slope stability assessment 262 king street oakville, … planning/14-1... · encountered compact...

Terraprobe Consulting Geotechnical & Environmental Engineering Construction Materials Inspection & Testing

Terraprobe Inc. Greater Toronto Hamilton – Niagara Central Ontario Northern Ontario 11 Indell Lane 903 Barton Street, Unit 22 220 Bayview Drive, Unit 25 1012 Kelly Lake Rd., Unit 1 Brampton, Ontario L6T 3Y3 Stoney Creek, Ontario L8E 5P5 Barrie, Ontario L4N 4Y8 Sudbury, Ontario P3E 5P4 (905) 796-2650 Fax: 796-2250 (905) 643-7560 Fax: 643-7559 (705) 739-8355 Fax: 739-8369 (705) 670-0460 Fax: 670-0558

www.terraprobe.ca

SLOPE STABILITY ASSESSMENT 262 KING STREET

OAKVILLE, ONTARIO

Prepared For: Kai Tukums PO Box 370 Port Carling, Ontario P0B 1J0

File No. 7-17-0013-01 February 9, 2017

© Terraprobe Inc.

Distribution: 1 copy (pdf): Mr. Kai Tukums 1 copy: Terraprobe Inc., Stoney Creek

Kai Tukums February 9, 2017 262 King Street, Oakville, Ontario File No. 7-17-0013-01

Terraprobe Page No. i

TABLE OF CONTENTS

1.0 INTRODUCTION .............................................................................................................. 1

2.0 SITE AND PROJECT DESCRIPTION .............................................................................. 1

2.1 EXISTING SITE CONDITIONS ....................................................................................... 1 2.2 SITE GEOLOGY ......................................................................................................... 1 2.3 SUBSURFACE CONDITIONS ........................................................................................ 2

3.0 ENGINEERED DEVELOPMENT SETBACK .................................................................... 2

3.1 EROSION ALLOWANCE ............................................................................................... 3 3.2 STABLE SLOPE ALLOWANCE ...................................................................................... 3 3.3 ENGINEERED DEVELOPMENT SETBACK ....................................................................... 4

4.0 LIMITATIONS AND RISKS .............................................................................................. 4

FIGURES

FIGURE 1 SITE PLAN FIGURE 2 SECTION A-A’

APPENDICES

APPENDIX A PHOTOGRAPHS APPENDIX B BOREHOLE LOGS APPENDIX C SLOPE STABILITY ANALYSIS RESULTS


Terraprobe Page No. 1

1.0 INTRODUCTION

Terraprobe Inc. has been retained by Mr. Kai Tukums to carry out a slope stability assessment at 262 King Street in Oakville, Ontario. A proposal and cost estimate to carry out the assessment were provided in our letter of January 23, 2017. Authorization to proceed with the work was provided by Mr. Kai Tukums on January 24, 2017. It is understood that the geotechnical assessment will be required as part of the permitting process for the proposed development of the property. It is further understood that it is proposed to subdivide the property into two separate parcels.

The slope stability assessment was completed to satisfy the intent of the policy guidelines outlined in the document entitled Understanding Natural Hazards Guide (Ministry of Natural Resources, 2001) and the Halton Region Conservation Authority (Conservation Halton) document entitled ‘Polices, Procedures and Guidelines for the Administration of O.Reg. 162/06 and Land Use Planning Policy Document’, dated April 27, 2006 (revised August 11, 2011). An update to the Conservation Halton Shoreline Polices (Sections 3.41 to 3.50 inclusive) is presented in a publication dated December 1, 2015.

2.0 SITE AND PROJECT DESCRIPTION

2.1 Existing Site Conditions

The site was examined by a senior geotechnical engineer from our staff on January 26, 2017 to obtain information regarding the existing site and slope features. Photographs illustrating the general features of the property are provided in Appendix A. The existing site features are shown on Figure 1, as derived from a topographical survey of the property, prepared by J.H, Gelbloom Surveying, OLS, dated January 26, 2010. It is noted that there is Municipal Right of Way (ROW) located to the immediate south of the property which separates it from Lake Ontario shoreline. There is an asphalt paved pathway currently located within the ROW.

Development on the property consisted of a single family dwelling overlooking Lake Ontario. The ground surface topography on the property was generally flat with a mild slope towards the top of an existing armourstone retaining. The wall (about 1.3 m high) is followed by a relatively flat area partly covered with stone riprap extending up to the water’s edge. During periods of high water levels, the lake water is expected to be in contact with the wall. The water level of Lake Ontario at the time of this investigation was at about elevation 74.8 metres. Figure 2 presents a representative cross-section of the site and shoreline slope, Sections A-A’.

2.2 Site Geology

Based on published geological information for the general area of the site, the near surface overburden soil at and in the vicinity of the subject property consists of Pleistocene Age Late Wisconsinan lacustrine



and outwash sand1. The sand is typically underlain by glacial till and bedrock of the Georgian Bay Formation2. The Georgian Bay Formation consists of blueish grey shale, interbedded with limestone and calcareous sandstone. The geological mapping and regional well records indicates that the bedrock beneath the site could be some 6 to 7 metres below ground surface.3

2.3 Subsurface Conditions

The subsurface conditions in the area of the subject property were confirmed previously by Terraprobe in 2011, at which time a borehole was drilled on the neighbouring property at 26 Trafalgar Road. The results of this borehole are shown on the Log of Borehole sheet in Appendix B. In general, the borehole encountered compact sand to silty sand, overlying a stratum of dense to very dense silt to sandy silt, hard clayey silt, and weathered shale bedrock. The borehole penetrated low permeability deposits which generally precludes the free flow of ground water. At this site the ground water levels will coincide with the level of Lake Ontario, which was at about elevation 74.8 metres at the time of this assessment.

3.0 ENGINEERED DEVELOPMENT SETBACK

Ontario Regulation 162/06 stipulates that permission is required from the Halton Region Conservation Authority to undertake development or redevelopment within the shoreline hazard limit. O.Reg 162/06 s.2(1) defines the hazardous lands adjacent to the shorelines of the Great Lakes - St. Lawrence River System as those lands, which are impacted by flooding, erosion, or dynamic beach hazards. The furthest landward limit of the three hazards defines the shoreline hazard limit. O.Reg 162/06 s.3(1) further provides that the Authority may grant permission for development within the shoreline hazard limit ‘if, in its opinion, the control of flooding, erosion, dynamic beaches, pollution or the conservation of land will not be affected by development’.

The erosion hazard limit is defined as the average annual recession rate for a 100 year planning horizon (erosion allowance), plus the stable slope allowance. In the absence of a site specific study, an average annual recession rate of 0.3 metres per year for Lake Ontario (30 metres) and a stable slope allowance (based on a 3 horizontal to 1 vertical stable profile) are typically applied by Conservation Halton to determine the baseline erosion hazard limit. Any reduction in the baseline erosion hazard limit is termed by Conservation Halton as the Engineered Development Setback (EDS). The EDS limit is applied as an offset from the toe of slope. Where there is existing shoreline protection, Conservation Halton requires that the back of the protection structure, from an elevation of about 75.0 metres, be used as the inferred toe of the slope.

1 Quaternary Geology of the Hamilton Area, Southern Ontario; Ontario Division of Mines; Map No. 2605;

1983. 2 Paleozoic Geology, Hamilton Area, Southern Ontario; Ontario Division of Mines; Map No. 2336; 1976. 3 Bedrock Topography of the Hamilton Area, Southern Ontario; Ontario Department of Mines; Map No. 2034;

1964.



The specific location of the EDS limit has not been determined, since this is subject to the review of the existing shoreline protection by Conservation Halton and/or an experienced coastal engineer. The following presents a discussion of each setback component to assist in the determination of the EDS Limit.

3.1 Erosion Allowance

Conservation Halton will provide guidance with respect to the applicable erosion allowance to be applied at this site. Based on our experience on other properties in this area, Conservation Halton may permit the reduction of the 100 year recession from 30 to 20 metres. This is subject to the existing or proposed shoreline protection works being in good order (as determined by a professional engineer with experience in coastal processes and approved by Conservation Halton), and assuming a 5 metre unobstructed access to and along those works (for maintenance and repair/replacement) will be maintained.

3.2 Stable Slope Allowance

A detailed engineering analysis of slope stability was carried out for a selected slope cross-section utilizing a commercially available slope stability program Rocscience - Slide 6.0. The slope stability assessment was based on an effective stress limiting equilibrium analysis for long term slope stability using Spencer, Bishop and Jambu methods. The methods of analysis allow for the calculation of Factors of Safety for hypothetical or assumed failure surfaces through the slope. The analysis method is used to assess potential for movements of large masses of soil over a specific failure surface which is often curved or circular.

For a specific failure surface, the Factor of Safety is defined as the ratio of available strength resisting movement, divided by the gravitational forces tending to cause movement. The Factor of Safety of 1.0 represents a ‘limiting equilibrium’ condition where the slope is at the point of pending failure since the soil resistance is equal to the forces tending to cause movement. The analysis involves dividing the sliding mass into many thin slices and calculating the forces on each slice. The normal and shear forces acting on the slides and base of each slice are calculated. It is an iterative process that converges on a solution. The typical Factor of Safety used for engineering design of slopes for stability in building applications, ranges from about 1.3 to 1.5. Conservation Halton policies are based on a minimum Factor of Safety of 1.5 for development applications.



The following average soil properties were assumed for the soil strata in the slope stability analysis.

Stratigraphic Unit Unit Weight (kN/cu.m) Effective Shear Resistance, c’ (kPa)

Effective Angle of Internal Friction

φ’ (degrees)

SILT/SANDY SILT, dense 21.0 0 32

CLAYEY SILT TILL, hard 21.0 4 32

GEORGIAN BAY FORMATION Weathered Shale Bedrock

Infinite Strength

A cross-section of the shoreline slope (Section A-A’) was derived from the topographic survey information provided by J.H, Gelbloom Surveying. Lake levels rising to the 100-year return period level of 76.0 m were considered in this assessment. The 100-year return period level means that on average there is a 1 percent chance in any given year that the lake water will reach that level. The results of the slope stability analyses are presented in Appendix C. Based on the results of the analyses, it is our opinion that a stable slope of 1.8 horizontal to 1 vertical for long-term conditions would be appropriate for the overburden strata.

3.3 Engineered Development Setback

The location of the EDS limit, determined on the basis of the erosion allowance (20 metres) and stable slope allowance is shown on Figures 1 and 2.

4.0 LIMITATIONS AND RISKS

This assessment has been carried out using engineering analysis methods consistent with those ordinarily exercised by Terraprobe and other engineering practitioners, working under similar conditions and subject to the time, financial and physical constraints applicable to this project. It must be recognized that the passage of time, natural occurrences, and direct or indirect human intervention at or near the site have the potential to alter subsurface conditions. In particular, caution should be exercised in the consideration of contractual responsibilities as they relate to control of seepage, disturbance of soils, and frost protection.

This report was prepared by Terraprobe Inc. for the exclusive use of Kai Tukums and his retained designers and consultants. The intent of the report was to provide a geotechnical engineering assessment at the subject site and not for other purposes. The report is site specific and not applicable to any other property. It is recognized that the Town of Oakville and Conservation Halton will make use of and rely upon this report, cognizant of the limitations thereof, both expressed and implied.



We trust the foregoing information is sufficient for your present requirements. If you have any questions, or if we can be of further assistance, please do not hesitate to contact us.

Terraprobe Inc.

Patrick Cannon, P. Eng. Associate

FIGURES

Terraprobe Inc.

PHOTOGRAPHS

APPENDIX A

Terraprobe Inc.

Site Inspection Photographs Appendix A 262 King Street, Oakville, Ontario File No. 7-17-0013-01

Terraprobe

Photograph 1

Photograph 2


Terraprobe

Photograph 3

Photograph 4


Terraprobe

Photograph 5

Photograph 6

LOGS OF BOREHOLES

APPENDIX A

Terraprobe Inc.

Terraprobe ABBREVIATIONS AND TERMINOLOGY

Terraprobe Inc.Greater Toronto Hamilton – Niagara Central Ontario Northern Ontario 11 Indell Lane 903 Barton Street, Unit 22 220 Bayview Drive, Unit 25 1012 Kelly Lake Rd., Unit 1 Brampton, Ontario L6T 3Y3 Stoney Creek, Ontario L8E 5P5 Barrie, Ontario L4N 4Y8 Sudbury, Ontario P3E 5P4 (905) 796-2650 Fax: 796-2250 (905) 643-7560 Fax: 643-7559 (705) 739-8355 Fax: 739-8369 (705) 670-0460 Fax: 670-0558

www.terraprobe.ca

SAMPLING METHODS AS auger sample CORE cored sample DP direct push FV field vane GS grab sample SS split spoon ST shelby tube WS wash sample

PENETRATION RESISTANCE Standard Penetration Test (SPT) resistance ('N' values) is defined as the number of blows by a hammer weighing 63.6 kg (140 lb.) falling freely for a distance of 0.76 m (30 in.) required to advance a standard 50 mm (2 in.) diameter split spoon sampler for a distance of 0.3 m (12 in.). Dynamic Cone Test (DCT) resistance is defined as the number of blows by a hammer weighing 63.6 kg (140 lb.) falling freely for a distance of 0.76 m (30 in.) required to advance a conical steel point of 50 mm (2 in.) diameter and with 60° sides on 'A' size drill rods for a distance of 0.3 m (12 in.)."

COHESIONLESS SOILS

Compactness ‘N’ value

very loose < 4 loose 4 – 10 compact 10 – 30 dense 30 – 50 very dense > 50

COHESIVE SOILS

Consistency ‘N’ value Undrained Shear Strength (kPa)

very soft < 2 < 12 soft 2 – 4 12 – 25 firm 4 – 8 25 – 50 stiff 8 – 15 50 – 100 very stiff 15 – 30 100 – 200 hard > 30 > 200

COMPOSITION Term (e.g) % by weight trace silt < 10 some silt 10 – 20 silty 20 – 35 sand and silt > 35

TESTS AND SYMBOLS

MH mechanical sieve and hydrometer analysis

w, wc water content

wL, LL liquid limit

wP, PL plastic limit

IP, PI plasticity index

k coefficient of permeability

γ soil unit weight, bulk

φ’ internal friction angle

c’ effective cohesion

cu undrained shear strength

Unstabilized water level

1st water level measurement

2nd water level measurement

Most recent water level measurement

Undrained shear strength from field vane (with sensitivity)

Cc compression index

cv coefficient of consolidation

mv coefficient of compressibility

e void ratio

FIELD MOISTURE DESCRIPTIONS Damp refers to a soil sample that does not exhibit any observable pore water from field/hand inspection.

Moist refers to a soil sample that exhibits evidence of existing pore water (e.g. sample feels cool, cohesive soil is at plastic limit) but does not have visible pore water

Wet refers to a soil sample that has visible pore water

80.40.6

79.21.8

76.44.6

74.36.7

WATER LEVEL READINGSDate Water Depth (m) Elevation (m)

August 16, 2011 6.6 74.4

1

2

3A

3B

4

5

6

7

8

4

9

36

45

43

30

70 /275mm

50 /25mm

SS

SS

SS

SS

SS

SS

SS

SS

80mm TOPSOIL

SILTY SAND, trace rootlets, organicstained, loose, dark brown, moist(DISTURBED)

SAND AND SILT to SILTY SAND, loose,brown, moist to wet

SILT to SANDY SILT, trace clay, tracegravel, dense, brown, moist

CLAYEY SILT, sandy, trace to somegravel, hard, grey, moist(GLACIAL TILL)

...shale fragment inclusions

END OF BOREHOLEAuger refusal

Borehole was dry and open upon completionof drilling.

19mm piezometer installed.

1 15 76 8

12 29 39 20

...at 6.5m, augerrefusal oninferred bedrockto 6.7m

ElevDepth

(m)

Ele

vatio

n S

cale

(m)

80

79

78

77

76

75

Dep

th S

cale

(m

)

0

1

2

3

4

5

6

Inst

rum

ent

Det

ails

GR SA SI CL

Hea

dspa

ceV

apou

r

Num

ber

Stick-up : 1m

81.0

NaturalWater Content

SOIL PROFILE

GROUND SURFACE

SAMPLES

PlasticLimit

Uns

tabi

lized

Wat

er L

evel Dynamic Cone

Undrained Shear Strength (kPa)

40 80 120 160

Moisture / Plasticity

10 20 30

PL LLMC

LiquidLimit

SP

T 'N

' Val

ue

Gra

phic

Log

GRAIN SIZEDISTRIBUTION (%)

(MIT) Unconfined Pocket Penetrometer

Field Vane Lab Vane

Typ

e

Description

Lab Dataand

Comments

Position : E: 608136, N: 4811157 (NAD83)

BOREHOLE LOG 1Terraprobe

Drilling Method : Solid stem augers

Clive and Melanie Maile

26 Trafalgar Road

Oakville, Ontario

Client :

Project :

Location :

Project No. :

Date started:

Sheet No. :

1-11-1097

August 8, 2011

1 of 1

Rig type : MINIMOLE,

Elevation Datum : Geodetic

lib

rary

: lib

rary

- t

erra

prob

e gi

nt.g

lb

rep

ort

: te

rrap

robe

soi

l log

Penetration Test Values(Blows / 0.3m)

10 20 30 40

>225 kPa

>225 kPa

Terraprobe SIEVE AND HYDROMETER ANALYSISTEST REPORT

PROJECT: 26 Trafalgar Road FILE NO.: 1-11-1097LOCATION: Oakville, Ontario LAB NO.: 1139A

CLIENT: Clive & Melanie Maile SAMPLE DATE: August 8, 2011BOREHOLE NUMBER: 1 SAMPLED BY: P.B.

SAMPLE NUMBER: 4SAMPLE DEPTH: 2.3 m

SAMPLE DESCRIPTION: SILT, some sand, trace clay, trace gravel

0

10

20

30

40

50

60

70

80

90

100 0

10

20

30

40

50

60

70

80

90

100

0.0001 0.001 0.01 0.1 1 10 100

PER

CEN

T R

ETAI

NED

(%)

PER

CEN

T PA

SSIN

G (%

)

GRAIN SIZE (mm)

U.S. STANDARD SIEVE SIZES

3/4"1.5" 3/8" #4 #20 #60 #200'''''''

#10'

#40' '

#1402.12"

UNIFIED SYSTEM GRAVEL SAND SILT AND CLAY

MEDIUM FINECOARSEFINE COARSE

MITSYSTEM GRAVEL SAND SILT

MEDIUM FINE COARSE

CLAY

GRAIN SIZE DISTRIBUTION

GRAIN SIZE CONTENTMIT System

Gravel………………1 %Sand……………… 15 %Silt…………………76 %Clay………….…… 8 %

Terraprobe SIEVE AND HYDROMETER ANALYSISTEST REPORT

PROJECT: 26 Trafalgar Road FILE NO.: 1-11-1097LOCATION: Oakville, Ontario LAB NO.: 1139B

CLIENT: Clive & Melanie Maile SAMPLE DATE: August 8, 2011BOREHOLE NUMBER: 1 SAMPLED BY: P.B.

SAMPLE NUMBER: 6SAMPLE DEPTH: 4.6 m

SAMPLE DESCRIPTION: CLAYEY SILT, sandy, some gravel (Glacial Till)

0

10

20

30

40

50

60

70

80

90

100 0

10

20

30

40

50

60

70

80

90

100

0.0001 0.001 0.01 0.1 1 10 100

PER

CEN

T R

ETAI

NED

(%)

PER

CEN

T PA

SSIN

G (%

)

GRAIN SIZE (mm)

U.S. STANDARD SIEVE SIZES

3/4"1.5" 3/8" #4 #20 #60 #200'''''''

#10'

#40' '

#1402.12"

UNIFIED SYSTEM GRAVEL SAND SILT AND CLAY

MEDIUM FINECOARSEFINE COARSE

MITSYSTEM GRAVEL SAND SILT

MEDIUM FINE COARSE

CLAY

GRAIN SIZE DISTRIBUTION

GRAIN SIZE CONTENTMIT System

Gravel…………… 12 %Sand………………29 %Silt…………………39 %Clay………….……20 %

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70 80 90 100

Pla

stic

ity In

dex

(PI,

%)

CL

CL

CH

Very High Extremely HighHighLow

Upper Plasticity Range

ML

CL - ML

Liquid Limit (LL, %)

MLorOL

MHor

OH

A - Line

1

HoleCLAYEY SILT TILL, SLIGHTLY PLASTIC

Description

4.6 76.4SS6

Sample Depth (m) Elev. (m)

1525

LL PL PI

10

Terraprobe11 Indell Lane, Brampton Ontario L6T 3Y3

(905) 796-2650

Title:ATTERBERG LIMITS CHART

Date:Project: 1-11-1097 August 19, 2011

SLOPE STABILITY ANALYSIS RESULTS

APPENDIX C

Terraprobe Inc.

1.56

71.

567

W

W

1.56

71.

567

Material N

ame

Color

Unit W

eigh

t(kN/m

3)Co

hesion

(kPa

)Ph

i(deg

)

SILT/SAN

DY SILT

210

32

CLAY

EY SILT

TILL

210

32

WEATH

ERED

SHA

LE BED

ROCK

22

STAB

LE S

LOPE

1.8H

: 1V

Safety Factor

0.000

0.250

0.500

0.750

1.000

1.250

1.500

1.750

2.000

2.250

2.500

2.750

3.000

3.250

3.500

3.750

4.000

4.250

4.500

4.750

5.000

5.250

5.500

5.750

6.000+

110 100 90 80 70

1020

3040

5060

70

Analy

sis D

escr

iptio

nSt

able

Slo

pe A

naly

ses

(wl 7

5.0)

Refe

renc

eSc

ale1:

300

DBP.

Cann

onFil

e Na

me

7-17

-001

3-01

Sta

ble

Slop

e 75

.slim

Date

2/9/

2017

Proj

ect

262

KIN

G S

TREE

T, O

AKVI

LLE

SLID

EINT

ERPR

ET 6

.029

1.52

11.

521

W

W

1.52

11.

521

Material N

ame

Color

Unit W

eigh

t(kN/m

3)Co

hesion

(kPa

)Ph

i(deg)

SILT/SAN

DY SILT

210

32

CLAY

EY SILT

TILL

210

32

WEATH

ERED

SHA

LE BED

ROCK

22

STAB

LE S

LOPE

:1.

8H to

1V

Safety Factor

0.000

0.250

0.500

0.750

1.000

1.250

1.500

1.750

2.000

2.250

2.500

2.750

3.000

3.250

3.500

3.750

4.000

4.250

4.500

4.750

5.000

5.250

5.500

5.750

6.000+

110 100 90 80 70

1020

3040

5060

7080

Analy

sis D

escr

iptio

nSt

able

Slo

pe A

naly

ses

(wl 7

6.0)

Refe

renc

eSc

ale1:

300

DBP.

Cann

onFil

e Na

me

7-17

-001

3-01

Sta

ble

Slop

e 76

.slim

Date

2/9/

2017

Proj

ect

262

KIN

G S

TREE

T, O

AKVI

LLE

SLID

EINT

ERPR

ET 6

.029

slope stability assessment 262 king street oakville, … planning/14-1... · encountered compact...

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