48891 WOMBARRA 95 Morrison Ave Jan 11

Report onGeotechnical Investigation

Proposed Subdivision95 Morrison Avenue, Wombarra

Prepared forMr Bryan Morrison

Project 48891January 2011

Geotechnical Investigation, Proposed Subdivision Project 4889195 Morrison Avenue, Wombarra Januray 2011

Executive Summary

A geotechnical investigation was carried out on the site of a proposed three lot subdivision at 95 Morrison Avenue, Wombarra. The investigation included a review of historical records held by Wollongong City Council, field mapping, the drilling of six boreholes and the excavation of eight test pits, monitoring of groundwater wells, laboratory testing or selected samples and engineering analysis. The interpreted subsurface profile is topsoil overlying very loose to medium dense and firm to stiff colluvium to depths ranging from 7.5 m to 12.0 m underlain by residual soil and weathered siltstone and sandstone. The bedrock is typically extremely low to very low strength in the upper 1 m to 2 m but then rapidly improves to medium to high strength. The site in its undeveloped state is assessed as being of moderate and high risk (for property damage) of instability resulting from a combination of a groundwater regime characterised by periodic artesian conditions within a pre-existing, landslide affected, deep colluvial profile. Five terrain units have been defined for each of the instability risk areas. Site surface and subsurface conditions indicate that periodic creep failure or localised slump failure may occur along the eastern boundary of site, along the face of a relict landslide identified in the central northern part of the site and along the buried watercourse. Any residential development should be limited to Terrain Unit 2, will require further assessment and engineering works to reduce the risk of instability to no greater than low risk to property and acceptable levels of risk to life. It is anticipated that such works would include improvement to surface drainage (for the entire site) and subsurface drainage (extending into Terrain Units 1, 3 and 5). As a consequence of the variability of the subsurface profile and indications of recent instability, it is considered that the construction of a trial subsoil drainage system would be required to fully assess the effectiveness of such a system in the longer term with a monitoring period of not less than 12 months, but possibly longer if dry conditions be encountered.


Table of Contents

Page

1. Introduction......................................................................................................................1

2. Site Description and Regional Geology...........................................................................1

3. Field Work .......................................................................................................................2 3.1 Site Inspection....................................................................................................... 2 3.2 Subsurface Investigation....................................................................................... 3

4. Laboratory Testing ..........................................................................................................4

5. Comments .......................................................................................................................5 5.1 Proposed Development......................................................................................... 5 5.2 Geological model .................................................................................................. 5 5.3 Slope Stability Assessment................................................................................... 5 5.4 Site Classification.................................................................................................. 9 5.5 Site Development.................................................................................................. 9

5.5.1 Remedial and Precautionary Works .......................................................... 9 5.5.2 Trial Works and Monitoring...................................................................... 10

5.6 Construction Guidelines ...................................................................................... 11 5.7 Wollongong City Council Geotechnical Development Control Plan .................... 12 5.8 Proposed Subdivision Layout.............................................................................. 12 5.9 Contamination ..................................................................................................... 13

6. Conclusions...................................................................................................................13

7. References ....................................................................................................................13

8. Limitations .....................................................................................................................14

Appendix A: About this Report

Results of Field Work

Photo Plates 1 4

Drawings 1 4

Appendix B: Results of Laboratory Tests

Appendix C: Extracts of Relevant Publications

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Report on Geotechnical Investigation Proposed Subdivision 95 Morrison Avenue, Wombarra 1. Introduction

This report presents the results of a geotechnical investigation undertaken for a proposed subdivision at 95 Morrison Avenue, Wombarra. The investigation was commissioned by Mr Bryan Morrison in an email dated 5 October 2010 care of Mr Scott Lester of Nathan Lester Architecture and was undertaken in accordance with Douglas Partners' proposal dated 8 September 2010. It is understood that the development of the site will include the subdivision of a large existing block into three residential lots. The aim of the investigation was to assess the surface and subsurface soil and groundwater conditions across the site in order to provide:

an assessment of the geotechnical suitability, include slope stability, of the site for the proposed development;

an appropriate site classification in accordance with the requirements of AS 2870 1996 (Ref 1); recommendations on site preparation and earthworks; recommendations on excavations and retaining structures; and an appropriate foundation system for the proposed development. The investigation included a review of historical records held by Wollongong City Council, field mapping, drilling of six boreholes, the excavation of eight test pits, monitoring of groundwater wells, laboratory testing of selected samples and engineering analysis. The details of the field work are presented in this report, together with comments and recommendations on the issues listed above. 2. Site Description and Regional Geology

The site, which is known as Lot 1 in DP 14039, is a trapezoidal shaped area of some 1.2 ha with a maximum north-south and east-west dimensions of 208 m and 77 m, respectively. It is bounded to the west by Morrisons Avenue, the north and south by low density residential dwellings, and to the east by a large lot which is densely wooded on the steep slope at the rear which is adjacent the site. The site topography is hummocky and irregular (refer Photo 1). Site levels fall variously to the southeast, east, northeast and north but mostly to the east, at grades ranging from 1 in 8 to 1 in 30 in the southern, eastern and north-western area of the site, including the existing dwelling, increasing to 1 in 2.5 at the central and north-eastern area of the site (refer Photo 2). The site is mostly covered by short, maintained, grass with some boulders scattered predominately around the central and lower portions of the site. Matured trees were also scattered across the site.

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Improvements to the site include a weatherboard cottage and separate garage located in the northern portion of the site. The site is mapped on the Geology and Natural Slope Stability Zones in the City of Greater Wollongong (Ref 2) as being underlain by Wombarra Claystone, part of the Narrabeen Group, which comprises greenish grey claystone with calcareous and quartz-lithic sandstone interbeds. The footslopes of the Illawarra Escarpment are, in places, blanketed with talus deposits and colluvium, comprising sandy clays with sandstone boulders which may exceed 10 m in thickness. Rocks intersected in the boreholes on the site were typical of rocks of the Narrabeen Group. 3. Field Work

3.1 Site Inspection

Inspection of the site and field mapping was carried out by an experienced engineering geologist on 5 November 2010. The main features observed are summarised below and also selected items are additionally shown on Drawing 1 (in Appendix A) and Photos 1 8 in Plates 1 4 (in Appendix A).

The perimeter walls of the existing dwelling in the northern portion of the site appears to be supported on brick piers, most likely founded at shallow depths within the overburden soils. The eastern wooden piers on the associated decking have cracking in the cement rendering and a masonry wall is leaning downslope (refer Photo 4).

The eastern brick piers and attached wooden panel underneath the house have minor cracking and there is an opening between weatherboard panels on the eastern side garage wall and slippage of a weatherboard panel on the southern side of the garage wall.

Some mature native tress on the steeply sloping land on the lot and on the land immediately are east leaning downslope (refer Photo 5) consistent with on-going soil creep (gradual movements with time in response to gravity and other factors affecting the near-surface soil layers).

Small to large (in excess of 3 m largest dimension) sandstone boulders (refer Photo 6), derived from ancient collapse of sections of the Illawarra Escarpment, are scattered in the central and eastern areas of the site.

Degraded scarps typically

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Water ponds in depressions on the western side of Morrison Avenue including near the south-western and north-western corners of the site. Water is discharged from a drain pipe on the south-western corner onto the site and flows through the grass to meet a creek on the property downslope.

3.2 Subsurface Investigation

The subsurface investigation comprised:

Six boreholes (Bores 1 6) drilled with a trailer-mounted Gemco 210B auger/rotary rig to V-bit refusal at depths ranging from 8.75 m to 13.44 m. Bores 3, 4 and 6 were extended into the underlying rock using NQ (48 mm diameter) diamond core drilling equipment to termination depths ranging from 11.59 m to 16.54 m. Standard penetration tests (SPT) were undertaken at regular intervals. On completion of the drilling, standpipe piezometers were installed in Bores 3, 4 and 6 to facilitate long-term monitoring of groundwater levels.

Groundwater monitoring and permeability testing at the location of the three standpipe piezometers.

Eight test pits (Pits 7 14) were excavated with a New Holland LB110.B backhoe fitted with a 450 mm wide bucket.

Logging by an engineering geologist and sampling of disturbed samples to assist in strata identification and for laboratory testing.

Dynamic cone penetrometer tests (AS 1289 6.3.2) at the test pit locations to assess the in-situ strength of the overburden soils.

The test locations are shown on Drawing 1 in Appendix A. The surface levels shown on the borehole and test pit logs were determined by interpolation from contours provided by Hill and Blume Pty Ltd, consulting surveyors. Details of the subsurface conditions encountered during the field investigation are given on the borehole and test pit logs in Appendix A, which should be read in conjunction with the notes defining classification methods and descriptive terms in Appendix A. Summary geological cross sections (Sections A A and B B) are given on Drawings 2 and 3. The field testing encountered variable conditions underlying the site, with the succession of strata broadly summarised as follows: TOPSOIL: clay and gravelly clay extending to depths ranging from 0.1 m to 0.7 m; COLLUVIUM: comprising firm to very stiff, clay and gravelly clay, and very loose to medium

dense gravel, clayey gravel and cobbly gravel with some boulders up to 1000 mm extending to depths ranging from 7.5 m to 12.0 m in Bores 1 6 and to the terminations depths ranging 1.6 m to 5.1 m in Pits 7 14;

RESIDUAL SOIL: very stiff to hard, clay and silty clay, 0.3 2.6 m thick, extending to depths ranging

from 7.8 m to 13.0 m in Bores 1 2 and 4 6;

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BEDROCK: initially extremely low to very low strength at depths ranging from 7.5 m to 16.0 m becoming very low to low strength at refusal of the V-bit at depths from 9.25 m to 16.0 m. Core drilling recovered typically medium to high strength siltstone, sandstone and laminite to the termination depths ranging from 11.59 m to 16.54 m.

Variable conditions were encountered initially in Pit 14 which encountered filling comprising clay to a depth of 1.0 m overlying the general succession described above. Free groundwater was observed in all boreholes during auger drilling at depths ranging from 1.7 m to 10.0 m. Free groundwater was also observed in Pits 7, 8 and 12 during excavation at depths ranging from 0.9 m to 2.7 m. No free groundwater was observed in the remaining test pit excavations for the short period they were left open. It is noted that excavations were immediately backfilled following logging and sampling which precluded longer term monitoring of groundwater levels. Groundwater monitoring in standpipe piezometers installed in Bores 3, 4 and 6 measured static water levels ranging from 1.55 m to 9.85 m below the surface, RL109.5 to RL114.0 (refer Drawings 2 and 3). Rising head slug tests indicate the colluvium is of moderate permeability (5.9 x 10-4 4.6 x 10-5 m/sec). It is noted that groundwater levels are affected by climatic conditions and soil permeability and will therefore vary with time. 4. Laboratory Testing

Selected samples from the boreholes and test pits were tested in the laboratory for measurement of field moisture content, Atterberg limits and linear shrinkage. The detailed test report sheets are given in Appendix B with the test results summarised in Table 1. Table 1: Summary of Laboratory Test Results

Bore/Pit No Depth (m)

FMC (%)

PL (%)

LL (%)

PI (%)

LS (%) Material

2 1.00 1.45 20.9 64 27 37 12.0 Silty clay

13 0.5 0.6 26.3 46 25 21 11.5 Gravelly silty clay where FMC = Field moisture content PL = Plastic limit LL = Liquid limit PI = Plasticity Index LS = Linear shrinkage The results indicate that the clay soils are of intermediate plasticity and as such, would be moderately susceptible to shrinkage and swelling movements as a result of changes in moisture content.

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5. Comments

5.1 Proposed Development

It is understood the proposed development comprises a three lot subdivision for low density residential housing. 5.2 Geological model

The geological model for the site comprises:

a deep (7.8 m to 13.0 m) colluvial profile, including boulders to greater than 3 m largest dimension, derived from ancient collapses of sections of the Illawarra Escarpment and subsequently affected by slope instability within and adjacent to the site.

local mantling of the colluvium by road embankment filling in the south-western corner of the site. a 0.3 m to 2.6 m thick residual clay profile which underlies the colluvium and grades into

extremely to highly weathered siltstone and sandstone which become slightly weathered to fresh with depth.

both perched and deeper groundwater tables, controlled in part by a buried watercourse in the southern of the site, which results in springs and saturation of near-surface soils and probably triggering instability in the steep slopes immediately east of the site.

5.3 Slope Stability Assessment

The site lies with the area mapped for stability by Bowman in 1972 (Ref 3) which indicates the lot is located in an area classified as stable land no landslip problems and near the boundary of an area classified as topographically unstable for development owing to steep slopes and/or topographic position and nature of soil immediately to the east. Due to the limited resolution of Bowmans mapping, it is not possible to delineate these areas with precision. The site also borders the area mapped by Walker et al. 1987 (Ref 4) which indicates hummocky, irregular slope to the south of the site on Morrison Avenue. Wollongong City Council records document instability (slumping and associated debris flows) having developed on the western side of Morrison Avenue to the west, and to the northeast of the site and also within, including the lower north eastern portion of the site. Stability of existing undeveloped slopes is typically dependant on a number of key factors including the slope of the ground, the type and strength of soil or rock and the presence of water. While an area may be assessed as being currently stable, unsuitable development or poor construction techniques may trigger instability. Alternatively, sites which are assessed as having some risk of instability may be improved by installation of such features as sub-surface drains or retaining structures.

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The site and adjacent areas have been divided into five terrain units based on observed slopes and features indicative of slope instability. The inferred distribution of these units is shown on Drawing 4 (Appendix A). Descriptions of each of the terrain units are outlined below and associated limitations on development are given in the following sections. TERRAIN UNIT 1 This unit is within the relatively flat southern portion of the site lying between

RL110 and RL120, affected by the presence of a buried drainage line or watercourse. While there are some minor irregularities in the south-east facing surface profile the overall profile is generally uniform. Elevated groundwater levels, the presence of springs and the lack of fine material in the near surface colluvium are a feature of this terrain unit. The inferred location of the buried watercourse is shown on Drawing 4. Whilst no ground movements are currently active, it is likely that any small change to this slope, increased saturation of the soil or increased piezometric pressure following prolonged rainfall, may destabilise the slope and reactive movement. This may include regression of instability into the site from the downslope property.

TERRAIN UNIT 2 This unit is within the central southern portion of the site and generally lies

between RL111.5 and RL122. Bedrock underlies the area at depths ranging 7.5 m to 10.7 m. Whilst no signs of deep-seated instability were observed in this unit, a hummocky, irregular surface was observed. Areas of slope instability (Terrain Unit 5) are noted immediately to the east of the site boundary and may regress into this terrain unit.

TERRAIN UNIT 3 This terrain unit is within the central northern and north eastern portion of the

site where the ground surface levels are within the range RL109 to RL124.5. Bedrock underlies the area at depths between 7.8 13.0 m and surface grades range from 1 in 2.5 to 1 in 9. Leaning trees along the toe face of the relict landslide indicates surface creep is occurring in an easterly direction.

TERRAIN UNIT 4 This terrain unit comprises the area where the existing dwelling is located

where surface ground levels are above RL117. Surface grades are generally between 1 in 8 to 1 in 15. Whilst no signs of deep-seated instability were observed in this unit, downslope movement of a masonry wall, separation between weatherboard walls and minor cracking were observed in the two structures and may indicate surface creep.

TERRAIN UNIT 5 This terrain unit is in the north-eastern portion of the site and extends to the

east into the adjacent property where ground surface levels are generally below RL114 and surface grades range from 1 in 2.5 to 1 in 30. Degraded scarps and leaning trees are a features of the steeper areas of this terrain unit.

The risk to property for the existing and proposed building areas has been assessed based on the four terrain units (refer Table 2) with reference to AGS Practice Note Guidelines on Landslide Risk Management (Ref 5), relevant extracts of which are included in Appendix C. Descriptions of each of the terrain units are outlined below and associated limitations on development are given in the following sections.

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Table 2: Slope Stability Risk Assessment for Property

Terrain Unit Hazard Likelihood Consequence Risk

Extremely slow soil creep Almost certain Insignificant Low

Rapid, near-surface, localised slumping in colluvial soils Possible Major High

1

Rapid, deep-seated slide Unlikely Catastrophic High

Extremely slow soil creep Likely Insignificant Low

Rapid, near-surface, localised slumping in colluvial soils Possible Medium Moderate

2

Rapid, deep-seated slide Unlikely Major Moderate

Extremely slow soil creep Almost certain Minor Moderate

Rapid, near-surface, localised slumping in colluvial soils Possible Major High

3

Rapid, deep-seated slide Unlikely Catastrophic High

Extremely slow soil creep Likely Insignificant Low

Rapid, near-surface, localised slumping in colluvial soils Possible Medium Moderate

4

Rapid, deep-seated slide Unlikely Major Moderate

Extremely slow soil creep Almost certain Minor Moderate

Rapid, near-surface, localised slumping in colluvial soils Likely Medium High

5

Rapid, deep-seated slide Unlikely Catastrophic High The site is assessed as having a risk to property of slope instability of high (Terrain Units 1, 3 and 5), moderate (Terrain Units 2 and 4). The AGS definitions of various risk categories are as follows: LOW RISK Usually acceptable to regulators. Where treatment has been required to

reduce the risk to this level, ongoing maintenance is required. MODERATE RISK Tolerated provided treatment plan is implemented to maintain or reduce

risks, may be accepted. These may also require investigation and planning of treatment options.

HIGH RISK Detailed investigation planning and treatment options required to reduce risk

to acceptable levels. Work would cost a substantial sum.

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The AGS Practice Note Guidelines for Landslide Risk Management (Ref 5) indicates that the regulator (i.e. Council) is the appropriate authority to set standards for risk levels but also suggest that, for most development in existing urban areas, criteria based on Tolerable Risk levels are applicable because of the trade-off between the risks, the benefit of development and the cost of risk mitigation. Definitions of acceptable and tolerable risks are included in the AGS Guidelines as follows: TOLERABLE RISK Risks within a range that society can live with so as to secure certain

benefits. It is a range of risk regarded as non-negligible and needing to be kept under review and reduced further if practicable.

ACCEPTABLE RISK Risk which everyone affected is prepared to accept. Action to further reduce

such risk is usually not required unless reasonably practicable measures are available at low cost in terms of money, time and effort.

Wollongong City Council policy requires the adoption of a low risk criterion for property and an acceptable risk to life assessed in accordance with AGS Landslide Risk Management Guidelines (2007) for the site development and a possible requirement of a monitoring period (possibly years) prior to construction so as to validate the success of measures installed to remediate landslide affected areas. For loss of life, the individual risk can be calculated from:

R(LoL) = P(H) x P(S:H) x P(T:S) x V(D:T) where: R(LoL) is the risk (annual probability of loss of life of an individual). P(H) is the annual probability of the hazardous event (e.g. deep seated slide).

P(S:H) is the probability of spatial impact by the hazard (e.g. of the slide reaching the element at risk taking into account the travel distance for a given event.

P(T:S) is the temporal probability (e.g. the affected section of the dwelling being occupied by the individual) given the spatial impact allowing for potential for excavation.

V(D:T) is the vulnerability of the individual (probability of loss of life of the individual given the impact).

A preliminary assessment of risk of life has been carried out for the assessed slope instability hazards. On the basis of velocity and consequences of previous failures within nearby sections of Morrison Avenue and Buttenshaw Drive, it is expected that there would be a high probability of safe evacuation of the structure in the event of a deep seated slide extending into the approximate footprint of the existing and newly proposed footprints recommended in the following sections of this report. The annual probability of a person most at risk losing his/her life as a result of an impact by a deep seated slide (considered to be the most dangerous of the assessed hazards) is summarised in Table 3 and assumes that:

the probability of non-evacuation taken as 0.1 typical occupation for the person most at risk of the dwelling averages 16 hours/day. a deep seated slide extends into 50% of the existing and newly proposed dwelling areas. the impacted section of the building collapses.

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Table 3: Summary of Estimated Annualised Risk of Slope Instability Person Most at Risk, Terrain Units 2 and 4

Scenario Hazard P(H) P(S:H) P(T:S) V(D:T) R(LoL)

Current site conditions

Rapid, deep seated slide 10

-4 1 3.3 x 10-2 1 3.3 x 10-6

Post precautionary works

Rapid, deep seated slide 10

-5 1 3.3 x 10-2 1 3.3 x 10-7

Whilst there are no established acceptance criteria for landslides in Australia or internationally for loss of life due to a hazardous event such as a landslide, AGS suggests that for new slopes or those affected by known or previous instability (eg those including new development), an acceptable risk of life of 10-6 is appropriate for the average person at risk. A tolerable risk level (to life) is taken as 10-5. On this basis, the risk of loss of life with respect to geotechnical hazards identified for Terrain Units 2 and 4 in Table 3 is considered to be acceptable after precautionary works described in the following sections have been undertaken. Therefore based on the assessment results and current site conditions, residential development within the high risk zone (Terrain Units 1,3 and 5) would be precluded and as such, would be nominated as restricted building zones. Whilst remedial works are also suggested for the high risk zones (Terrain Units 1, 3 and 5), development within is not considered feasible with the main purpose of these works being to provide a level of protection to Terrain Units 2 and 4 by minimising creep movements that are occurring as a result of elevated groundwater pressures and to reduce the likelihood of upslope regression of instability. 5.4 Site Classification

Due to the topographic location, indications of previous instability, an allowable bearing capacity of less than 100 kPa and the site being subject to probable severe moisture changes due to the presence of mature trees, the site is classified as Class P in accordance with requirements of AS 2870 1996 (Ref 1). The main requirement of a Class P lot is that the design of all footings must be undertaken by a structural engineer using engineering principles and construction techniques appropriate for hillside lots (refer AGS extracts, Appendix C) and guidelines given in this report. In terms of clay reactivity, the clay soils are moderately reactive (Class M) as defined in AS 2870 1996. 5.5 Site Development

5.5.1 Remedial and Precautionary Works

It is considered limited development will be feasible for Terrain Unit 2 following the undertaking of remedial and precautionary works to reduce the property risk to an acceptable level. These works will extend into the adjacent high risk zones and outside the site (subject to landowner agreement) in the eastern part. Works to be undertaken prior to the development should include the installation of

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subsoil drains to reduce pore water pressure at the interface between the colluvium and the residual soil/weathered rock interface. Works for Terrain Units 1, 3 and 5 are aimed at minimising the possible influence from the neighbouring high risk area. Appropriate remedial precautionary works to reduce risk for the neighbouring zones to an acceptable level would include:

Extensive subsoil and surface drainage within the high risk area with a maximum drain spacing of 20 m. A nominal drain depth of 5 m is suggested with drains orientated normal to the site contours with twin ag-pipes. Riser pipes should be included at regular intervals to permit periodic inspection and long term maintenance.

To minimise water along the buried watercourse (Terrain Unit 1), the individual drains (possibly in a herringbone arrangement) will need to be closely spaced, possibly in the order of 6 m.

Limit the removal of existing mature trees and the provision of vegetation cover to protect against erosion, including re-vegetation by deeply rooted trees species in Terrain Unit 1 and 3 in order to reduce the risk of further instability occurring in adjacent zones that could adversely impact on downslope areas.

Provided the precautionary works demonstrate effective dewatering of the buried watercourse (Terrain Unit 1), the relict landslide (Terrain Area 3) and the steeper slopes on the property to the east of the site (Terrain Unit 5), it is expected that development would be limited to single storey or split-level, light-weight structures capable of tolerating movement.

5.5.2 Trial Works and Monitoring

In order to assess the likely effectiveness of the precautionary works, it is suggested that a trial area be considered with the overall methodology to be agreed with Council as providing supporting data for development. It is envisaged that the trial works comprise:

The construction of a trial trench/drainage line extending upslope along the buried watercourse (near the southern boundary of the property). The drainage line would be excavated until a maximum practical depth of about 6 m was achieved, then extended upslope through the overlying strata to its head end. The drain would be finished with permanent structures including flushing points and a discharge point protected from damage and constructed to provide flushing access and monitoring of discharge volume.

It is anticipated that the trench drain would have a minimum width of 500 mm and include dual 100 mm diameter ag-lines set into geo-textile wrapped, free-draining aggregate extending to approximately 1 m below the surface. The upper 1 m of the trench would be backfilled with selected clayey material compacted in layers to provide a surface seal. It is anticipated that the trenching would commence from the downslope end and be progressively laid to minimise the length of trench open at one time. Where significant groundwater inflow was encountered at the trench head, it may be necessary to allow drainage of the upslope material prior to continuing the trenching, so as to minimise the risk of trench collapse. Excavation support, such as shoring may also be required, given the required depth of the excavation by conventional measures. Reinstatement with controlled filling will be required to minimise the potential for erosion scouring.

The installation of an additional two piezometers, one upslope and one downslope along the buried watercourse and the installation of an additional piezometer near Bore 1 to assist in the determination of the effective drainage radius. These piezometers (including the existing bores)

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would be finished as permanent monitoring points, with monitoring being carried out regularly from the time of installation.

The installation of two inclinometers, finished at permanent monitoring points, most likely adjacent to Bores 3 and 6, to assess the likelihood of on-going creep or intermittent slope movements.

The monitoring of groundwater levels would be carried out during drain construction and subsequently on a regular basis, so as to assess groundwater response and drainage rates over a period including at least a major rainfall event. It is envisaged that the minimum monitoring period of the piezometers and inclinometers would be approximately 12 months, but could be longer if the period was characterised by significantly lower than average rainfall. Progressive geotechnical assessment of the results during and at the completion of the monitoring period would be carried out to determine (if the results are positive) the final number and spacing of subsurface drains within the site.

5.6 Construction Guidelines

Following the undertaking of precautionary works and monitoring program described in Section 5.5, development within Terrain Unit 2 within the proposed building envelopes (refer Drawing 4) must take into account the site history and the instability classification, the variably relative density and composition of the colluvium as part of the overall design of a future dwelling(s). It must also be realised that the geology of the site are the area in general (ie rock at depths of excess of 10 m) means that any stabilisation works carried out may have little impact in reducing the effect of the longer term creep movements or deep seated movement in the colluvium profile. The works proposed however, will reduce the effects of differential movements occurring. The following guidelines therefore, are suggested for the development of concept design plans for the site should be favourable monitoring results being obtained in the trial:

cutting (excavations) and filling must not exceed a vertical height of 1 m above or below the existing ground surface. All batters should be constructed no steeper than 3:1 (H:V) and appropriately vegetated to reduce the effects of erosion. All other excavation or filling should be supported by engineer-designed retaining walls.

dwellings should be of single storey or split-level construction, generally following the ground contours (i.e. designed across the slope).

dwellings should be of light weight construction (such as timber) with limited masonry sections and metal roofing. They should have predominantly timber (bearers and joist) flooring, with the overall structures capable of tolerating movement.

whilst the dwelling will need to be inherently flexible, the footing systems must have structural rigidity, with the overall conceptual design to be reviewed by DP on ensure that the geotechnical requirements of the site are accommodated in the design. Design compliance to be confirmed following inspection by a suitably qualified engineer during construction.

footing systems could comprise shear walls founding below depths of near-surface soil creep at depths of at least 1 m orientated in the north-south direction or a grillage of ground beams again,

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orientated predominately in the north-south direction. Allowance may need to be made within the design of the footing system for re-levelling of the structure.

construction of a deep foundation system (such as piles founding in rock) is considered to be unsuitable for this site due to the depth of rock being in excess of 10 m and the resultant slenderness of the piles having little resistance to bending.

all stormwater drainage must be collected and discharged from the site in a controlled manner with allowance made for erosion control at the outlet. The site should be maintained in accordance with the CSIRO publication Guide to Home Owners on Foundation Maintenance and Footing Performance, a copy of which is included in Appendix C.

Structures designed in accordance with the above guidelines will enable the effect of creep induced movements to be minimised with the overall site development undertaken in such a way that the risk of instability is not increased. It must be realised however, that creep movements will be on-going during the life of all structures and that the movements must be accommodated in design as they cannot be eliminated.

5.7 Wollongong City Council Geotechnical Development Control Plan

Wollongong City Council has a Geotechnical Development Control Plan (GDCP) (Ref 6) which has been prepared to define methods of geotechnical assessment of sites which may be subject to slope instability. It includes items to be addressed as part of the development application, design and construction phases of site development. Items of significance to the proposed subdivision include:

adoption of a low risk criterion for property and an acceptable risk to life assessed in accordance with the AGS Landslide Risk Management Guidelines (2007) for the site development;

a possible requirement of a monitoring period (possibly years) prior to construction so as to validate the success of measures installed to remediate landslide affected areas.

It should be noted that modification of the risk assessment included in the previous sections may be required at a future date should revision to either Councils GDCP or the AGS guidelines be undertaken. 5.8 Proposed Subdivision Layout

Drawing 4 (Appendix A) shows a preliminary subdivision layout with nominated building envelopes proposed by the client prior to the current site investigation. This has been overlayed with the terrain units and proposed building envelope discussed in the previous sections. The following observations are made in relation to the detail shown:

A three lot subdivision is proposed with two nominated building areas located partly in high risk terrain units.

Two proposed driveways, one for each of the nominated building areas, both located partly in high risk terrain units.

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A new building envelopes recommended on the basis of this investigation is also shown in Drawing 4. Revision of the proposed lot boundaries and building envelopes will require consideration of the Wollongong City Councils Local Environment Plan (LEP) (Ref 7) which requires residential lots to provide a specific rectangular building envelope with minimum dimensions of 15 m (width) and 10 m (depth) where the subject site contains any inherent site constraints. The LEP has further minimum 12 m lot width requirement for residential allotments at the front of the building alignment and a minimum depth for a residential allotment of at least 25 m. 5.9 Contamination

No discernable signs of contamination were observed during the field work for the current site investigation. 6. Conclusions

The site in its undeveloped state is assessed as being variously of moderate and high risk (for property damage) of instability resulting from a combination of a groundwater regime characterised by periodic artesian conditions within a pre-existing, landslide affected, deep colluvial profile. Five terrain units have been defined for each of the instability risk areas. Site surface and subsurface conditions suggest that periodic creep failure or localised slump failure may occur along the eastern boundary of site, along the face of a relict slide identified in the central northern part of the site and along the buried watercourse. Any residential development, limited to Terrain Unit 2, will require further assessment and engineering works to reduce the risk of instability to no greater than low risk to property and acceptable levels of risk to life. It is anticipated that such works would include improvement to surface drainage (for the entire site) and subsurface drainage (extending into Terrain Units 1 and 3). As a consequence of the variability of the subsurface profile and indications of recent instability, it is considered that the construction of a trial subsoil drainage system would be required to fully assess the effectiveness of such a system within terrain units in the longer term with a monitoring period of not less than 12 months, but possibly longer should dry conditions be encountered. 7. References

1. Australian Standard AS 2870 (1996) Residential Slabs and Footings.

2. Bowman H N (1972) Natural Slope Stability in the City of Greater Wollongong, Sheet 5951, Geological Survey of NSW.

3. Bowman H N (1972) Natural Slope Stability in the City of Greater Wollongong, Geological Survey of NSW 14(2) pp 159 222.

14 of 15


4. Walker B F, Amaral B & MacGregor J P (1987) Slope Instability in the Coledale area of the Illawarra Escarpment, Soil Slope Instability and Stabilisation, Walker & Fells (Eds), Belkema, Rotterdam.

5. Australian Geomechanics Society (2007c) Practice Note Guidelines on Landslide Risk Management, Australian Geomechanics, 42(1).

6. Wollongong City Council (2009) Development Control Plan: Chpt E12 Geotechnical Assessment.

7. Wollongong City Council (2009) Local Environment Plan: Chpt B2 Residential Subdivision.

8. Limitations

Douglas Partners (DP) has prepared this report for a project at 95 Morrison Avenue, Wombarra, NSW in accordance with DP's proposal dated 8 September 2010 and acceptance received from Mr Bryan Morrison care of Scott Lester Nathan Lester Architects on 5 October 2010. The report is provided for the exclusive use of Mr Bryan Morrison for this project only and for the purpose(s) described in the report. It should not be used for other projects or by a third party. In preparing this report DP has necessarily relied upon information provided by the client and/or their agents. The results provided in the report are indicative of the sub-surface conditions only at the specific sampling or testing locations, and then only to the depths investigated and at the time the work was carried out. Sub-surface conditions can change abruptly due to variable geological processes and also as a result of anthropogenic influences. Such changes may occur after DP's field testing has been completed. DP's advice is based upon the conditions encountered during this investigation. The accuracy of the advice provided by DP in this report may be limited by undetected variations in ground conditions between sampling locations. The advice may also be limited by budget constraints imposed by others or by site accessibility. This report must be read in conjunction with all of the attached notes and should be kept in its entirety without separation of individual pages or sections. DP cannot be held responsible for interpretations or conclusions made by others unless they are supported by an expressed statement, interpretation, outcome or conclusion given in this report.

Douglas Partners Pty Ltd

Appendix A

About this ReportBorehole Logs

Test Pit LogsPhoto Plates 1 4

Drawings 1 4

July 2010

Introduction These notes have been provided to amplify DP's report in regard to classification methods, field procedures and the comments section. Not all are necessarily relevant to all reports. DP's reports are based on information gained from limited subsurface excavations and sampling, supplemented by knowledge of local geology and experience. For this reason, they must be regarded as interpretive rather than factual documents, limited to some extent by the scope of information on which they rely. Copyright This report is the property of Douglas Partners Pty Ltd. The report may only be used for the purpose for which it was commissioned and in accordance with the Conditions of Engagement for the commission supplied at the time of proposal. Unauthorised use of this report in any form whatsoever is prohibited. Borehole and Test Pit Logs The borehole and test pit logs presented in this report are an engineering and/or geological interpretation of the subsurface conditions, and their reliability will depend to some extent on frequency of sampling and the method of drilling or excavation. Ideally, continuous undisturbed sampling or core drilling will provide the most reliable assessment, but this is not always practicable or possible to justify on economic grounds. In any case the boreholes and test pits represent only a very small sample of the total subsurface profile. Interpretation of the information and its application to design and construction should therefore take into account the spacing of boreholes or pits, the frequency of sampling, and the possibility of other than 'straight line' variations between the test locations. Groundwater Where groundwater levels are measured in boreholes there are several potential problems, namely: In low permeability soils groundwater may

enter the hole very slowly or perhaps not at all during the time the hole is left open;

A localised, perched water table may lead to an erroneous indication of the true water table;

Water table levels will vary from time to time with seasons or recent weather changes. They may not be the same at the time of construction as are indicated in the report; and

The use of water or mud as a drilling fluid will mask any groundwater inflow. Water has to be blown out of the hole and drilling mud must first be washed out of the hole if water measurements are to be made.

More reliable measurements can be made by installing standpipes which are read at intervals over several days, or perhaps weeks for low permeability soils. Piezometers, sealed in a particular stratum, may be advisable in low permeability soils or where there may be interference from a perched water table. Reports The report has been prepared by qualified personnel, is based on the information obtained from field and laboratory testing, and has been undertaken to current engineering standards of interpretation and analysis. Where the report has been prepared for a specific design proposal, the information and interpretation may not be relevant if the design proposal is changed. If this happens, DP will be pleased to review the report and the sufficiency of the investigation work. Every care is taken with the report as it relates to interpretation of subsurface conditions, discussion of geotechnical and environmental aspects, and recommendations or suggestions for design and construction. However, DP cannot always anticipate or assume responsibility for: Unexpected variations in ground conditions.

The potential for this will depend partly on borehole or pit spacing and sampling frequency;

Changes in policy or interpretations of policy by statutory authorities; or

The actions of contractors responding to commercial pressures.

If these occur, DP will be pleased to assist with investigations or advice to resolve the matter.

July 2010

Site Anomalies In the event that conditions encountered on site during construction appear to vary from those which were expected from the information contained in the report, DP requests that it be immediately notified. Most problems are much more readily resolved when conditions are exposed rather than at some later stage, well after the event. Information for Contractual Purposes Where information obtained from this report is provided for tendering purposes, it is recommended that all information, including the written report and discussion, be made available. In circumstances where the discussion or comments section is not relevant to the contractual situation, it may be appropriate to prepare a specially edited document. DP would be pleased to assist in this regard and/or to make additional report copies available for contract purposes at a nominal charge. Site Inspection The company will always be pleased to provide engineering inspection services for geotechnical and environmental aspects of work to which this report is related. This could range from a site visit to confirm that conditions exposed are as expected, to full time engineering presence on site.

July 2010

Sampling Sampling is carried out during drilling or test pitting to allow engineering examination (and laboratory testing where required) of the soil or rock. Disturbed samples taken during drilling provide information on colour, type, inclusions and, depending upon the degree of disturbance, some information on strength and structure. Undisturbed samples are taken by pushing a thin-walled sample tube into the soil and withdrawing it to obtain a sample of the soil in a relatively undisturbed state. Such samples yield information on structure and strength, and are necessary for laboratory determination of shear strength and compressibility. Undisturbed sampling is generally effective only in cohesive soils. Test Pits Test pits are usually excavated with a backhoe or an excavator, allowing close examination of the in-situ soil if it is safe to enter into the pit. The depth of excavation is limited to about 3 m for a backhoe and up to 6 m for a large excavator. A potential disadvantage of this investigation method is the larger area of disturbance to the site. Large Diameter Augers Boreholes can be drilled using a rotating plate or short spiral auger, generally 300 mm or larger in diameter commonly mounted on a standard piling rig. The cuttings are returned to the surface at intervals (generally not more than 0.5 m) and are disturbed but usually unchanged in moisture content. Identification of soil strata is generally much more reliable than with continuous spiral flight augers, and is usually supplemented by occasional undisturbed tube samples. Continuous Spiral Flight Augers The borehole is advanced using 90-115 mm diameter continuous spiral flight augers which are withdrawn at intervals to allow sampling or in-situ testing. This is a relatively economical means of drilling in clays and sands above the water table. Samples are returned to the surface, or may be collected after withdrawal of the auger flights, but they are disturbed and may be mixed with soils from the sides of the hole. Information from the drilling (as distinct from specific sampling by SPTs or undisturbed samples) is of relatively low

reliability, due to the remoulding, possible mixing or softening of samples by groundwater. Non-core Rotary Drilling The borehole is advanced using a rotary bit, with water or drilling mud being pumped down the drill rods and returned up the annulus, carrying the drill cuttings. Only major changes in stratification can be determined from the cuttings, together with some information from the rate of penetration. Where drilling mud is used this can mask the cuttings and reliable identification is only possible from separate sampling such as SPTs. Continuous Core Drilling A continuous core sample can be obtained using a diamond tipped core barrel, usually with a 50 mm internal diameter. Provided full core recovery is achieved (which is not always possible in weak rocks and granular soils), this technique provides a very reliable method of investigation. Standard Penetration Tests Standard penetration tests (SPT) are used as a means of estimating the density or strength of soils and also of obtaining a relatively undisturbed sample. The test procedure is described in Australian Standard 1289, Methods of Testing Soils for Engineering Purposes - Test 6.3.1. The test is carried out in a borehole by driving a 50 mm diameter split sample tube under the impact of a 63 kg hammer with a free fall of 760 mm. It is normal for the tube to be driven in three successive 150 mm increments and the 'N' value is taken as the number of blows for the last 300 mm. In dense sands, very hard clays or weak rock, the full 450 mm penetration may not be practicable and the test is discontinued. The test results are reported in the following form. In the case where full penetration is obtained

with successive blow counts for each 150 mm of, say, 4, 6 and 7 as:

4,6,7 N=13

In the case where the test is discontinued before the full penetration depth, say after 15 blows for the first 150 mm and 30 blows for the next 40 mm as:

15, 30/40 mm

July 2010

The results of the SPT tests can be related empirically to the engineering properties of the soils. Dynamic Cone Penetrometer Tests / Perth Sand Penetrometer Tests Dynamic penetrometer tests (DCP or PSP) are carried out by driving a steel rod into the ground using a standard weight of hammer falling a specified distance. As the rod penetrates the soil the number of blows required to penetrate each successive 150 mm depth are recorded. Normally there is a depth limitation of 1.2 m, but this may be extended in certain conditions by the use of extension rods. Two types of penetrometer are commonly used. Perth sand penetrometer - a 16 mm diameter

flat ended rod is driven using a 9 kg hammer dropping 600 mm (AS 1289, Test 6.3.3). This test was developed for testing the density of sands and is mainly used in granular soils and filling.

Cone penetrometer - a 16 mm diameter rod with a 20 mm diameter cone end is driven using a 9 kg hammer dropping 510 mm (AS 1289, Test 6.3.2). This test was developed initially for pavement subgrade investigations, and correlations of the test results with California Bearing Ratio have been published by various road authorities.

July 2010

Description and Classification Methods The methods of description and classification of soils and rocks used in this report are based on Australian Standard AS 1726, Geotechnical Site Investigations Code. In general, the descriptions include strength or density, colour, structure, soil or rock type and inclusions. Soil Types Soil types are described according to the predominant particle size, qualified by the grading of other particles present:

Type Particle size (mm) Boulder >200 Cobble 63 - 200 Gravel 2.36 - 63 Sand 0.075 - 2.36 Silt 0.002 - 0.075 Clay

July 2010

Soil Origin It is often difficult to accurately determine the origin of a soil. Soils can generally be classified as: Residual soil - derived from in-situ weathering

of the underlying rock; Transported soils - formed somewhere else

and transported by nature to the site; or Filling - moved by man. Transported soils may be further subdivided into: Alluvium - river deposits Lacustrine - lake deposits Aeolian - wind deposits Littoral - beach deposits Estuarine - tidal river deposits Talus - scree or coarse colluvium Slopewash or Colluvium - transported

downslope by gravity assisted by water. Often includes angular rock fragments and boulders.

July 2010

Rock Strength Rock strength is defined by the Point Load Strength Index (Is(50)) and refers to the strength of the rock substance and not the strength of the overall rock mass, which may be considerably weaker due to defects. The test procedure is described by Australian Standard 4133.4.1 - 1993. The terms used to describe rock strength are as follows:

Term Abbreviation Point Load Index Is(50) MPa

Approx Unconfined Compressive Strength MPa*

Extremely low EL 200 * Assumes a ratio of 20:1 for UCS to Is(50)

Degree of Weathering The degree of weathering of rock is classified as follows:

Term Abbreviation Description Extremely weathered EW Rock substance has soil properties, i.e. it can be remoulded

and classified as a soil but the texture of the original rock is still evident.

Highly weathered HW Limonite staining or bleaching affects whole of rock substance and other signs of decomposition are evident. Porosity and strength may be altered as a result of iron leaching or deposition. Colour and strength of original fresh rock is not recognisable

Moderately weathered

MW Staining and discolouration of rock substance has taken place

Slightly weathered SW Rock substance is slightly discoloured but shows little or no change of strength from fresh rock

Fresh stained Fs Rock substance unaffected by weathering but staining visible along defects

Fresh Fr No signs of decomposition or staining Degree of Fracturing The following classification applies to the spacing of natural fractures in diamond drill cores. It includes bedding plane partings, joints and other defects, but excludes drilling breaks.

Term Description Fragmented Fragments of 1000 mm

July 2010

Rock Quality Designation The quality of the cored rock can be measured using the Rock Quality Designation (RQD) index, defined as:

RQD % = cumulative length of 'sound' core sections 100 mm long total drilled length of section being assessed

where 'sound' rock is assessed to be rock of low strength or better. The RQD applies only to natural fractures. If the core is broken by drilling or handling (i.e. drilling breaks) then the broken pieces are fitted back together and are not included in the calculation of RQD. Stratification Spacing For sedimentary rocks the following terms may be used to describe the spacing of bedding partings:

Term Separation of Stratification Planes Thinly laminated < 6 mm Laminated 6 mm to 20 mm Very thinly bedded 20 mm to 60 mm Thinly bedded 60 mm to 0.2 m Medium bedded 0.2 m to 0.6 m Thickly bedded 0.6 m to 2 m Very thickly bedded > 2 m

July 2010

Introduction These notes summarise abbreviations commonly used on borehole logs and test pit reports. Drilling or Excavation Methods C Core Drilling R Rotary drilling SFA Spiral flight augers NMLC Diamond core - 52 mm dia NQ Diamond core - 47 mm dia HQ Diamond core - 63 mm dia PQ Diamond core - 81 mm dia Water Z Water seep V Water level Sampling and Testing A Auger sample B Bulk sample D Disturbed sample E Environmental sample U50 Undisturbed tube sample (50mm) W Water sample pp pocket penetrometer (kPa) PID Photo ionisation detector PL Point load strength Is(50) MPa S Standard Penetration Test V Shear vane (kPa) Description of Defects in Rock The abbreviated descriptions of the defects should be in the following order: Depth, Type, Orientation, Coating, Shape, Roughness and Other. Drilling and handling breaks are not usually included on the logs. Defect Type B Bedding plane Cs Clay seam Cv Cleavage Cz Crushed zone Ds Decomposed seam F Fault J Joint Lam lamination Pt Parting Sz Sheared Zone V Vein

Orientation The inclination of defects is always measured from the perpendicular to the core axis. h horizontal v vertical sh sub-horizontal sv sub-vertical Coating or Infilling Term cln clean co coating he healed inf infilled stn stained ti tight vn veneer Coating Descriptor ca calcite cbs carbonaceous cly clay fe iron oxide mn manganese slt silty Shape cu curved ir irregular pl planar st stepped un undulating Roughness po polished ro rough sl slickensided sm smooth vr very rough Other fg fragmented bnd band qtz quartz

July 2010

Graphic Symbols for Soil and Rock General

Soils

Sedimentary Rocks

Metamorphic Rocks

Igneous Rocks

Road base

Filling

Concrete

Asphalt

Topsoil

Peat

Clay

Conglomeratic sandstone

Conglomerate

Boulder conglomerate

Sandstone

Slate, phyllite, schist

Siltstone

Mudstone, claystone, shale

Coal

Limestone

Porphyry

Cobbles, boulders

Sandy gravel

Laminite

Silty sand

Clayey sand

Silty clay

Sandy clay

Gravelly clay

Shaly clay

Silt

Clayey silt

Sandy silt

Sand

Gravel

Talus

Gneiss

Quartzite

Dolerite, basalt, andesite

Granite

Tuff, breccia

Dacite, epidote

TOPSOIL - dark brown grey clay with some silt, roots androotlets, dampCLAY - firm, slightly friable, orange grey clay with somefine to medium gravel (siltstone, sandstone) and silt, damp(COLLUVIUM)

- becoming slightly gravelly below 2.0m

- becoming slightly friable below 3.0m

GRAVEL - loose, orange brown, slightly clayey, fine tocoarse gravel (sandstone, siltstone), wet(COLLUVIUM)

- becoming medium dense below 7.5m

CLAY - very stiff to hard, yellow brown clay with someextremely low to very low strength bands, humid to damp(RESIDUAL)

SILTSTONE - extremely low strength, extremelyweathered, orange grey siltstone with some very lowstrength bandsBore discontinued at 10.61m(refusal on very low to low strength siltstone)

0.4

3.4

9.12

10.0

10.61

Type

118

117

116

115

114

113

112

111

110

109

108

107

106

105

104

103

102

101

100

99

Depth(m)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

RL

Wat

er

Dep

th

Sam

ple

Descriptionof

Strata Gra

phic

Log

Results &Comments

Sampling & In Situ Testing

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

BOREHOLE LOG BOREHOLE LOG BOREHOLE LOG BOREHOLE LOG BOREHOLE LOG BOREHOLE LOG BOREHOLE LOG CLIENT:PROJECT:LOCATION:

BORE No: 1PROJECT No: 48891DATE: 6/12/2010SHEET 1 OF 1

Mr Bryan MorrisonProposed Subdivision

LOGGED: RJHRIG: Gemco 210B

95 Morrison Avenue, Wombarra

DRILLER: Boers Drilling (Paul)

REMARKS:WATER OBSERVATIONS: Free groundwater observed at 4.0m, at 3.2m after 48 hoursTYPE OF BORING: SFA (V-bit) to 10.75m

SAMPLING & IN SITU TESTING LEGEND

CASING: UncasedSURVEY DATUM: MGA94

A Auger sample G Gas sample PID Photo ionisation detector (ppm)B Bulk sample P Piston sample PL(A) Point load axial test Is(50) (MPa)BLK Block sample Ux Tube sample (x mm dia.) PL(D) Point load diametral test Is(50) (MPa)C Core drilling W Water sample pp Pocket penetrometer (kPa)D Disturbed sample Water seep S Standard penetration testE Environmental sample Water level V Shear vane (kPa)

SURFACE LEVEL: 118 AHDEASTING:NORTHING:DIP/AZIMUTH: 90/--

WellConstruction

DetailsAA

AS

S

S

S

S

S

S

S

2,3,4N = 7

3,2,4N = 6

3,3,4N = 7

2,3,3N = 6

3,4,4N = 8

4,7,8N = 15

10,5/30refusal

11/110refusal

0.00.10.30.50.81.01.452.0

2.45

3.0

3.45

4.5

4.95

6.0

6.45

7.5

7.95

9.09.18

10.510.61

TOPSOIL - dark grey brown, friable clay with some silt,roots and rootlets, dampCLAY - stiff, orange grey brown, slightly friable clay withsome fine to medium gravel (siltstone, sandstone) andtrace rootlets, humid(COLLUVIUM)- becoming slightly gravelly below 1.0m- becoming very stiff, yellow brown mottled light grey claywith some gravel (fine to medium siltstone) below 2.0mGRAVEL - medium dense, orange brown, fine to mediumgravel (siltstone, sandstone) with some clay and silt, wet(COLLUVIUM)

GRAVELLY CLAY - stiff, orange brown, gravelly (fine tocoarse siltstone, sandstone) clay with some silt, damp towet(COLLUVIUM)

- becoming very stiff and slightly gravelly to gravelly below6.0m

CLAY - very stiff to hard, yellow brown mottled light grey,fissured, slightly silty clay with some extremely low to verylow strength siltstone bands, humid to damp(RESIDUAL)

- with some very low to low strength bands below 10.5mSILTSTONE - extremely low to very low strength,extremely weathered, yellow orange brown siltstone withsome low strength bandsBore discontinued at 11.91m(refusal on very low to low strength siltstone)

0.2

2.5

4.5

9.0

10.72

11.91

Type

115

114

113

112

111

110

109

108

107

106

105

104

103

102

101

100

9998

9796

Depth(m)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

RL

Wat

er

Dep

th

Sam

ple

Descriptionof

Strata Gra

phic

Log

Results &Comments


1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19







REMARKS:WATER OBSERVATIONS: Free groundwater observed at 2.5m, at 2.4m after 1 hourTYPE OF BORING: SFA (V-bit) to 11.91m




SURFACE LEVEL: 115 AHDEASTING:NORTHING:DIP/AZIMUTH: 90/--

WellConstruction

DetailsAA

AS

S

S

S

S

S

S

S

3,6,6N = 12

3,6,11N = 17

4,6,5N = 11

3,3,6N = 9

3,4,6N = 10

3,6,10N = 16

7,18,12/110refusal

12,7/50refusal

0.00.10.30.50.81.01.452.0

2.45

3.0

3.45

4.5

4.95

6.0

6.45

7.5

7.95

9.0

9.41

10.510.72

TOPSOIL - dark brown grey claywith some silt, roots and rootlets,dampCLAYEY GRAVEL - very loose toloose, orange brown, friable, slightlyclayey to clayey, fine to coarsegravel (sandstone, siltstone) withsome silt, damp(COLLUVIUM)- becoming damp to wet below 1.7m- becoming very loose below 2.0m- becoming very loose to loosebelow 3.0mCLAYEY GRAVEL - loose, greybrown, clayey, fine to medium gravel(siltstone, sandstone) with sand andsilt, damp to wet(POSSIBLE COLLUVIUM)

- becoming medium dense anddamp below 6.0m

SILTSTONE - extremely lowstrength, extremely weathered, lightgrey to yellow orange brownsiltstone- becoming very low strength withsome low strength bands below8.3mSANDSTONE - medium to highstrength, moderately weathered tofresh stained, slightly fractured,orange grey to light grey, fine tomedium grained, quartz sandstonewith some siltstone bandsSILTSTONE - typically highstrength, slightly weathered to freshrock, slightly fractured, light to midgrey siltstone with some fine tomedium grained quartz sandstonebandsBore discontinued at 11.59m(limit of investigation)

3,3,2N = 5

3,2,1N = 3

3,3,2N = 5

2,4,5N = 9

3,7,9N = 16

8,16,22N = 38

PL(A) = 1.1

PL(A) = 0.7

PL(A) = 0.5

PL(A) = 1.2

93

96

99

100

AAAS

S

S

S

S

S

C

C

*Unless otherwisestated, rock is fracturedalong smooth planar,ironstained,subhorizontal beddingpartings

9.29m: 10mm clay9.31m: J 20 - 25, 8mmclay9.37m: J 20 - 25, 2 -8mm clay

0.4

3.77

7.5

9.25

10.78

11.59

RockStrength

Wat

er

Degree ofWeathering

EW

HW

MW

SW

FS FR

Descriptionof

Strata

FractureSpacing

(m)

0.01

Depth(m)

Test Results&

Comments0.05

Discontinuities

B - BeddingS - Shear Ty

pe


Ex

Low

Ver

y Lo

wLo

wM

ediu

mH

igh

Ver

y H

igh

Ex

Hig

h

0.10

0.50

1.00 R

QD

%Cor

eR

ec. %

Gra

phic

Log

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

J - JointF - Fault

RL

113

112

111

110

109

108

107

106

105

104

103

102

101

100

9998

9796

9594




Standpipe installed: screen 7.60 - 11.59m, gravel 6.0 - 11.59m, bentonite 5.6 - 6.0m, backfill 0.0 - 5.6m




REMARKS:WATER OBSERVATIONS: Free groundwater observed at 1.7m, at 1.5m after 48 hoursTYPE OF BORING: SFA (V-bit) to 9.25m, coring (NQ) to 11.59m


CASING: NW to 9.25mSURVEY DATUM: MGA94


SURFACE LEVEL: 113.2 AHDEASTING:NORTHING:DIP/AZIMUTH: 90/--

TOPSOIL - dark brown, friable claywith some silt, roots and rootlets,dampGRAVELLY CLAY - firm, greybrown, friable, slightly gravelly togravelly (fine to coarse siltstone,sandstone) clay with trace rootlets,humid to damp(COLLUVIUM)- with some silt and damp below1.0m- becoming clay and gravel below2.0m

- becoming firm to stiff and grey toorange brown below 4.5m

GRAVEL - medium dense, orangebrown, friable, fine to coarse gravel(siltstone, sandstone) with someclay, humid to damp(COLLUVIUM)

CLAYEY GRAVEL - medium dense,orange brown, slightly clayey toclayey, fine to coarse gravel(siltstone, sandstone) with some silt,damp(COLLUVIUM)

GRAVEL - medium dense, orangebrown, fine to coarse gravel(siltstone, sandstone) with some silt,damp to wet(COLLUVIUM)

CLAY - very stiff to hard, yellowbrown to grey brown clay with somesilt and bands of very low strengthsiltstone, humid to damp(RESIDUAL)

SILTSTONE - extremely lowstrength, extremely weathered,orange brown siltstone with somevery low to low strength bandsSILTSTONE - typically very low tolow strength, extremely to highlyweathered, fractured to slightlyfractured, yellow brown greysiltstoneSILTSTONE - medium strength,slightly weathered, slightly fractured,yellow brown to grey siltstoneBore discontinued at 16.54m(limit of investigation)

2,2,3N = 5

2,3,2N = 5

2,2,4N = 6

3,4,4N = 8

3,4,4N = 8

8,7,11N = 18

3,5,7N = 12

4,6,10N = 16

10,22refusal

PL(A) = 0.1

PL(A) = 0.1

PL(A) = 0.05

PL(A) = 0.4

PL(A) = 0.5

0

0

84

85

100

100

AA

AS

S

S

S

S

S

S

S

S

C

C

C

*Unless otherwisestated, rock is fracturedalong smooth planar,ironstained,subhorizontal beddingpartings and subverticaljoints

13.81m: J 80 - 9013.94m: CORE LOSS:170mm14.1m: J 80 - 90

15.17m: J 60 - 65, FeV15.52m: J 65 - 7015.63m: J 75 - 80, FeV15.95m: 2mm clay

0.1

6.85

9.0

10.0

12.0

13.0

13.44

14.11

16.0

16.54

RockStrength

Wat

er

Degree ofWeathering

EW

HW

MW

SW

FS FR

Descriptionof

Strata

FractureSpacing

(m)

0.01

Depth(m)

Test Results&

Comments0.05

Discontinuities


pe


Ex

Low

Ver

y Lo

wLo

wM

ediu

mH

igh

Ver

y H

igh

Ex

Hig

h

0.10

0.50

1.00 R

QD

%Cor

eR

ec. %

Gra

phic

Log

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

J - JointF - Fault

RL

123

122

121

120

119

118

117

116

115

114

113

112

111

110

109

108

107

106

105

104


BORE No: 4PROJECT No: 48891DATE: 6 - 7/12/2010SHEET 1 OF 1






REMARKS:WATER OBSERVATIONS: Free groundwater observed at 10.0m, at 9.6m after 24 hoursTYPE OF BORING: SFA (V-bit) to 13.44m, coring (NQ) to 16.54m





TOPSOIL - dark brown, friable clay with some silt, rootsand rootlets, dampCLAY - firm, orange brown, friable, slightly gravelly (fine tocoarse siltstone, sandstone) clay with some silt and tracerootlets, damp(COLLUVIUM)

GRAVELLY CLAY - stiff, orange brown gravelly (fine tocoarse siltstone, sandstone) clay with some silt, damp(COLLUVIUM)

- damp to wet between 2.0 - 2.5m

- becoming stiff to very stiff, clay and gravel below 4.5m

CLAY - very stiff, light grey mottled orange brown, slightlysilty clay with some sand and some very low to lowstrength siltstone bands, humid to damp(RESIDUAL)- becoming wet below 9.7m- becoming light grey mottled yellow brown below 10.5m

SILTSTONE - extremely low strength, extremelyweathered, grey brown to light grey siltstoneBore discontinued at 12.14m(refusal on very low to low strength siltstone)

0.45

2.0

9.0

11.6

12.14

Type

117

116

115

114

113

112

111

110

109

108

107

106

105

104

103

102

101

100

9998

Depth(m)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

RL

Wat

er

Dep

th

Sam

ple

Descriptionof

Strata Gra

phic

Log

Results &Comments


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7

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12

13

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16

17

18

19







REMARKS:WATER OBSERVATIONS: Free groundwater observed at 2.0m, at 5.6m after 4 hoursTYPE OF BORING: SFA (V-bit) to 12.14m





WellConstruction

DetailsAA

AS

S

S

S

S

S

S

S

S

2,3,4N = 7

3,18,8N = 26

3,4,6N = 10

5,7,9N = 16

4,8,7N = 15

7,10,11N = 21

5,12,6/30refusal

5,8,13N = 21

7/90refusal

0.00.10.30.50.81.01.452.0

2.45

3.0

3.45

4.5

4.95

6.0

6.45

7.5

7.95

9.09.33

10.5

10.95

12.012.09

TOPSOIL - dark grey brown, friableclay with some roots and rootlets,dampCLAYEY GRAVEL - loose, orangebrown, friable, clayey, fine to coarsegravel (siltstone, sandstone) withsome silt, damp(COLLUVIUM)- becoming slightly clayey to clayeybelow 1.0mGRAVELLY CLAY - stiff, orangebrown, friable, slightly gravelly togravelly (fine to coarse siltstone,sandstone) clay with some silt,damp(COLLUVIUM)

CLAY - very stiff, yellow orangebrown mottled light grey, slightlysilty clay with trace root remains,humid to damp(PROBABLE COLLUVIUM)

GRAVEL - medium dense, orangebrown, slightly clayey, fine to coarsegravel (siltstone, sandstone) withsome silt, wet(PROBABLE COLLUVIUM)

CLAY - very stiff, yellow brownmottled light grey, slightly silty clay,humid to damp(RESIDUAL)

SILTSTONE - extremely lowstrength, extremely weathered,yellow brown grey siltstone- becoming very low to low strengthbelow 8.7mLAMINATE - medium to highstrength, slightly weatheredbecoming fresh stained, slightlyfractured, orange brown and light tomid grey laminiteBore discontinued at 11.61m(limit of investigation)

3,3,4N = 7

4,6,5N = 11

4,6,9N = 15

4,9,11N = 20

5,15,8N = 23

5,14,15/110refusal

PL(A) = 0.4PL(A) = 1

PL(A) = 0.9

PL(A) = 1.2

PL(A) = 0.6

51

100

99

100

AA

AS

S

S

S

S

S

C

C

*Unless otherwisestated, rock is fracturedalong smooth planar,ironstained,subhorizontal beddingpartings

8.81m: CIV

9.39m: J 55 - 60 S, P,FeS9.96m: J 20 - 25 S, P,FeV10m: J 75 - 80 S, P,FeV

0.3

2.0

4.5

5.0

7.57.8

8.75

11.61

RockStrength

Wat

er

Degree ofWeathering

EW

HW

MW

SW

FS FR

Descriptionof

Strata

FractureSpacing

(m)

0.01

Depth(m)

Test Results&

Comments0.05

Discontinuities


pe


Ex

Low

Ver

y Lo

wLo

wM

ediu

mH

igh

Ver

y H

igh

Ex

Hig

h

0.10

0.50

1.00 R

QD

%Cor

eR

ec. %

Gra

phic

Log

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

J - JointF - Fault

RL

112

111

110

109

108

107

106

105

104

103

102

101

100

9998

9796

9594

93








REMARKS:WATER OBSERVATIONS: Free groundwater observed at 5.0mTYPE OF BORING: SFA (V-bit) to 8.75m, coring (NQ) to 11.61m





TOPSOIL - brown grey, friable, slightly gravelly (fine tocoarse sandstone) clay with some cobbles, silt, roots androotlets, damp

GRAVEL - brown, friable, slightly clayey, cobbly, fine tocoarse gravel (sandstone, siltstone) with some silt andtrace rootlets(COLLUVIUM)- with some boulders below 1.4mPit discontinued at 1.6m(large collapses)

0.3

1.6

Results &Comments


1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Wat

er

Dep

th

Sam

ple

Descriptionof

Strata Gra

phic

Log

Type

CLIENT:PROJECT:



1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

RL

RIG: New Holland LB110.B (450mm bucket)

LOCATION:

115

114

113

112

111

110

109

108

107

106

105

104

103

102

101

100

9998

9796

REMARKS:

WATER OBSERVATIONS: Free groundwater observed at 0.9m

TEST PIT LOG

Depth(m)

LOGGED: RJH

PIT No: 7PROJECT No: 48891DATE: 6/12/2010SHEET 1 OF 1

Collapses from 1.6 - 0.2m


SURVEY DATUM: MGA94



5 10 15 20

Sand Penetrometer AS1289.6.3.3 Cone Penetrometer AS1289.6.3.2

Dynamic Penetrometer Test(blows per 150mm)

0.60.71.01.11.41.5

D

D

D

TOPSOIL - dark brown grey, friable clay with some silt,fine to coarse gravel (sandstone), roots and rootlets, dampGRAVEL - brown, friable, slightly clayey, fine to coarsegravel (sandstone, siltstone) with some silt and tracerootlets, damp(COLLUVIUM)- with some cobbles below 1.0m- becoming orange grey brown, fine to coarse gravel andwet below 1.2mCLAYEY GRAVEL - brown, slightly clayey to clayey,cobbly, fine to coarse gravel with gravel and cobble sizedpockets of clay, damp(COLLUVIUM)Pit discontinued at 3.6m(side walls collapsing)

0.4

2.2

3.6

Results &Comments


1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Wat

er

Dep

th

Sam

ple

Descriptionof

Strata Gra

phic

Log

Type

CLIENT:PROJECT:



1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

RL

RIG: New Holland LB110.B (450mm bucket)

LOCATION:

114

113

112

111

110

109

108

107

106

105

104

103

102

101

100

9998

9796

95

REMARKS:

WATER OBSERVATIONS: Water inflow at 1.2m to 2.7m

TEST PIT LOG

Depth(m)

LOGGED: RJH

PIT No: 8PROJECT No: 48891DATE: 6/12/2010SHEET 1 OF 1

Collapses between 3.6 - 1.2m


SURVEY DATUM: MGA94



5 10 15 20

Sand Penetrometer AS1289.6.3.3 Cone Penetrometer AS1289.6.3.2

Dynamic Penetrometer Test(blows per 150mm)

0.50.61.01.11.61.72.22.3

2.93.03.53.6

D

D

D

D

D

D

pp = 100kPa

pp = 60 - 200kPa

TOPSOIL - dark brown grey clay with some silt, roots androotlets, dampGRAVELLY CLAY - stiff to very stiff, orange brown,slightly friable, gravelly (fine to coarse sandstone,siltstone) clay with some silt and trace rootlets, damp(COLLUVIUM)

- becoming clay and gravel with some cobbles below 0.4m- sandstone boulder at 0.4m- sandstone boulder at 1.2m

CLAYEY GRAVEL - orange brown friable, slightly clayeyto clayey, fine to coarse gravel (sandstone, siltstone) withsome cobbles, damp(COLLUVIUM)- becoming slightly clayey below 3.8m- sandstone boulder at 4.1m- with some moisture on gravel surfaces below 4.4mPit discontinued at 4.8m(limit of investigation)

0.4

1.5

4.8

Results &Comments


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2

3

4

5

6

7

8

9

48891 WOMBARRA 95 Morrison Ave Jan 11

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