SITE INFORMATION ASSESSMENT...Boreholes (BH1 to BH7) were conducted within the site and supplemented with scala penetrometer soundings continued from the borehole base. BH1 was conducted

Job No: 7569 April 2014

Ashby Consulting Engineering Ltd Structural, Civil & Geotechnical Engineering 3 Elizabeth Street, P O Box 124, Warkworth 0941

Ph 09 425 9422 Fax 09 425 9431 E-mail: [email protected]

The Report has been prepared for the sole benefit of the client for the

purposes as outlined in the introduction. Anyone using this report for any other purpose does so at his or her own risk. The report contained here-in

remains the exclusive property and copyright of Ashby Consulting

Engineering Ltd.

SITE INFORMATION ASSESSMENT

AND

GEOTECHNICAL INVESTIGATION

FOR

LEN Mc.KEOWN

FOR

PROPOSED SUBDIVISION

AT

LOT 3 DP 452608

BLUE GUM DRIVE, WARKWORTH

Job No: 7569 April 2014

CONTENTS

Item Description Page

1.0 Introduction 3

2.0 Description 3

3.0 Previous Geotechnical Report 4

4.0 Site Information 4

4.1 Wind Exposure 4

4.2 Corrosion Zone 4

4.3 Surface Water Assessment 4

4.4 Ground Contamination Assessment 4

5.0 Geology of the Area 4

6.0 Investigation 5

7.0 Topsoil and Unsuitable Material 5

8.0 Groundwater 5

9.0 Soil Parameters 5

10.0 Findings 6

11.0 Retaining Walls 10

12.0 Earthworks 11

13.0 Foundations 14

14.0 Water supply and Sewage Disposal 15

15.0 Stormwater Disposal and Stormwater Neutrality 16

16.0 Access 16

17.0 Historical & Cultural Issues 16

18.0 Conclusion and Recommendations 16

19.0 Applicability 18

Appendix 19

Ashby Consulting Engineering Ltd The Report has been prepared for the sole benefit of the client for the

purposes as outlined in the introduction. Anyone using this report for any Structural, Civil & Geotechnical Engineering other purpose does so at his or her own risk. The report contained here-in 3 Elizabeth Street, P O Box 124, Warkworth 0941 remains the exclusive property and copyright of Ashby Consulting Ph 09 425 9422 Fax 09 425 9431 E-mail: [email protected] Engineering Ltd.

Ashby Consulting Engineering Ltd. - 7569

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1.0 Introduction

Ashby Consulting Engineering Ltd. has been requested by Len McKeown to carry out a geotechnical

investigation for proposed subdivision located at Blue Gum Drive in Warkworth.

The purpose of the investigation is to determine whether the proposed new building sites are stable

and suitable to be built upon.

2.0 Description

The property is designated as Lot 3 DP 452608, and is located approximately 1.0km south of

Warkworth town center on the southern end of Blue Gum Drive. The property has a total area of

14,140m², and the topography can be typified as grassed pasture orientated to the west with moderate

slopes of up to 12° or less and rolling into a stream below the western property boundary. Two

existing houses are located above the north-eastern part of the section and the two access ways for the

new subdivision will be shared with these two existing houses.

An overland flow path is located near the western boundary orientated in north-south direction which

collects the uphill runoff and discharges into the stream below the property which is a small tributary

of the Mahurangi River.

Discontinued effluent soakage trenches are located within the central part of the property which

previously serviced one of the upper dwellings. We understand that this field was decommissioned

and both the upper dwellings now pump wastewater into the public wastewater system. A small cut off

drain which protected the effluent field is still within the proposed Lots.

A public storm water manhole is also located within the central part of the property near the internal

fence which collects water from the uphill properties which we assume discharges it into the stream

but due to the overgrown nature of the stream banks we have not located the outfall structure.

A visual inspection of the stream bed indicates that the upper clay and silt layers have been eroded

down to the underlying rock layers that are thought to extend up under the property.

Three horizontal drains are also installed within the proposed lots which plans indicated extend up to

the building platform on 97 Blue Gum Drive (Lot 1 DP452608). A concrete chamber is installed just

below proposed Lot 2 where these daylight.

A previous geotechnical investigation for the dwelling located at 97 Blue Gum Drive done by Colin

Ashby of this office in 1997 notes that the recommended counterfort drains that were originally

suggested by the overlying subdivisional geotechnical report done by Harrision Grierson in 1991 are

not required for this platform which is immediately above the proposed subdivision. It was also noted

at the time that in the 18 months the three horizontal drains had been installed they had never been

seen discharging any water.

The proposal is to subdivide the property into 8 smaller lots with shared access ways with the two

existing properties Lot 2 DP 452608 (89 Blue Gum Drive) and Lot 1, DP 452608.

Earthworks will be required to develop level building platforms and the new access ways.


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3.0 Previous Geotechnical Report

Previous subdivision geotechnical report prepared by ‘Harrison Grierson Consultants Ltd’. ref no.

43.5158.1 dated August 1991 and a previous geotechnical investigation by this office on 97 Blue Gum

Drive in 1997 has been referred to whilst writing this report.

4.0 Site Information

4.1 Wind Exposure

The basis of the building wind zone for bracing design is based on our visual assessment of the

site having knowledge of the requirements of NZS 3604:2011. The site in our assessment

would have very high wind exposure.

4.2 Corrosion Zone

The proposed building site is within the inland coastal areas with medium risk from the

windblown sea-spray salt deposits. Therefore the site is within Zone C: Medium exposure in

accordance with NZS 3604:2011.

4.3 Surface Water Assessment

We are satisfied that the building is unlikely to flood in the future, and that water from

buildings or site works can be disposed of in a way that avoids the likelihood or damage or

nuisance to the other property.

From an event having a 2% probability of occurring annually (ie, 50 year return period storm)

water is unlikely to enter buildings.

4.4 Ground Contamination Assessment

Although part of the proposed subdivision is currently covered in rows of old apple trees, a

preliminary visual inspection has been carried out including the observation of flora and fauna

as well as a critical appraisal of the physical land features. From this visual inspection, no

unusual or non-conformity in the features of the site were apparent which would indicate past

use or the presence of hazardous agents or contaminants.

5.0 Geology of the Area

The following geological map references have been referred to;

1. NZ Geological Map Sheet 2A: at a scale of 1– 250,000. The map indicates that the site has the

underlying soil type – Waitemata Group, “Dark grey sandstone and mudstone, non calcareous,

often with intraformational slumping, slightly fossiliferous. Andesetic tuff and marine sandstone,

with local plant beds.”

2. The Institute of Geological and Nuclear Sciences map for Auckland defines the material as

Waitemata Group, Warkworth subgroup, Pakiri formation, alternating thick-bedded volcanic rich

graded sandstone and siltstone.

3. Rodney District Council Expansive Soils Map Sheet number RDC 15549 indicates the area to be

Category ‘B’ soils within the Alternative Solution 1 (AS1) to any foundation design. From the

inspection carried out we are satisfied that this category is applicable to this site.


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6.0 Investigation

The site was visited on the 28th

February, 3rd

March and on 6th

March 2014 and a geotechnical

investigation was conducted. This consisted of an initial walkover of the sites and identifying the

topography of the area. Hand drilled boreholes supplemented with shear vane readings and scala

penetrometer soundings were undertaken to determine the bearing strength of the underlying soils and

draw cross sections of the ground profile. The results of the field investigations are tabulated under

soil parameters section.

7.0 Topsoil and Unsuitable Material

We would estimate that the proposed building platforms having average topsoil depth of 300mm based

upon the borehole findings. Further unsuitable material has not been noted.

We note however, that soils by their nature are varied and it is possible that once the topsoil is stripped

pockets of unsuitable material not identified by this report may become apparent. Please contact us

and discuss, should you have any concerns.

8.0 Groundwater

No groundwater was encountered during our investigations. Although damp to moist soil were

encountered below 2.0m depth indicating possible winter ground water level to be at this level.

The previous geotechnical investigations encountered ground water at 2m in one of the boreholes.

9.0 Soil Parameters

From inspection for general design purposes, we would assess soil parameters as the following;

Upper 1.5m

Apparent Cohesion (in terms of effective stress) c’ = 5kPa,

Apparent Internal Angle of Friction (in terms of effective stress) ’ = 26°

Bulk Density (weight density) = 18 kN/m³

Between 1.5m -2.5m




Between 2.5-3.5m




Below 3.5m





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Boreholes

Soil Strengths kPa Bearing Capacities (kPa) Expansive

Soil

Category

Shear

(max)

Remould

r

Ultimate

(qu)

Allowable

(qa)

BH1 123 16 300 100

“B” or “M”

BH2 104 16 300 100

BH3 95 22 300 100

BH4 101 25 300 100

BH5 120 25 300 100

BH6 123 25 300 100

BH7 126 22 300 100

10.0 Findings

The proposed building sites are located on moderately sloping ground with slopes of up to 12°. The

ground below the western boundary falls steeply into a small stream. There is a 25m wide paper road

reserve between the western boundary of the property and these steeper stream banks.

Boreholes (BH1 to BH7) were conducted within the site and supplemented with scala penetrometer

soundings continued from the borehole base.

BH1 was conducted within the proposed Lot 1 and was taken to a depth of 3800mm. This revealed an

upper 250mm thick stratum of topsoil underlain by firm, dry, cohesive and plastic pale yellowish

orange with mottled pink silty-clay till 1000mm depth. Thereafter becoming friable, damp to moist,

light pinkish to pinkish red silt with traces of yellowish clay, light brown sand and black organics until

the borehole was concluded.

Shear vane tests were conducted at 500mm intervals throughout the borehole which revealed shear

strength ranging from 123kPa to 221kPa. Remould shear strength ranges from 16kPa to 54kPa.

SP1 was extended from the base of the borehole into the substrata and was taken to a total depth of

4800mm. This revealed medium density soundings (2-8 blows per 100mm of penetration) to 4400mm

depth, thereafter increasing to dense soundings (10-16 blows per 100mm of penetration).

BH2 was conducted down slope near the boundary within the proposed Lot 1 and was taken to a depth

of 4000mm. This revealed an upper 300mm thick stratum of topsoil underlain by firm, dry, cohesive

and plastic pale yellowish brown with orange and light greyish silty-clay till 1500mm depth.

Thereafter, becoming friable, damp to moist, light greyish white with yellow and orangey brown silty

soil till 2400mm depth and then changing to orangey brown with pinkish red silty soil silt with traces

of clay and black organics until the borehole was concluded.




5400mm. This revealed soft to medium density soundings (2-5 blows per 100mm of penetration) to

5100mm depth, thereafter increasing to dense soundings (12-25 blows per 100mm of penetration) with

hammer rebounding.


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BH3 was conducted down slope near proposed Lot 3 boundary and was taken to a depth of 4000mm.

This revealed an upper 300mm thick stratum of topsoil underlain by firm, dry, cohesive and plastic

pale yellowish brown with orange and light greyish silty-clay till 1500mm depth. Thereafter,

becoming friable, plastic, moist to wet, light greyish white with yellow silty soil with traces of clay

until the borehole was concluded.




5200mm. This revealed medium to dense soundings (5-12 blows per 100mm of penetration) till

4600mm depth with intermediate soft layer between 4600m to 4900mm with soundings (3.5-6 blows

per 100mm of penetration). Thereafter increasing to dense soundings (13-30 blows per 100mm of

penetration) with hammer rebounding.

BH4 was conducted within proposed Lot 4 and was taken to a depth of 3000mm. This revealed an


orange and light greyish white silty-clay till 1700mm depth. Thereafter, becoming friable, damp,

pinkish red with light brown and black mottled clayey-silt until the borehole was concluded.




5100mm. This revealed medium density soundings (3-7 blows per 100mm of penetration) till 4100mm




orange with pink mottled silty-clay till 1500mm depth. Thereafter changing to friable, damp to moist,

pinkish red with light brown and black mottled silty soil until the borehole was concluded.








brown with orange with pink mottled silty-clay till 1500mm depth. Thereafter changing to friable,

damp to moist, pinkish red with orange and black mottled clayey-silt until the borehole was

concluded.




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brown with orange silty clay till 700mm depth. Thereafter soil changes to friable, damp to moist,

pinkish red with traces of light brown and mottled black silt until the borehole was concluded.






A slightly weaker dilatant layer is encountered within boreholes 1 to 3 with shear strength decreasing

slightly between 2.5m and 3.5m depth with reasonably high moisture content. We assume that this

moisture is possibly due to the rising ground water level during winter seasons.

From the acquired borehole data, 3 cross section profiles have been drawn.

Cross section A-A

Borehole BH1 and BH2 are considered in the profile. The ground slopes at 10° between BH1 and

BH2. The underlying soil comprises of 1.5m of clay underlain by weathered Waitemata silt to 5.0m

depth before reaching an inferred rock layer. We recommend locating the building site within the

uphill part of the lot.

Cross section B-B

Borehole BH3 and BH4 are considered in the profile. The ground slopes at 9° between BH3 and BH4.

The underlying soil comprises of plastic clay for 1.5m in depth underlain by weathered Waitemata silt

to 5.2m depth before reaching the inferred rock layer.

Cross section C-C

Borehole BH5, BH6 & BH7 are considered for drawing the soil profile. The ground slopes with 7°

between BH6 and BH7. The underlying soil comprises of plastic clay for 1.5m in depth with the

exception of the 700mm in found in BH7. This clay layer is underlain by weathered Waitemata silts

we estimate that the underlying rock layer to be below 6.0m.

Note; It is important that shrub and tree species, such as willow and gum, etc, which have high

groundwater demands during summer, be kept an appropriate distance from buildings, as their water

demands can effect expansive soils significantly, leading to differential settlement of adjacent

buildings. Therefore, it would be prudent to seek professional advice, before planting such tree

species, in order to ensure that sufficient separation distances, from any buildings, are maintained. As

a “rule of thumb” trees should be planted no closer to a building when their equivalent height at

maturity.


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Core Sampling and Laboratory Testing

To confirm the soil strength and frictional angle parameters, undisturbed soil samples were retrieved

from the ground on 21st March 2014, at three different locations as shown on the site plan. ‘Pro Drill

NZ’ was engaged in extracting the sample using a drill rig and push tube sampling technique.

The core logging confirmed our earlier borehole logs with the upper 1.5m depth of silty-clay underlain

by light greyish silty soil with traces of clay. This is followed by a hard underlying layer of weathered

orangey brown sandstone layer at varying depth of 2.5m to 3.5m depth.

Push tube (PT1) sample was taken between 2.5-2.8m and consisted of upper greyish layer followed by

weathered sandstone. Not enough light greyish material was retrieved in this tube to triaxial test.

Push tubes (PT2 & PT3) sample were taken between 2.0m to 2.3m and 2.5m to 3.0m. These consist of

light greyish silty material with traces of clay. PT3 had a slightly higher clay content.

Push tube (PT4) sample consist more of pinkish to light orange silty sand.

From site assessment of the core sampling and the shear strengths recorded during the borehole

investigations we suspect the light greyish silty layer as having the lowest soil parameters and

therefore Push tube (PT2) sample retrieved at 2.0m depth was sent to ‘Opus’ laboratory for triaxial

testing. The laboratory results are attached in the Appendix.

The frictional angle (Ø’) determined from lab testing is 20° and the cohesion (c’) was 28kPa.

Fig.1: Push Tube sampling location 1 Fig.2: Push Tube sampling location 2

Slope Stability Analysis

A Slope stability analysis using Galena 5.02 was undertaken on cross sections A-A, B-B and C-C.

All three cross sections were analysed with ground water at 1.5m maximum for long term conditions,

and with groundwater levels at the surface for short term conditions. Given the proximity of the stream

we believe these to be reasonable assumption.


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For long term conditions a minimum factor of safety of 1.5 would be appropriate and for short term

conditions which are unlikely but could occur during intense storm events a minimum factor of safety

of 1.2 would seem appropriate.

Soil strength parameters as modelled;

Top Silty clay layer - c’=5, Ø’=26° (considered conservative values)

Silt layer between 1.5-2.5m - c’=0, Ø’=26°

Silt layer between 2.5-3.5m - c’=0, Ø’=20° (ignoring any cohesion)

Lower weathered silt layers c’=0, Ø’=26° (considered conservative values)

Soil strength parameters from lab test;

Cohesion c’= 28kPa

Angel of friction Ø’= 20°

For cross section A-A the result shows a factor of safety of 1.22 with the groundwater level at the

surface and 2.04 with ground water below 1.5m.

For cross section B-B the result shows a factor of safety of 1.23 with the groundwater level at the


For cross section C-C the result shows a factor of safety of 1.58 with the groundwater level at the


Based on the stability analysis, the geotechnical investigation including triaxial testing and the gently

sloping nature of the property we are satisfied that the building sites are stable and suitable to be built

upon without the need for any additional stability measures like counterfort drains or horizontal drains.

We are also of the opinion that the three existing horizontal drains that run through the property are

redundant with the physical changes that have occurred within the upstream catchment areas as Blue

Gum Drive has been developed over the past 20 years.

The road reserve below the property boundary provides a suitable setback from the steeper areas of the

stream banks so no additional setbacks requirements are necessary.

11.0 Retaining Walls

For retaining walls, design parameters shall be taken as above with the exception that cohesion shall

be taken as zero, c’ = 0 kPa.

For cantilever timber retaining walls up to 3m not supporting a building or driveway, some deflection

of the wall and minor settlement of the ground supported may be acceptable, and the coefficient for

“Active Earth Pressure” may be used (KA).

For 3m or higher, or more critical walls supporting a rigid structure which has not been underpinned,

the coefficient of “At Rest Pressure” shall be utilised (KO).

For intermediate cases to be considered on their merits by a Chartered Engineer, a coefficient of back

pressure of ½( KA + KO) would be acceptable.


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Note: Where any retaining wall exceeds 1.0m in height a specific design may be required as certain

safety features need to be taken into consideration in accordance with the requirements of the Building

Act 2004. Ashby Consulting can provide a proposal for specific design on request.

12.0 Earthworks

Fills

It is best to avoid the use of moderately and highly expansive fill materials beneath buildings because

of long term likely settlement and consolidation. Any fill over 400mm deep (even if properly

compacted in accordance with NZS 4431:1989) is of potential concern.

For the reasons set out in the discussion below, we would recommend that with any filling work over

400mm deep using expansive soils, the following methodologies be considered;

1. Foundation to be piled through and taken into firm original ground, pre-drilling the pile hole

through the fill so as to reduce the possibility of negative skin friction punching the pile down.

Note: while the piling method can support the building, on deep fills adjacent to a high

retaining wall, ground shrinkage of as much as 200mm has been observed leaving a 200mm

gap which would be visually unacceptable and can play havoc with patio areas.

2. Hydrated Lime stabilisation of the expansive fill material can be a solution particularly when

soil conditions are too wet and the site too confined to permit windrowing. This method has

been trialled on a house site and found to work well and to have been competitive with under-

piling. However, trenching for drains and cables should be completed as soon as possible

subsequently and the ground will become hardened to the point where it may become difficult

to dig. If this method is to be used, a test needs to be carried out to ensure the soil is reactive.

On slopes, benching will be required in the normal manner and the entire depth of fill will need

to be placed, stabilized and compacted at 200mm thick layers.

3. Where downhill retaining walls are in close proximity to the foot print of the house the use of

compacted hard-fill such as GAP 65 would be recommended. With the approval of the

engineer, 500mm back from the wall to allow for drainage, this GAP 65 backfill could be

supplemented by first placing and compacting to engineering standard up to 400mm of clay fill

so as to minimise cut to waste and also minimise the volume of imported hard fill required.

--//--

Discussion on Fills

In terms of the Australian Standard for Residential Slabs and Footings Construction AS2870:

1996; Refer to 2.4.6.

From the above, for Controlled Shallow Fills up to 0.4m deep these may be treated as for the

natural site prior to filling.

For Uncontrolled Shallow Fills up to 0.4m deep, all edge beams, internal beams and load

support thickenings are founded on natural soil through the fill”.


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For Controlled Deep Fills, the assessment shall consider the movement of the fill and the

underlying soils from the as-constructed condition to the long-term equilibrium moisture

conditions. Allowance shall be made for construction variations of moisture conditions.

Alternatively the movement may be estimated by reference to established knowledge of the

behaviour of similar fills in similar areas.

With respect to the “underlying soils”, generally fills are unlikely to exceed 3m in depth, and

the underlying soils usually encountered are insitu residual Waitemata soils not likely to be a

noticeable problem with respect to compressibility and can be ignored. However if present,

the compressibility of softer underlying alluvium deposits particularly if deep will require

consideration.

The Australian Standard AS 2870; 1996 goes on to imply that long term moisture equilibrium

is unlikely to be established within a fill within 5 years. In essence the fill will need to go

through a number of summers and is likely to be subject to “post construction consolidation”

during those periods due soil suction as the summer heat dries the ground out, or capillary

action even if well compacted as an ‘Controlled’ fill at optimum moisture content (OMC),

further consolidation will most probably occur.

Obviously in most situations it is not a practical option to wait 5 years before building and so

alternatives to supporting buildings on deep expansive soils fills need to be considered.

“Controlled Deep Fills” require special attention.

Consider an expansive soil from a laboratory measured shrinkage test, dried out from the

liquid limit state the soil may shrink 20%.

The same soil, even when properly compacted using appropriate compaction equipment at

Optimum Moisture Content (OMC), will dry out under prolonged summer conditions and can

be expected to shrink as much as 10%, at least near the surface.

This problem can be exacerbated by the close proximity of high downhill retaining walls

which can have a significant effect on the drying out and consolidation of the fill.

The potential for disaster when working with expansive or reactive soils is very real. NZS

4431:1989 the New Zealand Code of Practice for Earth Fill for Residential Development

does not seem to fully comprehend the risks with reactive soils. Never the less, we would

recommend that any fill placed under or within 3 m of the footprint of a building shall be

properly constructed and compacted in general accordance with NZS 4431:1989 the New

Zealand Code of Practice for Earth Fill for Residential Development. Such Engineered earth

fill can end up denser and stronger than the original ground (but still consolidate). This fill

shall be tested and a Producer Statement Construction Review provided by a Chartered

Engineer familiar with this report.

NZS 4431 Section 7.4.2.4 states “For many cohesive soils it is found that an acceptable

minimum shear strength is 150kPa and the maximum air voids is 10%. For particular soil

types, and for reserve areas or road subgrades, some variations from the above value may be

appropriate”.


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When considering residual silty clay it has been found locally that minimum shear strength of

150kPa cannot be achieve unless the soils are lime stabilized. Given the above, target shear

strength of 100kPa in the soil should be acceptable.

Fill shall be compacted at optimum moisture content (or just dry of), and may be tested using

a “Dynamic cone Penetrometer Test” (Scala Penetrometer) which shall achieve soundings of

not less than 4 blows per 100mm of penetration for a depth of twice the footing width or 1.2m

whichever is the deeper, below the bottom of the footing. No account shall be taken of

readings where the top of the probe hole is less than 300mm above the tip of the

penetrometer. Any testing by penetrometer may need to be augmented by an insitu hand held

shear strength test, as if soils are dry of optimum penetrometer tests can give higher readings

and hence inferred higher densities than are not actually the case.

The tracks of a hydraulic digger were designed to walk across swamps, therefore anyone

using the tracks of a hydraulic digger to compact fill will be required to re-excavate all fill

material and re-compact it properly using appropriate compaction equipment. As a general

rule reactive clay materials generally do not tend to make good fill as outlined above and its

use under a building should preferably be limited or avoided, possibly by building in empathy

to the land to limit fills, or by use of the methodologies outlined in this report.

Further considerations are;

i) On small sites if the fill material is too wet there is often insufficient space to

spread it out to windrow it to dry so that compaction at OMC can be achieved.

ii) Building tends to be an all year around process, and therefore earthworks for

house sites are often attempted at times when ground conditions are really too

wet to achieve OMC and the weather is too wet to adequately dry windrowed

Materials. Providing the soils are reactive to hydrated lime and suitable, the

use of hydrated lime stabilisation may prove a useful tool under such

circumstances as it will dry the soil out and strengthen it reducing shrink –

swell characteristics at the same time.

ii) With varying fill depths, differential settlement is a larger concern than if fill

were of uniform thickness across a site.

--//--

Cuts

Cut batters up to 0.6m high in these soils, may stand at up to 1v to 0.176h (80°) without being

retained. Any near vertical cuts over 0.6m high shall be retained.

With the exception of cut batters up to 0.6m high, cut or fill batters should be constructed no steeper

than 1v in 4.0h (14.03°) for no more than 3m in elevation unless otherwise approved by the engineer.


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13.0 Foundations

From our investigations, the soil has good insitu shear strength and a safe bearing capacity of 100kPa

is likely to be achieved for foundations. The building may be constructed in general accordance with

NZS 3604 - 2011, with due allowance for extra depth to allow for the seasonal shrinkage - swelling

nature of the soils.

The soil parameters and ground strengths should be confirmed on site at the time of construction.

Rodney District Council’s Expansive Soils Category “B” equates to the Australian Standard “AS 2870

– 1996 Residential Slabs and Footings – Construction” to be classification “M” sites. Under local very

dry summer conditions, vertical surface shrinkage movement (ys) is of the order of 20mm to 40mm,

with the active depth of shrinkage (Hs) anticipated to extend down to 1.5m in this case. AS 2870

assumes that shrinkage decreases lineally with depth, however we consider that shrinkage will

decrease rapidly with depth in parabolic fashion.

Shrinkage under a concrete slab can theoretically extend back as much as 1.0m in category “B” or

“M” soils, while the ground under the centre of a slab will have reached moisture equilibrium. The

result can be that the ground falls away below the footing, leaving the footing to be supported by the

cantilever action of the floor slab.

The parts of the building that will be most affected by ground shrinkage are the external outer corners

where the ground can dry out on ¾ of a circle around the corner point. This leads to greater differential

settlement at the corners, which in turn can lead to cracking at the corners, potentially affecting the

footing, slab and cladding.

To mitigate this risk we recommend that if the building is on a concrete slab or waffle slab, and the

building has heavy wall cladding or a tiled roof, or is two storeys, that the external walls and outer

corners be underpinned.

With respect to under-piling we would normally suggest under piling at external corners at

approximately 2.0m centers under external foundations. The piles should be specifically design for all

design loads with a minimum embedment depth of at least 1500mm taken into the original ground

unless specified otherwise.

In the case where piles are required through fill, a pilot hole shall be predrilled through the fill to

reduce the risk of negative skin friction of consolidating fill dragging the pile down. The pile shall be

secured firmly into the underlying ground.

For all 8 Lots

Foundation can be designed for safe bearing strength of 100kPa for category “B” or “M” expansive

soil.

Continuous reinforced concrete strip footings tied into a reinforced concrete slab, shall be taken to a

minimum of 600mm depth below finished ground level and underpinned at external outer corners as

outlined above if necessary. Slabs shall be at least 100mm thick with at least grade 500E super ductile

mesh SE-62 or equivalent used as reinforcement laid on damp proof course, on sand blinding, on

100mm of compacted hard fill, on the prepared subgrade.


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Waffle Slabs may be laid directly on damp proof course, on sand blinding, on 100mm of compacted

hard fill, on the prepared subgrade, with exterior foundation underpinned if necessary as outlined

above. However, underpinning of the exterior foundation will not be required where a waffle slab is

specifically designed to support super-imposed loads by cantilever action underground shrinkage

conditions. Please note however that where fill depth using expansive soils are in excess of 400mm

depth, it is intended under-piling will be required.

Isolated Pile Foundations shall be taken to a minimum of 600mm depth below ground level. Where

isolated piles are located in fill, these shall be founded through the fill into firm original ground, and

shall be sleeved through the fill with PVC to prevent possible consolidation of the fill punching down

the pile.

Driven Timber Piles shall be in general accordance with NZS 3604 Section 6.6. except that founding

depth shall be not less than 1.5m. Pilot holes shall first be predrilled through any fill to reduce the

potential for negative skin friction.

Bored & Poured Pile Foundations shall be taken to a minimum of 600mm depth below ground level.

The bottom of any foundation bored hole shall have a minimum insitu shear strength in excess of 80

kPa, shall be scrupulously clean and free of water, sponged out (as required with a sponge on the end

of a stick). The use of an “Ezi-Yaka” precast concrete punch pad of largest practical size, dropped

into the bottom of the hole is recommended if water ingress is likely to be a problem.

If foundations are bored and poured, care needs to be taken to ensure that the boreholes are if possible

bored and poured the same day to prevent ingress of water and softening of the soil. One trick is to

pre-drill all but the last 0.5m of hole the day before, then on the day pump out as much water as

possible and drill the last 0.5m to mop up any water.

Alternatively driven piles should be drilled through the fill layer and driven either to refusal or to a

shallower depth calculated on the depth of embedment required for the piles to resist lateral soil creep

within the fill, and resist superimposed loads.

Note: If placing a concrete slab on expansive soils, moisture content at time of construction is critical.

Do not allow areas of the building platform under the building footprint to become over dry in summer

or over wet during winter. Best controlled by placing compacted base course, PAP7 and/or sand

binding immediately after platform cut, filled, compacted and trimmed. Also place DPC as soon as

practicable. If excavated footings are used 25mm or more of concrete in base of trench is

recommended.

Where a specific foundation design is required, Ashby Consulting can provide a proposal for

foundation design options based on this geotechnical report

14.0 Water supply and Sewage Disposal

Water supply connection is available at the end of Blue Gum Drive. We suggest either contacting

Watercare for to enable the installation of new connections to the individual lots or alternatively, two

25,000L rainwater tank could be installed on individual lots collecting the roof runoff. The overflows

from any stormwater tanks should be connected into a piped reticulation system.

The property is shown on councils web map as within Watercares reticulated service area and will

require pressure wastewater collection systems to discharge into the public reticulated network.


16

Each dwelling will need an individual pump station to enable them to discharge into the public

reticulation which is located on Blue Gum Drive.

15.0 Stormwater Disposal and Stormwater Neutrality

The proposed subdivision will create considerable impervious areas and all runoff from these

impervious areas should be collected into a piped system. As part of the proposed subdivision it will

be necessary to upgrade and modify the route of the existing public reticulated stormwater and install

additional pipelines enabling a stormwater connection to be installed on each of the 8 lots and collect

the existing upstream stormwater flows which currently drain into the existing pipeline.

Appropriate storm water treatment devices should be installed to remove any sediments and heavy

metals from discharges to protect the downstream environment.

The existing public pipe line and outlet structure into the stream will most likely require upgrading as

part of this subdivision.

All stormwater surface flow should be kept well clear of the building platforms and directed to a point

where it is unlikely to contribute to land instability or erosion.

Council may require that a Stormwater Neutrality design with respect to this site be undertaken to

ensure that the runoff after development is no greater than before development. Should a Stormwater

Neutrality Design be required, such would need to be covered under separate report which Ashby

Consulting Engineering Ltd if engaged to do so.

16.0 Access

Access to all building sites can be formed at gradients of less than 1 in 5. For Lot 1 to Lot 4, the

proposed access is proposed by sharing the existing driveway with Lot 1 DP 452608. For Lots 5 to 8,

the access way is proposed by sharing the driveway with Lot 2 DP 452608.

17.0 Historical & Cultural Issues

From our inspection of the site and from checking the NZAA digital site recording scheme database

there were no apparent issues of a Historical or Cultural nature evident.

However, if during construction, previously unrecorded historic sites are exposed, all work in the

immediate vicinity will cease and the site will be investigated. If appropriate, an authority to continue

operations will be obtained from the New Zealand Historic Places Trust, as prescribed in the Historic

Places Act 1993.

18.0 Conclusion and Recommendations

It is the considered opinion of Ashby Consulting Engineering Ltd. that -

1. The land on which the construction of the building is proposed is not subject to and is not

likely to be subject to instability, erosion or inundation etc, subject to the recommendations as

outlined in this report.


17

2. The building work itself is not likely to lead to instability, erosion or inundation etc, of the site

itself or any other property, subject to the recommendations as outlined in this report.

3. The proposed building is not likely to be exposed to any other geotechnical hazard.

4. From the visual inspection, no unusual or non-conformity in the features of the site were

apparent which would indicate past use or the presence of hazardous agents or contaminants.

Soil testing can be very expensive and probably is not warranted.

5. Soil Parameters for structural or retaining wall design may be adopted as outlined in this

report.

6. Retaining walls, earthworks and foundations may be constructed as outlined in this report.

7. Foundations may be constructed as modified in this report. The Safe Bearing Pressure of the

subsoils may be taken as at least 100kPa. The soils have been classified as category ‘B’ or ‘M’.

8. The property is located within a pressure wastewater zoned area. A pump station will be

needed to collect the sewage from the individual building sites to discharge it into the public

sewage reticulation system.

9. The short section of existing public stormwater system will require modification and upgrading

as part of the proposed subdivision works.

10. Council may require a Stormwater Neutrality report for this subdivision which would need to

be covered under separate report.

11. Access to the Building site can be formed at gradients of less than 1 in 5 and will formed by

extending the two existing access ways.

12. From our inspection of the site there were no apparent issues of a historical or a cultural nature

evident.

13. The site has been assessed as having very high wind exposure.


19

Appendix

Borehole logs, Penetrometer sounding logs, Lab results, Slope Stability Results, Site Plan, Cross

Section.

Client : Len McKeown.

Location : Blue Gum Drive, Warkworth

Job Number : 7569 Date : 03rd March 2014

SOIL DESCRIPTION

Auger Borehole No. 1

Sheet 1 of 10

Diameter 50 mm

Samples -

No.

Type

Depth

Other

Tests

Remarks : LOGGED: I.C. CHECKED : A.H

R.L. : m. TYPED BY : I.C.

Topsoil

Fill

Clay

Silt

Sand

Gravel

Peat

Rock

0.5

1.0

2.25

1.5

2.0

2.5

2.75

3.0

Ashby Consulting Engineering Ltd 3 Elizabeth Street Warkworth Phone (09) 425 9422 Fax (09) 425 9431

E-mail [email protected]

1.75

1.25

0.75

0.25

Dep

th

(m

)

Leg

en

d

Wa

ter L

evel

Sh

ea

r V

an

e

(

kp

a)

R

em

ou

ld

Str

en

gth

(k

pa)

0-250mm: Topsoil

250-500mm: silty CLAY; light yellowish brown; firm; dry;

cohesive; friable.

500-1000mm: silty CLAY; pale yellowish orange with orangey

mottled; dry; friable; firm; cohesive; with pink

inclusions at 1000mm depth and increasing in

silt.

1000-1500mm: clayey SILT to SILT; pale yellowish orange

with pink and traces of clay changing to light

pink with yellowish orange; friable; silty; damp;

dense underlying layer with resistance to shear

vane penetration.

1500-2000mm: SILTY; light pink and pinkish red with light

brown mottled; friable; damp to moist; dilatant;

resistance to vane penetration.

2000-2500mm: SILTY; pinkish red with light yellowish and

brown mottled; with traces of sand; friable;

damp; dilatant; dense underlying layer.

2500-3000mm: SILTY; pinkish red with charcoal organic

black and bright yellowish clayey material;

damp; dilatant; friable; with traces of sand.

Continued on Sheet 2

183

151

44

44

221

221

221

221

16

25

54

32

X X X — — — X X X — — —X X X — — — X X X — — —X X X — — — X X X — — —X X X — — —X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — —X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X

* * * * * * * * *

* * * * * * * * *




SOIL DESCRIPTION

Auger Borehole No. 1 contd.

Sheet 2 of 10

Diameter 50 mm

Samples -

No.

Type

Depth

Other

Tests



Topsoil

Fill

Clay

Silt

Sand

Gravel

Peat

Rock

3.5

4.0

5.25

4.5

5.0

5.5

5.75

6.0



4.75

4.25

3.75

3.25

Dep

th

(m

)

Leg

en

d

Wa

ter L

evel

Sh

ea

r V

an

e

(

kp

a)

R

em

ou

ld

Str

en

gth

(k

pa)

Continued from Sheet 1



damp to moist; dilatant; friable; with traces of

sand.



damp to moist; dilatant; friable.

3800mm: E.O.B.

123

221

25

38

X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X

* * * * * * * * *

* * * * * * * * *




SOIL DESCRIPTION


Sheet 3 of 10

Diameter 50 mm

Samples -

No.

Type

Depth

Other

Tests



Topsoil

Fill

Clay

Silt

Sand

Gravel

Peat

Rock

0.5

1.0

2.25

1.5

2.0

2.5

2.75

3.0



1.75

1.25

0.75

0.25

Dep

th

(m

)

Leg

en

d

Wa

ter L

evel

Sh

ea

r V

an

e

(

kp

a)

R

em

ou

ld

Str

en

gth

(k

pa)

0-300mm: Topsoil

300-500mm: silty CLAY with organic; dark brown with black;

dry; friable; cohesive; mouldable.

500-1000mm: silty CLAY; pale yellowish brown with orangey

mottled; dry to damp; friable; firm; cohesive;

mouldable.

1000-1500mm: silty CLAY; pale yellowish orange with light

grey; firm; cohesive; plastic; dry; increasing in

silt.

1500-2000mm: clayey SILT to SILT; light greyish with yellow

and white; friable; damp; traces of clay;

cohesive.

2000-2500mm: SILTY; light greyish white with yellow;

friable; dilatant; damp to moist; slightly

cohesive; changing to orangey brown at

2400mm depth; dense underlying layer.

2500-3000mm: SILTY; orangey brown with pinkish mottled;

friable; dense underlying layer; damp to moist;

dilatant with traces of clay; slightly cohesive.


139

155

57

82

158

151

192

221

76

41

16

25

X X X — — — X X X — — —X X X — — — X X X — — —X X X — — — X X X — — —X X X — — —X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — —X X X — — — X X X — — —X X X — — — X X X — — —X X X — — —X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X

* * * * * * * * *

* * * * * * * * *




SOIL DESCRIPTION


Sheet 2 of 10

Diameter 50 mm

Samples -

No.

Type

Depth

Other

Tests



Topsoil

Fill

Clay

Silt

Sand

Gravel

Peat

Rock

3.5

4.0

5.25

4.5

5.0

5.5

5.75

6.0



4.75

4.25

3.75

3.25

Dep

th

(m

)

Leg

en

d

Wa

ter L

evel

Sh

ea

r V

an

e

(

kp

a)

R

em

ou

ld

Str

en

gth

(k

pa)


3000-3500mm: SILTY; orangey brown with pink becoming

pinkish red with orangey at 3400mm depth;

friable; damp to moist; dilatant; traces of clay.

3500-4000mm: SILTY; pinkish red with black mottled and

traces of clay; moist; friable; silty soil with soft

layer at 4000mm depth.

4000mm: E.O.B.

205

104

25

32

X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X

* * * * * * * * *

* * * * * * * * *




SOIL DESCRIPTION


Sheet 5 of 10

Diameter 50 mm

Samples -

No.

Type

Depth

Other

Tests



Topsoil

Fill

Clay

Silt

Sand

Gravel

Peat

Rock

0.5

1.0

2.25

1.5

2.0

2.5

2.75

3.0



1.75

1.25

0.75

0.25

Dep

th

(m

)

Leg

en

d

Wa

ter L

evel

Sh

ea

r V

an

e

(

kp

a)

R

em

ou

ld

Str

en

gth

(k

pa)

0-300mm: Topsoil

300-500mm: silty CLAY; yellowish brown; firm; cohesive;

dry; friable.

500-1000mm: silty CLAY; pale yellowish brown with orange

mottled; dry; friable; firm; cohesive; mouldable.

1000-1500mm: silty CLAY; pale yellowish orange with light

grey and orange; firm; cohesive; plastic; dry;

mouldable.

1500-2000mm: clayey SILT; light greyish with yellowish;

with sandy silt inclusions; friable; damp to

moist; cohesive; compressible.

2000-2500mm: silty CLAY; light greyish white with mottled

yellow; highly plastic clay; with yellowish

sand; friable; cohesive; mouldable; damp.

2500-3000mm: clayey SILT; light greyish with yellowish white

damp; cohesive; with increasing in silt; friable.


202

145

47

73

148

139

95

101

63

54

44

35

X X X — — — X X X — — —X X X — — — X X X — — —X X X — — — X X X — — —X X X — — —X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — —X X X — — — X X X — — —X X X — — — X X X — — —X X X — — —X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — —X X X — — — X X X — — —X X X — — — X X X — — —X X X — — —

* * * * * * * * *

* * * * * * * * *




SOIL DESCRIPTION


Sheet 6 of 10

Diameter 50 mm

Samples -

No.

Type

Depth

Other

Tests



Topsoil

Fill

Clay

Silt

Sand

Gravel

Peat

Rock

3.5

4.0

5.25

4.5

5.0

5.5

5.75

6.0



4.75

4.25

3.75

3.25

Dep

th

(m

)

Leg

en

d

Wa

ter L

evel

Sh

ea

r V

an

e

(

kp

a)

R

em

ou

ld

Str

en

gth

(k

pa)


3000-3500mm: clayey SILT to SILT; light greyish white with

yellow; very soft; moist to wet; silty; slightly

cohesive; compressible.

3500-4000mm: clayey SILT to SILT; light greyish white with

yellow; soft; wet; dilatant; silty; slightly

cohesive; compressible with hard layer at

4000mm depth.

4000mm: E.O.B.

139

221

22

25

X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X

* * * * * * * * *

* * * * * * * * *



Job Number : 7569 Date : 28th February 2014

SOIL DESCRIPTION


Sheet 7 of 10

Diameter 50 mm

Samples -

No.

Type

Depth

Other

Tests



Topsoil

Fill

Clay

Silt

Sand

Gravel

Peat

Rock

0.5

1.0

2.25

1.5

2.0

2.5

2.75

3.0



1.75

1.25

0.75

0.25

Dep

th

(m

)

Leg

en

d

Wa

ter L

evel

Sh

ea

r V

an

e

(

kp

a)

R

em

ou

ld

Str

en

gth

(k

pa)

0-350mm: Topsoil

350-500mm: silty CLAY; yellowish brown with organics;

firm; cohesive; dry; friable.


mottled; firm; dry; cohesive; mouldable.

1000-1500mm: silty CLAY; pale yellowish orange with orange

and greyish mottled; firm; cohesive; plastic;

dry; mouldable.

1500-2000mm: clayey SILT; pale yellowish orange with

orangey and greyish white changing to mix of

pale yellow, pink, creamish and white at

1700mm depth; increasing in silt; damp;

cohesive; friable; compressible.

2000-2500mm: clayey SILT; pinkish red with white and orange

changing to pale yellowish orange at 2200mm

depth; damp soft; friable; mouldable; cohesive.

2500-3000mm: clayey SILT; pale orangey brown; soft; damp;

cohesive; friable; changing to pinkish red with

black and light brown at 2700mm depth;

friable; damp; dilatant.

3000mm: E.O.B

211

155

50

57

126

136

155

101

69

60

54

25

X X X — — — X X X — — —X X X — — — X X X — — —X X X — — — X X X — — —X X X — — —X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — —X X X — — — X X X — — —X X X — — — X X X — — —X X X — — —X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — —X X X — — — X X X — — —X X X — — — X X X — — —X X X

* * * * * * * * *

* * * * * * * * *




SOIL DESCRIPTION


Sheet 8 of 10

Diameter 50 mm

Samples -

No.

Type

Depth

Other

Tests



Topsoil

Fill

Clay

Silt

Sand

Gravel

Peat

Rock

0.5

1.0

2.25

1.5

2.0

2.5

2.75

3.0



1.75

1.25

0.75

0.25

Dep

th

(m

)

Leg

en

d

Wa

ter L

evel

Sh

ea

r V

an

e

(

kp

a)

R

em

ou

ld

Str

en

gth

(k

pa)

0-200mm: Topsoil

200-500mm: silty CLAY; yellowish brown with orange

mottled; firm; cohesive; dry; friable.


mottled; firm; dry; cohesive; friable.

1000-1500mm: silty CLAY; pale yellowish orange pink

mottled changing to pinkish red and yellowish

orange at 1400mm depth; damp; cohesive;

friable; with increasing in silt.

1500-2000mm: clayey SILT; pinkish red to light pink mottled

with charcoal black organic at 1700mm depth;

damp; friable; slightly cohesive; silty.

2000-2500mm: clayey SILT to SILT; pinkish red with light

pink with mottled light brown and charcoal

black; friable; silty; damp to moist.


brown and black mottled; damp to moist;

friable; silty; dilatant.

3000mm: E.O.B

221

180

35

60

192

139

132

120

88

41

25

25

X X X — — — X X X — — —X X X — — — X X X — — —X X X — — — X X X — — —X X X — — —X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — —X X X — — — X X X — — —X X X — — — X X X — — —X X X — — —X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — —X X X — — — X X X — — —X X X — — — X X X — — —X X X — — —X X X — — — X X X — — —

* * * * * * * * *

* * * * * * * * *




SOIL DESCRIPTION


Sheet 9 of 10

Diameter 50 mm

Samples -

No.

Type

Depth

Other

Tests



Topsoil

Fill

Clay

Silt

Sand

Gravel

Peat

Rock

0.5

1.0

2.25

1.5

2.0

2.5

2.75

3.0



1.75

1.25

0.75

0.25

Dep

th

(m

)

Leg

en

d

Wa

ter L

evel

Sh

ea

r V

an

e

(

kp

a)

R

em

ou

ld

Str

en

gth

(k

pa)

0-200mm: Topsoil

200-500mm: silty CLAY; pale yellowish brown; firm;

cohesive; dry; friable.

500-1000mm: silty CLAY; pale yellowish brown with orange

mottled; firm; dry; cohesive; friable.

1000-1500mm: silty CLAY; pale yellowish brown mottled with

orange changing to pale yellowish orange at

1400mm depth; dry; cohesive; firm; mouldable.

1500-2000mm: clayey SILT; pale yellowish orange changing to

pinkish red with black mottled; dry to damp;

friable; cohesive; increasing in silt.

2000-2500mm: clayey SILT to SILT; pinkish red with orange

and black mottled; friable; silty; damp; dilatant.

2500-3000mm: clayey SILT; pinkish red with black mottled

with traces of pale yellow, plastic and damp

clay; friable; silty.

3000mm: E.O.B

199

170

47

73

221

173

164

123

76

54

44

25

X X X — — — X X X — — —X X X — — — X X X — — —X X X — — — X X X — — —X X X — — —X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — —X X X — — — X X X — — —X X X — — — X X X — — —X X X — — —X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — —X X X — — — X X X — — —X X X — — — X X X — — —X X X — — —X X X — — — X X X — — —

* * * * * * * * *

* * * * * * * * *



Job Number : 7569 Date : 06th March 2014

SOIL DESCRIPTION


Sheet 10 of 10

Diameter 50 mm

Samples -

No.

Type

Depth

Other

Tests



Topsoil

Fill

Clay

Silt

Sand

Gravel

Peat

Rock

0.5

1.0

2.25

1.5

2.0

2.5

2.75

3.0



1.75

1.25

0.75

0.25

Dep

th

(m

)

Leg

en

d

Wa

ter L

evel

Sh

ea

r V

an

e

(

kp

a)

R

em

ou

ld

Str

en

gth

(k

pa)

0-200mm: Topsoil

200-500mm: silty CLAY; pale yellowish brown with orange;

firm; cohesive; dry; friable.

500-1000mm: clayey SILT; pale yellowish orange changing to

pinkish red at 700mm; damp; friable; silty;

compressible.


brown sand and white mottled; damp to moist;

friable; compressible.

1500-2000mm: SILT; pinkish red with light brown and black

mottled; friable; damp to moist; silty;

compressible.

2000-2500mm: SILT; pinkish red with light brown mottled;

friable; damp to moist; silty; compressible.

2500-3000mm: SILT; pinkish red with light brown mottled;

friable; damp to moist; silty; compressible.

3000mm: E.O.B

221

186

57

44

126

164

129

170

22

41

25

41

X X X — — — X X X — — —X X X — — — X X X — — —X X X — — — X X X — — —X X X — — —X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — — X X X — — —X X X — — — X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X

* * * * * * * * *

* * * * * * * * *

SITE

START D. START D.

50mm 2050 4050 8 50mm 2050 4050 4

100 2100 4100 100 2100 4100

150 2150 4150 6 150 2150 4150 3

200 2200 4200 200 2200 4200

250 2250 4250 8 250 2250 4250 3

300 2300 4300 300 2300 4300

350 2350 4350 4 350 2350 4350 2

400 2400 4400 400 2400 4400

450 2450 4450 10 450 2450 4450 2.5

500 2500 4500 500 2500 4500

550 2550 4550 12 550 2550 4550 2

600 2600 4600 600 2600 4600

650 2650 4650 10 650 2650 4650 2

700 2700 4700 700 2700 4700

750 2750 4750 16 750 2750 4750 1

800 2800 4800 800 2800 4800

850 2850 4850 850 2850 4850 3

900 2900 4900 900 2900 4900

950 2950 BH1 4950 950 2950 4950 4

1000 3000 5000 1000 BH2 3000 BH2 5000

1050 BH1 3050 5050 1050 3050 5050 5

1100 3100 5100 1100 3100 5100

1150 3150 5150 1150 3150 5150 12

1200 3200 5200 1200 3200 5200

1250 3250 5250 1250 3250 5250 25

1300 3300 5300 1300 3300 5300

1350 3350 5350 1350 3350 5350 25+

1400 3400 5400 1400 3400 5400 rebound

1450 3450 5450 1450 3450 5450

1500 3500 5500 1500 3500 5500

1550 3550 5550 1550 3550 5550

1600 3600 5600 1600 3600 5600

1650 3650 5650 1650 3650 5650

1700 3700 5700 1700 3700 5700

1750 3750 5750 1750 3750 5750

1800 3800 5800 1800 3800 5800

1850 3850 2 5850 1850 3850 5850

1900 3900 5900 1900 3900 5900

1950 3950 6 5950 1950 3950 5950

2000 4000 6000 2000 4000 6000

Dep. End Dep. End

Job No.: Client:

Site: Logged:

Date: Weather:

SCALA PENETROMETER TEST RESULTSTABLE OF BLOWS PER 50mm INCREMENT

SP1 SP2

Blue Gum Drive, Warkworth

ASHBY CONSULTING ENGINEERING LTD

CIVIL & STRUCTURAL ENGINEERING 7569

Blue Gum Drive

email: [email protected]

Len McKeown

IC

Occasional Shower

3 Elizabeth Street, P.O. Box 124, Warkworth

Ph. (09) 425 9422, Fax. (09) 425 9431 3-Mar-14

SITE

START D. START D.

50mm 2050 4050 2 50mm 2050 4050 7

100 2100 4100 100 2100 4100

150 2150 4150 5 150 2150 4150 9

200 2200 4200 200 2200 4200

250 2250 4250 12 250 2250 4250 8

300 2300 4300 300 2300 4300

350 2350 4350 11 350 2350 4350 9

400 2400 4400 400 2400 4400

450 2450 4450 12 450 2450 4450 8

500 2500 4500 500 2500 BH4 4500

550 2550 4550 11 550 2550 4550 6

600 2600 4600 600 2600 4600

650 2650 4650 6 650 2650 4650 8

700 2700 4700 700 2700 4700

750 2750 4750 3.5 750 2750 4750 8

800 2800 4800 800 2800 4800

850 2850 4850 6 850 2850 4850 11

900 2900 4900 900 2900 4900

950 2950 4950 13 950 2950 4950 24

1000 3000 5000 1000 BH4 3000 5000

1050 BH3 3050 BH3 5050 20 1050 3050 1 5050 20

1100 3100 5100 rebound 1100 3100 5100

1150 3150 5150 30+ 1150 3150 1.5 5150

1200 3200 5200 rebound 1200 3200 5200

1250 3250 5250 1250 3250 1.5 5250

1300 3300 5300 1300 3300 5300

1350 3350 5350 1350 3350 3 5350

1400 3400 5400 1400 3400 5400

1450 3450 5450 1450 3450 2 5450

1500 3500 5500 1500 3500 5500

1550 3550 5550 1550 3550 3 5550

1600 3600 5600 1600 3600 5600

1650 3650 5650 1650 3650 4 5650

1700 3700 5700 1700 3700 5700

1750 3750 5750 1750 3750 5 5750

1800 3800 5800 1800 3800 5800

1850 3850 5850 1850 3850 6 5850

1900 3900 5900 1900 3900 5900

1950 3950 5950 1950 3950 7 5950

2000 4000 6000 2000 4000 6000

Dep. End Dep. End

Job No.: Client:

Site: Logged:

Date: Weather:



SP3 SP4


CIVIL & STRUCTURAL ENGINEERING 7569 Len McKeown


3 Elizabeth Street, P.O. Box 124, Warkworth Blue Gum Drive IC

Ph. (09) 425 9422, Fax. (09) 425 9431 3-Mar-14 Occasional Shower

SITE

START D. START D.

50mm 2050 4050 5 50mm 2050 4050 7

100 2100 4100 100 2100 4100

150 2150 4150 7 150 2150 4150 10

200 2200 4200 200 2200 4200

250 2250 4250 7 250 2250 4250 9

300 2300 4300 300 2300 4300

350 2350 4350 8 350 2350 4350 6

400 2400 4400 400 2400 4400

450 2450 4450 9 450 2450 4450 4

500 2500 BH5 4500 500 2500 BH6 4500

550 2550 4550 8 550 2550 4550 4

600 2600 4600 600 2600 4600

650 2650 4650 7 650 2650 4650 6

700 2700 4700 700 2700 4700

750 2750 4750 8 750 2750 4750 7

800 2800 4800 800 2800 4800

850 2850 4850 10 850 2850 4850 7

900 2900 4900 900 2900 4900

950 2950 4950 9 950 2950 4950 8

1000 3000 5000 1000 BH6 3000 5000

1050 BH5 3050 1 5050 11 1050 3050 1 5050 10

1100 3100 5100 1100 3100 5100

1150 3150 3 5150 9 1150 3150 3 5150 10

1200 3200 5200 1200 3200 5200

1250 3250 2 5250 9 1250 3250 4 5250 10

1300 3300 5300 1300 3300 5300

1350 3350 4 5350 10 1350 3350 3 5350 5

1400 3400 5400 1400 3400 5400

1450 3450 4 5450 10 1450 3450 4 5450 7

1500 3500 5500 1500 3500 5500

1550 3550 6 5550 1550 3550 3 5550 8

1600 3600 5600 1600 3600 5600

1650 3650 5 5650 1650 3650 4 5650

1700 3700 5700 1700 3700 5700

1750 3750 5 5750 1750 3750 8 5750

1800 3800 5800 1800 3800 5800

1850 3850 4 5850 1850 3850 5 5850

1900 3900 5900 1900 3900 5900

1950 3950 5 5950 1950 3950 5 5950

2000 4000 6000 2000 4000 6000

Dep. End Dep. End

Job No.: Client:

Site: Logged:

Date: Weather:



Ph. (09) 425 9422, Fax. (09) 425 9431 28-Feb-14 Fine





SP5 SP6

SITE

START D. START D.

50mm 2050 4050 7 50mm 2050 4050

100 2100 4100 100 2100 4100

150 2150 4150 10 150 2150 4150

200 2200 4200 200 2200 4200

250 2250 4250 9 250 2250 4250

300 2300 4300 300 2300 4300

350 2350 4350 8 350 2350 4350

400 2400 4400 400 2400 4400

450 2450 4450 8 450 2450 4450

500 2500 BH7 4500 500 2500 4500

550 2550 4550 8 550 2550 4550

600 2600 4600 600 2600 4600

650 2650 4650 9 650 2650 4650

700 2700 4700 700 2700 4700

750 2750 4750 9 750 2750 4750

800 2800 4800 800 2800 4800

850 2850 4850 9 850 2850 4850

900 2900 4900 900 2900 4900

950 2950 4950 9 950 2950 4950

1000 3000 5000 1000 3000 5000

1050 BH7 3050 3 5050 9 1050 3050 5050

1100 3100 5100 1100 3100 5100

1150 3150 5 5150 9 1150 3150 5150

1200 3200 5200 1200 3200 5200

1250 3250 5 5250 11 1250 3250 5250

1300 3300 5300 1300 3300 5300

1350 3350 5 5350 12 1350 3350 5350

1400 3400 5400 1400 3400 5400

1450 3450 4 5450 12 1450 3450 5450

1500 3500 5500 1500 3500 5500

1550 3550 4 5550 1550 3550 5550

1600 3600 5600 1600 3600 5600

1650 3650 4 5650 1650 3650 5650

1700 3700 5700 1700 3700 5700

1750 3750 5 5750 1750 3750 5750

1800 3800 5800 1800 3800 5800

1850 3850 4 5850 1850 3850 5850

1900 3900 5900 1900 3900 5900

1950 3950 7 5950 1950 3950 5950

2000 4000 6000 2000 4000 6000

Dep. End Dep. End

Job No.: Client:

Site: Logged:

Date: Weather:



Ph. (09) 425 9422, Fax. (09) 425 9431 6-Mar-14 Fine





SP7

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BH5/SP5

BH1

BH2

BH3

BH4

BH6

BH5

BH4

A

A

B

B

Lot 11,200m²

Lot 31,200m²

Lot 41,780m²

Lot 81,250m²

Lot 71,200m²

Lot 61,100m²

Lot 5890m²

Lot 1DP 452608

ROW

ROW

N

0 20 5010 30 40

ExistingManhole

Existing SW lineas per GIS

Lot 21,200m²

Discontinuedeffluent trenchs

C

C

Lot 2DP 452608

Building Sites

Stream

BH7

Pt. Lot 11DP 1159860

ROAD

Legal,

not fo

rmed

ROAD

Legal, not formed

Ø600concrete chamber

Assumed alignmentof 3nos Ø40mmHorizontal drains

Drain

Note: The horizontal drains alignment shown on this drawing isassumed from visual inspection.The cross section slope is based on the levels shown on GIS map

PT-1

PT-2

PT-3

PT - Push tube soil samplelocation for Lab Testing

CLIENT: PROJECT:

LOCATION:

DRAWING:

SCALE: DRAWN: CHECKED:

REV: SERIES OF:SHEET:

NO. DATE: REVISION DESCRIPTION: JOB NO.:

DATE:

A

B

C

Infered rockLayer

BH2BH1

Bdy

Silty Clay - up to 1.5m

RL 20.0m

Top soil - up to 300mm

Weatherd Silt - between 1.5 to 5.4mWaitemata series

Section A-A

Section B-B

Infered rockLayer

BH3

BH4Silty Clay - up to 1.5m


Clayey Silt ofWaitemata series

RL 20.0m

Subdivision boundary

Assumed wintergroundwater level


RL 20.0m

Section C-C

Infered rockLayer

BH6

BH5

Silty Clay - up to 1.5m


Clayey Silt ofWaitemata series


Subdivision boundary

BH7

CLIENT: PROJECT:

LOCATION:

DRAWING:

SCALE: DRAWN: CHECKED:

REV: SERIES OF:SHEET:

NO. DATE: REVISION DESCRIPTION: JOB NO.:

DATE:

A

B

C

Documents

SITE INFORMATION ASSESSMENT...Boreholes (BH1 to BH7) were conducted within the site and supplemented with scala penetrometer soundings continued from the borehole base. BH1 was conducted