la guarde creek bridge crossing, siphon creek … · the scope of our work is outlined in our...

GEOTECHNICAL REPORT

LA GUARDE CREEK BRIDGE CROSSING,SIPHON CREEK ROAD, 40 KM NORTHEAST

OF FORT ST. JOHN, B.C.

Prepared for

B.C. MINISTRY OF TRANSPORTATION AND INFRASTRUCTUREPRINCE GEORGE, B.C.

Prepared by

GEONORTH ENGINEERING LTD.3975 18 AVENUEth

PRINCE GEORGE, B.C., V2N 1B2Phone: 250-564-4304 Fax: 250-564-9323

PROJECT No. K-4274

January 18, 2016

GEONORTH ENGINEERING LTD.

B.C. Ministry of Transportation and Infrastructure January 18, 2016Geotechnical Report, La Guarde Creek Bridge Crossing,Siphon Creek Road, 40 km Northeast of Fort St. John, B.C. File No. K-4274

TABLE OF CONTENTS

Page No.

1.0 INTRODUCTION 1

2.0 SITE AND PROJECT DESCRIPTION 2

3.0 GEOLOGICAL BACKGROUND 3

3.1 Surficial Geology 3

3.2 Bedrock Geology 3

3.3 Review of Aerial Photographs 3

4.0 SITE INVESTIGATION 4

5.0 SUBSURFACE CONDITIONS 5

5.1 Bridge Foundations 5

5.2 Existing Pavement Structure 7

6.0 DISCUSSIONS AND RECOMMENDATIONS 8

6.1 Bridge Foundations 9

6.2 Bridge End Fill 12

6.3 Pavement Structure 12

6.4 Aggregates and Fill 13

7.0 CONSTRUCTION REVIEW 15

8.0 CLOSURE 15



APPENDICES

APPENDIX A

Site Location Plan Drawing 4274-A1

Site Plan and Profile Drawing 4274-A2

APPENDIX B

Summary Logs 6 pages

Materials Classification Legend 1 page

APPENDIX C

Transition Detail: Existing to New Road Structure Plate 4274-C1

Typical Embankment Widening Detail Plate 4274-C2

APPENDIX D

Site Photographs Plates 4274-P1 to P2



1.0 INTRODUCTION

The British Columbia Ministry of Transportation and Infrastructure (BCMoT) is planning

to replace an existing multiplate culvert crossing of La Guarde Creek on Siphon Creek Road with

a 28 m long, clear span bridge. The crossing is located about 40 km northeast of Fort St. John,

B.C., and is accessed by the Rose Prairie Road, then about 22 km east on Cecil Lake Road and

30 km north on Siphon Creek Road. The site location is shown on Drawing 4274-A1, in

Appendix A.

BCMoT commissioned GeoNorth Engineering Ltd. to carry out a geotechnical

investigation for design and construction of the proposed bridge foundations and approaches.

The scope of our work is outlined in our proposal dated September 29, 2015 to Mr. Brent Case,

P.Eng. of BCMoT. Mr. Case authorized us to proceed with the work in an email dated

September 30, 2015.

Conceptual design sketches by BCMoT show that the new bridge will be a 28 m long,

12 m wide two lane bridge. At the time of this report, design of the proposed bridge had not

been carried out but we understand the structure will likely use precast concrete or steel girders

and precast concrete abutments placed on pile or spread footing foundations. A site plan

showing the existing crossing is on Drawing 4274-A2, in Appendix A.

This report presents the results of our site investigation, and provides geotechnical

recommendations for design and construction of the proposed bridge foundations and

approaches.

Page 1 of 17



2.0 SITE AND PROJECT DESCRIPTION

The present crossing consists of a 3.6 m diameter, 28.3 m long, structural plate

corrugated steel pipe (SPCSP). The upstream (south) side of the SPCSP was recently damaged

and about 12 m length of pipe was removed. An emergency repair was made to the road

consisting of rip-rap slope protection, a short concrete locking block wall on the south side and

fill placed out over the north side to shift the road north, away from the eroded upstream bank.

The road is currently open for singe-lane traffic only.

Site plans and cross section profiles dated August 2015 by McElhanney Consulting

Services Ltd., survey consultants for the project, show there is between 2.0 to 2.5 m of soil cover

over the culvert. The pipe inlet and outlet are at elevations 672.1 and 671.3 m, respectively. The

lowest point of the creek bed upstream of the culvert is at about elevation 670.6 m, lower than

the culvert inlet and the high water mark is at approximately elevation 674.2 m. The site plans

show an existing beaver dam located near the original culvert inlet.

The cause of the culvert failure is unknown, but might have been due to buoyant uplift

forces caused by air inside the pipe when it became partially blocked by the beaver dam and

other debris. Other possible causes include joint separation from differential settlement or poor

construction, piping or scour below the culvert inlet due to poorly compacted backfill, inadequate

erosion protection, or holes in the pipe from corrosion.

The existing road consists of two 3.6 m wide, paved lanes and about 0.5 m wide gravel

shoulders, for a total width of about 8.2 m. The bridge surface will likely consist of two 3.6 m

wide lanes, 2.0 m wide shoulders and an allowance for bridge parapets, for a total width of about

12 m. To accommodate an increased road width, we understand the grade of the road at the

proposed bridge crossing will be slightly lowered. Conceptual design sketches show the existing

creek channel will be moved slightly east and the channel skew angle relative to the bridge will

be increased from 29 to 35 . Overview photos of the site are shown on Plates 4274-P1 and P2o o

in Appendix D.

Page 2 of 17



3.0 GEOLOGICAL BACKGROUND

To obtain geological background information for this project, we reviewed published

surficial and bedrock geological maps and reports, and aerial photographs.

3.1 Surficial Geology

Map 1460A, by Geological Survey of Canada, at a scale of 1:250,000, shows the area

along the Doig River valley is underlain by deposits from Glacial Lake Peace and the uplands

on each side of the valley are underlain by drumlinized till. The site, located near the south edge

of the Doig River valley at about elevation 670 m, is well below the level of Glacial Lake Peace,

shown at about elevation 700 m on the map. Glacial lake sediments typically consist of layered

silt, clay and fine grained sand. Glacial till is typically a heterogeneous mixture of sand to cobble

size particles in a silt and clay matrix, deposited from below glacial ice that once covered

the area.

3.2 Bedrock Geology

Map NO-10-G, by Geological Survey of Canada, at a scale of 1:500,000, shows that

bedrock in the area is Lower to Upper Cretaceous in age. The bedrock is identified as fine clastic

sedimentary rocks including dark grey marine shale, siltstone and sandstone of the Fort St. John

Group and the Kotaneelee Formation.

3.3 Review of Aerial Photographs

We reviewed digital aerial photographs available from GeoBC from flight lines

30BCB95008 dated 1995, 15BCB97013 dated 1997, and 15BCC05124 dated 2005. The photos

show the project area on flat terrain that has a mottled surface and dendritic drainage patterns,

characteristic of areas underlain by glacial lake sediments. Starting just upstream of the bridge

crossing, La Guarde Creek channel has cut into the flat lying glacial lake sediments, and created

Page 3 of 17



a steep-sided, incised draw that becomes progressively deeper and with more unstable sidewalls

to the confluence with Doig River. Most of the surrounding land is cultivated farmland or tree

covered. The photos show Siphon Creek Road, the culvert crossing at La Guarde Creek and

ponded water at the culvert inlet. In the 1995 photos the ponded water can be seen extending

more than 1 km upstream. In the later photos, ponding is mostly isolated to a marshy area

directly upstream of the culvert.

4.0 SITE INVESTIGATION

On October 7 and 8, 2015, personnel from our office observed soil and groundwater

conditions in two drill holes, designated DH15-1 and 2, that were advanced to 27.2 and 24.4 m

depth, respectively, on each side of the crossing. The holes were advanced by Peace Drilling and

Research Ltd. of Fort St. John using a truck-mounted rig and solid-stem augers. Sampling was

carried out at regular intervals using Standard Penetration Tests (SPTs) (ASTM D1568) and

Shelby tubes (ASTM D1587). We also collected samples from the auger flights and carried out

shear vane (ASTM D2573) tests in the drill holes. Drill hole locations were measured from site

landmarks and elevations were surveyed using an engineering level and rod. The locations of

the drill holes are shown on Drawing 4274-A1, in Appendix A. Drill hole elevations were

referenced to the culvert inlet and outlet elevations and are shown on the drill hole logs. A cross

section profile showing the existing centre line profile and stick logs of subsurface conditions

are also shown on Drawing 4274-A1.

We logged soil and groundwater conditions encountered in the drill holes as they were

advanced and collected representative samples for laboratory tests and classification. Selected

samples were tested in our laboratory for natural moisture content, Atterberg plasticity limits

(ASTM D4318) and grain size distribution. Drill hole summary logs describing subsurface

conditions and showing the laboratory test results are in Appendix B. An explanation of terms

and symbols used on the logs is also included in Appendix B.

Page 4 of 17



The SPT involves driving a standard 50 mm diameter sampling tube into the bottom of

the drill hole using a 62 kg weight, free-falling from a height of 760 mm. The SPT provides

information on the relative density of the soil and allows a sample to be collected. Shelby tube

sampling involves pushing a 75 mm diameter thin-walled tube into the ground to obtain a

relatively undisturbed sample. Field shear vane tests involve pushing a four-bladed vane into

undisturbed soil below the bottom of the drill hole and rotating it from surface while measuring

the torque required to shear a cylindrical surface. The shear vane is used to measure the

undrained shear strength of the soil.

5.0 SUBSURFACE CONDITIONS

5.1 Bridge Foundations

The drill holes encountered similar conditions consisting of the following soil units:

Unit 1 - Loose to compact granular fill with trace to some fines, over

Unit 2 - Stiff to very stiff silty clay fill with a variable amount of sand and gravel, over

Unit 3 - Varved and layered, soft to stiff clay and silt, over

Unit 4 - Very stiff, silty clay till with a trace of sand and gravel, over

Unit 5 - Extremely weak to very weak siltstone bedrock.

Unit 1, the granular fill was encountered in both drill holes to about 0.9 m depth. The

granular fill in DH15-1 consists of loose sandy gravel used to shift the road north. In DH15-2,

the granular fill consists of compact sand and gravel used in the existing pavement structure.

The existing pavement structure is described in the following section.

Unit 2, the silty clay fill was encountered below Unit 1 in both drill holes to 3.1 and

5.5 m depth, respectively. Field shear vane and pocket penetrometer tests indicate the strength

of the silty clay fill decreases with depth with an undrained shear strength between 75 and

125 kPa. Laboratory Atterberg limit tests, used to define the plasticity of the soil and to infer its

Page 5 of 17



general engineering characteristics, were carried out on four samples of the silty clay fill. The

results indicate the fill has properties of intermediate to high plasticity, with a plastic limit of

about 24% and a liquid limit between 45% and 52%. The plastic limit defines the moisture

content at which soil behaviour changes from a semisolid to a plastic material, and the liquid

limit defines the moisture content at which soil behaviour changes from a plastic material to that

of a viscous liquid. The natural moisture content of the silty clay fill is typically near the

plastic limit.

Unit 3, the varved and layered clay and silt was encountered below Unit 2 to 16.5 m

depth in DH15-1 and 17.5 m depth in DH15-2. The unit is from Glacial Lake Peace and contains

frequent gypsum crystals throughout the deposit. The undrained shear strength of the natural

clay and silt for the full depth of the unit is between about 25 and 60 kPa based on field shear

vanes. Atterberg limit tests indicate the clay has properties of high plasticity, with a plastic limit

of about 26% and a liquid limit between 58% and 71%. The silt layers are low to intermediate

plasticity, with a plastic limit of about 22% and a liquid limit between 33% and 37%. The

natural moisture content of the clay is typically higher than the plastic limit but lower than the

liquid limit and the natural moisture content of the silt is typically near the liquid limit.

Over-consolidation ratio (OCR) is an important geotechnical parameter to evaluate the

potential for foundation settlement. It is defined as the preconsolidation pressure divided by the

present effective stress state of the soil. Soil preconsolidation pressure is the maximum stress

that the soil has previously experienced and can be higher than the existing stress conditions due

to changes in groundwater levels, erosion of materials that previously covered an area, or

construction of a preload fill. Foundation loads that do not cause the effective stress in the

underlying soil to exceed the preconsolidation pressure will result in less settlement than loads

that exceed the preconsolidation pressure.

A correlation based on normalized field vane strength to OCR shows the natural clay and

silt is over-consolidated to about 8.5 m depth, with an OCR between 1.3 and 5, and normally to

slightly over consolidated below 8.5 m depth, with an OCR between 1 and 1.3. This indicates

Page 6 of 17



that the natural clay and silt at depth has not experienced significantly more vertical stress than

the existing overburden pressure and will therefore be susceptible to significantly more

settlement than if the deposit was over-consolidated.

Unit 4, the clay till was encountered below Unit 3 in DH15-1 and extends to 18.6 m

depth. The clay till has properties of intermediate plasticity, with a plastic limit of 19% and a

liquid limit of 37%. The natural moisture content of the till is about 15%. The undrained shear

strength of the clay till is about 100 kPa based on pocket penetrometer tests.

Unit 5, the siltstone bedrock was encountered below Unit 4 to the end of both drill holes

at 27.2 m and 24.4 m depth, respectively. The bedrock was easily penetrated with augers during

drilling. The siltstone bedrock is poorly lithified, extremely weak and highly weathered in the

top 1 to 3 m depth. Below 1 to 3 m depth the bedrock has isolate shale layers, is very weak and

moderately weathered. We estimate the uniaxial compressive strength of the siltstone is between

1 and 5 MPa.

No groundwater seepage was observed in the drill holes.

5.2 Existing Pavement Structure

DH15-2, located at the south side of the east approach, generally encountered the

following pavement structure:

• 75 mm of Asphalt Pavement, over

• 775 mm of Base Coarse and Subbase, over

• Geogrid and non-woven geotextile, over

• Clay subgrade

Page 7 of 17



The base coarse and subbase generally consists of a mixture of gravel and sand sized

particles with between 7% and 13% fines. The aggregate is typically less than 75 mm diameter

and is rounded to subangular. The subgrade consists of very stiff, intermediate to high plastic,

silty clay fill with a variable amount of sand and gravel.

6.0 DISCUSSIONS AND RECOMMENDATIONS

The crossing is generally underlain by a significant thickness of embankment fill, over

glaciolacustrine sediments from Glacial Lake Peace, over a thin layer of gravelly clay till below

one side of the crossing, over bedrock at between 17.5 and 18.6 m depth.

The natural soft to firm clay and silt has low bearing capacity, high potential for

settlement and is highly susceptible to frost heave caused by the development of ice lenses. The

glacial lake sediments in the region are also known to contain minerals that cause it to shrink and

swell in response to changes in moisture content. The existing embankment fill is susceptible

to differential settlement and is not suitable for support of spread footing foundations.

Given the relatively weak, compressible soil conditions, the shrink and swell potential

of the soil, and the significant thickness of existing fill, we recommend against using spread

footing foundations to support the proposed bridge. Instead, we recommend supporting the

bridge structure on driven pile foundations end-bearing on the relatively shallow bedrock, as

described below.

The following recommendations are based on the necessary assumption that ground

conditions encountered in the drill holes are representative of conditions elsewhere below the

project site. The bedrock surface appears to be relatively flat but could be deeper than

encountered in the drill holes. Please contact our office for additional recommendations if

conditions encountered during construction differ in any way from those described in this report.

Page 8 of 17



6.1 Bridge Foundations

Steel pipe piles driven to the bedrock will be suitable for support of the proposed bridge

structure. The piles will gain most of their capacity from end-bearing in the bedrock.

6.1.1 Axial Capacity

To estimate bridge foundation loads we assume the bridge will be constructed using

Type 2 concrete box stringers, concrete abutments, and a 100 mm thick concrete overlay. We

also assume the bridge will be designed to carry BCL-625 live loads. Based on these

assumptions we estimate the ultimate limit states (ULS) live and dead loads will be about

7,000 kN at each abutment.

Based on information from the drill holes, we carried out preliminary pile capacity

analyses using several methods outlined in the Canadian Foundations Engineering Manual

(CFEM) (Canadian Geotechnical Society, 2006). The methods use undrained shear strength,

effective stress and SPT ‘N’ values. BCMoT’s Supplement to the Canadian Highway Bridge

Design Code specifies a geotechnical resistance factor of 0.35 for design based on SPT

information. Assuming each abutment will have six piles connected to a pile cap, each pile will

need to have a geotechnical resistance of about 1,200 kN and the required ultimate geotechnical

resistance of 3,400 kN.

Pile capacity will depend largely on end-bearing resistance, as well as shaft friction, the

pile stiffness (wall thickness and length), the energy of the pile driving equipment, and the

penetration resistance at end-of-driving. We analysed the estimated embedment depth and

driveability of 610 mm and 762 mm diameter open-ended steel pipe piles. The piles are likely

to penetrate the siltstone bedrock between 1 and 3 m. We analysed pile driveability using the

computer program GRLWEAP (GRLWEAP, 2005), assuming end bearing in the bedrock at

about elevation 658 m. A summary of the analyses is shown in Table 1, below.

Page 9 of 17



Table 1, Summary of Pile Driving Analyses for 610 and 762 mm Diameter Open-End Pipe Piles

610 mm Diameter,

12.7 mm Wall Thickness

762 mm Diameter,

12.7 mm Wall Thickness

Factored Geotechnical Resistance 1,200 kN 1,500 kN

Anticipated Tip Elevation 657 m 657 m

Driving Energy 120 kJ 160 kJ

Penetration Resistance 250 blows/m 260 blows/m

Maximum Pile Stress 250 MPa 280 MPa

Based on the estimated maximum pile stress we recommend using piles manufactured

with Grade 3 steel (ASTM A252). Use an inside-fit cutting shoe to reduce the potential for

damage to the tip of the pile while driving into the bedrock. We recommend the axial capacity

be confirmed using Pile Driving Analysis (PDA) (ASTM D4945) method Case Pile Wave

Analysis Program (CAPWAP) if conditions do not appear to be straightforward or if there are

any concerns regarding the efficiency of the hammer energy being delivered to the pile, or if

there are any indications of damage to the pile. Information on pile capacity from a PDA with

a CAPWAP will also allow the use of a geotechnical resistance factor of 0.5 (BCMOT, 2007).

Allow at least 72 hours between pile installation and testing.

We recommend that additional analyses be carried out once bridge design and loads are

known.

6.1.2 Pile Settlement

Pile settlement occurs primarily due to the transfer of stress to the soil and elastic

shortening of the pile. Settlement in the granular soil around the pile will generally occur as the

pile begins to carry loads during construction of the bridge, although a small portion of the

settlement will occur as plastic creep over time.

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We estimate the settlement of the soil around and below a pile using methods described

in the CFEM. Using specified loads of 1,000 and 1,400 kN for 610 and 762 mm diameter piles,

respectively, with the load evenly distributed between shaft and end bearing resistance, both pile

sizes will settle less than 5 mm. Differential settlement between each abutment could be as high

as the total settlement.

6.1.3 Lateral Pile Capacity

The abutment will be subjected to lateral loads from earth pressures and vehicle breaking.

These loads generally act along the long axis of the bridge and will likely be transmitted through

bridge girders to the opposite abutment wall and bridge end fill, resulting in no significant loads

being transferred to the piles. We recommend additional analyses be carried out once the bridge

design loads are known.

6.1.4 Seismic Design Considerations

The 2012 British Columbia Building Code defines the “Site Classification for Seismic

Site Response”, Table 4.1.8.4.A, which is based on the soil conditions to a depth of 30 m. Based

on our drill hole observations, we estimate the silty clay and clayey silt underlying the site has

an average undrained shear strength between 50 and 100 kPa, and the Site Classification for

Seismic Site Response is no worse than Site Class “D”, as defined in Table 4.1.8.4.A.

Based on our observations that the site is underlain by a thick deposit of soft to stiff silty

clay and clayey silt over bedrock, we recommend the following Canadian Highway Bridge

Design Code (2014) seismic hazard values for the project:

Site

ClassSa(0.2) Sa(0.5) Sa(1.0) Sa(2.0) Sa(10.0) F(0.2) F(0.5) PGA PGV

D 0.138 g 0.088 g 0.050 g 0.024 g 0.0031 g 1.24 1.47 0.079 g 0.058 g

Note: Determined for a 2% in 50 year (0.000404 per annum) probability of exceedence.

Page 11 of 17



6.2 Bridge End Fill

BCMoT’s Standard Specifications for Highway Construction (BCMoT, 2011) requires

bridge end fill (BEF) extend a distance of 8 m from the bridge abutment with a 1.5 Horizontal

to 1.0 Vertical (1.5H:1V) backslope. Prior to placing BEF, remove organic material and soft,

wet or deleterious soil and compact the subgrade surface to at least 98% Standard Proctor

Density (SPD) (ASTM D698). Place BEF in layers not exceeding 150 mm thickness and

compact each layer to at least 100% SPD.

6.3 Pavement Structure

The recommended base and subbase thicknesses are intended to provide for a long first

cycle life and long-term support for moderate axle loads, provided the pavement surface is

rehabilitated at appropriate intervals. We recommend the following pavement structure to

provide similar strength to that of the existing:

• 75 mm of Asphalt Pavement (Class 1), over

• 200 mm of 25 mm Well Graded Base (WGB), over

• 600 mm of Select Granular Subbase (SGSB), over

• Biaxial geogrid, over

• Nonwoven geotextile, over

• A prepared subgrade.

Construct all components of the new pavement structure with at least a 2% crossfall to

the outside. Where the new structure ties into the existing structure we recommend using a saw

cut between 20E and 30E from perpendicular to road centreline. At the face of the saw cut, leave

an undisturbed width of existing crushed base 500 mm wide, then begin excavation of a

transition slope of 4 Horizontal to 1 Vertical (4H:1V) to accommodate the new pavement

structure thickness. A conceptual transition detail are shown on Drawing 4274-C1, in Appendix C.

Page 12 of 17



Use a medium weight nonwoven geotextile that meets or exceeds the following

Minimum Average Roll Values (MARV):

• Minimum Grab Tensile Strength (ASTM D4632), 900 N

• Minimum Puncture Strength @ 50% or More Elongation (ASTM D6241), 2.3 kN

• Minimum Trapezoidal Tear (ASTM D4533), 350 N

• Apparent Opening Size (ASTM D4751), 0.2 mm ± 0.02 mm

Use a polypropylene biaxial geogrid that meets or exceeds the following values:

• Minimum Tensile Strength in Machine Direction @ 5% Strain

(ASTM D6637), 11 KN/m

• Minimum Tensile Strength in Cross Machine Direction @ 5% Strain

(ASTM D6637), 19 KN/m

• Aperture Size, 15 to 35 mm

• Minimum Flexural Stiffness (ASTM D5732), 750 mg-cm

6.4 Aggregates and Fill

6.4.1 Base, Subbase and Bridge End Fill

Three material types are specified for construction of the pavement structure and bridge

embankment noted above:

• 25 mm Well Graded Base (WGB),

• Select Granular Subbase (SGSB),

• Bridge End Fill (BEF).

Use material that meets BCMoT’s specifications noted in Section 202 of the 2012

Standard Specifications for Highway Construction.

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6.4.2 Highway Embankment and Subgrade Fill

We recommend constructing the embankment using mineral soil free of organic and

deleterious material and containing less than 15% by volume of rock larger than 150 mm.

Granular material excavated from the existing embankment at the start and end of the project and

from both new bridge end-fill areas, can be reused as embankment fill. We recommend using

embankment fill slopes no steeper than 2H:1V for granular fill and slopes no steeper than 3H:1V

for cohesive embankment fill and the natural clay and silt. The stream channel below the bridge

may require revetment to prevent on-going channel erosion from undermining the slopes leading

up to the bridge abutments.

In some areas the surface of the existing embankment will be covered with winter road

sand, grass, and brush. We recommend stripping the surface of the embankment to expose

compact mineral soil. Key new fill into the existing embankment using benches. Cut the

benches into the existing embankment using a minimum bench width of 1.5 m and a maximum

height of 1.2 m. If suitable, the material from the bench can be incorporated into the new

embankment. Slope the bench surface at a gradient of 2% towards the outside slope face. A

conceptual cross section showing this detail is on Drawing 4274-C2, in Appendix C.

Place the embankment fill in thin, uniform layers and compact each layer to at least 95%

SPD, and to at least 100% SPD within 300 mm of the top of subgrade, at a moisture content

within 2% of optimum. The maximum layer thickness will depend on several factors, including

compactor type, size and energy, and the soil type and moisture content, but do not use a layer

thickness more than 200 mm. Add water and dry the fill as necessary to attain the specified

density and moisture content. Where the embankment is relatively narrow between about

Stations 102+20 and 102+50, if necessary, construct the embankment slopes no steeper than

3H:1V by widening the base as described above. Protect the toe of the slope from erosion as

required for that length of slope below the projected 200 year return period flood level.

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7.0 CONSTRUCTION REVIEW

We recommend that we review final design drawings to confirm that the intent of our

recommendations have been applied, that the recommendations in this report are appropriate and

that sufficient geotechnical investigation has been carried out.

We recommend that an experienced geotechnical engineer, or their designate, review

critical aspects of the project to confirm that soil conditions are as expected and that construction

materials, their placement and their level of compaction are as specified. If soil conditions or

construction materials are different than expected, we can provide additional recommendations

to address the actual conditions. We consider the following geotechnical aspects of the work as

being critical to the project:

• Removal of soft or deleterious soil below areas of fill,

• Gradation, durability, placement and compaction of fill, and

• Pile installation, and whether a PDA with a CAPWAP are required.

8.0 CLOSURE

This report was prepared by GeoNorth Engineering Ltd. for the use of B.C. Ministry of

Transportation and Infrastructure and their consultants. The material in it reflects GeoNorth

Engineering’s judgement in light of the information available to us at the time of preparation.

Any use which Third Parties make of this report, or any reliance on decisions to be made based

on it, are the responsibility of such Third Parties. GeoNorth Engineering Ltd. accepts no

responsibility for damages, if any, suffered by any third party as a result of decisions made or

actions based on this report.

Page 15 of 17



REFERENCES

B.C. Ministry of Transportation and Infrastructure, 2007. Bridge Standards and Procedures

Manual, Volume 1, Supplement to CHBDC S6-06.

B.C. Ministry of Transportation and Infrastructure, 2011. 2012 Standard Specifications for

Highway Construction, Volume 1.

Canadian Geotechnical Society, 2006. Canadian Foundation Engineering Manual, 4 Edition.th

Canadian Standards Association, 2014. CSA-S6 - Canadian Highway Bridge Design Code.

GRLWEAP Wave Equation Analysis of Pile Driving, 2005. [Computer Software], Cleveland,

Ohio, USA, Pile Dynamics, Inc.

McElhanney Consulting Services Ltd., 2015. Plan & Profiles, Siphon Creek Road, La Guarde

Creek. Drawing NR-XXX-101, August 6, 2015. Submitted to British Columbia Ministry

of Transportation and Infrastructure.

Natural Resources Canada (2015): Determine 2015 Seismic Hazard Values for Nation Building

Code and Canadian Highway Bridge Design Code, URL<http://www.earthquakescanada.

nrcan.gc.ca/hazard-alea/interpolat/index_2015-eng.php>, November 2015.

Page 17 of 17



A P P E N D I X A



A P P E N D I X B

GW-GM

CL

CH

0.91m

3.05m

1

2

34

5

6

7

8

9

10

11

12

23

112

95

87

95

GRAVEL, sandy, trace fines, loose, brown,damp (FILL).

CLAY, silty, trace gravel, trace sand, stiffto very stiff, intermediate plasticity, brown,rust staining, MC<PL (FILL).- between 1.2 and 1.8m, some gravel.

CLAY, silty, varved, firm, high plasticity,grey, occasional gypsum crystals, MC>PL.- between 3.0 and 3.8m, frequent gypsumcrystals.

- between 5.8 and 6.4m, layered with lowplasticity, clayey silt.

Sieve (Sa#1)G:59% S:34% F:7%

Atterberg (Sa#3):PL:24% LL:47%



ELE

VA

TIO

N (

m)

1

2

3

4

5

6

7

8

9

LegendSample Type:

S-SplitSpoon

O-Odex(air rotary)

T-ShelbyTube

C-CoreA-Auger G-Grab V-Vane

1

2

3

4

5

6

7

8

9

Driller: Jesse Rushton

Drill Make/Model: Truck Mounted

CLA

SSIF

ICAT

ION

Location: Siphon Creek Road, 40 km northeast of Fort St. John, B.C.

Date(s) Drilled: Oct. 7, 2015

Drilling Method: Solid Stem AugersCoordinates taken with GPS

Project: La Guarde Creek Bridge Crossing

SUMMARY LOG

L#-Lab SampleW-Wash(mud return)

Elevation: 677.87 m

677

676

675

674

673

672

671

670

669

668

Geonorth Engineering LtdPrepared by:

Logged by: JAH Reviewed by:

SO

IL S

YM

BO

L

RE

CO

VE

RY

(%

)

SA

MP

LE N

O

SA

MP

LE T

YP

E

SOILDESCRIPTION

00

Page 1 of 3

DE

PT

H (

m)

DR

ILLI

NG

DE

TA

ILS

Datum: 10V

Alignment: Existing

10

0

Station/Offset: 101+84 6.4m Lt

Northing/Easting: 6267211 , 657491

Final Depth of Hole: 27.2 mDepth to Top of Rock: 18.6 m

Drill Hole #: DH15-1

COMMENTSTESTING

Drillers Estimate{G % S % F %}

Drilling Company: Peace Drilling

DYNAMIC CONE (BLOWS/300 mm)

MO

T-S

OIL

-RE

V1

427

4-G

INT

-RE

V1B

-MO

T-D

H L

OG

S.G

PJ

MO

T-D

RA

FT

-RE

V1A

.GD

T 1

6/0

1/14

LW %W %

20 40 60 80P W%

SPT "N" (BLOWS/300 mm)

SHEAR STRENGTH (kPa) POCKET PEN

Natural Vane (KPa) Remold Vane (KPa)

100 200 300 400

110

7

8

7

6

CL-ML

CH

CL

12.8m

14.02m

16.46m

18.59m

13

14

15

16

17

18

92

105

92

103

103

CLAY, silty, varved, firm, high plasticity,grey, occasional gypsum crystals, MC>PL.(continued)

CLAY, and SILT, trace fine grained sand,layered, soft, intermediate plasticity, grey,MC>PL, slow dilatancy.

CLAY, silty, varved, firm, high plasticity,grey, MC>PL.

- at 14.6m, 20mm thick layer of mediumgrained, wet sand.

CLAY, silty, trace to some gravel, tracesand, very stiff, intermediate plasticity,brown-grey, MC<PL (TILL).

BEDROCK, siltstone, poorly lithified,extremely weak (R0), highly weathered,light grey.


Atterberg (Sa#17):PL:19% LL:37%Sieve (Sa#17)G:24% S:15% F:61%

ELE

VA

TIO

N (

m)

11

12

13

14

15

16

17

18

19

LegendSample Type:

S-SplitSpoon

O-Odex(air rotary)

T-ShelbyTube


11

12

13

14

15

16

17

18

19



CLA

SSIF

ICAT

ION





SUMMARY LOG


Elevation: 677.87 m

667

666

665

664

663

662

661

660

659

658



SO

IL S

YM

BO

L

RE

CO

VE

RY

(%

)

SA

MP

LE N

O

SA

MP

LE T

YP

E

SOILDESCRIPTION

1010

Page 2 of 3

DE

PT

H (

m)

DR

ILLI

NG

DE

TA

ILS

Datum: 10V

Alignment: Existing

20

10





COMMENTSTESTING




MO

T-S

OIL

-RE

V1

427

4-G

INT

-RE

V1B

-MO

T-D

H L

OG

S.G

PJ

MO

T-D

RA

FT

-RE

V1A

.GD

T 1

6/0

1/14

LW %W %

20 40 60 80P W%




100 200 300 400

6

9

BR

27.2m

19

20

21

22

4

16

10

BEDROCK, siltstone, poorly lithified,extremely weak (R0), highly weathered,light grey. (continued)

- below 21.0m, isolated shale layers, veryweak (R1), moderately weathered, darkgrey.

End of drill hole at 27.2m.No seepage encountered.

ELE

VA

TIO

N (

m)

21

22

23

24

25

26

27

28

29

LegendSample Type:

S-SplitSpoon

O-Odex(air rotary)

T-ShelbyTube


21

22

23

24

25

26

27

28

29



CLA

SSIF

ICAT

ION





SUMMARY LOG


Elevation: 677.87 m

657

656

655

654

653

652

651

650

649

648



SO

IL S

YM

BO

L

RE

CO

VE

RY

(%

)

SA

MP

LE N

O

SA

MP

LE T

YP

E

SOILDESCRIPTION

2020

Page 3 of 3

DE

PT

H (

m)

DR

ILLI

NG

DE

TA

ILS

Datum: 10V

Alignment: Existing

30

20





COMMENTSTESTING




MO

T-S

OIL

-RE

V1

427

4-G

INT

-RE

V1B

-MO

T-D

H L

OG

S.G

PJ

MO

T-D

RA

FT

-RE

V1A

.GD

T 1

6/0

1/14

LW %W %

20 40 60 80P W%




100 200 300 400

Refusal, 50 for 1"

Refusal, 50 for 4"

Refusal, 50 for 3"

AP

GM1

CL-CH

CH

0.08m

0.85m

5.49m

1

2

3

4

5

6

7

8

9

10

11

36

43

89

84

92

ASPHALT.SAND, and GRAVEL, some fines,compact, brown, damp (FILL).- at 0.85m, geogrid over nonwovengeotextile.CLAY, silty, trace gravel, trace sand, stiffto very stiff, intermediate to high plasticity,brown, rust staining, MC>PL (FILL).- at 0.9m, a layer of geogrid andgeotextile.- at 1.5m, organic soil layer about 5cmthick.

- between 2.7 and 3.5m, trace to someorganic soil content.

- below 4.3m, isolated gypsum crystals.

CLAY, silty, varved, soft, high plasticity,grey, isolated gypsum crystals, MC>PL. PP=30 to 50

Sieve (Sa#1)G:40% S:47% F:13%





ELE

VA

TIO

N (

m)

1

2

3

4

5

6

7

8

9

LegendSample Type:

S-SplitSpoon

O-Odex(air rotary)

T-ShelbyTube


1

2

3

4

5

6

7

8

9



CLA

SSIF

ICAT

ION





SUMMARY LOG


Elevation: 677.15 m

677

676

675

674

673

672

671

670

669

668



SO

IL S

YM

BO

L

RE

CO

VE

RY

(%

)

SA

MP

LE N

O

SA

MP

LE T

YP

E

SOILDESCRIPTION

00

Page 1 of 3

DE

PT

H (

m)

DR

ILLI

NG

DE

TA

ILS

Datum: 10V

Alignment: Existing

10

0

Station/Offset: 102+22 2.8m Rt




COMMENTSTESTING




MO

T-S

OIL

-RE

V1

427

4-G

INT

-RE

V1B

-MO

T-D

H L

OG

S.G

PJ

MO

T-D

RA

FT

-RE

V1A

.GD

T 1

6/0

1/14

LW %W %

20 40 60 80P W%




100 200 300 400

11

8

ML-CL

CL

12.65m

13.72m

17.53m

12

13

14

15

16

17

18

19

20

110

110

92

108

36

CLAY, silty, varved, soft, high plasticity,grey, isolated gypsum crystals, MC>PL.(continued)

- at 11.3m, dropstone.

SILT, and CLAY, trace sand, layered, soft,low to intermediate plasticity, grey,MC>PL, rapid dilatancy.

CLAY, silty, varved, layered with clayeysilt, stiff, intermediate plasticity, grey,MC>PL.

- below 16.8m, no silt layering.

BEDROCK, siltstone, poorly lithified,extremely weak (R0), highly weathered,light grey.



ELE

VA

TIO

N (

m)

11

12

13

14

15

16

17

18

19

LegendSample Type:

S-SplitSpoon

O-Odex(air rotary)

T-ShelbyTube


11

12

13

14

15

16

17

18

19



CLA

SSIF

ICAT

ION





SUMMARY LOG


Elevation: 677.15 m

667

666

665

664

663

662

661

660

659

658



SO

IL S

YM

BO

L

RE

CO

VE

RY

(%

)

SA

MP

LE N

O

SA

MP

LE T

YP

E

SOILDESCRIPTION

1010

Page 2 of 3

DE

PT

H (

m)

DR

ILLI

NG

DE

TA

ILS

Datum: 10V

Alignment: Existing

20

10





COMMENTSTESTING




MO

T-S

OIL

-RE

V1

427

4-G

INT

-RE

V1B

-MO

T-D

H L

OG

S.G

PJ

MO

T-D

RA

FT

-RE

V1A

.GD

T 1

6/0

1/14

LW %W %

20 40 60 80P W%




100 200 300 400

7

10

9

51

BR

24.38m

21

22

31

52

BEDROCK, siltstone, poorly lithified,extremely weak (R0), highly weathered,light grey. (continued)

- below 21.0m, isolated shale layers, veryweak (R1), moderately weathered, darkgrey.

End of drill hole at 24.4m.No seepage encountered.

ELE

VA

TIO

N (

m)

21

22

23

24

25

26

27

28

29

LegendSample Type:

S-SplitSpoon

O-Odex(air rotary)

T-ShelbyTube


21

22

23

24

25

26

27

28

29



CLA

SSIF

ICAT

ION





SUMMARY LOG


Elevation: 677.15 m

657

656

655

654

653

652

651

650

649

648



SO

IL S

YM

BO

L

RE

CO

VE

RY

(%

)

SA

MP

LE N

O

SA

MP

LE T

YP

E

SOILDESCRIPTION

2020

Page 3 of 3

DE

PT

H (

m)

DR

ILLI

NG

DE

TA

ILS

Datum: 10V

Alignment: Existing

30

20





COMMENTSTESTING




MO

T-S

OIL

-RE

V1

427

4-G

INT

-RE

V1B

-MO

T-D

H L

OG

S.G

PJ

MO

T-D

RA

FT

-RE

V1A

.GD

T 1

6/0

1/14

LW %W %

20 40 60 80P W%




100 200 300 400

Refusal, 50 for 3"

Refusal, 50 for 6"



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A P P E N D I X D

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