HADDAD GEOTECHNICAL INC. - jbarch.ca · Haddad Geotechnical Inc was authorized by John ... conduct...

---------------------------------------------------------------------------------------------------------------------------------------------------------- 7321 Victoria Park Avenue, Unit 21 (905) 475-0951 Fax: (905) 475-8338 Markham, Ontario, Canada L3R 2Z8 1-888-214-4285 [email protected]

HADDAD GEOTECHNICAL INC. Geotechnical and Environmental Engineers

Slope Stability Assessment

Proposed Additions 641 Bob-O-Link Road

City of Mississauga, Ontario

Prepared for:

Mr. and Mrs. Pateropolous c/o John Boone Architect

51 Arundel Avenue Toronto, Ontario

M4K 3A3

Project: 12-7786

May 28, 2012

------------------------------------------------------------------------------------------------------------------------------------------- 7321 Victoria Park Avenue, Unit 21 (905) 475-0951 Fax: (905) 475-8338 Markham, Ontario, Canada L3R 2Z8 1-888-214-4285 [email protected]

HADDAD GEOTECHNICAL INC. Geotechnical and Environmental Engineers

May 28, 2012 Project: 12-7786 Mr. and Mrs. Pateropolous c/o John Boone Architect 51 Arundel Avenue Toronto, Ontario M4K 3A3 Re: Slope Stability Assessment Proposed Additions 641 Bob-O-Link Road Mississauga, Ontario Dear Mr. and Mrs. Pateropolous: Haddad Geotechnical Inc was authorized by John Boone Architect, on your behalf, to conduct a slope stability assessment for the proposed additions to be constructed at the subject site. The following report presents our findings with regards to the stability of adjacent slope and recommendations for the position of the long-term stable slope line. 1. INTRODUCTION 1.1 Project 1. It is understood that the client proposes to construct a second storey addition over the

existing house as well as extending the rear portion of the house in the area of the garage, on the subject property. The approximate proposed siting and orientation of the additions are shown on the Site Plan, Drawing No. 1, which has been supplied by the architect.

2. Based on the drawings provided by the architect, the ground floor and basement floor

elevations are to remain the same as that of the existing house.

1.2 Purpose The objectives of the subsurface investigation were to: - provide subsurface information with regards to the types, thicknesses and variability of the

subsoils underlying the area of the proposed additions. - assess stability of the slope in existing condition and effect of the above noted construction

on the stability of the existing slope.

Project: 12-7786 641 Bob-O-Link Road, Mississauga Page No. 2 ____________________________________________________________________________

1. INTRODUCTION (cont=d) 1.3 Site Description – Present 1. The site under consideration is located on the north side of Bob-O-Link Road, east of

Meadow Wood Road, in the City of Mississauga. 2. At the time of our investigation, the subject property was occupied by a one storey brick

dwelling with full basement and an attached garage. 3. An asphalt paved driveway extends southward from the attached garage to Bob-O-Link

Road, at the southwest portion of the site. A deck of wooden construction is located in the backyard area along the northwest portion of the existing house and property. An in-ground pool is located in the backyard at the northeast portion of the property.

4. The subject site is relatively flat in the front yard area with a slight slope extending

southward toward the street. In the backyard, the grades slope sharply to the west and north from the existing deck, to the westerly and northerly property line where the grades flatten in the area of a creek, which flows northeast towards Rattray Marsh Conservation Area.

5. The remainder of the site consists mainly of grassed lawn with various hard and soft

landscape features. 2. FIELD AND LABORATORY WORK 2.1 Fieldwork 1. The fieldwork, conducted on April 25, 2012, consisted of excavation by hand shovel of a

test pit, on the exterior, in the area of the proposed rear addition in order to verify conditions of existing footings below the existing garage, and examination of the existing footings in two test pits excavated, by the client, in the existing mechanical room of the basement. The field work also comprised of visual examination and measurements of the existing slope.

2. The exterior test pit, i.e. Test Pit No. 1, was located on the exterior west wall of the existing

garage, 2.7±m south of the northwest corner. Test Pit No. 1 indicated the top of footing to be 0.3±m (12”) below existing grades. The footing was observed to have a projection of 200±mm and a thickness of 80±mm. The base of the footing was observed to be supported on fill materials consisting of sand with some silt, brown in colour with organic staining and moist condition. The fill materials extended to 430±mm below the underside of the existing footing. Natural undisturbed subsoils consisting of medium dense to dense sand with some silt in moist condition were observed at a depth of 810±mm below existing grades.

3. Test Pit No. 2, was located in the basement, in the existing mechanical room on the west

wall, 1.2±m north of the southwest corner of the room. A concrete floor slab was observed with a thickness of 60±mm. The footings were observed directly below the concrete slab with a projection of 83±mm and a thickness of 160±mm. The footing was observed to be sitting on natural medium dense to dense sand subsoils in moist conditions.


4. Test Pit No. 3, was located in the basement, in the existing mechanical room on the south

wall, 1.0±m east of the southwest corner of the room. A concrete floor slab was observed with a thickness of 40±mm. The footings were observed directly below the concrete slab with a projection of 83±mm and a thickness of 160±mm. The footing was observed to be sitting on natural medium dense to dense sand subsoils in moist conditions.

5. The existing slope was examined, with approximate gradients measured along one section

extending westward from the northwest corner of the existing garage and perpendicular to the existing slope, as shown on Drawing No. 1, with measurements presented in section, Drawing No. 2. Elevations are reference to the ground floor level at the rear of the existing house, which is assumed to have elevation 100.00m, for the purpose of this report.

6. The location of the above mentioned measured section was chosen based on the closest proximity of the proposed addition to the top of slope.

2.2 Examination of Existing Slope 1. The existing slope was examined, with approximate gradients measured along one section

extending westward from the northwest corner of the existing garage and perpendicular to the existing slope, as shown on Drawing No. 1, with measurements presented in section on Drawing No. 2.

2. The surface elevations for the slope sections are referenced to a local datum, i.e. main floor level at the rear entrance, with assumed elevation of 100.00m.

3. The face of the slope along the section examined was observed to be covered by large

sized, erect, mature trees with some low ground cover vegetation and foliage.

4. Several test pits were excavated by hand along the length of the slope to determine the depth of natural subsoils. Natural subsoils consisting of medium dense to dense sand with some silt were observed in Test Pit Nos. 4 and 5 at a depth of 380±mm at both locations. The approximate locations of test pits are shown on section drawing, Drawing No. 2. The sand subsoils in Test Pit No. 5 were observed to be in wet condition, as the location of the test pit was in close proximity to the existing creek at the base of the slope.

5. No areas of previous or active slope instability were observed along the section examined

or in the adjacent areas of the subject property.

6. Our measurements indicated the slope to have total height of 5m.

7. At Section A-A=, average gradients were observed to be 1.7 horizontal to 1 vertical along the top portion of the slope and 3.0± horizontal to 1 vertical at the bottom portion of the slope where the slope flattens out in the area of the existing creek.


3. STABILITY OF EXISTING SLOPE 1. On the basis of our site observations, a stable slope gradient of 2H:1V is used to

represent the natural medium dense to dense sand subsoils found at the subject site. A stable slope gradient of 3H:1V is used for the fill materials, as per Ontario Ministry of Natural Resources suggested value for soil types, see Appendix “A”. These stable slope gradients for each layer are shown on the slope section, Drawing No. 2.

2. Ministry of Natural Resources guidelines3, Table 3, indicates an erosion allowance of 2m is required where sand is present and erosion is not currently evident (see Appendix “A”).

3. The position of the long-term stable slope line, defined as the intersection of the stable slope gradient with the existing grade on the tableland, is shown in section on Drawing No. 2, and in plan on Drawing No. 1. The long-term stable slope line lays 0.10±m to the west, beyond the limit of the existing garage and 0.5±m west of the proposed addition to the north side of the existing garage.

4. It is our opinion that the construction of the proposed additions to the existing single family

dwelling, on the upper tableland within the limits of the long-term-stable slope line as indicated on Drawing Nos. 1 and 2, will not endanger the integrity of the existing slope, provided that the following measures are strictly observed:

a. The foundations of the house are advanced to competent, natural subsoils, as per geotechnical recommendations in Section 4, below.

b. Under no circumstances should any fill, construction materials or debris be dumped on the surface of the slope, beyond the limits of the construction area. The above action will be detrimental to the existing vegetation, and may lead to local instability of the slopes.

c. Runoff water should not be discharged directly, in a concentrated fashion, onto the slope. Any runoff from the ground surface and/or perimeter subsurface drainage should be discharged either into the municipal sewers or into an infiltration trench or dry well, located well away from the top of slope.

d. Prior to commencement of construction, a sedimentation control fence must be installed at top of bank, along the west perimeter of the construction area, to minimize the effects of surface erosion on the surrounding area. A typical detail of a sedimentation control fence is shown on Drawing No. 3.

4. GEOTECHNICAL DESIGN CONSIDERATIONS 1. Conventional spread foundations established on the natural, medium dense to dense

sand observed at a depth of 810±mm below existing grades at Test Pit No. 1 and below the existing foundations in Test Pit Nos. 2 and 3, may be designed for a serviceability limit states (SLS) bearing pressure of 150 kPa (3,000± p.s.f.), with total and differential settlements of less than 25mm. An ultimate limit states (ULS) bearing pressure of 300 kPa may be assumed for the above footings.

3 “Technical Guide - River and Stream Systems: Erosion Hazard Limit”, Ontario Ministry of Natural

Resources, 2002.


2. The fill materials observed below the base of footing at location of Test Pit No. 1 are not suitable for the support of permanent structures. It will be necessary to underpin the footings of the existing garage along the west and north foundation walls, in order to extend structural loadings to more competent medium dense to dense sand subsoil underlying the existing footings, i.e. 810±mm below existing grades in area of Test Pit No. 1.

3. At present, it is known that underpinning of the existing footings will be required in the area of Test Pit No. 1, with the full extent of required underpinning becoming apparent upon excavation for the proposed additions. Our recommendations for procedures for underpinning are presented in Drawing No. 4.

4. The base of excavations for underpinning should be inspected by a geotechnical engineer from our office to verify presence of competent subsoil to safely support the design loadings to confirm adequate founding.

5. Excavation to the anticipated levels for foundations should be relatively straightforward with no significant groundwater problems anticipated.

6. The excavations for foundations should extend to natural, undisturbed soils below the extent of previous excavations and a minimum footing width of 0.6m is highly recommended due to point-loading effects in sand subsoils.

7. Footings and/or grade beams for portions of the structure in exterior and unheated interior areas must be protected against frost action by at least 1.2m earth cover.

8. For purpose of design of the proposed structure for earthquake loads and effects as per Table 4.1.8.4A, in the Ontario Building Code (2006), Site Class “D” conditions may be assumed for foundations established on the natural, medium dense to dense sand subsoils.

HADDAD GEOTECHNICAL INC.7321 Victoria Park Avenue, Unit 21Markham, Ontario, Canada, L3R 2Z8

905-475-0951, fax: [email protected]

SITE PLAN SHOWING APPROXIMATE LOCATION OFSLOPE SECTION & LONG-TERM STABLE SLOPE LINE

641 BOB-O-LINK ROAD, MISSISSAUGA

SCALE : AS NOTEDDRAWN BY: VT

PROJECT: 12-7786DRAWING No.1

DATE: MAY 28, 2012

HADDAD GEOTECHNICAL INC.7321 Victoria Park Avenue, Unit 21Markham, Ontario, Canada, L3R 2Z8

HADDAD GEOTECHNICAL INC.


SLOPE SECTION A - A'

SCALE AS NOTEDDRAWN BY: VT

7321 Victoria Park Avenue, Unit 21Markham, Ontario, Canada, L3R 2Z8

PROJECT: 12-7786DRAWING No. 2

DATE: MAY 28, 2012

(905) 475-0951, 1-888-214-4285fax: (905) 475-83387

[email protected]

HORIZONTAL DISTANCE, WEST OF NORTHWESTCORNER OF EXISTING HOUSE, +/-m

0 5 10 1590

95

100

105

ELE

VA

TIO

N, +

/-m

-5

Existing footing level

Existing Culvert

Existing Creek

SAND

Test Pit #4

Test Pit #5

1

3

1

2

Test Pit #1

Ground Level at Rear Entrance

Long-term StableSlope Line

Proposed Footing

Existing House

Proposed House

0.1+/-m

2.0+/-m

Toe Erosion Allowance

Extent ofRear Addition

Existing GradeBelow Deck

0.5+/-m

1

2

FILL

FILL

1

3

Stable Slope Gradient

SCHEMATIC SECTION SHOWINGSEDIMENTATION CONTROL FENCE



DATE: MAY 28, 2012

SCALE: AS NOTEDDRAWN BY: VT




TYPICAL SECTION, UNDERPINNING OFEXISTING FOUNDATION WALLS



DATE: MAY 28, 2012

SCALE: AS NOTEDDRAWN BY: VT




APPENDIX A

1. Ontario Ministry of Natural Resources: Watercourse & Valleyland Protection Policies, Figure 3

2. Ontario Ministry of Natural Resources: River and Stream Systems: Erosion Hazard Limit, Table 3.

SLOPE STABILITY DEFINITION & DETERMINATION GUIDELIN E

September 2011 4/9

SHALE BEDROCK

Figure 3. Generalized Stability Setback Guidelines

SLOPE TOE

H

1.4 = H

1

1.4

SETBACK GRADIENT LINE

SLOPE TOE

H

2.5 = H

1

2.5


CLAY TILLS

SLOPE TOE

H

2 = H

1

2


SAND AND GRAVELLY SAND “DRY” SLOPE

SLOPE TOE

H

1 = H

1

1


LIMESTONE / DOLOMITE BEDROCK

GUIDELINES FOR ESTABLISHING STABILITY COMPONENT OF TOTAL SETBACK FOR TYPICAL BEDROCK / SOIL CLASSIFICATIONS WITHIN THE C REDIT RIVER

WATERSHED

N.T.S.

FOR: • CLAY (NON TILL) SLOPES • SAND SLOPES WITH WATER SEEPAGE • FILL SLOPES • THE SETBACK GRADIENT LINE IS TO BE

DETERMINED BY GEOTECHNICAL ENGINEER

SHALE BEDROCK

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