phillips engineering ltd - vancouver

Phillips Engineering Ltd901West 23rd Avenue, Vancouver, BC, V5Z 2B2Phone (604) 716-8881 / Fax (604) 739-6782

File 671: 1920 S.W. Marine Drive, Vancouver, BC

Stuart Howard Architects Inc. April 16, 2013#405 - 375 West 5th Avenue Our File: 671 Vancouver, B.C.V5Y 1J6

Attention: Ms. Nan Legate,

Re: Geotechnical Investigation Report - Proposed Development Located at 1920 S.W. Marine Drive, Vancouver, BC

1.0 INTRODUCTION

As requested, we have completed an investigation of the soil and groundwater conditions for the site notedabove. It is our understanding that it is proposed to redevelop the property and to complete a new additionto the west side of the existing house. The new three storey structure would have a basement to the northhalf of the proposed building and at grade on the southern half. The new structure to the south would beconstructed approximately 33 feet from the top of the south bank. The existing in-ground pool is proposedto be removed.

This report has been prepared exclusively for Stuart Howard Architects Inc., for their use and the use ofothers in their design and construction team for this project. This report presents the results of aninvestigation of the soil and groundwater conditions at the site and provides recommendations for theconstruction of the proposed development.

2.0 SITE DESCRIPTION AND OBSERVATIONS

The property consists of a single residential lot and is rectangular in shape and approximately 230 feet wideby 285 feet long. At the time of our investigation, the site was occupied by the existing residential house andswimming pool along the west side of the property and from 23 to 50 feet north of the shoulder of the slope.

Based upon the contour lines provided on the City of Vancouver’s GIS mapping website (Vanmap) the westslope is approximately 33 feet high and contains an average slope angle of around 30 degrees. A relativelyflat portion exists at the bottom of the slope. The slope is vegetated with mixed deciduous and cedar treesand various bushes and other undergrowth. We also noted the presence of some organic debris near the topof the slope consisting mainly of yard clippings. The existing swimming pool is about 53 feet from the topof the slope.

A site reconnaissance was conducted of the slope and we did not observe any indications of past groundmovements, or signs of slope instability. No groundwater seepages were noted along the slope. Someexposed soil was noted beneath the cedar tree to the west on the slope and the ground surface was dry.


3.0 FIELD INVESTIGATION

Phillips Engineering Ltd. was present on site February 20, 2013 to conduct a drill-based site investigationusing the subcontracted services of Uniwide Drilling Co. Ltd. of Burnaby, BC. At that time two solid stemauger test holes were drilled to depths of up to 50 feet. An engineer from our office logged the soils andcollected samples for further laboratory analysis. All test holes were backfilled and compacted withexcavated soil upon completion of logging. The approximate test hole locations are shown on our Sketch-1located following the text of this report and the detailed test hole logs are attached as Figures TH-1 and TH-2.

4.0 SUBSURFACE CONDITIONS

The soil profile from the surface downwards consists of topsoil and fill, over weathered sand to sand and silt,then compact to very dense sand (glacial till). The topsoil and fill range in thickness up to 5 feet in depth.Underlying this layer is approximately 15 ft of compact to dense fine sand with some silt and a trace ofgravel. In turn, underlying this material, is compact to very dense sand and some silt. The sand (glacial till)consists of a fine grained silty sand with gravel and cobbles and is moderately cemented.

Groundwater was encountered at about a depth of 30 feet in TH-1. Groundwater may be encountered duringconstruction and can be expected to vary seasonally. Excavations below the groundwater table or belowperched groundwater levels are likely to encounter groundwater flows and may require a temporary de-watering system to keep the excavation dry.

5.0 RECOMMENDATIONS FOR DEVELOPMENT

5.1 Discussion

Our analysis indicated that the possibility of a deep seated slope movement is extremely remote due to thepresence of the dense, cemented soils that underlie the site. However due to the steepness of the slope (30to 38 degrees), the surficial topsoil and weathered soils could be prone to creep and movement during periodsof rainfall, erosion, freeze-thaw cycles, changes in vegetation cover and human activity. The long termstability of the slope relies upon the continued presence of the vegetation which currently exists on the slopeand control of any water discharges.

The proposed building setback of approximately 33 feet from the top of the slope, is considered feasible froma geotechnical perspective.

5.2 Spread Foundations

Building loads can be supported directly on the very dense glacial till using normal pad and strip footings.Pad and strip footings can be designed using a factored geotechnical resistance at a Serviceability Limit Stateof 4,000 psf (190 kPa) and at a factored geotechnical resistance at an Ultimate Limit State of 6,500 psf (311kPa).


5.3 Seismic Design of Foundations

The dense soils underlying this site as defined in Table 4.1.8.4.A. of the 2006 British Columbia BuildingCode are classified as Site Class C. The native soils are not considered prone to ground liquefaction or otherforms of ground softening caused by earthquake induced ground motions.

5.4 Grade Supported Floor Slabs

It is recommended that the floor slab be directly underlain by a polyethylene moisture barrier and 100 mmof 19 mm clear crushed gravel to inhibit upward migration of moisture beneath the slab. It is recommendthat any grading fills placed under the slab should be compacted in 300 mm loose lifts to a minimum of 98%of the ASTM D698 SPMDD.

5.5 Foundation Drainage Systems

Any structure with below grade construction (crawl space/basement) must be designed with a perimeterdrainage system as required in the 2006 BCBC. All storm water must be collected and discharged into theCity of Vancouver’s storm water system. Storm water is not permitted to be discharged onto the south slope,or into a rock pit near the west slope as this could cause erosion, increase the groundwater table which couldresult in the slope becoming unstable.

5.6 Temporary Excavations

We would expect that slopes cut at 1V to 1H can be constructed in the compact to dense soils underlying thissite. Temporary cut slopes in excess of 1.2 metres in height require inspection by a professional engineerin accordance with the Worker’s Compensation Board (WCB) guidelines. Light to moderate seepage maybe encountered within the surficial sands that overly the low permeable glacial till.

5.7 Earth Pressures on Foundation Walls

We recommend that buried foundation walls be designed to resist a static triangular soil pressure distributionof 6.2 H (kPa), or 40 H (psf), where H is equal to the total wall height in metres and feet respectively. Thedynamic loading induced by the 2006 BCBC design earthquake should be added to the static loads andshould be taken as 4.7 H (kPa), or 30 H (psf) inverted triangular. The dynamic earth pressure is based uponunfactored soil parameters. The earth pressures presented assume that the area behind the wall is fullydrained with free draining sand backfill. 5.8 Re-Use of On-Site Soils

From the sample of soil retrieved from the auger holes, it was noted the soils are generally silty and sensitiveto small changes in moisture content, therefore they would not be suitable for re-use as a structural fill duringperiods of rain, or the wetter months of the year.

6.0 FIELD REVIEWS


As required by the BC Building Code (2006) “Letters of Assurance”, Phillips Engineering Ltd. will carryout sufficient field reviews during construction to ensure that the Geotechnical Design recommendationscontained within this report have been adequately communicated to the design team and to the contractorsimplementing the design. These field reviews are not carried out for the benefit of the contractors, thereforethey do not in any way effect the contractors obligations to construct the works in accordance with thedesign.

It is the contractors’ responsibility to advise Phillips Engineering Ltd. (a minimum of 24 hours in advance)that a field review is required. Geotechnical field reviews are normally required at the time of theseactivities:

1. Stripping Review of subgrade condition.2. Foundation Foundation subgrade.3. Slab-on Grade Subgrade and under slab fill.4. Fill Review of compaction of engineered fills.

7.0 CLOSURE

This report has been prepared exclusively for Stuart Howard Architects Inc and their design and constructionteam. The report remains the property of Phillips Engineering Ltd. and unauthorized use of, or duplicationof, is prohibited.

We are pleased to be of assistance to you on this project and we trust that our comments andrecommendations are both helpful and sufficient for your current purposes. If you would like further detailsor would like clarification of any of the above, please do not hesitate to call.

For:Phillips Engineering Ltd.

Ward Phillips, P.Eng.Principal

Test Hole Log: TH-lFile:Project:Client:Locotion:

671Proposed New ResidenceStuort Howord Architects1920 S.W. Morine Drive, Voncouver, Bc i|l"y,XT"'|f G"i"!|,

PHILLIPS ENGINEERING LTD.

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gravel f i l l ,compact I i .a2 I l l

Fine sand with some Silt and trace of gravel,compact to dense

Sand, trace silt and trace of gravel, dense

Fine grey sand, lrace of silt, dense

Equiprneil: True* MeriTbd Dffi RbSampling [ffitod: Lump $arplo

HamnnType: N/A

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Datum: ExiEling Gnade$urface Ebvation: SEE PLAN

Water Depth: Approx 30 fi belor gnade

Logged By:Drilling Date:

Dwg No.:Page:

WPFeb. 20,2013TH.11 otz

Test Hole Log: TH-lFile: 67jProject: Proposed New ResidenceClient: Stuort Howord ArchitectsLocotion: 1920 S.W. Morine Drive, Voncouver,

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i F .€ F; soir Description F'E ,f5fi,1il.1,6.80r0 Remark' ,,

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Sandy silt and trace ofgravel fill, compact

Grey sand, hace of gravel, dense, moist- - - i

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Equipment Truck Mounbd Drill RigSampling Method: Lump Sample

HammuType:hUA

Datum: Existing GnadeSurface Elevation: SEE PLAN

Water Depfi: Approx 30 ft below gnade

End ofTest Hole @ 50ft


R,^ 901 West 23rd Avenue"" Voncouver, BC YSZ 2B.2

Tel: 604 716-8881 Fox: 604 739-6782

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Logged By:Drilling Date:

hrg No.:Page:

WPFeb.20,2013TH.12ot2

i Test Hole Log: TH-zFile: 671Project: Proposeci New ResidenceClient: Stuort Howord ArchitectsLocotion: 1920 S.W. Morine Drive, Voncouver,

Equipment Tru* Mounted DdllRrgSampling Me$od: Lump Sample

HammerType: MASurface Elevation: SEE PI-AN

Water Depth: Approx 30 fi belov gnade

Stiff to firm Silt to 10 ft

Fine sand with some Silt and trace of gravel,dense

Silt and some fine sand and trace of gravel,dense

Fine Sand, trace silt and trace of gravel,dense

End ofTest Hole @ 35fr

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Remarks


Datum: Existing Gnade Logged By: WPDrillingDate: Feb.20,2013

Dwg No.: TH-2Page: 1 ofl

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phillips engineering ltd - vancouver

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