programming of piezometer
Therefore it will be important for the participants of the deployment to be well
familiarized with the logistics described in this report to avoid these pitfalls. Strout
and Tjelta (2005) mention communication about deployment as being critical to
achieve successful piezometer deployment. Their experience with a deployment
offshore Norway at the Ormen Lange Gas Field resulted in this conclusion.

67
6.3 Data Collection Discussion
The piezometer test deployments to be retrieved in May 2016 contain a month of
data from the April freshet. The data can be analyzed to determine how significant
the excess pore pressure is. Unfortunately the mean annual pore pressure will not
be available for comparison. The dissipation curve that would have been created by
the induced pressure during deployment will not be retained in the logging memory.
The dissipation curve can be used to measure the permeability of the sediment at
the deployment location (Strout and Tjelta, 2005). A calibration value measurement
will need to be taken from the test deployment piezometers before they are
redeployed.
The long term measurement curve to be captured by the May 2016 piezometer
deployments will be valuable because they will contain a dissipation test and after
the sediment re-equilibrates to the environmental conditions, an insitu pore
pressure (Strout and Tjelta, 2005). Delays in the in situ pore pressure in response to
the tide and seasonal signals will be valuable information (Vanneste et. al, 2013).
Along with this, the relationship between piezometers that are proximal to one
another will produce a spatial understanding of the sediment fluid mechanics.
6.4 Future Piezometer Deployment Discussion
Future piezometer deployments may include a multi-sensor instrument that
can capture a pressure profile with depth. This was noted as ideal by Vanneste et. al.
(2013) in their attempt to monitor the Finneid fjord slope stability with piezometers
off shore Norway. This kind of setup would reveal the hydraulic permeability of the
sediment package it transects as long as the fluid pathway along the steel shaft is
restricted. The instrument utilized by Lintern et. al (2002) on the Fraser delta has
multilevel pressure sensors. This system also can be calibrated in situ by
intermittently exposing all of the sensors to the known seabed pressure and
measuring the drift. This design may be valuable for the Kitimat Arm but requires
significantly greater costs in research and development.

68
Vanneste et al. (2013) also explain the importance of long term deployments
(5-10 yrs) to capture enough data to investigate the effects of rainfall, snow melt,
seasonal change and tide interactions. The cabled piezometer array may survive for
about 5 – 10 yrs but the autonomous piezometers will only provide a one-year
glimpse of this system. Remembering Nyquist’s (1928) theorem, double the period
is necessary to capture a valuable data signal. In the case of seasonal change two
years would be the minimum. If you consider the effects on precipitation of El Niño,
which occurs ~3-5 years (NOAA, 2016) the required period of measurement would
be 6 – 10 yrs. This kind of infrastructure would be a significant investment.
6.5 Conclusion
In conclusion, five zones in the Kitimat Arm have been outlined here as
recommended locations to deploy piezometers, as part of a slope stability hazard
assessment being undertaken by Natural Resources Canada. The purpose of
deploying piezometers is to measure positive excess pore pressure. Positive excess
pore pressure can destabilize a slope. The controlled gravity deployment strategy is
presented as an effective way of deploying piezometers in Kitimat Arm.

69
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Duncan, J. M. & Wright, S. G. (2014). Soil Strength and Slope Stability. New Jersey: John Wiley and
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Geotech (Feb, 2015). Piezometer-Pore water pressure. Retrieved from:
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