Geotechnical and Hydrotechnical Overview Assessment

M A D R O N E E N V I R O N M E N T A L S E R V I C E S L T D .

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DISTRICT OF KITIMAT LAND CONSTRAINT AND SUITABILITY STUDY

Geotechnical and Hydrotechnical

Overview Assessment

FOR:

Westland Resources Limited, and District of Kitimat BY:

Roberta Adams, M.Sc., G.I.T. Gordon Butt, M.Sc., P.Geo. Madrone Environmental Services Ltd. February 16, 2018 (updated August 24, 2018)

D O S S I E R : 1 7 . 0 3 5 7 M A D R O N E E N V I R O N M E N T A L S E R V I C E S L T D .

F I L E : \ \ F S 4 \ A C T I V E D O S S \ P R O J E C T S \ 1 7 . 0 3 5 7 \ F I N A L R E P O R T \ 1 7 . 0 3 5 7 T E R R A I N A S S E S S M E N T

D O K L C S S _ F I N A L T O C L I E N T . D O C X

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TABLE OF CONTENTS

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

1.1 BACKGROUND INFORMATION ......................................................................................... 4

2 METHODOLOGY ............................................................................... 5

2.1 LIDAR ANALYSIS ............................................................................................................... 5

2.2 AIR PHOTO ANALYSIS ...................................................................................................... 5

2.3 TERRAIN CLASSIFICATION SYSTEM ................................................................................. 8

2.3.1 SURFICIAL MATERIAL ................................................................................................. 9

2.3.2 GEOMORPHOLOGICAL PROCESSES ........................................................................11

2.4 TERRAIN STABILITY CLASSIFICATION ............................................................................ 12

2.5 HYDROTECHNICAL ANALYSIS .........................................................................................13

3 GEOMORPHIC SETTING ................................................................... 14

3.1 BEDROCK GEOLOGY ....................................................................................................... 14

3.2 SURFICIAL GEOLOGY AND QUATERNARY HISTORY ..................................................... 14

3.3 CLIMATE .......................................................................................................................... 18

3.4 HYDROLOGY ................................................................................................................... 18

3.5 RESOURCES .................................................................................................................... 20

3.5.1 MINERAL POTENTIAL............................................................................................... 21

4 GEOTECHNICAL IMPLICATIONS ...................................................... 23

4.1 NATURAL HAZARDS ....................................................................................................... 23

D I S T R I C T O F K I T I M A T P A G E T O C - I I

G E O T E C H N I C A L A N D H Y D R O T E C H N I C A L O V E R V I E W A S S E S S M E N T F E B R U A R Y 1 4 , 2 0 1 8


4.1.1 FLOODING ................................................................................................................ 23

4.1.2 STREAM EROSION AND AVULSION ......................................................................... 26

4.1.3 LANDSLIDES ............................................................................................................. 30

4.1.4 SNOW AVALANCHES ............................................................................................... 36

4.2 SEISMIC CONSIDERATIONS ............................................................................................ 36

4.3 SENSITIVE CLAYS ............................................................................................................. 37

5 CONCLUSION AND RECOMMENDATIONS ....................................... 40

5.1 HAZARD ACCEPTABILITY THRESHOLDS ........................................................................ 40

5.2 DEVELOPMENT PERMIT AREAS ..................................................................................... 41

5.2.1 FLOOD HAZARD ....................................................................................................... 44

5.2.2 STREAM EROSION HAZARD .................................................................................... 44

5.2.3 HILLSLOPES AND UPLANDS HAZARD ..................................................................... 47

6 CLOSURE ........................................................................................ 49

7 REFERENCES .................................................................................. 50

8 LIMITATIONS .................................................................................. 52

8.1 LIMITATIONS ON LIABILITY ............................................................................................ 53

8.2 INTELLECTUAL PROPERTY ............................................................................................. 53

D I S T R I C T O F K I T I M A T P A G E T O C - I I I



LIST OF FIGURES

FIGURE 1: LAND CONSTRAINT AND SUITABILITY STUDY PROJECT AREA MAP. .......................... 3

FIGURE 2: DIGITAL ELEVATION MODEL OF THE STUDY AREA FROM LIDAR DATASET OF 1 M RESOLUTION PROVIDED BY DOK. ..................................................................................... 6

FIGURE 3: AIR PHOTO COVERAGE FROM DOK (BLUE) AND GEOBC (RED LINES, 2003). ............... 8

FIGURE 4: DOMINANT SURFICIAL MATERIAL OF THE STUDY AREA, AS DETERMINED BY DESKTOP ANALYSIS OF LIDAR AND AIR PHOTO ANALYSIS. ....................................................... 17

FIGURE 5: MINERAL POTENTIAL IN THE DOK REGION. ............................................................... 22

FIGURE 6: FLUVIAL FANS (ORANGE) AND FLUVIAL PLAINS (YELLOW) WITHIN THE STUDY AREA. .................................................................................................................................... 28

FIGURE 7: WATERCOURSE DISTRIBUTION AS MAPPED BY FRESHWATER ATLAS WITHIN THE STUDY AREA. ........................................................................................................... 29

FIGURE 8: OBSERVED LANDSLIDES AND OTHER EVIDENCE OF INSTABILITY IN THE STUDY AREA, AS DISCOVERED THROUGH DESKTOP ANALYSIS OF LIDAR DATA. .....................31

FIGURE 9: DOMINANT GEOMORPHOLOGICAL PROCESSES WITHIN THE STUDY AREA. ........... 34

FIGURE 10: RECONNAISSANCE TERRAIN STABILITY MAPPING (RTSM). ..................................... 35

FIGURE 11: MAPPED GLACIOMARINE SEDIMENTS (PURPLE) AND FIELD CONFIRMED LOCATIONS OF SENSITIVE CLAYS FROM LITERATURE (PINK DOTS). ......................................... 39

FIGURE 12: HAZARD ACCEPTABILITY DEVELOPMENT, FROM CAVE (1993). ............................... 40

FIGURE 13: GENERAL GEO-HAZARD DPA MAP FOR THE STUDY AREA. ...................................... 42

FIGURE 14: AREAS POTENTIALLY SUSCEPTIBLE TO FLOODING. ................................................ 46

FIGURE 15: POTENTIAL EXTENT OF HILLSLOPE AND UPLANDS HAZARD AREA WITHIN THE STUDY AREA. ........................................................................................................................ 48

D I S T R I C T O F K I T I M A T P A G E T O C - I V



LIST OF TABLES

TABLE 1: DESCRIPTION OF TERRAIN MAPPING PROJECT DATA, ADAPTED FROM STANDARDS FOR DIGITAL TERRAIN DATA CAPTURE ................................................................... 8

TABLE 2: DOMINANT SURFICIAL MATERIAL WITHIN THE STUDY AREA WITH APPROXIMATE AREA COVERAGE. ............................................................................................... 16

TABLE 3: CLIMATIC CONDITIONS OF THE STUDY AREA DURING THE PERIOD 1981 TO 2010. ......................................................................................................................................... 18

TABLE 4. WATERSHED CHARACTERISTICS .................................................................................. 20

TABLE 5. ESTIMATED 200-YEAR MAXIMUM DAILY MEAN DISCHARGE ...................................... 24

TABLE 6: GEOLOGICAL PROCESSES THAT OCCUR IN THE STUDY AS OBSERVED THROUGH DESKTOP ANALYSIS OF LIDAR .................................................................................. 32

TABLE 7: SLOPE STABILITY CLASS OF THE STUDY AREA, AS DETERMINED FROM DESKTOP ANALYSIS OF LIDAR. ................................................................................................... 33

TABLE 8. PEAK GROUND ACCELERATION AND SPECTRAL ACCELERATIONS AT ........................ 37

TABLE 9: HAZARD ACCEPTABILITY THRESHOLDS FOR A NEW BUILDING, AS PER CAVE (1993). ......................................................................................................................................... 41


DISTRICT OF KITIMAT LAND CONSTRAINT AND SUITABILITY STUDY

Geotechnical and Hydrotechnical

Overview Assessment

1 Introduction

Madrone Environmental Services Ltd has been contracted by Westland

Resources Limited to provide a geotechnical and hydrotechnical overview as part of a Land Constraint and Suitability Study for the District of

Kitimat.

The Land Constraint and Suitability Study Project Area (LCSS Project Area or Study Area) focuses on an undeveloped portion of the District of

Kitimat located on the west side of the Douglas Channel. The boundary

extends from the old Eurocan facility in the north to Miskatla Inlet in the

south.

The Study Area is divided into two areas:

The West Douglas Channel Corridor Analysis Study Area

(WDCCA Study Area): The Ministry of Transportation commissioned the West Douglas Channel Corridor Analysis to

assess existing infrastructure and future infrastructure needs of

potential industrial developments within the District of Kitimat

(WSP Canada Inc. 2016). The WDCCA study area is a corridor running from the old Eurocan facility in the north to Bish Cove in

the south. It includes the industrial lands along Haisla Boulevard

and Alcan Road and forested lands close to the shoreline around

the Bish Creek Forest Service Road (FSR).

D I S T R I C T O F K I T I M A T P A G E 2



The Land Constraint and Suitability Study Area (LCSS

Study Area): The LCSS Study Area encompasses the portion of the Project Area that falls outside of the WDCCA Study area.

The LCSS Study Area will be the focus of the land constraints and

suitability analysis carried out in Phase 3 of the LCSS Project. Generally, the LCSS Study Area is the focus of overview assessments carried out in

Phase 2 of the Project; however, in some cases overview assessments

address the LCSS Study Area and/or other portions of the District of

Kitimat.

This report is an overview assessment of the geotechnical and

hydrotechnical hazards within the study area. This overview is intended to

identify and report hazard features and constraints through high level desktop analysis, and provide a comprehensive list of indicators for

assessing suitability of various land use through GIS analysis in

consultation with Westland Resources and the District of Kitimat’s GIS

technician.




FIGURE 1: LAND CONSTRAINT AND SUITABILITY STUDY PROJECT AREA MAP.




1.1 Background Information

For this assessment, we reviewed:

West Douglas Channel Corridor Analysis: Overview Geotechnical,

Terrain and Terrain Hazards Analysis. Report Number 1314470529-

013-R-Rev2 by Golder Associates, submitted to WSP Canada Inc., 17 June 2016.

Surficial geology and terrain maps

Surficial Geology, north Kitimat Arm, Douglas Channel Area1

Surficial Geology, south Kitimat Arm, Douglas Channel Area2

Climate data3

Seismic data4

In addition to the West Douglas Channel Corridor Analysis, Madrone was

provided with a PDF copy of the Terrain Stability Mapping of Jesse-Miskatla, Wathlsto-Clio Bay and Kowesas River Planning Units, TFL 41 by

Skeena Sawmills. These maps were not used to supplement our terrain

mapping, nor was our terrain mapping edge mapped. These two sets of

maps were used for comparison purposes only, as they differed in their mapping extent, the information available and general mapping criteria.

1 Maynard, D.E., Weiland, I.C., Blais-Stevens, A., and Geertsema , M., 2017. Surficial

geology, north Kitimat Arm , Douglas Channel area, British Columbia, parts of NTS 103-H/15 and 103-I/2; Geological Survey of Canada, Canadian Geoscience Map 300 (preliminary), scale 1:25 000. doi:10.4095/300850

2 Maynard, D.E., Weiland, I.C., Blais-Stevens, A., and Geertsema , M., 2017. Surficial geology, south Kitimat Arm , Douglas Channel area ,British Columbia , part of NTS 103-H/15; Geological Survey of Canada , Canadian Geoscience Map 301 (preliminary),scale 1:25 000. doi:10.4095/300851

3 Environment Canada. (modified January 25, 2017). 1981 – 2010 Climate Normals and Averages – Normals. Retrieved January 2018 from http://climate.weather.gc.ca/climate_normals/index_e.html

4 Natural Resources Canada. (modified 2016, February 10). 2015 National Building Code of Canada seismic hazard calculator. Retrieved March 2017 from http://www.earthquakescanada.nrcan.gc.ca/hazard-alea/interpolat/index_2015-en.php




2 Methodology

2.1 LiDAR Analysis

Light Detecting and Ranging (LiDAR) analysis is a remote sensing technique that uses laser light to create mass point datasets of the earth’s

surface with highly accurate x-y-z measurements. These datasets are

processed to create digital elevation models (DEM) that can be analyzed

in geographical information systems (GIS). The LiDAR dataset analyzed for this study was provided by the DOK at a scale of 1 m resolution (Figure

2). The DEM has been processed to remove all buildings and trees from

the model, allowing the bare earth to be realized.

Madrone’s geoscientists used ArcGIS to create terrain polygons from the

DEM, delineating distinct features throughout the study area. These

features were categorized based on the Terrain Classification System (see

section 2.3).

2.2 Air Photo Analysis

Air photo (also known as aerial photography) analysis is the

interpretation of landforms and geography through visual identification from an overhead perspective. Before the digital recording of remote

sensing data, air photos were used to provide a large scale perspective on

geological processes as well as a record of change over time. For the

purposes of this study, we used air photo interpretation in conjunction with LiDAR to map surficial geology and terrain components, geological

processes, and slope stability. Using both datasets together provided a

broader understanding of the recent conditions within the study area.

Small scale air photos were provided by the District of Kitimat (10-20 cm

scale) for a limited area of the study area (Figure 3). Large scale air photos

as well as aerial imagery from Google Earth Pro, was used to supplement

the remaining study area. These data sets were also used to gain an extended understanding of geological processes that initiate outside of the

study area but affect the study area.




FIGURE 2: DIGITAL ELEVATION MODEL OF THE STUDY AREA FROM LIDAR DATASET OF 1 M RESOLUTION PROVIDED BY DOK.







FIGURE 3: AIR PHOTO COVERAGE FROM DOK (BLUE) AND GEOBC (RED LINES, 2003).

2.3 Terrain Classification System

The Terrain Classification System for British Columbia (Howes and Kenk,

1998) is a standardized mapping system produced by the Ministry of

Environment and has been adopted by professionals in BC for over 20 years. The system assigns a unique terrain tag based on a series of

attributes and is meant to be used in conjunction with the Guidelines and

Standards for Terrain Mapping in British Columbia (1996), and the

Standard for Digital Terrain Data Capture in British Columbia (1998). For the purposes of this study, we captured the following attributes (when

applicable) for each terrain polygon: Surficial and subsurface materials,

surface expression, geomorphological processes, and drainage. We

followed the digital standards for attribute allocation and within the digital dataset, which accompanies this report. The attributes listed in

Table 1 are the minimum attributes applied (where applicable). Due to the

high-level desktop analysis, detailed attributes like surficial texture,

qualifiers, and subtypes were not applied. Table 1: Description of Terrain Mapping Project Data, Adapted from Standards

for Digital Terrain Data Capture5

Attribute Name Terrain Data Field Name Description

TDEC_1 Decile of terrain component 1

Describes proportion of polygon covered by component 1.

SURFM_1 Surficial material of component 1

Formative geomorphological process of first stratum of surficial material of component 1 of current terrain polygon.

SURF_E1 (A-C) Surface expression of component 1

Used in combination to describe three-dimensional shape of upper surface and thickness of first stratum in the component of terrain polygon. Up to 3 lower case codes, with first code as most dominant surface expression.

SSURFM_1 Subsurface material of component 1

Formative geomorphological process of first subsurface stratum of first component.

SSURF_E1 (A-C) Subsurface expression of component 1

A series of 1-3 lower case letter codes used in combination to describe three-dimensional shape of upper surface and thickness of second stratum in component 1 of the current terrain polygon. First code is the most dominant surface expression.

TDEC_2 Decile of terrain Describes proportion of polygon covered by component 2.

5 Resources Inventory Committee. 1998. Standard for digital terrain data capture in

British Columbia. Government of British Columbia, Victoria, B.C.




Attribute Name Terrain Data Field Name Description

component 2

SURFM_2 Surficial material of component 2

Formative geomorphological process of first stratum of surficial material of component 2 of current terrain polygon.

SURF_E2 (A-C) Surface expression of component 2

Used in combination to describe three-dimensional shape of upper surface and thickness of first stratum in the component of terrain polygon. Up to 3 lower case codes, with first code as the most dominant surface expression.

SSURFM_2 Subsurface material of component 2

Formative geomorphological process of first subsurface stratum of first component.

SSURF_E2 (A-C) Subsurface expression of component 2

A series of 1-3 lower case letter codes used in combination to describe three-dimensional shape of upper surface and thickness of second stratum in component 2 of current terrain polygon. First code is the most dominant surface expression.

GEOP_1 1st Geomorphological process class

Represents sole or most significant geomorphological process to affect terrain.

GEOP_Q1 1st Process qualifier A code used to specify whether first geomorphological process is active or inactive.

GEOP_SCM1 (A-C) 1st Process subclass 1-3 standard lower case letters attached to second geomorphological process within current terrain polygon. Subclass modifiers are used to further describe the process and are usually mapped at a more detailed level.

GEOP_2 2nd Geomorphological process class

Represents second most significant geomorphological process to affect the terrain.

GEOP_Q2 2nd Process qualifier A code used to specify whether second geomorphological process is active or inactive.

GEOP_ST2 2nd Process subclass 1-3 standard lower case letters attached to second geomorphological process within current terrain polygon. Subclass modifiers are used to further describe the process and are usually mapped at a more detailed level.

DRAIN_1 1st Soil drainage class of the polygon

Soil drainage class for all or most of the terrain polygon. Refers to the rapidity and extent of water removal from the soil in relation to additions.

DRAIN_SEP Soil drainage separator of polygon

Used where terrain polygon includes two areas of relative uniform drainage, indicating proportion of polygon occupied by each class.

DRAIN_2 2nd Soil drainage class of the polygon

Drainage class for less than half the current terrain polygon.

SLPSTB_CLS Slope stability class A code representing a class of slope stability. For this project area, it is reconnaissance terrain stability system (see section 2.4).

POLY_COM Comments Any potential comments related to the polygon.

2.3.1 Surficial Material

Surficial materials, also known as quaternary sediments or unconsolidated materials, are geologically relatively young. In the study

D I S T R I C T O F K I T I M A T P A G E 1 0



area, the thickness of these materials varies depending on elevation and

overall topography. Within the Howes and Kenk (1998) surficial material classification, there is an assumed status of activity. For the majority of

the study area these assumed statuses are unchanged, however, fluvial

material, which is normally assumed to be inactive, may be active in some

areas. The extent of modern fluvial activity cannot be discerned through a desktop study. Colluvium has an assumed status of active, and through

the desktop analysis, these assumptions are consistent with our

observations.

Anthropogenic material is material modified by human activities where

the original physical properties have been drastically altered.

Colluvium occurs when a parent material has reached its present position as a result of gravity induced movement, and is altered to a point where it

no longer has the properties of its parent material. Colluvium can consist

of slide and slump deposits.

Fluvial materials, also known as alluvial, are materials that are

transported by water, traditionally streams and rivers. Fluvial deposits

tend to consist of gravels and sands.

Glaciofluvial deposits are materials that have been deposited by glacial

meltwater streams or have been in direct contact with glacial ice.

Glaciofluvial deposits can have a slightly higher elevation than modern

fluvial deposits and can be shown as terraces on a map. Glaciofluvial deposits generally tend to have a courser, yet similar, texture when

compared to modern fluvial materials.

Morainal material, also known as till, is deposited directly by glacial ice and is not modified by any other transportation method6. The texture,

structure, and topographic characteristics of till are highly variable and

depend on source material incorporated by a glacier and mode of deposition. In general, tills contain a heterogeneous mixture of particle

sizes and are relatively dense. The thickness of till is highly variable,

6 Howes, D.E. and E. Kenk. 1997. Terrain classification system for British Columbia.

Version 2. B.C. Min. Env., Lands and Parks, MOE Manual 10, Victoria, B.C.




depending on the mode of deposition and its location; within the study

area there are areas of thin veneer of till and in other areas where till is thick enough to obscure underlying bedrock topography.

Glaciomarine materials were laid down within a marine environment

during the last glaciation when land was depressed due to the weight of ice. In the study area, these glaciomarine sediments tend to consist of silt,

sand, or clay with some boulders that have melted out of ice-bergs in the

near-shore environment. Glaciomarine materials are prevalent in the

study area up to an elevation of approximately 200 m. In some cases, these deposits can be sensitive, in that a disturbance (such as an

earthquake or construction) could destabilize soil fabric resulting in a

catastrophic loss of strength and liquefaction leading to flows. The Mink

Creek landslide near Lakelse Lake, north of the study area, is one local example of glaciomarine flow.

Bedrock outcrops, and bedrock covered by a thin mantle of the

unconsolidated materials mentioned above, are present throughout the study area. We did not discern between types of bedrock during our

mapping, and for the purposes of this study the bedrock appears to be

massive and generally controls landscape topography.

2.3.2 Geomorphological Processes

Geomorphological processes are natural mechanisms of weathering, erosion, and deposition that result in modification of surficial materials

and landforms at the earth's surface. Like surficial materials,

geomorphological processes have an assumed active or inactive status.

Three main geomorphological processes occur within the study area: gully erosion, slow mass movement, and rapid mass movement. Incidents of

snow avalanches, braiding channels, meandering channels, and

inundation also occur, but represent less than 3% of the study area.

The process of modification of surfaces by running water, mass

movement, and snow avalanches resulting in the formation of parallel and

sub-parallel long narrow ravines, is called gully erosion7. The gullies that






are created can have either steep or gently sloping slides and can occur on

steep to gently sloping surfaces. This type of gully tends to be smaller than most valleys but are larger and more distinct than surficial rills.

Slow mass movement is defined as the slow downslope movement of

masses of cohesive or non-cohesive surficial material and/or bedrock by creeping, flowing, or sliding8. This can occur in various types of trade, and

can include the initiation, transportation, and depositional zones of a

moving mass. Some examples of slow mass movement include earthflows,

rotational slumps, and lateral spreads. In the study area, we find that slow mass movement has occurred in the forms of earth flows and rotational

slumps, however that does not mean that the area is not subject to other

forms of slow mass movement.

Rapid mass movement is defined as rapid downslope movement by

falling, rolling, sliding, or flowing of dry, moist, or saturated debris

derived from surficial material and or bedrock9. Just as in slow mass

movement, this term is applied to all terrain that includes initiation, transportation, and depositional zones of the movement. Examples

include rock and earth falls, rock slides, debris slides, debris flows and

torrents.

2.4 Terrain Stability Classification

Following the Mapping and Assessing Terrain Stability Guidebook

produced in 1999 by the Forest Practices Code of British Columbia, we

performed a Reconnaissance Terrain Stability Mapping (RTSM). RTSM is used to identify all unstable or potentially unstable land areas. This type of

mapping is useful for identifying land areas when completing a desktop

analysis of an area where scale of mapping is limited for a wide area. This

classification was originally used in the forest industry to assess areas that would be affected by timber harvesting or road construction. Due to the

scale of mapping done, RTSM mapping is known to be applicable for large

regional studies when no field analysis has been undertaken. Additional

detailed mapping for those areas considered potentially unstable or



9 Howes, D.E. and E. Kenk. 1997. Terrain classification system for British Columbia. Version 2. B.C. Min. Env., Lands and Parks, MOE Manual 10, Victoria, B.C.




unstable is warranted. In general, a terrain polygon that is interpreted to

be unstable typically shows evidence of natural instability and is expected to have a high likelihood of landslides following land modification such as

timber harvesting or road construction. Potentially unstable terrain

polygons may show no obvious signs of instability under natural

conditions, but have characteristics similar to nearby unstable areas. An area delineated as stable tends to have negligible or low likelihood of

landslides. All RTSM should be done at a scale of 1:15,000 to 1:40,000.

The terrain map produced for this study area is 1:20,000.

Detailed Terrain Stability Mapping (DTSM) occurs at a more refined

resolution than RTSM. Specific areas undergo terrain stability field

assessments in DTSM and field verification of terrain mapping in 20 to

50% of the polygons is required. Mapping of this kind usually employs a five-class stability system (Class I through Class V). We did not believe

this classification system was appropriate for the broad scale and desktop

nature of this assessment.

Other aspects of terrain stability and hazard risk include the potential for

landslide debris to enter streams, soil erosion, and sediment delivery

potential. This will be discussed at a high level in the following sections.

2.5 Hydrotechnical Analysis

We conducted a desktop hydrotechnical analysis of the four watercourses

(Anderson Creek, Bish Creek, Emsley Creek, and Jesse Creek) that pass

through the study area and drain watersheds larger than 20 km2. It is impractical to perform a desktop study on the hundreds of smaller

streams in the study area because of their very number and the lack of

sufficient resolution in available data. For example, Moore Creek is just

south of Anderson Creek, but since Moore Creek’s watershed is less than 20 km2 it is not discussed in this report. Due to proximity and shape,

Moore Creek watershed will likely be similar to that of Anderson Creek.

Our assessment included a GIS analysis of channel gradients and hypsometry of the four watersheds using TRIM mapping, and a review of

imagery for channels within the study area to identify reaches that may be

subject to overbank flooding and bank erosion. We also reviewed

hydrometric data from the two nearby Water Survey of Canada gauged




streams (Little Wedeene River and Renegade Creek) and estimated peak

discharges using a modified regional correlation method developed by Coulson and Obedkoff10.

3 Geomorphic Setting

The District of Kitimat is within the Coast Mountains physiographic region of BC, specifically the Kitimat Mountain Range. Kitimat lies at the

head of Douglas Channel which extends south-southwest towards Hecate

Straight 121 km away. To the north is the Kitsumkalum-Kitimat Trough, a

3 to 10 km wide valley, extending towards the Hazelton Mountains 55 km to the north-northwest. The study area is composed of a small portion of

the Kitsumkalum-Kitimat Trough near the marine shoreline, and a large

portion of the Coast Mountains that run along the northwestern shores of Douglas Channel. The current physiology of the Kitimat area is a direct

result of geological events that occurred in the quaternary and tertiary

periods, as well as the bedrock structures formed between the Jurassic

and Paleogene periods.

3.1 Bedrock Geology

Bedrock geology within the District of Kitimat is composed of eight

different igneous and metamorphic units, ranging in age from Early

Jurassic to Late Paleogene. The dominate bedrock types are quartz diorites, gneissic and intrusive volcanics11. While bedrock topography

controls most of the landscape, Quaternary deposits can be thick

(exceeding 20 m) over bedrock in lower elevations12.

3.2 Surficial Geology and Quaternary History

Due to the proximity of the District of Kitimat to the coast, advance and

retreat of ice sheets during the Quaternary period drastically modified the

10 Coulson and Obedkoff.1998. Inventory of BC Streamflow Parameters, BC Minstry of

Environment

11 Bellefontaine, K., Alldrick, D. and Desjardins, P.J., 1994: Mid Coast (all or parts of 92F, G, J, K, L, M, N; 93D; 102P; 103A), Ministry of Energy, Mines and Petroleum Resources, Open File 1994-17.

12 Clague, J.J. (1984) “Quaternary Geology and Geomorphology, Smithers-Terrace-Prince Rupert Area, British Columbia”, Geological Survey of Canada Memoir 413.




valleys and drainage patterns within this mountainous area. In BC,

alternating glacial and interglacial periods were both responsible for shaping the current landscape.

The Olympia Interglacial preceded the last major glaciation, the Fraser

Glaciation. During the Olympia, valleys and coastal lowlands were free of ice, and subject to depositional environments similar to those that exist

today; fluvial and organic sediments were deposited, floodplains were

formed at different levels and deltas pro-graded into lakes and the sea.

Today it is uncommon to find these Olympia age deposits undisturbed, as they were later reworked and eroded during the Fraser glaciation.

The Fraser Glaciation was the last major glaciation in BC and was most

likely due to climatic cooling, which triggered the growth of alpine glaciers. As these glaciers grew, they ultimately travelled down the

mountains into the lower elevations and coalesced into sheets of ice.

Within the study area, the existing drainage system that began during the

non-glacial period was disrupted, resulting in deposition of new deposits. During the last glacial period, glaciers advanced and receded, leading to

meltwater deposits that were subsequently re-buried during later

advances. Recession created temporary lakes as masses of stagnant ice

blocked drainage. In general, glaciofluvial and glaciolacustrine sediments accumulated within the valleys and till was deposited along the mountain

slopes.

As ice continued to expand, its weight resulted in depression of the lowlands, changing the marine shoreline dynamics. These lowlands

remained depressed after the retreat of ice, resulting in the advance of

marine water inland to elevations of up to 200 m above the modern sea

level.

Within the Kitsumkalum-Kitimat Trough, a wide variety of sediments

were deposited and this provides a more refined record of late glacial events. For the purposes of this study, it is important to note that changes

in the depositional environment during glaciation have resulted in a

complex stratigraphy of Quaternary deposits. In general, the study area is

composed of morainal mantles (till) over bedrock, with glaciomarine deposits found along the shore lines and into the valleys up to an elevation

of 200 m above sea level. Glaciofluvial sediments deposited by meltwater




rivers issuing from retreating glaciers can be found at lower elevations

within the mountain valleys, with various mantles, cones or aprons of colluvium that have accumulated since the final retreat of glacial ice about

12,000 years ago.

The valley bottoms are cloaked with a mosaic of alluvial fans, modern but inactive floodplains and active modern alluvial plains subject to flooding

and channel shifting.

Table 2: Dominant Surficial Material within the Study Area with Approximate

Area Coverage.

Dominant Surficial Material Area (km2) Percentage of Study Area

Till/morainal mantle 68 48 %

Glaciomarine 43 30%

Colluvium 10 7%

Bedrock 7 5%

Fluvial 6 4%

Glaciofluvial 5 4%

Other* 3 2%

*Other surficial materials include lacustrine, organics, marine, and anthropogenically modified.




FIGURE 4: DOMINANT SURFICIAL MATERIAL OF THE STUDY AREA, AS DETERMINED BY DESKTOP ANALYSIS OF LIDAR AND

AIR PHOTO ANALYSIS.

Green polygons represent till, blue is glaciomarine, colluvium is brown, and red is bedrock. Glaciofluvial material is dark orange, with fluvial material as yellow.




3.3 Climate

Climatic conditions of the study area are likely very similar to those

recorded at the nearest Environment Canada weather stations (Table 3).

Snow accumulation will be higher due to the elevation difference between the stations and the study area extent. In general, the study area sees a

significant amount of precipitation and extreme daily precipitation events

tend to occur in the fall. Table 3: Climatic Conditions of the Study Area during the Period 1981 to 2010.

Station Mean Annual

Precipitation (mm)

Mean Annual Snowfall

(cm)

Extreme Daily

Precipitation (mm)

Kitimat 2 2775 302 179; Oct 31, 1978

Kitimat 3 2332 424 159; Oct 9, 1991

Kitimat Townsite 2211 325 145; Oct 26, 1976

3.4 Hydrology

The District of Kitimat contains five significant rivers (Kitimat River, Anderson Creek, Bish Creek, Emsley Creek, and Jesse Creek) and one

large lake (Jesse Lake), in addition to Douglas Channel. The study area

does not include any portion of the Kitimat River. Approximately 1.6 km

of Anderson Creek, 7.0 km of Bish Creek, 7.5 km of Emsley Creek, and 2.5 km of Jesse Creek are contained within the study area.

The largest watersheds in the study area are Bish Creek and Jesse Creek

(126 km2 and 150 km2 respectively). The headwater area of Jesse Creek is occupied by a small glacier, but glaciers are absent in the Bish Creek

watershed. The middle reaches of the mainstems of these creeks exhibit

low channel gradients (>1%) in long, U-shaped valleys with flat bottoms.

The lower reaches flow through broader valleys with gentler sidewalls and wide, flat bottoms. Bish Creek debouches directly into Douglas Channel

and Jesse Creek debouches into Jesse Lake, which in turn flows over a

waterfall into Douglas Channel. Only the lower 2.5 km of Jesse Creek and

the lower 7 km of Bish Creek, both segments contained in the broader valleys, are within the study area. The lower portions of Bish Creek

watershed have been extensively logged from 1997 to the present. The




Jesse Creek watershed appears to be unlogged. Some logging near the

eastern height of land above Jesse Lake has occurred since 2015. An LNG facility has been under construction near the mouth of Bish Creek since

2013.

Emsley Creek drains the smallest of the assessed watersheds at 20 km2, much of which is in the study area. In the middle reaches, the channel has

steep gradients (>8%) and flows through a narrow, V-shaped valley,

before emerging onto a broad plain and flowing to Douglas Channel. All 5

km of the channel on the plain and 2.5 km upstream in the valley are within the study area. The lower portions of Emsley Creek watershed

experienced some logging in 2002 to 2008, and a considerable amount of

logging since 2015.

Anderson Creek drains an intermediate-size watershed of 38 km2. The

lower reaches cross the study area, west to east, before flowing onto the

Kitimat River estuary. Of the 1.5 km of the channel within the study area,

only the lower-most 200 m, immediately upstream of Highway 37, is not contained within a narrow V-shaped valley. The channel upstream of the

study area is also contained in the narrow valley. The channel gradient in

the valley is moderately steep (2%-5%). Some logging occurred in the

1970s near the front of the watershed, but the watershed appears to be mostly unlogged.




Table 4. Watershed Characteristics

Anderson Creek

at Kitimat River

Bish Creek

at Bish Cove

Emsley Creek

at Emsley Cove

Jesse Creek

at Jesse Lake

Watershed Area 38 km2 126 km2 20 km2 150 km2

Watershed fraction

below 300 m

16% 27% 33% 15%

Watershed fraction,

300 – 800 m

52% 44% 47% 35%

Watershed fraction

above 800 m

32% 29% 20% 50%

Fraction of watershed

above Study Area**

89% 75% 20% 97%

Maximum elevation in

watershed

1320 m 1560 m 1180 m 1900 m

Length of mainstem

channel in Study area

1.6 km* 7.0 km* 7.5 km 2.5 km

Mainstem channel

type in Study Area*

Confined, mainly non-alluvial

Unconfined alluvial Unconfined alluvial for lower 5 km; Confined, non-alluvial for upper 2.5 km

Unconfined alluvial

Channel width in

Study Area*

~15 m 40 – 60 m Alluvial reaches: 10-15 m non-alluvial: ~10 m

40 – 60 m

* - includes WDCCA study area

** - watershed area above the point where the mainstem enters the Study Area

3.5 Resources

Within the last hundred years, this region has experienced economic

growth and development based on fishing, tourism, forestry and resource processing. The economy has continued to grow along with its population

in the demand for natural resources, aluminum, kraft paper, methanol,

and ammonia both at home and abroad. While a description of the extent

of resource development is beyond the scope of this project, it should be noted that historical alterations to the landscape are visible decades after

completion. In some cases, the utilization of existing infrastructure can be

used to expand the viability of an area for new land uses such as

recreational or residential.




3.5.1 Mineral Potential

The region contains several different bedrock types with varying

potentials for mineralization. The majority of the region is underlain by the Quottoon Plutonic Suite, a Late Cretaceous to Paleocene-aged quartz

diorite, and the Central Gneiss Complex, a Paleozic to Cenozoic aged

orthogneiss; neither of which display significant mineral potential.

Within the northeast portion of this region are three other bedrock units:

an unnamed Middle Jurassic Quartz Diorite; the Poison Pluton, a Jurassic

to Cretaceous Quartz Diorite; and The Telkwa Formation (Hazelton

Group), a Lower Jurassic calc-alkaline volcanic rock assemblage. The Hazelton Group strata have undergone continued mineral exploration

over the last several decades within northwestern British Columbia. At

present, and most proximal to this region, is the Wedeene property owned

by Decade Resources Ltd., where recent exploration has found the area underlain by volcanogenic massive sulphide (VMS) copper-gold

mineralization. The Wedeene property is located just north of the study

area and is underlain by the Telkwa Formation. An unnamed local fault

cross cuts the northern portion of the property adding to the potential for hydrothermal mineralization.




FIGURE 5: MINERAL POTENTIAL IN THE DOK REGION.

Yellow stars represent two small historic mines, the black triangle is approximate location of Wedeene Project Property, and the yellow dashed line is potential mineral extraction within the study area.

No recorded historic mining sites were discovered during this

investigation. The only potential mineral extraction site is indicated in

Figure 5, and underlain by the same bedrock and local fault as the Wedeene property. Figure 5 is an overview of the study area showing the

regional bedrock geology, two small historic mine sites which extracted

less than 10,000 tonnes of an unknown ore13, and the Dacade Resources

13 http://webmap.em.gov.bc.ca/mapplace/HistoricMines/main.asp




Ltd. Wedeene Project Property location14. The yellow dashed line

highlights the only potential mineral extraction site.

4 Geotechnical Implications

4.1 Natural Hazards

Natural hazards can pose a risk to life and property. It is important to

assess the probability and capability of natural hazards to cause damage.

Through this assessment, appropriate land use designs and mitigation measures can be put in place.

4.1.1 Flooding

Floodplains, as their name suggests, are prone to flooding. In the study

area there is a mosaic of active and inactive floodplains, as well as

glaciofluvial terraces deposited early in post-glacial history (and now well above any modern flood elevation). In general, we cannot distinguish

active from inactive floodplains in an overview assessment. More detailed

field assessment is required to accurately map the extent of potential

flooding.

With the exception of the Kitimat River floodplain, floodplains of the

systems assessed in this report (Anderson, Bish, Emsley, and Jesse

Creeks) are uninhabited; however, Bish Cove has been subject to industrial use and active forest service and industrial roads are located

within the floodplain.

Water Survey of Canada records for Little Wedeene River below Bowbyes

Creek (Station 08FF003) show bimodal annual peak flows with the

highest annual discharge usually occurring in the period from September

through November and lesser peak discharges occurring during the freshet in May or June. The Little Wedeene River watershed is similar in

size and elevation distribution to the Jesse Creek and Bish Creek

watersheds with maximum elevation of approximately 1800 m and a

substantial fraction of the watershed in the nival zone above about 800 m.

14http://www.decaderesources.ca/s/QwikReport.asp?IsPopup=Y&printVersion=now&X

B0B=381449,408237




Like the Jesse Creek watershed, but unlike Bish Creek, Little Wedeene

watershed hosts a small glacier in its headwater area. The Little Wedeene watershed is somewhat larger than the Anderson Creek and Emsley Creek

watersheds, but all have a similar distribution of elevation.

Records for the Renegade Creek gauge (WSC Station 08FF006) show a pattern that is somewhat similar to the Little Wedeene River, but with a

proportionately smaller freshet occuring in April. This watershed is

different from the assessed watersheds in that it is significantly smaller

(3.2 km2) and, with a maximum elevation of 700 m, has little area in the nival (permanent snow) zone.

While larger rivers such as the Kitimat River will experience peak flows

due to snowmelt which therefore occur in summer, the smaller systems assessed in this report are more strongly influenced by rainfall or rain-on-

snow events due to the significant portions of their watersheds that are in

the rain-dominated zone (below about 300 m elevation) and the transient

snow zone between 300 m and 800 m elevation. Like the Little Wedeene, larger rivers are likely to experience the largest floods during rain-on-

snow storms in the period between September and November inclusive.

Smaller floods may occur during the freshet which is likely to occur in

May and/or June.

We have estimated the 200-year maximum daily mean discharge (i.e., the

daily mean discharge with an annual probability of being exceeded of

1/200) for each of the assessed creeks at the point where they enter the study area and at the point where they debouche into Douglas Channel (or

into the Kitimat River estuary in the case of Anderson Creek). Discharges

will differ between the two points primarily due to tributaries that join the

mainstem downstream of where it enters the study area. The estimates, shown in Table 5, were derived using a modification of a regional

correlation method developed by Coulson and Obedkoff10, and should be

considered to be approximations only. More accurate estimates would require a level of effort beyond the scope of this report.

Table 5. Estimated 200-Year Maximum Daily Mean Discharge

At Upstream Study Area Boundary At Mouth




Anderson Creek 140 m3/s 160 m3/s

Bish Creek 320 m3/s 400 m3/s

Emsley Creek 25 m3/s 90 m3/s

Jesse Creek 440 m3/s 450 m3/s

Note: 200-year maximum instantaneous discharge will be approximately twice the 200-year maximum daily mean discharges

While the largest floods are likely to occur during rain-on-snow events in

the fall, smaller floods may occur at other times of year, especially during spring freshet. Flooding can be triggered by seasonal changes related to

snowpack melt or increased precipitation over short periods. Flooding

may be influenced by changes in climate, however, changes in peak

discharges due to climate change over the next 100 years will not likely exceed uncertainty in the peak flow estimates contained in Table 5.

Determination of the areal extent of flooding requires detailed modeling,

which is also beyond the scope of this report. As a first approximation, areas along assessed creeks that have been mapped as having fluvial

deposits (but not including glaciofluvial deposits) may be considered as

potentially flood-prone. Additional areas along smaller creeks, including areas alongside tributaries to the assessed streams, may also be flood-

prone.

Another potential type of flooding may arise due to landslides that dam a channel in the middle reaches of a watershed, impound large volumes of

water, then breach catastrophically. Landside-dam-breach floods are

potentially much larger that “normal” extreme floods. For a landslide-

dam-breach flood to occur, three conditions must exist:

1 There must be landslide-prone slopes (usually steep) above the

channel

2 The valley bottom must be narrow enough to be blocked by a landslide

3 The creek channel gradient immediately upstream of a landslide must be sufficiently low that large volumes of water can be impounded.

Middle reaches of Anderson and Emsley creeks exhibit channel gradients

that are too steep for significant volumes of water to be impounded. Consequently, there is little potential for landslide-dam-breach floods in

the lower reaches of these creeks.




For Bish and Jesse creeks, channel gradients in the middle reaches are low, and there are potentially landslide-prone slopes above the channel.

However, for most reaches, the valley bottoms are quite wide (up to 500

m), so only very large (and consequently less probable) landslides could

impound these creeks. Consequently, while landslide-dam-burst events are possible, our preliminary estimate is that the probability of one

occurring is very low. However, it must be emphasized that accurate

estimation of the likelihood of such events requires detailed topographic

maps of the valley bottoms, terrain stability mapping of the slopes above the channel, and modeling of the downstream attenuation of the flood

resulting from the dam burst. Data required were either unavailable or

outside the scope of this study.

4.1.2 Stream Erosion and Avulsion

Significant erosion of stream banks generally occurs where bank material is unconsolidated, particularly in alluvial material. With the exception of

the lowermost 200 m, the part of Anderson Creek that is within the study

area appears to be largely contained in non-alluvial material. All portions

of Bish Creek and Jesse Creek within the study area and the portion of Emsley downstream of 53o 55’ 18” N, 128o 50’ 19” W are contained in

alluvial material.

Bish Creek and Jesse Creek could experience bank erosion amounting to several tens of metres over the typical design life of residential or

commercial structures or roads. Because of its lower flow rates, Emsley

Creek may experience lesser, though not inconsequential, amounts of

erosion. Erosion could also reactivate old channels or create new ones. More precise estimates of the potential extent of erosion should be

determined by on-site investigations.

It is important to maintain existing forest cover in broad riparian strips along Bish Creek, Jesse Creek, and Emsley Creek. Bank support from

roots retards erosion. Removing trees creates a self-reinforcing process

whereby erosion of banks introduce sediment into the channel; that sediment is deposited in mid-channel bars which divert flow against the

banks, thus increasing erosion. The result is that creeks in alluvial

material tend to widen substantially when forest cover along the banks is

removed.




Velocity of water has a powerful effect on erosion and scour that occurs along banks. In steep channels, bank erosion during high flow events can

result in large volumes of unconsolidated sediments slumping into the

river resulting in debris floods and debris flows. Depending on where

slumping occurs along the course of the river, the amount of debris within the stream channel, in addition to the high velocity and high water

content, can exacerbate the erosion resulting in further damage to the

banks and avulsion i.e., a stream flows downslope from a higher elevation

to the lower elevation, gaining velocity as it decreases in altitude.

The rate of erosion within a river is subject to gradient, water velocity, and the nature of unconsolidated sediments. The process described above for

larger streams also operate in smaller streams, though at a smaller scale

and with the added potential for avulsion near fan apex.




FIGURE 6: FLUVIAL FANS (ORANGE) AND FLUVIAL PLAINS (YELLOW) WITHIN THE STUDY AREA.

The activity of the fluvial plain is assumed inactive, although that is not representative of potential flood scenarios.




FIGURE 7: WATERCOURSE DISTRIBUTION AS MAPPED BY FRESHWATER ATLAS WITHIN THE STUDY AREA.

Thick blue line outlines the Douglas Channel and the smaller dendritic lines are streams that mostly feed into the four major rivers within the study area.




4.1.3 Landslides

There are many areas in the study area where risk of landslides is high.

There are numerous factors related to the probability of failure, such as relative relief and elevation, duration and abundance of precipitation,

nature of the unconsolidated sediments, and presence of sensitive clays.

In the study area there is evidence of slow mass movement in

glaciomarine sediments, debris slides and flows from steeper slopes and high elevations, snow avalanches, and rockfalls.

Post-glacial settling of materials resulted in some instability within the

study area, specifically along steeper sloping terrain, resulting in colluvial deposition. The colluvium is a mixture of parent material that has been

affected by instability and therefore is not one particular type of sediment

but rather an amalgamation of local sediments, i.e., till and glaciofluvial,

bedrock and glaciomarine, etc. The combinations are numerous and therefore predictability of the strength and potential reactivation of these

materials needs to be evaluated on a case-by-case basis.

Figure 8 is a general representation of landslide-related geotechnical hazards found in the study area. These hazards include debris flows,

debris slides, debris avalanches, and rockfalls. These are point

representations of a geotechnical hazard, as they can be related to the

head scarp of a failure (because the resulting material or fan was either eroded by fluvial or marine actions), or a debris flow fan with a large

catchment area.




FIGURE 8: OBSERVED LANDSLIDES AND OTHER EVIDENCE OF INSTABILITY IN THE STUDY AREA, AS DISCOVERED THROUGH

DESKTOP ANALYSIS OF LIDAR DATA.

Points may represent failure headscarps, debris flow tracks, slump blocks, or a fan apex, and other distinct evidence of failure.




Geological or geomorphological processes affect almost 50% of the study

area; these include rapid mass movement, slow mass movement, and gully erosion. Rapid and slow mass movement can affect a large

geographical area, whereas gully erosion is more of a linear event.

Secondary processes may occur in the same area: for example where gully

erosion occurs, there is a probability of rapid mass movement if gully sidewalls collapse when there is water flowing through the gully, resulting

in a debris flow within the gully. Table 6: Geological Processes that Occur in the Study as Observed through

Desktop Analysis of LiDAR

More than one process can occur within an area, therefore processes may be primary or secondary.

Geological Process

Primary Secondary

Area (km2) Percentage of Study

Area Area (km2)

Percentage of

Study Area

Rapid Mass Movement 52 36% 5 4%

Slow Mass Movement 4. 3% 5 4%

Gully Erosion 13 9% 10 7%

Other** 1 <1% 2 1%

** Other geological processes include braiding and meandering streams, avalanche, and inundation.

The reconnaissance terrain stability analysis approximated 49% of the

study area as either potentially unstable or unstable; more site-specific

field analysis would refine these values. Given the rugged terrain of the

study area, this assessment is not surprising, however, future development within DOK will likely be limited to areas where access is

possible, and therefore changing the ratio of stable to

potentially/unstable. Rougher terrain such as bedrock ridges and mountain peaks tend to be less stable due to their slope and active

geological processes, whereas flat lying and gentle slope terrain is more

stable and easily accessible through ports and inlets.




Table 7: Slope stability class of the study area, as determined from desktop

analysis of LiDAR.

Stability Class Area (km2) Percent of Study Area

Stable 73 51%

Potentially unstable 47 33%

Unstable 22 16%




FIGURE 9: DOMINANT GEOMORPHOLOGICAL PROCESSES WITHIN THE STUDY AREA.

Red represents rapid mass movement, orange is slow mass movement, and gully erosion is blue.




FIGURE 10: RECONNAISSANCE TERRAIN STABILITY MAPPING (RTSM).

Slope stability classes stable (S, green)-potential unstable (P, yellow)- unstable (U, red), in study area.




4.1.4 Snow Avalanches

Snow avalanches are a significant hazard; large and recent events are

obvious in air photos and some LiDAR imaging, and therefore noted during the terrain mapping, The overview scale of this project, however,

cannot guarantee that avalanches cannot and do not occur in other areas.

4.2 Seismic Considerations

There are two unnamed faults that run through the District of Kitimat. Within the study area, one fault runs parallel to the western bank of the

Douglas Channel, terminating approximately 12 km southwest of

Kitamaat Village, BC15. We were unable to find a record of activity directly

attributed to the faults that run through the District; however, given the seismic history of western BC, it is reasonable to assume that there is

some seismic risk associated with the area.

Most of the seismic energy released along western BC occurs along the Fairweather-Queen Charlotte fault system. When an earthquake occurs

along this fault system, it may have a reverberating effect along other

smaller local fault systems, however, this transfer of energy is hard to

quantify. The study area has a history of intermediate size earthquakes at a low frequency. November 5th 1973 a magnitude 4.7 earthquake occurred

20 km southwest of Terrace along the Kitsumkalum-Kitimat Trough.

Damage was limited but the earthquake was felt to distances of 120 km from its epicenter. The earthquake did not occur along any known fault

line at the time.

PGA, or peak ground acceleration, is what is experienced by a particle on

the ground. SA (spectral acceleration) is approximately what is

experienced by a building, as modeled for the natural period(s) of vibration as the building16. Estimated seismic accelerations for a Class C

site (i.e. underlain by very dense soil or soft rock) having a probability of

2% in 50 years are shown in Table 8 below.

15 Bellefontaine, K., Alldrick, D. and Desjardins, P.J., 1994: Mid Coast (all or parts of

92F, G, J, K, L, M, N; 93D; 102P; 103A), Ministry of Energy, Mines and Petroleum Resources, Open File 1994-17.

14https://earthquake.usgs.gov/hazards/learn/technical.php. Accessed February 15, 2018

https://earthquake.usgs.gov/hazards/learn/technical.php




Table 8. Peak Ground Acceleration and Spectral Accelerations at

53o 54’ N, 128o 48’ W (G’s)16

PGA Sa[0.05] Sa[0.1] Sa[0.2] Sa[0.3] Sa[0.5] Sa[1] Sa[2] Sa[5] Sa[10]

0.09 0.09 0.14 0.17 0.18 0.18 0.15 0.10 0.04 0.01

4.3 Sensitive Clays

Glaciomarine sediments consist primarily of silt and clay. They were deposited in the lower elevations early in post-glacial time when the land

was submerged (and had not yet rebounded) due to the weight of the ice.

As the land rebounded after glacial retreat, these glaciomarine sediments were raised and exposed to stream and river erosion.

Because of this glacial history, the Kitimat Ranges host sensitive

glaciomarine sediments in lower elevations. Certain glaciomarine sediments may be ‘sensitive’ meaning that due to special conditions

during their formation they may be subject to catastrophic loss of strength

upon disturbance. When this happens, sensitive clays may liquefy and

flow downslope.17. The exact distribution of these clays is still unknown due to extensive fluvial erosion and deposition involving the rapid

development and evolution of floodplains, fans, and deltas throughout the

region.

Past research has found that glaciomarine sediments are visible in the

sidewalls of most streams in the Kitsumkalum-Kitimat Trough, which

explains the presence of certain large landslides or displacements that are

still occurring in that region18. The most common trigger for these large low-gradient landslides is fluvial bank erosion of glaciomarine sediments.

Figure 11 shows the regional distribution of glaciomarine clays as mapped

by the Geological Survey of Canada19. It is likely the clays extend up some 16 Halchuk, S C; Adams, J E; Allen, T I. 2015. Fifth generation seismic hazard model for

Canada: grid values of mean hazard to be used with the 2015 National Building Code of Canada. Geological Survey of Canada, Open File 7893

17 The Landslide-Modified Glacimarine Landscape of the Terrace-Kitimat Area, BC (Geertsema, Cruden, & Clague, 2017)

18 The Landslide-Modified Glacimarine Landscape of the Terrace-Kitimat Area, BC (Geertsema, Cruden, & Clague, 2017)

19 CGS-South Kitimat Arm, Douglas Channel Area maps 300 and 301.




of the valleys extending north off the Kitimat Arm. However, due to the

steeper slopes and narrow valley bottoms associated with these valleys most of the clays were likely removed by either alluvial or fluvial processes

following regression as a result of post glacial rebound.




FIGURE 11: MAPPED GLACIOMARINE SEDIMENTS (PURPLE) AND FIELD CONFIRMED LOCATIONS OF SENSITIVE CLAYS FROM

LITERATURE (PINK DOTS).




5 Conclusion and Recommendations

5.1 Hazard Acceptability Thresholds

The Local Government Act of BC empowers local governments to address geotechnical hazards in their development policies, bylaws and permits.

Generally, the procedure involves the characterization and mapping of a

hazard for all areas within the jurisdiction of a local government. Any development proposals, subdivisions, building permits or other activities

may trigger the need for a geotechnical hazard assessment, or a flood

hazard assessment, depending on the nature of the hazard.

A qualified person, as defined in the local bylaw, would evaluate the type

of risk, the type of proposed development, and the potential remedial or

protective measure for said development. Figure 12 is an example of

hazard acceptability for development prepared by Dr. Peter Cave (1993). In his report, he outlines the geotechnical hazards, the types of

development, and the acceptability of risk within the Fraser-Cheam

District (now referred to as the Fraser Valley Regional District). For

example, Table 9 demonstrates the level of hazard acceptability for a new single family dwelling, relative to the possible geohazards.

FIGURE 12: HAZARD ACCEPTABILITY DEVELOPMENT, FROM CAVE (1993).




Table 9: Hazard Acceptability Thresholds for a New Building, as per Cave

(1993).

Hazard-Related Responses to Building Approval Applications

Not approvable

Approval, but

with a

covenant

including

“save

harmless”

conditions as

well as siting

conditions,

protective

works or both

Approval, but

with siting

requirements

to avoid the

hazard, or with

requirements

for protective

works to

mitigate the

hazard

Approval

without siting

conditions or

protective

works, but with

a covenant

including

“save

harmless”

conditions

Approval

without

conditions

relating to

hazards

Ne

w B

uil

din

g

TYPE OF HAZARD Annual Return Frequencies

Inundation by

Flood Waters N/A >1:40 1:40 – 1:200 N/A < 1:200

Mountain

Stream Erosion

or Avulsion

>1:100 1:100 – 1:200 N/A 1:200 – 1:500 < 1:500

Debris Flood N/A >1:50 1:200 - 1:500 N/A

1:500 – 1:10,000

Debris Flow /

Debris Torrent > 1:200 1:200 – 1:500

1:500 – 1:10,000

N/A <1:10,000

Localized

Landslip > 1:50 1:50 – 1:500

1:500 – 1:10,000

N/A < 1:10,000

Snow

Avalanche > 1:30 1:30 – 1:10,000 N/A N/A < 1:10,000

Rock Fall > 1:100 1:100 – 1:1,000 N/A N/A < 1:1,000

Catastrophic

Landslide > 1:1,000 N/A N/A N/A < 1:1,000

There are other examples of hazard acceptability thresholds that have

been created for local government. We recommend that the DOK either creates their own hazard acceptability threshold or adopts an existing one

from another local government.

5.2 Development Permit Areas

Development permit areas (DPA) allow a local government to delineate

location-specific bylaws related to areas susceptible to geological hazards.

Official Community Plans (OCP) refer to these areas when addressing

zoning and building code bylaws, making site-specific assessments a requirement when permits are requested within a geohazard DPA. We

have created a general geohazard DPA map that approximates the two

major geohazards in the study area: flooding and hillslopes and uplands.




FIGURE 13: GENERAL GEO-HAZARD DPA MAP FOR THE STUDY AREA.

Red demarks potential hillslope and upland hazards, and blue is potential flood hazards. This is for illustration only; a DPA map should be constructed after detailed field survey and more investigation.







5.2.1 Flood Hazard

Flooding within the study area is a significant concern. The study area

includes four large streams, Jesse Lake, and numerous smaller and unnamed streams. The Kitimat River, while not in the immediate study

area, is within the District of Kitimat and also poses a flood hazard. Flood

Hazard Area Land Use Management Guidelines (2004) were meant to

aid local governments in developing and implementing land use management plans and approval decisions for flood hazard areas. The

guidelines outline minimum provincial requirements, and lay out a

template for local governments to expand upon. In general, these

minimums are used in the absence of site-specific studies and information for land use management in flood hazard areas. From a geohazard

standpoint, the guidelines prescribe flood construction levels (the vertical

setback from watercourse) and a floodplain setback (horizontal setback

from watercourse) as determined by size of the watercourse.

Through our terrain mapping of DOK, we have outlined the possible

extent of flooding (susceptible units) from main channels and tributaries

within the study area (Figure 14); this is a high-level analysis and should be used in a general context only. This area is not representative of a

particular size of event, such as the 200-year flood, nor does it take into

account sea level raise. “Over time, the frequency of floods on some rivers

may also increase due to factors that include riverbed aggradation, river channel alterations, land use change, insect infestation, wild fire, and

climate change.”20

5.2.2 Stream Erosion Hazard

There is potential for substantial stream bank erosion (up to tens of

metres over typical design lives of structures and infrastructure) in the alluvial reaches of Bish Creek, Jesse Creek, and Emsley Creek in the study

area. Site-specific assessment of potential erosion should be undertaken

before areas along these creeks are developed. As well, existing forest

20 Association of Professional Engineers and Geoscientists of British Columbia

(APEGBC) (2012) Professional Practice Guidelines - Legislated flood assessments in a changing climate in BC. Association of Professional Engineers and Geoscientists of British Columbia, Burnaby, B.C.




cover should be maintained in broad riparian strips along these reaches to

prevent widening of the channels.




FIGURE 14: AREAS POTENTIALLY SUSCEPTIBLE TO FLOODING.

This does not take into account raises in sea level or areas outside of the study area.




5.2.3 Hillslopes and Uplands Hazard

A development permit area consisting of hillside and uplands may be

subject to natural hazards such as instability, erosion, and debris floods and flows. Unlike flooding hazards, there are no provincial guidelines

relating to setbacks from hazards; a Qualified Professional (QP) on a site-

specific basis would undertake this type of assessment. The governing

body that regulates professional practice of geoscientists and engineers in British Columbia (EGBC) has produced a series of professional practice

guidelines, which outline the required analysis by a QP when geohazards

are encountered. These standards are applicable to all QP within BC and

are regarded as a minimum requirement. Local government can require a QP provided additional information in their assessments, in conjunction

with a hazard acceptability threshold.

Figure 15 is a generalized map of areas of hillslopes and uplands within the study area, and as with the flood hazards map, it is a high-level

depiction and should be used in a general context only. We recommend

that DOK determine a set of criteria that would define the extent of this

DPA. Some local governments define the hillslope and upland area as those with slopes greater than 20% or 60%, whereas others focus on

existing hazards, delineating an area that encompasses similar topography

with or without known geohazards. The hazard acceptability threshold

can also be incorporated to reflect more strict or lenient requirements depending on the zoning.




FIGURE 15: POTENTIAL EXTENT OF HILLSLOPE AND UPLANDS HAZARD AREA WITHIN THE STUDY AREA.

Extent can be refined based on DOK criteria.




6 Closure

Prepared by: Prepared and Reviewed by:

Roberta Adams, M.Sc., G.I.T.

Geoscientist

Gordon Butt, M.Sc., P.Geo.

Senior Geoscientist




7 References

Association of Professional Engineers and Geoscientists of British Columbia (APEGBC) (2010) Guidelines for legislated landslide assessments for proposed residential development in British Columbia. Association of Professional Engineers and Geoscientists of British Columbia, Burnaby, B.C. Association of Professional Engineers and Geoscientists of British Columbia (APEGBC) (2012) Professional Practice Guidelines - Legislated flood assessments in a changing climate in BC. Association of Professional Engineers and Geoscientists of British Columbia, Burnaby, B.C. B.C. Ministry of Forests and B.C. Ministry of Environment (1999) Mapping and assessing terrain stability guidebook, 2nd edn. Forest Practices Code of British Columbia, Victoria, B.C. Clague, J.J. (1984) “Quaternary Geology and Geomorphology, Smithers-Terrace-Prince Rupert Area, British Columbia”, Geological Survey of Canada Memoir 413. Geological Survey of Canada (1983), Surficial Geology, Skeen a River – Bulkley River Area, Map 1557A Sheet 2, Scale 1:100,000. Golder Associates (2016) “Overview Geotechnical, Terrain and Terrain Hazards Analysis”, West Douglas Channel Corridor Analysis, Report Number 1314470529-013-R-Rev2. Howes, D.E. and E. Kenk. 1997. Terrain classification system for British Columbia. Version 2. B.C. Min. Env., Lands and Parks, MOE Manual 10, Victoria, B.C. Resources Inventory Committee. 1996. Guidelines and standards for terrain mapping in British Columbia. Government of British Columbia, Victoria, B.C. Resources Inventory Committee. 1998. Standard for digital terrain data capture in British Columbia. Government of British Columbia, Victoria, B.C. Maynard, D.E., Weiland, I.C., Blais-Stevens, A., and Geertsema , M., 2017. Surficial geology, north Kitimat Arm , Douglas Channel area, British Columbia, parts of NTS 103-H/15 and 103-I/2; Geological Survey of Canada, Canadian Geoscience Map 300 (preliminary), scale 1:25 000. doi:10.4095/300850




Maynard, D.E., Weiland, I.C., Blais-Stevens, A., and Geertsema , M., 2017. Surficial geology, south Kitimat Arm , Douglas Channel area ,British Columbia , part of NTS 103-H/15; Geological Survey of Canada , Canadian Geoscience Map 301 (preliminary),scale 1:25 000. doi:10.4095/300851




8 Limitations

To properly understand the recommendations and opinions contained in

this report, its limitations, and Madrone’s rights and responsibilities,

reference must be made to the entire report, including, without limitation,

all appendices, drawings, and figures.

A geotechnical hazard site investigation can reduce, but not wholly

eliminate uncertainty regarding the natural hazards at a site, given

reasonable limits of time and cost. Madrone Environmental Services Ltd. (Madrone) has conducted this investigation and prepared this report in a

manner consistent with the level of care normally exercised by qualified

professionals currently practicing in the area under similar conditions and budgetary constraints. No other warranties, either expressed or implied,

are made. If unexpected environmental conditions are encountered on the

site, Madrone must be notified in order that we may determine if

modifications to our findings are necessary.

Madrone has made reasonable efforts to investigate the study area

through a desktop analysis; the extent and properties of soil, rock and

water are intended to be are representative of conditions in the relevant portions of the project site. However, due to the nature of geology, there is

an inherent risk that some conditions were not detected, and that actual

subsurface conditions may vary substantially from our assumptions. In

addition, conditions may change with the passage of time. You are responsible for ensuring that any other party making use of any

documents prepared by Madrone regarding the project also acknowledges

and accepts this risk.

Madrone has prepared this report for the exclusive use of its client. This

report is intended to assist the client in a land use assessment and official

community planning. This report was prepared considering circumstances

applying specifically to the client and applies only to the specific property identified in the report. It is intended only for internal use by the client for

the purposes for which it was commissioned and for use by government

agencies regulating the specific activities to which it pertains. It is not

reasonable for other parties to rely on the observations or conclusions contained herein.




Where practical, Madrone has attempted to verify the information provided to us by you or other individuals or organizations. However,

Madrone does not accept any responsibility for any inaccuracies,

deficiencies, or omissions resulting from receipt of incorrect or fraudulent

information.

Madrone’s investigation and findings specifically does not address

regulatory compliance of your subject property per requirements of the

B.C. Environmental Management Act and its subordinate regulations including, but not limited to, the Contaminated Sites Regulation.

Any verbal advice provided by Madrone, though given in good faith, may

be subject to misinterpretation. Consequently Madrone does not accept

responsibility for any verbal advice unless the advice is confirmed in writing. Madrone will not be responsible for any project decisions you,

your agents or contractors make if the decisions were made without

Madrone’s advice or are inconsistent with Madrone’s advice.

8.1 Limitations on Liability

The total amount of all claims you may have against Madrone or any

present or former partner; executive officer, director, stockholder,

employee or agent thereof under this engagement, including but not limited to claims for negligence, negligent misrepresentation and breach

of contract, are strictly limited to the amount of any professional liability

insurance that Madrone may have available for such claims.

Madrone is not liable for any consequential loss, injury or damages you

suffer, including but not limited to loss of use, earnings and business

interruption.

No claim may be brought against Madrone in contract or tort more than

two (2) years after Madrone’s involvement in the project.

8.2 Intellectual Property

Copyright in this report and associated documents prepared by Madrone, including those prepared at your request or direction, remain the property

of Madrone. We hereby grant you alone a non-transferable license to use

documents in connection with the particular project for which the




documents were prepared. This license does not apply to any draft version

of any document. You will not use the documents in connection with any other work, or project without the prior written approval by Madrone. If

you are in breach of any obligation to make payment to Madrone,

Madrone may revoke the license referred to above and you will cause to be

returned to Madrone all the documents and all copies thereof and you will remove from your computer systems any electronic copies of any of the

documents. Field notes and technical documents used by and/or

produced by Madrone are not subject to distribution.

Documents

Geotechnical and Hydrotechnical Overview Assessment