86249.00.R.001.Rev2 Geotechnical Assessment

Report on Geotechnical Assessment

Orchard Hills North Orchard Hills

Prepared for Legacy Property

Project 86249.00 March 2018

Geotechnical Assessment, Orchard Hills North 86249.00.R.001.Rev2 Orchard Hills March 2018

Executive Summary

This report presents the results of a geotechnical assessment undertaken for the proposed Orchard

Hills North project at Orchard Hills. It is understood that rezoning is proposed to allow residential

development of the site. The assessment provides advice on geotechnical aspects of developing the

rezoning area (the site) for residential purposes and any mitigation measures that will be required.

The assessment comprised a visual inspection of the site from the public roads in the area and review

of available information from published maps and reports and other projects Douglas Partners (DP)

has undertaken in the area. No intrusive investigations have been undertaken for this assessment.

It is concluded that the site is generally suitable for residential development.

The key geotechnical constraints that have been identified for the site are:

• potential for slope instability on the steeper slopes (particularly on south facing slopes);

• moderately to highly reactive soils;

• moderate and high potential of saline soils; and

• a high soil erosion hazard, particularly along drainage lines.

Provided these constraints are investigated further during the design development phase and the

development designed to mitigate the risks, then the proposed rezoning should be able to proceed

without serious impact on slope stability, soil erodibility or contamination of the local streams.

The main implications for the design and construction of the development are:

• further geotechnical investigations are required at the DCP stage to investigate the areas of

potential slope instability;

• a salinity investigation is required at the DCP stage in order to prepare a Salinity Management

Plan for the development,

• standard earthworks controls for construction on the reactive soils are required; and

• due to the high erodibility of the soils, particularly along drainage lines, the surface drainage

should be designed to avoid concentrated flows of water and vegetation should be established as

soon as possible once final slopes are completed.


Orchard Hills North

Legacy Property is proposing to rezone a site in Orchard Hills North, located within the Penrith Local

Government Area (LGA). The proposed rezoning area is approximately 146.1 hectares (ha) with

frontages to Caddens Road to the north, Kingswood Road to the west, the Western Motorway to the

south and Claremont Meadows residential lots to the east.

Orchard Hills North, is well located being north of the Western Sydney Motorway, in close proximity to

the University of Western Sydney (to the north), Nepean Hospital (to the north) and to the Penrith City

Centre. South of the Motorway is currently mostly Orchard Hills rural lands, Defence Lands and to the

south west is Glenmore Park. Further south, will be the Badgerys Creek Airport.

Figure 1 Regional Context

Source: Design and Planning 2018


The rezoning site comprises 54 existing lots (including the school and uniting church) within the

proposed rezoning area, located at the following addresses:

» 80-154 Caddens Road, Orchard Hills

» 26-48 Kingswood Road, Orchard Hills

» 79-101 Kingswood Road, Orchard Hills (school)

» 117-149 Castle Road, Orchard Hills


» 182-226 Caddens Road, Orchard Hills


» 1-5 Castle Road, Claremont Meadows

» 7 Castle Road, Claremont Meadows

» 5, 9,13,19,23,29,33 and 35 Frogmore Road, Orchard Hills

The proposed rezoning area is identified in Figure 1 below

Figure 2 Proposed rezoning area

Source: Nearmap/ Design and Planning 2018


The existing fragmented ownership of the site has historically been a barrier to coordinated planning or

development of the area, however Legacy Property has now secured agreements covering the

majority of the rezoning area.

Legacy Property nominated the Orchard Hills North site under Penrith City Council’s Accelerated

Housing Delivery Program (AHDP) in October 2017. In November 2017 the site was endorsed by

Penrith City Council as a short-term rezoning opportunity to provide for housing delivery over the next

3-5 years.

Structure Plan and Rezoning Area

The Planning Proposal (PP) for Orchard Hills North aims to rezone the 146.1ha site from agricultural

land to mixed land uses, forming around 1,800-2,000 residential lots, a neighbourhood centre and

numerous areas of green space.

Discussions with the Department of Planning and Environment (DP&E) and Council have highlighted

the need to consider the logical extension of the rezoning area west (namely the Structure Plan area)

to The Northern Road, to ensure that future land uses and connections for the entire Orchard Hills

North precinct are planned in a holistic manner.

In order to ensure that the future development is fully integrated, a high level Structure Plan has been

prepared for the entire precinct, covering an area of approximately 263.09ha. The Structure Plan

considers how the rezoning area (146.1ha) integrates with the balance of the precinct (116.9 ha) and

identifies potential future land uses as well as key road connections. It is expected that the Structure

Plan will provide a framework for the future rezoning of the remaining area, either through a Council

Local Environmental Plan (LEP) amendment or a developer/owner led Planning Proposal

Council has endorsed proceeding with the rezoning area at present to meet the objectives of its

Accelerated Housing Delivery Program. A significant factor in this approach is that Legacy Property

has secured agreements covering a majority of the rezoning area and is therefore in a position to

progress with the planning proposal and provide greater certainty for coordinated future development.

Council is also proposing to undertake a strategic corridor study for The Northern Road and any

proposal to rezoned that land may pre-empt the outcome of this study.

As a result, the same level of technical investigations undertaken for the rezoning area have not yet

been undertaken for the wider Structure Plan area. The balance of the Structure Plan area has been

considered as part of investigations for this planning proposal, however not at a detailed level to

support rezoning.

Background

The cultural landscape of the Orchard Hills North site has developed as a rural landscape over the

past 100 years with constantly evolving pastoral practices and declining Cumberland Plain Woodland.

Within the last 50 years Orchard Hills North has typically been associated with orchard food

production, grazing farming practices with some specialisation in agricultural farming and rural

residential communities.

Although genuine food production practices have steadily declined over recent years, and only two lots

within the site are currently used for any form of agricultural production, the site remains zoned as

RU4 Primary Production Small lots. Today, the majority of the site is utilised for residential purposes

and has been substantially cleared.


Our Vision

Orchard Hills North will be a residential community set amongst rolling hills in the rich natural

landscape of Western Sydney, offering panoramic views to the Blue Mountains and surrounding

areas. The development will incorporate a diverse mix of housing types across 1,800 – 2,000

residential lots, focused around a new neighbourhood centre that forms the focal point of the future

community and offers a high level of convenience for residents.

The overarching vision of Orchard Hills North is to support a safe and connected community. This will

be achieved through the provision of a wide variety of green spaces and links, connecting each of the

future neighbourhood precincts with one another as well as the wider regional community, thereby

placing a focus on active transport such as walking and cycling.

Design principles

A site analysis, supported by extensive technical studies, has informed the following design principles

for the Structure Plan and rezoning area:

» Retain key creek lines and capitalise on the opportunity to create a central green link

» Retain existing significant vegetation as natural bushland.

» Manage and retain views into and out of the site.

» Provide opportunities for a diverse mix of housing types, with medium density housing located

around the neighbourhood centre and major open space

» Create a new neighbourhood centre combined with a relocated primary school to establish a

community focal point

» Respect heritage buildings and the character of the area

» Integrate with the community to the north, west and east.

» Link O’Connell Lane, Caddens Road, Frogmore Road and The Northern Road into a meaningful

urban road network.

» Improve water quality and water flow.

» Utilise landscaping and topography on the southern boundary to manage noise.

» Promote pedestrian and cycle linkages.

» Generate employment opportunities along the Northern Road.

Master Plan and Rezoning description

It is proposed to rezone the site from RU4 Primary Production Small Lots, under Penrith Local

Environmental Plan (PLEP) 2010, to part R1 General Residential, B2 Local Centre, RE1 Public

Recreation, E2 Environmental conservation and E4 Environmental living in the south eastern corner of

the site, as well as provide for appropriate controls relating to minimum lot size, height, heritage items,

and visual landscape.

The rezoning of Orchard Hills North will provide between 1,800-2,000 residential lots. It is expected

that the site will ultimately provide a broad mix of housing types ranging from larger environmental

living lots (2,000m2) to traditional detached residential lots (primarily 300-600m

2) and smaller compact


and attached housing lots (125-300m2). The proposed neighbourhood centre will provide around

6,000-8,000m2 of retail space supported by cycle and pedestrian links with approximately 17.5ha of

open space, bushland and riparian corridors.

A new/relocated primary school is proposed adjacent to the neighbourhood centre, supported by open

space to facilitate share usage. The location of parks and open space areas have been carefully

selected to enhance the existing value of the natural landscape, such as hill tops and creek lines, and

to retain the significant bushland areas, in order to provide the highest level of amenity for future

residents.

The site is physically and strategically suited for urban development, noting that:

» It is a discrete area formed by the boundary of an existing urban area and major road

infrastructure.

» it adjoins an existing residential subdivision, and in close proximity to the hospital, Western Sydney

University and the Penrith CBD.

» there are limited environmental or physical constraints that would prevent redevelopment

» it is outside the Western Sydney Priority Growth Area and is therefore better placed to be rezoned

through a developer led PP

» upgrades are currently being undertaken to the Northern Road, which the Orchard Hills site is

located east thereof, and gains access thereto. Thus, the rezoning of the land will support the

Government’s cost of infrastructure and will result better utilisation of the land

» it is able to capitalise on the availability of new and existing infrastructure, such as the recently

completed Werrington Arterial Road and new M4 on and off-ramps, the signalisation of the

Frogmore Road/Northern Road intersection as part of The Northern Road upgrade, and four train

stations within 4.5km of the site (Penrith, Kingswood, Werrington, St Marys).

The indicative Concept Master Plan for the site is identified in Figure 3 below.


Figure 3 Concept master plan for Orchard Hills North

Source: Design and Planning 2018


Table of Contents

Page

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

2. Site Description .............................................................................................................................. 1

3. Regional Geology and Hydrogeology ............................................................................................ 5

3.1 Geology ................................................................................................................................ 5

3.2 Hydrogeology ....................................................................................................................... 6

4. Soil Landscapes ............................................................................................................................. 6

5. Hydrogeology ................................................................................................................................. 9

6. Proposed Development .................................................................................................................. 9

7. Geotechnical Advice ...................................................................................................................... 9

7.1 Interpreted Geological Model ............................................................................................... 9

7.2 Groundwater ......................................................................................................................10

7.3 Slope Stability ....................................................................................................................10

7.4 Salinity ...............................................................................................................................11

7.5 Earthworks .........................................................................................................................11

7.6 Foundations .......................................................................................................................12

7.7 Erosion ...............................................................................................................................12

8. Conclusions .................................................................................................................................. 12

9. Further Investigations ................................................................................................................... 13

10. Limitations .................................................................................................................................... 14

Appendix A: About This Report

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Report on Geotechnical Assessment

Orchard Hills North

Orchard Hills

1. Introduction

This report presents the results of a geotechnical assessment undertaken for the proposed Orchard

Hills North project at Orchard Hills. The assessment was commissioned by Mr Mike Williams of

Legacy Property and was undertaken in accordance with Douglas Partners' proposal SYD171588

dated 11 December 2017.

It is understood that rezoning is proposed to allow residential development of the site. This

assessment has been undertaken in accordance with the s117 directions issued by the NSW Minister

of Planning under Section 117(2) of the Environmental Planning and Assessment Act 1979. The

assessment provides advice on geotechnical aspects of developing the rezoning area (the site) for

residential purposes and any mitigation measures that will be required.

The application for rezoning is required to also consider a Structure Plan Area located to the west of

the rezoning area. While Douglas Partners has not specifically assessed the Structure Plan Area it is

likely that most of the geotechnical features of that area are similar to those present on the rezoning

area.

The assessment comprised a visual inspection of the site from the public roads in the area and review

of available information from published maps and reports and other projects Douglas Partners (DP)

has undertaken in the area. No intrusive investigations have been undertaken for this assessment.

2. Site Description

The Orchard Hills North Rezoning Area (the site) comprises a large irregularly shaped area

approximately bounded by Caddens Road to the north, Kingswood Road to the west and the M4

Motorway to the south. It has a total area of 146.12 hectares. The adjacent Structure Plan Areas is

116.96 ha, giving a total development area of 263.09 ha.

The site has been mostly cleared and is currently used for grazing and market gardens, with scattered

houses and other farm buildings.

The site topography is undulating, extending across two ridges which trend in a north-easterly

direction, across the valley between the two ridges, and down the eastern slope of the eastern ridge.

The site topography is illustrated in Figure 1 which presents the 2 m contours of the ground surface in

the area.

There are two creeks crossing the site. Werrington Creek runs in a northerly direction between the

two ridges in the central section of the site, and Claremont Creek crosses the eastern corner of the

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site and flows in a north-easterly direction. Both creeks ultimately flow into South Creek to the north-

east of the site.

Within the site the maximum elevation is about RL 85 m (AHD), near the western boundary of the site,

and the lowest elevation is about RL 35 m along Claremont Creek in the eastern corner of the site. On

top of the ridges, at the base of the valley between the ridges, and adjacent to Claremont Creek the

ground is flat to gently sloping. On the sides of the ridges the ground typically slopes at about 6-9

degrees from horizontal, but in some local areas the slopes increase to 13-15 degrees.

Figure 1 – Site Location and Topography (2m contours)

There is visible evidence of springs on the upper slopes, with a number of small farm dams

constructed in these areas. One such dam can be seen on Photo 1 below. The vegetation

surrounding the dam is indicative of seepage, both from the dam and from the underlying ground.

Photographs of selected site features are included below.

Structure Plan Area

Rezoning Area

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Photo 1 – Western part of site, looking south-west from Kingswood Road towards Castle Road (note farm dam on other side of Castle Road and lush vegetation around dam area)

Photo 2 – Looking east along Castle Road towards eastern ridge (Werrington Creek crosses below Castle Road in the foreground)

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Photo 3 – Looking north-east from top of eastern ridge on Castle Road towards Ulm Road

Photo 4 – Looking north from the eastern end of Castle Road (note small dam and irregular

ground surface – soil creep)

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3. Regional Geology and Hydrogeology

3.1 Geology

Reference to the Penrith 1:100,000 Geological map indicates that the site is mostly underlain by

Bringelly Shale of the Wianamatta Group of Triassic age, with some more recent alluvial sediments

(Quaternary alluvium) present along Claremont Creek.

An extract of the map is copied in Figure 2 below. The Bringelly Shale is shown coloured light blue

and has the abbreviation Rwb, while the alluvial soils are coloured yellow.

Figure 2 – Extract of Regional Geological Map

Bringelly Shale typically comprises shales, siltstones, and claystones which weather to form clays of

high plasticity. The alluvial soils are likely to consist of a range of sands, silts and clays which have

been deposited by the creek.

The regional geological map also shows some geological structures in the area. A series of igneous

dykes which trend in a north-easterly direction have been mapped to the south-west of the site. These

dykes are aligned parallel to the ridges. It is considered likely that one or more dyke will pass through

the site. The mapped dykes were typically vertical features with widths ranging from 2.4 m to 3.7 m.

In addition the regional map shows some major structural lineaments oriented north and north-east,

along which the major creeks in the area flow.

Site

Alluvial soils

Bringelly Shale

Lineaments

Dykes

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Review of available mine subsidence maps suggests that there has not been any underground mining

in the area.

3.2 Hydrogeology

Extensive investigations by DP have been undertaken on the Bringelly Shale Formation at Eastern

Creek. The results of in situ testing indicate that:

• The transmissivity of the shale/siltstone is low to very low with estimated hydraulic conductivity of

10-6 to 10

-8 m/sec;

• The groundwater is highly saline and therefore unsuitable for stock watering or irrigation.

Historical data published by Old A.N (1942) reported chloride concentrations in the Blacktown area of

6000 – 8000 mg/L with a peak value from the Bringelly Shale of 31,750 mg/L

4. Soil Landscapes

Reference to the regional soil landscape maps for the area suggest that the site is mostly underlain by

Luddenham soil landscape (shown in pink on Figure 3 below), with some South Creek soil landscape

along Claremont Creek (shown in light green on Figure 3).

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Figure 3 – Extract of Regional Soil Landscapes Map

The Luddenham soil landscape is an erosional soil landscape formed on undulating to rolling low hills

underlain by the Wianamatta Group shales. These soils are typically shallow on crests and

moderately deep on slopes and drainage lines. The soils are moderately erodible, have a high erosion

hazard and are moderately reactive.

The South Creek soil landscape is a fluvial soil landscape formed in the floodplains, valley flats and

drainage depressions of the creek channels on the Cumberland Plain. These soils have a high

erodibility and a very high erosion hazard. The soils are also commonly in areas that get flooded so

they may be waterlogged.

Regional mapping of soil salinity hazard in Western Sydney has been undertaken by the Department

of Infrastructure and Planning. An extract of this map is given in Figure 4.

Site

Luddenham soil landscape

Blacktown soil landscape

South Creek soil landscape

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Figure 4 – Extract of Regional Salinity Map

The whole Penrith area is shown as having a moderate salinity potential (yellow), with high salinity

potential along the lower slopes and creek lines where water accumulation is high (orange). Observed

occurrences of saline soils are shown in red.

No acid sulphate soils have been mapped in the area.

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5. Hydrogeology

The hydrogeology of the Bringelly Shale is usually characterised by shallow seepage along the soil

and shale interface and a deep fractured rock aquifer tens of metres below surface levels. Aquifer

recharge is minimal due to the low permeability of the near surface clays, and horizontal flow velocities

in the soil and rock are commonly less than 10 m per year.

Two registered water bores (GW060794 and GW103764) are located within the site, both on a

property to the south of Castle Road and east of Kingswood Road. GW060794 was drilled in 1985 to

a depth of about 78 m (within the shales) to provide water for stock. The drillers recorded low yields of

0.02 and 0.06 L/s at depths of 18.8 m and 75 m. The salinity of the water was not recorded but, based

on previous experience, it is expected that the water is relatively saline due to the minerals contained

within the Bringelly Shale.

The second water bore (GW103764) was drilled in 1995 to provide water for irrigation. This bore was

drilled to a depth of 232 m and the drillers recorded water bearing zones at depths of 208 m and

216 m from within the sandstones below the shales. The yield from these water bearing zones were

measured at 0.4-0.8 L/s.

6. Proposed Development

It is understood that rezoning of the site for residential development is proposed in order that about

146 hectares of the site can be subdivided to allow around 1800 dwellings to be constructed.

The residential development will require construction of roads, installation of services and construction

of building platforms. On the steeper slopes DP expects that excavation and filling will be required to

construct roads and building platforms, however, the extent of the excavation and filling has not yet

been determined. During the detailed design stage of the project it will be necessary to closely

consider the extents and heights of the proposed cuts and fills and design the project elements to suit.

7. Geotechnical Advice

7.1 Interpreted Geological Model

Based on other investigations DP has carried out in the area, it is expected that the subsurface

conditions on the site will generally comprise the following:

• topsoil (clayey silt) typically less than 0.3 m thick, over

• stiff to hard silty clays and clays to depths of 3-7 m, over

• weathered, low strength shale or siltstone, becoming stronger and less weathered with depth.

The thickness of the soils is likely to be less on the crests of the ridges and upper slopes and greater

on the lower slopes and in drainage lines.

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The silty clays and clays are likely to be moderately to highly reactive, that is, they are likely to shrink

or swell when the moisture content of the soil changes.

There may be some igneous dykes crossing the site, but these will be local features, typically less

than 3 m wide. The dyke rock and other rocks immediately adjacent to the dyke may be either much

higher strength or, alternatively, much lower strength than the typical rocks in the area. Intrusion of

the dykes can sometimes cause fracturing of the surrounding rocks and can also cause damming of

groundwater seepage.

The exact location of the dykes is not known, and will not be known unless they are exposed in

excavations. The presence of dykes will probably not affect standard earthworks or the construction of

houses or roads, but if dykes are encountered when excavating drainage or services trenches then

there may be some locally harder rock which is more difficult to excavate.

There may be some softer and wetter soils along the drainage lines. If filling platforms or roads are to

be constructed across drainage lines then some allowance should be made for removing and

replacing soft and/or wet soils.

7.2 Groundwater

While it is expected that the main groundwater table is located at depths of many metres below the

existing ground surface on the higher parts of the site, there is visible evidence of seepage occurring

on some of the upper slopes. This suggests that the flow of natural seepage through the soils above

the weathered rock has met a barrier of lower permeability which causes the water to flow out of the

ground surface rather than continuing through the soils.

On the lower parts of the site, along the drainage lines it is expected that groundwater will be present

at relatively shallow depths within the alluvial soils.

The groundwater at depth below the site is expected to be moderately saline due to the mineral salts

contained within the Bringelly Shales.

If the proposed development significantly alters the existing groundwater flow patterns then it is

possible that the seepage could concentrate salts in the soil and groundwater, potentially resulting in

areas of saline soils which could adversely affect buildings, roads and vegetation. The works should

be designed to minimise changes to existing groundwater flows. It is recommended that a salinity

investigation should be carried out prior to development of the site and a Salinity Management Plan

prepared.

7.3 Slope Stability

While no existing or historic landslips were observed on site during the brief site inspection, it is quite

common in the Sydney area for landslips to occur on steep slopes with the geology and seepage

conditions as observed on this site, particularly on south facing slopes. A review of the existing site

contours has identified a number of areas where slope instability may be an issue (see Figure 5

below).

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Figure 5 – Areas of Potential Slope Instability

Evidence of shallow soil creep was observed on some of the steeper slopes (see Photo 4).

Further investigations will be required on the steeper parts of the slope during the DCP stage to

quantify the risk of slope instability and provide specific advice for development. Construction in these

areas will require careful control of surface and subsurface drainage. Depending on the overall

earthworks plan for the site, options for building in these areas of potential slope instability could

include minimising the depths of cutting and filling, or alternatively reshaping the areas to reduce the

potential for instability.

7.4 Salinity

All the soils on the site are likely to have a moderate potential for salinity, with a high potential for

salinity on the lower parts of the slopes and along the drainage lines. The risk is that the proposed

development will alter the surface and groundwater flows such that salts within the soils can be

dissolved by the water and carried to other areas in concentrations which can affect plant growth and

damage pavements and buildings.

During the design development phase it will be necessary to carry out detailed salinity investigations

on the site to quantify the risk and develop management strategies to minimise the impact of the

development. The management strategies required may include minimising water infiltrations, sealing

stormwater detention ponds and/or minimising soil disturbance by cutting and filling.

7.5 Earthworks

The natural clay soils on site are likely to be moderately to highly reactive. If these soils are

compacted too dry or too wet they may swell or shrink as the moisture content of the soil changes.

Possible slope instability

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Accordingly the soils are likely to be suitable for reuse on the site provided that the moisture content of

the soils is carefully controlled during compaction and the soils are protected against drying out after

compaction is completed.

On the steeper upper slopes the earthworks will need to be designed to avoid causing instability of the

slopes. This could comprise minimise the cutting and filling required, or alternatively could involve

reshaping of the existing contours to achieve flatter overall slopes. The impact of any such works on

salinity would need to be carefully considered during the design development phase, however we

understand that similar development has been undertaken on the adjacent Caddens site in similar

topography.

While excavation of the soils and weathered shale should be readily achieved using conventional

earthmoving equipment such as bulldozers or excavators, if any igneous dykes are intersected by the

works, such as in service trenches, they may contain much harder rock which could require rock

hammers for excavation.

7.6 Foundations

Site classifications will depend on the location of the individual lots and the amount of earthworks that

has been carried out in each area.

In general, for buildings constructed directly on the in-situ residual soils derived from weathering of

Bringelly Shale the site classification (in accordance with Australian Standard AS2870) is likely to be

Class M, unless there is likely to be significant alteration to the natural drainage. For sites on areas

with deep clay layers and potential significant changes in water level a Class H classification may be

assigned, while sites prone to landslip may be Class P.

7.7 Erosion

The soils on the upper parts of the site are moderately erodible and the soils along the drainage lines

have been identified as being highly erodible. Surface and subsurface drainage will need to be

designed to avoid concentrated flows of water which could accelerate the soil erosion.

Standard erosion control measures should be adopted along creeks and vegetation should be

established as soon as possible after earthworks are completed.

8. Conclusions

On the basis of a review of available information and a visual inspection of the area it is concluded that

the site is generally suitable for residential development.

The key geotechnical constraints that have been identified for the site are:

• potential for slope instability on the steeper slopes (particularly on south facing slopes);

• moderately to highly reactive soils;

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• moderate and high potential of saline soils; and

• a high soil erosion hazard, particularly along drainage lines.

Provided these constraints are investigated further during the design development phase and the

development designed to mitigate the risks, then the proposed rezoning should be able to proceed

without serious impact on slope stability, soil erodibility or contamination of the local streams.

The main implications for the design and construction of the development are:

• further geotechnical investigations are required at the DCP stage to investigate the areas of

potential slope instability and, depending on the findings of the investigations and the overall

cut/fill plan for the site, the recommendations for these areas may be to:

o install additional drainage;

o minimise cut and fill in the steeper areas; or

o reshape the contours to achieve flatter slopes.

• a salinity investigation is required at the DCP stage in order to prepare a Salinity Management

Plan for the development, depending on the findings of the investigation, the plan may

recommend:

o minimising the potential for water seeping into the soils and increasing the groundwater

levels, this may require lining of stormwater retention ponds and avoiding stormwater

infiltration systems; and

o reducing the potential for cuts intercepting shallow groundwater.

• the reactive soils on the site are common all over Western Sydney. Standard controls required

for development on these soils include:

o close control of moisture content during construction;

o lot classifications to be based on the earthworks carried out on each site; and

o soft and/or wet soils along drainage lines should be removed and replaced if filling or roads

are to be constructed over these areas.

• due to the high erodibility of the soils, particularly along drainage lines, the surface drainage

should be designed to avoid concentrated flows of water, and vegetation should be established

as soon as possible once final slopes are completed.

• If igneous dykes are intersected on the site then the main potential issue is that there may be

locally harder rock encountered during excavation of trenches for drains or services.

9. Further Investigations

No further geotechnical investigations are required at this stage to support the rezoning application.

During the development of the plans for the DCP, however, there will be a need for detailed

geotechnical investigations to identify the geotechnical limitations of different areas of the site and to

develop specific design and construction guidelines for the development.

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The additional investigations required would include (but not necessarily be limited to):

• a detailed slope stability assessment of the steeper parts of the site;

• a detailed salinity assessment;

• detailed geotechnical investigations on a stage by stage basis for the determination of site

classification, excavatability, soil erosion, soil permeability, groundwater flow and foundation

design.

10. Limitations

Douglas Partners (DP) has prepared this report (or services) for this project at Orchard Hills in

accordance with DP’s proposal dated 11 December 2017 and acceptance received from Mr Mike

Williams dated 12 December 2017. The work was carried out under DP’s Conditions of Engagement.

This report is provided for the exclusive use of Legacy Property Pty Ltd for this project only and for the

purposes as described in the report. It should not be used by or relied upon for other projects or

purposes on the same or other site or by a third party. Any party so relying upon this report beyond its

exclusive use and purpose as stated above, and without the express written consent of DP, does so

entirely at its own risk and without recourse to DP for any loss or damage. In preparing this report DP

has necessarily relied upon information provided by the client and/or their agents.

This report must be read in conjunction with all of the attached 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 stated in this report.

This report, or sections from this report, should not be used as part of a specification for a project,

without review and agreement by DP. This is because this report has been written as advice and

opinion rather than instructions for construction.

The contents of this report do not constitute formal design components such as are required, by the

Health and Safety Legislation and Regulations, to be included in a Safety Report specifying the

hazards likely to be encountered during construction and the controls required to mitigate risk. This

design process requires risk assessment to be undertaken, with such assessment being dependent

upon factors relating to likelihood of occurrence and consequences of damage to property and to life.

This, in turn, requires project data and analysis presently beyond the knowledge and project role

respectively of DP. DP may be able, however, to assist the client in carrying out a risk assessment of

potential hazards contained in the Comments section of this report, as an extension to the current

scope of works, if so requested, and provided that suitable additional information is made available to

DP. Any such risk assessment would, however, be necessarily restricted to the geotechnical

components set out in this report and to their application by the project designers to project design,

construction, maintenance and demolition.

Douglas Partners Pty Ltd

Appendix A

About This Report

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.

86249.00.R.001.Rev2 Geotechnical Assessment

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