Lowes Creek & Maryland (Barkers Mill) Rezoning

Report on Land Capability Study

Lowes Creek Maryland Precinct, Bringelly, NSW

Prepared for

Department of Planning & Environment and Camden Council, c/- Macarthur Developments Pty Ltd

Project 76742.00 September 2018

Document History

Document details Project No. 76742.00 Document No. R.001.Rev2 Document title Report on Land Capability Study Proposed Rezoning Site address Lowes Creek Maryland Precinct, Bringelly Department of Planning & Environment and Camden Council, Report prepared for c/- Macarthur Developments Pty Ltd File name 76742.00.R.001.Rev2

Document status and review Status Prepared by Reviewed by Date issued Rev 0 Emily McGinty Chris Kline 6 January 2017 Rev 1 Emily McGinty Chris Kline 1 March 2017 Rev 2 Emily McGinty Chris Kline / Rod Gray 13 September 2018

Distribution of copies Status Electronic Paper Issued to Macarthur Developments Pty Ltd Rev 0 1 0 Mr Stephen McMahon Macarthur Developments Pty Ltd Rev 1 1 0 Mr Stephen McMahon Department of Planning & Environment Rev 2 1 0 Ms Evelyn Ivinson

The undersigned, on behalf of Douglas Partners Pty Ltd, confirm that this document and all attached drawings, logs and test results have been checked and reviewed for errors, omissions and inaccuracies.

Signature Date Author 13 September 2018

Reviewer 13 September 2018

Douglas Partners Pty Ltd ABN 75 053 980 117 www.douglaspartners.com.au 18 Waler Crescent Smeaton Grange NSW 2567 FS 604853 Phone (02) 4647 0075 Fax (02) 4646 1886

Table of Contents

Page

1. Introduction...... 1

2. Scope of Works ...... 1

2.1 Geotechnical (refer Appendix A – Section 2 for further detail) ...... 1

2.2 Salinity (refer Appendix B – Section 1 for further detail) ...... 2

2.3 Contamination (refer Appendix C – Section 2 for further detail) ...... 2

3. Current Site Conditions ...... 2

4. Constraint Maps ...... 3

5. Summary of Land Capability for Site Development ...... 3

5.1 Geotechnical ...... 3

5.2 Salinity ...... 4

5.3 Contamination ...... 5

6. Further Investigation ...... 5

6.1 Geotechnical ...... 5

6.2 Salinity ...... 6

6.3 Contamination ...... 6

7. Conclusion...... 7

8. References ...... 7

9. Limitations ...... 7

Appendix A: Report on Geotechnical Investigation

Appendix B: Report on Salinity Assessment and Salinity Management Plan

Appendix C: Report on Preliminary Site Investigation

Appendix D: Draft Indicative Layout Plan

Report on Land Capability Study Project 76742.00.R.001.Rev2 Lowes Creek Maryland Precinct, Bringelly, NSW September 2018

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Report on Land Capability Study Proposed Land Rezoning Lowes Creek Maryland Precinct, Bringelly

1. Introduction

This report presents the results of a land capability assessment undertaken, by Douglas Partners Pty Ltd (DP), on a 517 ha parcel of land known as the “Lowes Creek Maryland Precinct”, (henceforth “the Precinct”, refer Drawing A1 in Appendix A). The work was undertaken for the Department of Planning & Environment and Camden Council. The site has been previously been identified by the Growth Centres Commission for potential rezoning and urban development under the State Environmental Planning Policy (Sydney Regional Growth Centres) 2006.

This Land Capability Study summarises three individual studies produced as part of the overall assessment. These studies are provided as appendices to this document and must be read in conjunction with this report. The Land Capability Assessment was to address: • Slope instability (Appendix A – Report on Geotechnical Investigation); • Soil erosion risks (Appendix A – Report on Geotechnical Investigation); • Geotechnical factors (Appendix A – Report on Geotechnical Investigation); • Soil salinity hazard (Appendix B – Report on Salinity Assessment and Salinity Management Plan (SMP)); and • Site contamination (Appendix C – Report on Preliminary Site Investigation).

A copy of the current draft Indicative Layout Plan (ILP) for the proposed subdivision as provided by the NSW Department of Planning and Environment is presented in Appendix D.

2. Scope of Works

To prepare the Land Capability Assessment the work was divided into three core components. The scopes of works for each component are summarised in the following sections.

2.1 Geotechnical (refer Appendix A – Section 2 for further detail)

The scope of work comprised: • Site mapping for slope instability and erosion features. A senior geotechnical engineer undertook a site walkover and produced maps based on observations, of current and historic landslips and soil erosion features; and • Soil testing for geotechnical purposes was undertaken from selected test pits excavated across the site (refer Section 3). This data allowed the development of preliminary recommendations on geotechnical conditions likely to affect footings, pavement design, and site preparation.

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2.2 Salinity (refer Appendix B – Section 1 for further detail)

The scope of work comprised: • Baseline review of regulatory documents, Council requirements, salinity mapping and hydrological landscape data; • An electromagnetic survey to assess for salinity potential was undertaken. This involved using a GSSI EMP400 profiler mounted to a 4wd ute which traversed the site collecting ground conductivity, hence salinity data, for salinity mapping. Salinity data was collected for three depth ranges: <0.2 m, <1 m and >1.5 m; • Samples were collected from 20 test pits to ground truth the GSSI EMP400 data and process the EM dataset that has been correlated with the findings of the soil sampling and analysis; and • Samples were analysed and the results interpreted to estimated soil aggressivity to concrete and steel and measure sodicity.

2.3 Contamination (refer Appendix C – Section 2 for further detail)

The scope of work comprised: • Site walkover and interviews completed by an environmental engineer to identify potential constraints to development, with respect to the contamination status of the site; • Desk top study of regional data to assess site conditions as well as possible current and historical land practises that may impact the proposed development of the site; and • Compilation of a list of Potential Areas of Environmental Concern (PAEC) for the site based on the findings of the PSI, with each PAEC assessed individually to determine likely presence of and risk from contamination. Certain PAEC have been determined to be Areas of Environmental Concern (AEC) that will require further investigation and/or management.

3. Current Site Conditions

The Precinct comprises an irregular shaped area totalling 517 ha lying to the west of The Northern Road in the suburb of Bringelly within the Camden Local Government area. It has a 2.8 km frontage to The Northern Road (refer Drawing A1). It is understood that a 493 ha section of Maryland and Lowes Creek are controlled in partnership by major landholders. The remaining 35 ha portion (refer Drawing A1) is currently subdivided into multiple lots and is used for a combination of residential, agricultural and commercial purposes.

Report on Land Capability Study Project 76742.00.R.001.Rev2 Lowes Creek Maryland Precinct, Bringelly, NSW September 2018

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4. Constraint Maps

Based on the geotechnical, salinity and contamination investigations, maps were developed for: • Geotechnical Constraint (refer Drawing A6 in Appendix A): This map shows areas of constraint with respect to geotechnical factors such as filling, landslip and erosion; • Salinity Constraint (refer Drawings in Appendix B): These maps show areas of constraint based on preliminary EM survey findings with respect to very saline soil conditions and moderately saline soil conditions. Management strategies for both soil types are provided in Appendix B, Sections 12 and 13; • Aggressivity and Sodicity Mapping (refer Drawings B3 and B4 in Appendix B). Soils at the Precinct have been shown to be aggressive and dispersive, with risk areas by depth shown on the maps. Response strategies to these constraints are provided in Appendix B, Sections 12 and 13; and • Identified Areas of Environmental Concern [AEC] (refer Drawings C4 and C5 in Appendix C) have been mapped which are cross referenced to Table C2 (Section 7) in the Preliminary Site Investigation (PSI) Report.

5. Summary of Land Capability for Site Development

5.1 Geotechnical

Assessment of the urban capability of the study area has principally been carried out on the basis of geotechnical considerations, specifically risk of slope instability, soil erodibility and foundation conditions. Items such as flooding hazard from the Lowes Creek systems are also noted as these may be locally overcome by appropriate design and construction.

For discussion, the capability for urban development may be related to the degree of surface disturbance involved in the following categories of site development: Extensive building complexes – the development of commercial complexes such as offices or shopping centres, which require large scale clearing and levelling of broad areas of floor space and parking bays. Residential development – infers a level of construction which provides for roads, drainage, and services to cater for housing allotments of approximately 600 square metres or larger. Strategic residential development – refers to areas unsuitable for widespread development, but where closer investigation may permit isolation of pockets of land for individual house sites, or definition of engineering measures required to maintain stability of what would otherwise be unsuitable land for development. Reserves – The development of reserves, which may require shaping and modification of the ground surface and vegetation improvement, but no building and minimal roadway construction, is envisaged.

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General development considerations will require the classification of residential lots to comply with the requirements of AS 2870 – 2011 (Ref 1). The requirements of AS 1170 – 2002 Structural Code (Ref 2) are particularly noted in relation to earthquake loading requirements for commercial or industrial development.

The distribution of the geotechnical constraints (slope instability, erosion and water logging) is summarised in Drawing A6.

While no landslide activity has yet been identified within steeper hillsides within the steeper sections (refer Drawing A6) of the site, there were observed incidences of soil creep and for further potential for surficial soil creep and possible shallow slumping of residual soils. These are likely to impose only minor to moderate constraints (i.e. able to be addressed by good engineering practices for residential or strategic residential hillside development including site specific investigation and engineering of structures). The remainder of the gently sloping hillsides areas are considered to be suitable for residential development and extensive building complexes.

Other than erosion-triggered slumping of a material (probably a few cubic metres at any event) from the low height banks of the gullies within the alluvium infilled valley floors, there does not appear to be a significant risk of stream bank instability. It is considered that stream bank instability impose only minor constraints on development.

It is considered that the erosion hazard within the areas proposed for development would be within usually accepted limits which could be managed by good engineering and land management practices (refer Sections 8.4 and 8.5).

The engineering and management practices applicable to erosion control will also be required to address flood hazard and localised waterlogging limitations of soils along the course of Lowes Creek, its associated gullies and localised areas about existing farm dams. These hazards are considered to impose minor to moderate geotechnical constraints to development (i.e. limited to significant placement of new engineered filling and drainage) to development of residential development or extensive building complexes.

Uncontrolled filling (or suspected uncontrolled filling) was identified in numerous locations across the site. It is considered that the presence of uncontrolled filling will impose a minor geotechnical constraint to development and will generally involve the removal of uncontrolled filling (and if in situ materials are considered geotechnically suitable) replacement under controlled conditions.

5.2 Salinity

The inferred constraints to development related to soil salinity are: • The mild to moderate aggressivity to concrete, the mild to moderate aggressivity to steel, the presence of moderate to occasionally very saline materials and the highly sodic soils are naturally occurring features of the local landscape and are not considered significant impediments to the proposed development, provided appropriate remediation or management techniques are employed (refer to Section 13; Appendix B);

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• Salinity and aggressivity affects the durability of concrete and steel by causing premature breakdown of concrete and corrosion of steel. This has impacts on the longevity of structures in contact with these materials. As a result management will be required (refer to Sections 13 and 14; Appendix B); and • Highly sodic soils which appear widespread across the precinct will require management to reduce dispersion, erosion and to improve drainage as detailed in Appendix B, Section 13.

5.3 Contamination

• A total of 23 AECs were identified across the site, including areas of suspected filling (AEC 3) and stockpiles (AEC 15). The AECs are generally associated with the historical use of the site, including agricultural land use as well as rural residential land use. Of the 23 AECs identified, five are located on separate ownership lots that were not accessible at the time of the site walkover (being AEC 3 (four areas of possible filling), AEC15 (three possible stockpile areas) and AEC 18 to 20). A future site walkover completed by a suitably qualified environmental consultant can be used to amend the list of identified AECs for separate ownership lots (i.e. some areas may be deemed to be no longer an AEC once inspected). The 23 identified AECs are detailed in Appendix C, Section 7. • Groundwater in shales beneath the site is unlikely to be suitable for irrigation purposes owing to its generally low yield and reasonably high levels of salinity. The permeability of the shales is generally very low (typically <1 L/s), therefore significantly inhibiting the potential for contamination to migrate from the site. Based on the findings of the PSI, groundwater investigation is not required for the areas outside of the AEC; and • Targeted sampling and / or a site walkover (for the separate ownership lots) will be required in each of the 23 AECs together with a lower density sampling regime in the remainder of the site area prior to development application. (refer to Appendix C, Section 8).

6. Further Investigation

Further investigation will be required as conceptual design / planning progresses together with additional work during the construction phase. Specific investigations would include but not necessarily be limited to those described in the following sections.

6.1 Geotechnical

Site specific investigations would include: • Detailed geotechnical investigations on a stage-by-stage basis for determination of pavement thickness designs and lot classifications; • Routine inspections and earthworks monitoring during construction.

Report on Land Capability Study Project 76742.00.R.001.Rev2 Lowes Creek Maryland Precinct, Bringelly, NSW September 2018

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6.2 Salinity

Site specific investigations would include: • Additional investigation should be undertaken in development areas which are to be excavated deeper than 3 m or into rock at shallower depth, where direct sampling and testing of salinity has not been carried out. Salinity management strategies given herein may need to be modified or extended following additional investigation by deep test pitting and/or drilling, sampling and testing for soil and water pH, electrical conductivity, total dissolved solids (TDS), sodicity, sulphates and chlorides; and • The salinity investigation has been undertaken for the purpose of providing preliminary advice. A detailed salinity investigation will be required prior to construction in order to provide more detailed recommendations for individual lots.

6.3 Contamination

Site specific investigations would include: • Further intrusive investigation works in the form of a Detailed Site Investigation (DSI) in accordance with SEPP 55 and NSW EPA guidelines will be necessary prior to development applications; • Targeted sampling and/or a site walkover (for the separate ownership lots) is required in each of the 23 AECs together with a lower density sampling regime in the remainder of the site area. Further assessment of the AEC areas will determine appropriate remediation requirements, if any, to render the site suitable for the proposed development. These further investigations will be required prior to development application; • Based on observations made during the site walkover, there is the potential for ACM to be present in current structures in several areas at the site. It is therefore recommended that a hazardous building materials survey is completed prior to any demolition of structures; • There is the potential that hidden, below ground structures (such as USTs, septic tanks, ACM pipes and ACM fence footings) may be present at the site and this should be considered accordingly during the DSI and subsequently during bulk earthworks for the proposed development. Based on DP’s experience on similar sites, below ground ACM features (ACM pipes in particular) are commonly encountered during earthworks and subsequent remediation works can delay site formation and general construction. DP therefore recommends that the proposed DSI should include an inspection of soils around the perimeter of the current building footprints to identify any buried ACM pipes; and • An Unexpected Finds Protocol will therefore need to be established for use during earthworks during redevelopment, in order to ensure that due process is carried out in the event of a possible contaminated find.

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7. Conclusion

In conclusion, it is noted that the land within the Precinct is considered suitable for urban redevelopment and is not constrained by geotechnical, salinity or contamination factors to such an extent as to render the land undevelopable.

8. References

1. Australian Standard AS 2870 – 2011 Residential Slabs and Footings. 2. Australian Standard AS 1170 – 2002 Structural Code.

9. Limitations

Douglas Partners Pty Ltd (DP) has prepared this report (or services) for this project at Lowes Creek Maryland Precinct, Bringelly in accordance with DP’s proposal dated 22 April 2016 and email acceptance received from Stephen McMahon dated 4 May 2016. The work was carried out under DP’s Conditions of Engagement. This report is provided for the exclusive use of the Department of Planning & Environment, Camden Council and Macarthur Developments 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.

The results provided in the report are indicative of the sub-surface conditions on the site only at the specific sampling and/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 human 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 affected by undetected variations in ground conditions across the site between and beyond the sampling and/or testing locations.

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.

Douglas Partners Pty Ltd

Report on Land Capability Study Project 76742.00.R.001.Rev2 Lowes Creek Maryland Precinct, Bringelly, NSW September 2018

Appendix A

Report on Geotechnical Investigation

Land Capability Study

Lowes Creek Maryland Precinct, Bringelly, NSW

Prepared for Department of Planning & Environment and Camden Council c/- Macarthur Developments Pty Ltd

Project 76742.00 March 2017

Document History

Document details Project No. 76742.00 Document No. R.002.Rev2 Document title Report on Geotechnical Investigation Land Capability Study Site address Lowes Creek Maryland Precinct, Bringelly, NSW Department of Planning & Environment and Camden Council, c/o Report prepared for Macarthur Developments Pty Ltd File name 76742.00.R.002.Rev2

Document status and review Status Prepared by Reviewed by Date issued DftA Tom Mrdjen Grahame Wilson 21 September 2016 Rev0 Tom Mrdjen Grahame Wilson 11 November 2016 Rev1 Tom Mrdjen Grahame Wilson 1 March 2017 Rev2 Tom Mrdjen Grahame Wilson 11 September 2018

Distribution of copies Status Electronic Paper Issued to Macarthur Developments Pty Ltd DftA 1 0 Mr Stephen McMahon Macarthur Developments Pty Ltd Rev0 1 0 Mr Stephen McMahon Macarthur Developments Pty Ltd Rev1 1 0 Mr Stephen McMahon Department of Planning & Environment Rev2 1 0 Ms Evelyn Ivinson

Signature Date Author 11 September 2018

Reviewer 11 September 2018

Douglas Partners Pty Ltd ABN 75 053 980 117 www.douglaspartners.com.au 18 Waler Crescent Smeaton Grange NSW 2567 Phone (02) 4647 0075 Fax (02) 4646 1886

Table of Contents Page

1. Introduction...... 1 2. Scope of Works ...... 1 3. Site Description ...... 2 4. Regional Geology and Soil Landscapes ...... 3 4.1 Geology ...... 3 4.2 Soil Landscapes ...... 4 5. Field Work Methods ...... 4 5.1 Horizontal and Vertical Control ...... 4 5.2 Site Mapping ...... 5 5.3 Test Pitting ...... 5 6. Field Work Results ...... 5 6.1 Field Mapping ...... 5 6.2 Subsurface Investigation ...... 7 7. Laboratory Testing ...... 7 8. Comments ...... 10 8.1 General ...... 10 8.2 Slope Instability ...... 10 8.3 Erosion Potential ...... 11 8.4 General Development Considerations ...... 11 8.4.1 Site Classification ...... 11 8.4.2 Footings ...... 12 8.4.3 Site Preparation and Earthworks ...... 12 8.4.4 Desilting of Dam Reservoirs ...... 13 8.4.5 Site Maintenance and Drainage ...... 14 8.4.6 Pavements ...... 14 8.4.7 Drainage ...... 16 8.4.8 Mine Subsidence...... 17 8.5 Soil and Water Management Plan ...... 17 9. Summary of Geotechnical Land Capability ...... 20 10. Further Investigation ...... 21 11. References ...... 21 12. Limitations ...... 22

Appendix A: Drawings A1 – A6 Summary of Observations at Mapping Reference Points (MRP) Appendix B: Notes About this Report Test Pit Logs (Pits 1 – 20) Appendix C: Laboratory Test Report Sheets Appendix D: AGS Extracts CSIRO Publication

Geotechnical Investigation, Land Capability Study Project 76742.00.R.002.Rev1 Lowes Creek / Maryland (Barkers Mill), Bringelly, NSW September 2018

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Report on Geotechnical Investigation Land Capability Study Lowes Creek Maryland Precinct, Bringelly, NSW

1. Introduction

This report presents the results of a geotechnical investigation undertaken by Douglas Partners Pty Ltd (DP) as part of an overall land capability study at Lowes Creek Maryland Precinct, Bringelly, NSW. The investigation was commissioned in an email, dated 4 May 2016, from Stephen McMahon of Macarthur Developments on behalf of Department of Planning & Environment and Camden Council and was undertaken in accordance with DP’s proposal MAC160123.P.Rev1, dated 22 April 2016. The site has been previously been identified by the Growth Centres Commission for potential rezoning and urban development under the State Environmental Planning Policy (Sydney Regional Growth Centres) 2006. The site is currently zoned RU1 (primary production) and is proposed to be rezoned for various purposes, including (and primarily) residential type land use.

DP understands that MD intends to identify if the site is suitable for potential rezoning for predominantly residential land use and concurrently to inform future planning proposals for the site. The objective of the study was to determine the geotechnical suitability of the site for development and to provide comments to assist in the conceptual planning for the project.

The investigation comprised a review of published information and field mapping by a senior geotechnical engineer followed by test pit excavation, laboratory testing of selected samples, engineering analysis and reporting. Details of the work undertaken and the results obtained are given in the report, together with comments relating to development potential, conceptual planning, design and construction practice.

A site concept plan was supplied by the client for use in the assessment and selected details have been incorporated into Drawings A1 – A6 (refer Appendix A of this report).

2. Scope of Works

The task required by the land capability phase of the project brief comprises the identification of geotechnical constraints to urban development, particularly with respect to slope instability and erosion. Furthermore, a preliminary soil and water management plan (SWMP) is required to provide guidelines on procedures and development criteria that will apply during subdivision construction. It is noted however that the SWMP is preliminary only and will require further review and refinement once the development footprint is determined.

DP has carried out salinity and contamination investigations in conjunction with the geotechnical investigation. The salinity and contamination investigations are reported separately and a Land Capability Study Report provides an overview of all investigations and results.

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Based on the above scope of work, the geotechnical investigation comprised: • A review of published soils and geological information; • A scoping study of the site, comprising site inspections to identify potential zones for sample collection with regard to geotechnical factors; • Site walkover assessments by a senior geotechnical engineer identifying areas of potential site instability, erosion risks and other geotechnical constraints; • A services search via the dial-before-you-dig service; • Location of the test pits and other site features by a dGPS receiver; • Excavation and logging of 20 test pits (Test Pits 1 – 20); • Collection of regular disturbed samples to assist in strata identification and for laboratory testing. • Laboratory testing (in-house) of selected samples for a range of geotechnical properties, including moisture content, Atterberg limits, shrink-swell index, Emerson Class Number and California bearing ratio (CBR); • Storage of remaining soil samples pending the need for additional chemical or other testing and evaluation; • Preparation of constraints maps, indicating areas of site instability, erosion hazards and areas suitable for urban development; and • Preparation of this report, outlining the scope of work with details of the results obtained, assessment of constraints, recommendations regarding management and mitigation issues and comments with respect to design and construction practice.

3. Site Description

The site is located on The Northern Road, approximately 9 km north-west of Narellan town centre and approximately 7 km west of Leppington town centre. The site is approximately 517 hectares (ha) in size and is expected to deliver an anticipated yield of approximately 7,000 dwellings. It has a 2.8 km frontage to The Northern Road (refer Drawing A1). The site is located within the Camden Council local government area (LGA) and is currently used for a combination of rural residential and agricultural (predominantly pastoral) purposes. The site comprises the following lots: • Part Lot 101 on Deposited Plan (D.P) 1203966 (‘Lot 101’); • Lot 3 on D.P. 218798 (‘Lot 3’); • Lot 4 on D.P. 119173 (‘Lot 4’); • Lot 29 on D.P. 872135 (‘Lot 29’); • Lot 1 on D.P. 218779 (‘Lot 1 north’); • Lots 21 to 23 on D.P. 836540 (‘Lots 21 to 23’); • Lots 1 and 8 on D.P. 1216380 (‘Lot 1 south’ and ‘Lot 8’); • Lots 10 and 15 on D.P. 1218155 (‘Lot 10’ and ‘Lot 15’); and • Lot 102 on D.P. 746955 (‘Lot 102’).

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The site is irregular in shape and is bordered by The Northern Road along the eastern boundary, mixed rural residential and agricultural land to the north, west and south. Lowes Creek (watercourse) runs west to east through the centre of the site. The site is accessed via The Northern Road and is currently being used for mixed rural residential, agricultural and grazing purposes. Maryland Homestead, heritage site is located on Lot 1, near to the centre of the site. Lots 3 and 4 north were until recently occupied by Birling Avian Laboratories where testing of veterinary treatments and chemicals occurred.

DP understands that Lot 1 (south) is to be retained and continue occupancy by the current occupants as part of the development works. Heritage buildings located in Lot 1 (north) and Lot 280, near to Lot 1 will also be retained.

The site may be divided into three main topographic units: 1. Sloping ridgeline extending centrally from the southern edge of the site towards north-east falling both eastward and westward to the course of Lowes Creek and its associated gullies. Lower ground slopes are typically less than 7° but increase towards the crest to approximately 22°. The ridgeline comprises three crests and two saddles with the highest elevation along the ridgeline is RL 126 (relative to Australian Height Datum [AHD]). The lower portions of the slopes and saddles have been cleared for grazing, whilst the crests range from open wooded areas to densely wooded areas. 2. The western edge of the site in which the dendritic drainage system of Lowes Creek (an initially easterly flowing tributary) has entrenched the bedrock forming side slopes mostly to approximately 10 – 12°, but locally steeper towards the crests of ridgelines, along eroded gully or stream beds. The gullies have been dammed in some locations for watering of stock. The highest elevation within this portion is RL 132. The lower portions of the slopes have been cleared for grazing, whilst the crests range from open wooded areas to densely wooded areas. 3. The remainder of the site comprises alluvium infilled valley floors of the eastward flowing Lowes Creek and gentler sloping hillsides feeding the creek. Surface levels range from approximately RL 100 along the western side of the site to RL 68 at the intersection of Lowes Creek with The Northern Road.

While most of the unit has been cleared for use as grazing land, there is a discontinuous zone of remnant vegetation along the central section of the creek line.

4. Regional Geology and Soil Landscapes

4.1 Geology

The Penrith 1:100 000 Geological Series Sheet (Ref 1) indicates that the site is underlain by Bringelly Shale of the Wianamatta Group of Triassic age. This formation typically comprises shale, carbonaceous claystone, laminite, fine to medium grained lithic sandstone and some minor coal bands. The results of the test pitting were consistent with the geological mapping with shale, siltstone and sandstone encountered in those pits that intersected bedrock.

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The bedrock is locally mantled by Quaternary alluvium (fine sand, silt and clay) of recent age within the valley floors of Lowes Creek and its associated gullies. The inferred distribution of the stream and gully floor alluvium (indicated as South Creek Soils) is shown on Drawing A3.

4.2 Soil Landscapes

The Soil Landscapes of the Penrith 1:100 000 Sheet (Ref 2) indicates that the site includes three soil landscapes, the mapped distribution of which are shown on Drawing A3: Blacktown Soil Landscape (bt) – which is mapped over most of the central and western sections of the site and is characterised by topography of "gently undulating rises on Wianamatta Group Shale, with local relief to 30 m and slopes usually less than 5%". This is a residual landscape which the mapping indicates comprises up to four soil horizons that range from shallow red-brown hard-setting sandy clay soils on crests and upper slopes to deep brown to yellow sand and clay soils overlying grey plastic mottled clay on mid to lower slopes. These soils are typically of low fertility, are moderately reactive and have a generally low wet-bearing strength. Luddenham Soil Landscape (lu) – which is mapped in the eastern section of the site and is characterised by "undulating to rolling low hills on Wianamatta Group Shales, often associated with Minchinbury Sandstone with local relief 50 – 80 m, and slopes 5 – 20%. The mapping indicates that it is an erosional unit with shallow (<1.0 m) Brown Podsolic Soils and massive earthy clays on crests and ridges and moderately deep (0.7 – 1.5 m) Red Podsolic Soils on upper slopes. South Creek Soil Landscape (sc) – which is mapped along Lowes Creek and associated minor creek extending south through easternmost dam on Lot 29 and is characterised by “Floodplains, valley flats and drainage depressions of the channels on the Cumberland Plain. Usually flat with incised channels; mainly cleared.” Mapping indicates soils associated with this landscape comprise very deep layered sediments over bedrock or relict soils. Red and yellow podsolic soils occur.

5. Field Work Methods

5.1 Horizontal and Vertical Control

All field measurements and mapping for this project have been carried out using the Geodetic Datum of Australia 1994 (GDA94) and the Map Grid of Australia 1994 (MGA94), Zone 56. Digital mapping has been carried out in a Geographic Information System (GIS) environment using Mapinfo and AutoCAD software, with hard copies produced in A3 format at scales of 1:1000 (Drawings A1 – A4) or 1:1100 (Drawing A5 and A6).

All reduced levels are given in relation to AHD.

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5.2 Site Mapping

Inspections of the bulk of the site (493 ha majority share) was undertaken on 10 and 31 August 2016 and 1 September 2016 by a senior geotechnical engineer in order to identify geotechnical constraints (such as areas of instability and erosion). Mapping reference points (MRP 1 – 101) shown on Drawing A5 were located using a hand held GPS receiver with accuracy typically approximately 4 – 5 m. Observations of the minor land holdings along the eastern boundary were made from road frontages, within the neighbouring site and aerial photographs.

5.3 Test Pitting

The excavation of 20 test pits (Pits 1 - 20) was undertaken to depths of 1.5 – 3.0 m using a backhoe fitted with a 450 mm wide bucket. The pits were logged on site by a geotechnical engineer who collected representative disturbed samples to assist in strata identification and for laboratory testing. Dynamic cone penetrometer (DCP) testing was undertaken adjacent to each test pit location in order to assess the penetration resistance of the near-surface soils.

The test locations were nominated by DP and are shown on Drawing A4. The surface levels (to AHD) and coordinates (to MGA) given on the borehole logs were determined on site using a high precision differential GPS unit with a typical accuracy of 20 mm.

6. Field Work Results

6.1 Field Mapping

The principal geotechnical and geological observations at MRPs are included in Appendix A and are further detailed on Drawings A2 and A3 or summarised below: • There are localised piles of soil, ripped rock and building rubble (eg: concrete, steel, tile, brick and fibre-board fragments) within the site, the larger examples being at MRP 12, 19, 21, 27, 29, 42, 50, 51 and 62. • There are numerous areas where previous site filling (not including the dam walls and access roads) appears to have occurred within the site, with some evidence that some areas have even involved burial of carcasses and other areas as part of movie sets. The larger examples of previous filling being at being at MRP 20, 30, 24, 40, 44, 46, 54, 68, 70, 72, 79, 80, 87 and 88. • There are only isolated, small exposures of bedrock in cuttings within the site. These typically comprise fine grained sandstone or siltstone (MRP 43, 54, 55 and 57). • Along the course of Lowes Creek and its associated gullies, bedrock is mantled by recent alluvium including clayey silt and silty clay. The alluvium is susceptible to water logging and overland flow which has resulted in erosion channels ranging from 0.5 - 2 m deep and up to 20 m wide (refer Drawing A6). An example of this type of erosion (near MRP 13), which intersects a 0.5 – 0.8 m deep, partially cemented clayey silt layer underlain by silty clay, is shown in Figure A1 (following page). • Numerous tributaries of Lowes Creek is also infilled with recent alluvium which is characterised by water logging and discontinuous channel erosion (refer Drawing A6).

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Figure A1: Gully erosion in Bonds Creek at MRP 10 • Sheet and gully erosion 0.5 – 1.5 m deep is also locally developed on hillsides where there has been disruption of the surface cover by previous development (e.g. access track construction) or as the result of over-grazing. An example (at MRP 98) of this type of erosion, which exposes extremely weathered shale at depths of 0.5 – 1 m, is shown in Figure A2.

Figure A2: Sheet and gully erosion at MRP 98

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• The moderately sloping upper hillsides on the central ridgeline and western end of Lowes Creek are susceptible to soil creep (marked by leaning trees, soil terracing or disturbed ground surface) (refer Drawing A6). The examples observed have head scarps less than 1 m high and to approximately 30 m in length (refer MRP 53 and 92).

6.2 Subsurface Investigation

Details of the subsurface conditions encountered in the pits are given in the test pit logs included in Appendix A2. The logs should be read in conjunction with the accompanying notes defining classification methods and descriptive terms.

Relatively uniform conditions were encountered underlying the accessible areas of the site, with the general succession of strata broadly summarised as follows: • TOPSOIL – typically brown silty clay to depths ranging from 0.2 – 0.5 m in Pits 1 – 4 and 6 – 20. The topsoil was encountered beneath uncontrolled filling at a depth of 0.8 m in Pit 5 and continued to a depth of 1 m; • FILLING – silty clay filling to a depth of 0.8 m in Pit 5; • CLAY – firm to hard (but typically stiff to very stiff), residual and alluvial clay to depths of 0.5 m to in excess of 3.0 m in in most pits, with the exception of Pit 2, and to the termination depths of 3.0 m in Pits 6 and 9; • BEDROCK – variably extremely low up to very low to low strength shale, siltstone and/or sandstone below depths of 0.3 – 2.5 m in in most pits with the exception of Pits 6 and 9. Pits 2, 5, 10, 12, 14 – 17 and 19 reached bucket refusal on low to medium up to medium strength rock at depths of 1.2 – 2.5 m.

Localised seepage of groundwater was noted only in Pits 1, 3 and 18 at depths of 1.8 m, 2.8 m and 2.4 m, respectively. The pits were immediately backfilled following excavation which precluded long term monitoring of groundwater levels. Groundwater levels are affected by factors such as soil permeability and weather conditions and will vary with time.

Site observations indicated that some filling was used to form the access roads, level building platforms, as well as the dam walls (in addition to other purposes). In addition, numerous small stockpiles of filling are also scattered across the site (refer Drawing A6).

7. Laboratory Testing

Selected samples from the test pits were tested in the laboratory for measurement of field moisture content, Atterberg limits, shrink-swell index and Emerson Class Number. The detailed test report sheets are given in Appendix C, with the results summarised in Table A1 (following pages).

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The plasticity and shrink-swell index test results indicate that the tested materials may be expected to exhibit foundation soil reactivity (shrink-swell) movements equivalent to a range of Class M to Class H2 sites using approximate in-house correlation between plasticity and reactivity and with reference to AS 2870 - 2011 "Residential Slabs and Footings" (Ref 3). Such classification is dependent upon the continuity of soil type with depth and whether or not rock is present within the depth of the design suction change.

The results of the Emerson crumb tests (Emerson Class Numbers ranging from 5 to 6) indicate that the soils tested are non-dispersive.

Table A1: Results of Laboratory Testing Pit Depth FMC LL PL PI I ECN ss Material No. (m) (%) (%) (%) (%) (%/∆pF) (%) 1 0.5 20.2 52 23 29 - 5 Clay 1 0.9 – 1.3 18.9 - - - 1.9 - Clay 2 0.5 8.3 36 11 15 - - Siltstone 3 0.5 24.7 55 24 31 - - Clay 4 0.5 16.2 45 23 22 - 5 Clay 5 1.0 18.2 46 22 24 - - Clay 6 0.5 23.3 54 24 30 - - Clay 7 0.5 21.8 56 26 30 - - Clay 7 0.9 – 1.3 25.4 - - - 3.7 - Clay 8 0.5 20.4 48 21 27 - - Clay 8 0.5 – 0.9 18.9 - - - 1.3 - Clay 9 0.5 19.9 42 20 22 - - Clay 10 0.5 23.0 51 23 34 - 6 Clay 10 0.5 – 0.9 18.9 - - - 3.9 - Clay 11 0.5 22.2 57 25 32 - - Clay 11 0.6 – 1.0 19.4 - - - 2.8 - Clay 12 0.5 20.2 55 23 32 - 6 Clay 13 0.5 22.9 58 24 34 - 6 Clay 13 0.7 – 1.1 27.1 - - - 2.2 - Clay 14 0.5 24.4 51 22 29 - - Clay 15 0.5 15.7 43 23 20 - - Clay 16 0.5 23.2 59 31 28 - - Clay 17 0.5 26.3 53 22 31 - - Clay 17 0.4 – 0.8 17.4 - - - 2.7 - Clay

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Table A1: Results of Laboratory Testing (Continued) 18 0.5 22.5 45 22 23 - 5 Clay 19 0.5 26.8 52 24 28 - - Clay 19 0.5 – 0.9 14.0 - - - 1.9 - Clay 20 0.5 22.1 56 25 31 - - Clay Where FMC = Field moisture content PL = Plastic limit LL = Liquid limit PI = Plasticity Index

LS = Linear shrinkage Iss = Shrink-swell index ECN = Emerson Class Number

The CBR tests were carried out on samples compacted nominally to a dry density ratio of 100% relative to standard compaction at approximately standard optimum moisture content. The samples were then soaked for four days under surcharge loadings of 4.5 kg. The results are summarised in Table A2.

Table A2: Summary of CBR Test Results

Pit Depth WF OMC MDD Swell CBR 3 Material No (m) (%) (%) (t/m ) (%) (%) 1 0.6 – 0.8 20.0 19.3 1.72 1.6 3.0 Clay 3 1.0 – 1.2 20.3 20.1 1.72 1.5 3.0 Clay 6 0.5 – 0.7 22.9 22.2 1.64 0.5 4.5 Clay 7 0.5 – 0.7 11.1 14.0 1.83 1.4 4.5 Clay 10 1.3 – 1.5 17.3 19.9 1.70 0.5 4.5 Shale 11 1.0 – 1.2 18.2 17.0 1.82 0.1 3.5 Clay 14 0.5 – 0.7 23.1 20.6 1.68 1.0 3.0 Clay 15 0.5 – 0.7 17.9 20.4 1.66 1.6 2.5 Clay 19 1.0 – 1.2 11.2 14.2 1.93 0.5 6 Siltstone 20 1.0 – 1.2 19.4 20.2 1.69 3.8 2.5 Clay

Where WF = Field moisture content OMC = Optimum moisture content MDD = Maximum dry density CBR = California bearing ratio

The results of the field moisture content tests (at the time of the sampling) listed in Table A2 indicate the proposed subgrade soils ranged between approximately 3.0% dry to 0.7% wet of standard optimum moisture content (SOMC). All pavement subgrades should be moisture conditioned to within 2% of SOMC during subgrade preparation to reduce the risk of cracking due to adverse shrink and swell movements within the pavement post-construction.

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8. Comments

8.1 General

The following comments are based on a review of available information, the results of field mapping, test pitting, laboratory testing and our involvement in similar projects in the South Western Sydney area. Comments are provided on development constraints related to geotechnical and geological factors to assist in the conceptual planning of the proposed development. Further investigations will therefore be required to be undertaken at the appropriate times as the planning, design and construction of the development proceeds and accordingly, this report and the comments given within must be considered as being preliminary in nature.

8.2 Slope Instability

Thick residual soil profiles of the Blacktown and Luddenham Soil Landscapes can be prone to slope instability due to slumping and soil creep, particularly on steep south-facing slopes underlain by shale. The high clay content of these soils results in poor drainage, and therefore reduced cohesion during periods of high rainfall or where natural drainage has been disturbed by development. Instability due to slumping is typically associated with thick soils and slopes in excess of 20% gradient (or greater than 11º) as described by Fell (Ref 4).

Although no distinct slope instability (slump flow landslides) affecting the soil and bedrock profile has been identified within the moderately steep and steep hillslope sections, there are localised areas of with gradients in excess of 20% and some minor creep movements were noted in these areas (i.e. consistent with the descriptions of Ref 5). Associated with these are areas identified as being affected by potentially older degraded landslip features.

The soil creep features impose site development constraints which include: • Restriction of residential and infrastructure development in areas characterised by steep topography (grades greater 20%) and stratigraphy. For initial planning purposes, the restricted use area should include an upslope buffer of at least 20 m; • Restriction of soil creep areas adjacent to landslides from development unless site specific investigation is able to ensure that appropriate engineering works (e.g. retaining walls and drainage measures) can provide acceptable levels of risk for the development; • Restriction of development adjacent to creek and gully banks, where erosion and/or soil creep may be present, unless appropriate engineering works (e.g. re-contouring or bank support) can be put in place to provide acceptable levels of risk for the development; • A program of revegetation of the soil creep affected areas, noting that the instability may have been triggered by the original clearing of the hillsides for grazing purposes; and • Additional subsurface investigation of hillsides with gradients in excess of 20% to further assess the susceptibility for slope instability.

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8.3 Erosion Potential

Water erosion hazard forms a landscape limitation for the site. The site inspections identified gullies entrenching of recent alluvial deposits within stream courses and the residual soil and bedrock profiles. Localised areas of sheet and rill erosion were also noted in areas of previous surface disturbance and where over-grazing has occurred. In general, however, existing farm dams across gullies and vegetated areas between gully sections appear to act as effective catch points for eroded soils.

Soils of the Blacktown and Luddenham Soil Landscapes are typically of moderate erodibility (erodibility factor [K] values of 0.02 – 0.04, the value being determined by a combination of laboratory tests as well as soil structure and permeability). The more sodic or saline soils of the Blacktown Soil Landscape can have high erodibility and the erosion hazard for this landscape is estimated as moderate to very high (Ref 2). The soil erosion hazard for the Luddenham Soil Landscape is moderate to extreme and extreme respectively, for non-concentrated flows. The soil erosion hazard for the alluvial South Creek Soil Landscape is estimated as moderate to high for non-concentrated flow, and very high for concentrated flow.

To minimise the constraints imposed by extreme erosion potential, the steep sections within all soil landscape groups should be generally avoided by earthworks and provided with remedial works (e.g. replanting and drainage improvement) where appropriate. It is considered that the erosion hazard within the remaining areas of the site would be within usually accepted bounds which may be managed by good engineering and land management practices.

It is anticipated that the treatment of the existing gullies as part of an overall site development would include: • Filling using select materials (i.e. non–dispersive or erodible) placed under controlled conditions; • Provision of temporary surface cover (e.g. pegged matting) during the period of gully floor revegetation; • Channel lining in sections of rapid change in gully floor grade; and • Piping of flow where appropriate. • The re-establishment of a zone of tree cover or appropriate vegetation along gully banks.

8.4 General Development Considerations

8.4.1 Site Classification

Classification of individual allotments within the site should comply with the requirements of AS 2870 – 2011 "Residential Slabs and Footings" (Ref 3). Based on previous experience in similar geological settings, the subsurface profiles would most likely be equivalent to Class M (moderately reactive) or Class H1/H2 (highly reactive), with the final classifications dependent on soil reactivity, soil strength and rock depth.

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Class P conditions may be present in the floodplain/drainage depressions should weak soils be encountered during project-specific subsurface investigation. Re-classification of such areas to M or H1/H2 may be possible subject to the extent of earthworks undertaken during construction. In areas of moderate to steep relief, P (hillside) classifications would likely result.

8.4.2 Footings

All footing systems for residential type structures should be designed and constructed in accordance with AS 2870 – 2011 (Ref 3) for the appropriate classification. Whilst conventional high level footing systems would be appropriate for M or H1/H2 sites, suitable foundation systems for Class P lots could include (depending on the depth of suitable founding stratum and the presence of groundwater) backhoe excavated block-downs, pier and beam, screw piles or possible driven timber piles and mini piles founding on the underlying stiff clays or weathered rock.

For hillside construction, reference should be made to the Australian Geomechanics Society (AGS) publication Practice Note on Landslide Risk Management (Ref 5), relevant extracts of which are included in Appendix D. The principal recommendation for hillside development is for footings to found below the zone of potential soil creep within the underlying weathered rock.

Footings for all other structures should be based on the results of specific geotechnical investigations. As a guide, preliminary design could be based on maximum allowable bearing pressures of 150 kPa for stiff to very stiff clays and 800 kPa for highly weathered rock of at least very low strength.

8.4.3 Site Preparation and Earthworks

Site preparation for the construction of residential structures should include the removal of topsoils and other deleterious materials from the proposed building areas.

In areas that require filling, the stripped surfaces should be test rolled in the presence of a geotechnical engineer. Any areas exhibiting significant deflections under proof rolling should be appropriately treated by over-excavation and replacement with low plasticity filling placed in near horizontal layers no thicker than 250 mm compacted thickness. In accordance with Camden Council requirements, each layer should be compacted to a minimum dry density ratio of 95% relative to standard compaction with placement moisture contents maintained within 3% of standard optimum. The upper 0.5 m in areas of pavement construction should achieve a minimum dry density ratio of 100% relative to standard compaction.

All batters should be constructed no steeper than 3H:1V (horizontal:vertical) and appropriately vegetated to reduce the effects of erosion.

To validate site classifications, sufficient field inspections and in-situ testing of future earthworks should be undertaken in order to satisfy the requirements of a Level 1 inspection and testing service as defined in AS 3798 – 2007 Guidelines on Earthworks for Commercial and Residential Developments (Ref 6).

Earthworks required for pavement construction will need to be based on batters formed no steeper than 3H:1V in the residual clays. All batters should be suitably protected against erosion, with toe and spoon drains constructed as a means of controlling surface flows on the batters.

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Within hillside lots, excavation and filling should generally be limited to a maximum vertical height of 1 m respectively below or above the existing ground surface. Proposed earthworks that exceed the above requirements should be subject to review by a geotechnical engineer during the design phase of the individual project. Excavations that exceed 1 m must be supported by engineer-designed retaining walls founded on bedrock. However, it must be accepted that creep movement in retaining walls constructed perpendicular to the slope is probably inevitable, due to the high active pressures of the retained material.

If embankments are proposed for use as water quality control ponds, then the results of testing completed to date indicates that the site soils would be suitable for re-use as embankment materials. Subject to the detailed design, detention basins (i.e.: short term storage only) could be dimensioned with maximum batter slopes of 4:1 (H:V), with allowance made for accommodating the results of erosion (such as topsoiling and turfing) if soils with an ECN of less than 4 are proposed for use. Subject to design permeability requirements, the use of lines on both the embankments and within parts of the reservoir area may also be necessary.

Site observations have indicated the presence of silty topsoils and silty clays which could be adversely affected by inclement weather. Whilst these soils are typically stiff to very stiff consistency when dry, they can rapidly lose strength during rainfall and saturation, and result in difficult trafficability conditions. As a result, surface drainage which directs runoff away from work areas should be installed prior to construction, possibly in conjunction with the designation of construction equipment haul routes to minimise trafficking of stripped areas.

Conventional sediment and erosion control measures should be implemented during the construction phase, with exposed surfaces to be topsoiled and vegetated as soon as practicable following the completion of earthworks.

8.4.4 Desilting of Dam Reservoirs

If the existing farm dams are to be drained and filled to design level. The following general procedure is recommended: • Pump out ponded water and discharge across land a minimum distance of 50 m from any existing waterways; • Strip all vegetation and other deleterious material (such as saturated silt and clay) to expose the underlying stiff clay/weathered rock; • Suitably bench the exposed surface to facilitate near-horizontal filling placement; • Test rolling of the surface to receive filling with six passes of a 10 tonne dead weight roller operating in static mode, with final pass undertaken in the presence of a geotechnical engineer in order to identify areas requiring remedial work; • Filling should be placed in near horizontal layers no thicker than 250 mm compacted thickness. In accordance with Camden Council requirements, each layer should be compacted to a minimum dry density ratio of 95% relative to standard compaction with placement moisture contents maintained within 3% of standard optimum;

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• Saturated ‘organic’ soils from the pond base can be spread out and dried. Once dried the material can be blended with stockpiled topsoil and spread across the finished surface of lots; and • Any saturated ‘non-organic’ soils can be spread out and dried. Once moisture conditioned, the materials can be reused as engineered filling (refer Section 9.4.5.2) subject to inspection and approval.

Prior to discharging, an assessment of the pond water should be undertaken to confirm the adequacy of the above disposal method. The assessment should include (as a minimum) turbidity testing to the satisfaction of Camden Council.

8.4.5 Site Maintenance and Drainage

The developed site should be maintained in accordance with the CSIRO publication "Guide to Home Owners on Foundation Maintenance and Footing Performance" (Ref 7), a copy of which is included in Appendix D. Whilst it must be accepted that minor cracking in most structures is inevitable, the guide describes suggested site maintenance practices aimed at minimising foundation movement to keep cracking within acceptable limits.

Surface drainage should be installed and maintained at the site. All collected stormwater, groundwater and roof runoff should be discharged into the stormwater disposal system. Similarly, effluent flows should be directed to the sewerage system.

8.4.6 Pavements

8.4.6.1 General

In order to assist in the conceptual design process, preliminary pavement thickness designs for arterial, boulevards, collectors and local access roads are provided in Table A3 (following page). Each category has been determined in accordance with Camden Council's requirements and has been assigned the road categories according to the following: • Category B (boulevard) – ESA = 2 x 106 • Category C (collector) – ESA = 1 x 106 • Category E (local access road) – ESA = 5 x 105 • Category F (minor access road) – ESA = 1 x 105 • Category G (shareway) – ESA = 2 x 104

The preliminary pavement thickness designs given in Table A3 are based on the requirements of Camden Council, AUSTROADS – 2012 (Ref 8), the design parameters detailed above and a range of likely CBR values. Additional Investigations will need to be undertaken at the appropriate time to provide a final pavement thickness design.

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Table A3: Preliminary Pavement Thicknesses Total Pavement Thickness (mm) for Design CBR (%) Design ESA 2% 3% 4% 5% 7% 5 x 106 800 660 570 500 420 2 x 106 730 600 520 470 390 1 x 106 680 570 490 440 370 5 x 105 630 520 470 410 350 1 x105 510 420 390 340 290 2 x 104 470 390 340 310 260

It is anticipated that some pavements will likely encounter a rock subgrade. As a result, a design CBR value of 7% will most likely be feasible for those conditions but will need to be confirmed once geometric design and subdivision layout is finalised.

It is expected that most of the clay subgrades will generally encounter clays of CBR 2 – 4%. Pavement thickness design, however, may be optimized when a detailed subgrade investigation is undertaken.

In accordance with Council's requirements, surfacing should consist of 50 mm (two 25 mm thick layers) of AC10 over a single coat flush seal. Furthermore, it is noted that in accordance with Council's design specification, the asphalt thickness is assumed to not contribute to the structural strength of the pavement and therefore has not been considered in overall pavement thickness determination. Analysis however, does indicate that a 50 mm AC layer will act as a structural element and, over time, will be subject to fatigue. Notwithstanding this, it must be accepted that this is the case regardless of the pavement type adopted and allowance must be made within the maintenance scheduling for periodic sealing of cracks and re-sheeting to ensure ingress of water is minimised.

8.4.6.2 Roundabouts, Cul-de-sacs and Braking Zones

At roundabouts, cul-de-sacs and braking zones with a design traffic loading of greater than 5 x 105 ESAs, the wearing course should be 75 mm thick and comprise SBS polymer modified asphaltic concrete, thus satisfying Council's minimum requirement. As above (refer Section 8.4.6.1), it is noted that in accordance with Council's design specification, the asphalt thickness is assumed to not contribute to the structural strength of the pavement and therefore has not been considered in overall pavement thickness determination.

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8.4.6.3 Materials and Compaction

The suggested minimum material quality and compaction requirements are given in Table A4.

Table A4: Pavement Material Quality and Compaction Layer Material Quality Minimum Compaction

Wearing Course To conform to Council requirements To conform to Council requirements

To conform to Council requirements Minimum dry density ratio of 98% Base Course Soaked CBR ≥80%, PI ≤6% Modified (AS 1289 Test 5.2.1) To conform to Council requirements Minimum dry density ratio of 98% (1) Sub-base Course Soaked CBR ≥50%, PI ≤12% Modified (AS 1289 Test 5.2.1) Subgrade Minimum dry density ratio of 100% Replacement Soaked CBR ≥15% Standard (AS 1289 Test 5.1.1) (where required) Minimum dry density ratio of 100% Subgrade - Standard (AS 1289 Test 5.1.1) Where: PI = plasticity index Note 1: Council requirement.

Whilst the use of lesser quality pavement materials than that detailed in Table A4 may be feasible, some compromise in either performance and/or pavement life must be anticipated and accepted. It is also suggested that advice be sought from Council if lesser quality pavement materials are proposed.

8.4.7 Drainage

Surface and subsurface drainage must be installed and maintained to protect the pavement and subgrade. The subsurface drains should be located at a minimum of 0.5 m depth below the excavation level. Guidelines on the arrangement of subsurface drainage are given on Page 20 of ARRB – SR41 (Ref 9). It should be noted that if the sub-base is of low permeability relative to the base layer, then the subsurface drain is required to intersect all pavement layers as shown in ARRB – SR41.

It is suggested that subsurface drainage, as a minimum, be provided for on the cut sides of the road pavements. It should be noted that such drainage could be integral with other drainage works proposed, such as bedding for stormwater lines. However, to facilitate drainage of the bedding layer, inlets to the pits via, say, a 3 m length of slotted pipe, will need to be incorporated into the works.

Additional subsoil drainage may also be required within development lots in footslope locations abutting where water logging forms a constraint to development. Within these areas, filling and/or deep drainage is likely to be required to permit trafficability during construction and subsequent lot development.

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Since it is typically sometime after pavement construction before the final AC layer is placed, it is also suggested that diversion mounds be constructed as part of the initial AC layer to ensure that all sheet flow following inclement weather are directed into the kerb and guttering. If such mounds are not constructed, most flows will run within the pavement (as the 25 mm 'lip' acts as a barrier) with the most likely result being premature pot-holing and pavement failure due to saturation in the wheel path adjacent of the kerb.

Collected water from development areas should not be discharged over areas of potential or actual slope instability.

8.4.8 Mine Subsidence

A review of the Mine Subsidence Board district mapping indicates the site is located outside existing mine subsidence districts and is not underlain by any registered mines.

8.5 Soil and Water Management Plan

Soil and water management is an integral part of the development process and should adopt a preventative rather than a reactive approach to the site limitations, such that the work can proceed without undue pollution of receiving streams.

Once consent is given, a detailed soil and water management plan (SWMP) developed in accordance with the methods of the NSW Department of Housing (Ref 10) will be required and will be incorporated into the engineering design of the development methods for: • Minimising water pollution due to erosion of soils or the development of saline conditions; • Reducing or managing salinity to provide acceptable conditions for building and revegetation works; • Minimisation of soil erosion during and after construction; • Maximising the re-use of materials on site; and • Ensuring that buildings and infrastructure are within acceptable risk of instability (for both property and life).

The following provides a conceptual SWMP with the objectives of controlling site works: General Instructions: These conditions include methods to ensure compliance with the SWMP, specially: • the SWMP will be read with the engineering plans and site specific instructions issued in relation to the development; • contractors will ensure that all soil and water management works are undertaken as instructed in the specification and constructed in accordance with AS 3798 - 2007 (Ref 6); and • All subcontractors will be informed by the Superintendent of their responsibilities in minimising the potential for soil erosion and pollution of downslope areas.

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Land Disturbance: These conditions provide methods to minimise soil erosion, the exposure of potentially or known saline subsoils and direction of overland drainage into areas of potential slope instability, specifically: • The erosion hazard will be kept as low as possible by limiting of construction area size at any one time and clearly defining the area by barrier fencing upslope and sediment fencing downslope (to be installed before the commencement of construction activities); • Access areas will be clearly defined and limited in size while being considerate of the needs of efficient work areas. All site workers will clearly recognise these boundaries; • The prohibition of entry into areas outside physical works except for essential management works; • Restriction of work in creek lines during periods of rainfall, with programming of works in these areas to be within periods of anticipated lower rainfall; • The programming of development roadworks and major excavations to minimise the time of soil exposure and to coincide with periods of anticipated lower rainfall; • Placement of topsoils and subsoils in separate stockpiles (where required) with appropriate sediment fencing and dimensions selected to minimise the surface area of soils exposed to rainfall and hence erosion and leaching of saline materials; • The creation of larger lots on steeper slope sections to permit the more sensitive development of the individual site; • Orientation of access roads and services to minimise the requirements of excavation and possible retaining structures; • Where excavation of filling of batters is required, the construction of these at as low as practical gradient with a maximum 3:1 (H:V) in the clay soil profiles; • The placement of excavated soils in filled areas in the sequence of excavation (i.e. to place potentially saline or sodic subsoils below a capping of non-saline material); • During windy conditions, large, unprotected areas will be kept moist by sprinkling with water to keep dust under control. In the event that water is not available in sufficient quantities, soil binders and/or retardants will be used or the surface will be left in a cloddy state that resists removal by wind; • The inclusion of techniques, such as spray coating or a secured protective turf overly on cut and fill batters to minimise erosion; • The maximisation and/or replacement of native tree cover and deep-rooted plants, particularly in areas of known or potential slope instability; • Where vegetation cover is not adequate to control erosion, the improvement of soil resistance to erosion by the addition of lime and gypsum (the proportion to be determined by site specific testing); • Maintenance including watering of lands established with grass cover until an effective cover has been established. Where there has been inadequate vegetation establishment, further application of seed should be carried out. During establishment, trafficking of the treated areas should be minimised;

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• The design of stormwater drainage, including lined catch drains at the crest of cut slopes, stormwater pipes and dissipators as required to minimise concentrated runoff and to provide controlled discharge of the collected runoff; and • The sampling and analysis of groundwater samples from monitoring bores installed prior to construction in order to assess impacts on groundwater quality.

Pollution Control: These conditions provide measures to protect downstream areas for water-borne pollution, specifically: • The installation of sediment fences to contain the coarser sediment fraction as near as possible to their source; • Ensuring that stockpiles are not located within hazard areas, including areas of likely high velocity flow, such as waterways, paved areas and driveways; • The installation of sediment basins downslope of areas to be disturbed, with the design based upon a design storm event; • The inclusion of one or more pegs in the floor of the sediment basins to indicate the level at which design capacity occurs and when collected sediment will be removed; • Disposal of trapped materials from sediment basins to locations where further erosion and consequent pollution to downslope lands and waterways will not occur; • Sampling and laboratory analysis of collected waters to ensure compliance with benchmark parameters prior to discharge; • The treatment of collected waters by gypsum and settling of flocculated particles before any discharge occurs (unless the design storm event is exceeded); and • The removal of sediment basins (where not required as part of the on-going site management) only after the lands they are protecting are stabilised. Site Inspection and Maintenance: These conditions provide for self and external auditing of the performance of construction and pollution protection measures, together with appropriate maintenance of erosion and sedimentation structures, specifically: • A self-auditing program against an established checklist to be completed by the site manager at least weekly, immediately before site closure and immediately following rainfall events in excess of 5 mm in any one 24 hour period. The audit should include the recording of the condition of temporary sediment and water control devices, any maintenance requirements for these structures, volumes and disposal sites of material removed from sediment retention systems. A copy of the audit should be provided to the project superintendent; • Provision for periodic inspection of records and site conditions by an external, suitably qualified person, for oversight of soil and water management works. The person will be responsible for ensuring that the SWMP is being implemented correctly, repairs are being undertaken as required and modifications to the SWMP are made if and when necessary. A short written report will be provided at appropriate intervals and will confirm that the works have been carried out according to the approved plans.

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9. Summary of Geotechnical Land Capability

For discussion, the capability for urban development may be related to the degree of surface disturbance involved in the following categories of site development: Extensive building complexes - the development of commercial complexes such as offices or shopping centres, which require large scale clearing and levelling of broad areas of floor space and parking bays. Residential development - infers a level of construction which provides for roads, drainage, and services to cater for housing allotments of approximately 600 square metres or larger. Strategic residential development - refers to areas unsuitable for widespread development, but where closer investigation may permit isolation of pockets of land for individual house sites, or definition of engineering measures required to maintain stability of what would otherwise be unsuitable land for development. Reserves - The development of reserves, which may require shaping and modification of the ground surface and vegetation improvement, but no building and minimal roadway construction, is envisaged.

General development considerations will require the classification of residential lots to comply with the requirements of AS 2870 – 2011 (Ref 3). The requirements of AS 1170 – 2002 Structural Code (Ref 11) are particularly noted in relation to earthquake loading requirements for commercial or industrial development.

The distribution of the geotechnical constraints (slope instability, erosion and water logging) is summarised in Drawing A6.

While no landslide activity has yet been identified within steeper hillsides (refer Drawing A6) of the site, there were observed incidences of soil creep and for further potential for surficial soil creep and possible shallow slumping of residual soils. These are likely to impose only minor to moderate constraints (i.e. able to be addressed by good engineering practices for residential or strategic residential hillside development including site specific investigation and engineering of structures). The remainder of the gently sloping hillsides areas are considered to be suitable for residential development and extensive building complexes.

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10. Further Investigation

The geotechnical investigation undertaken to date has indicated that most of the site will be suitable for residential development, with comments given on geotechnical limitations, development guidelines, likely site classification, stability considerations and indicative pavement thicknesses. Conceptual comments on design and construction aspects are also given in the report. Detailed geotechnical investigation and assessment will be required as the design of the development proceeds and as such, this report must be considered as being preliminary in nature. Specific geotechnical investigation would include (but not necessarily be limited to): • Detailed geotechnical investigations on a stage-by-stage basis for determination of pavement thickness designs and lot classifications. • Routine inspections and earthworks monitoring during construction.

11. References

1. Geological Survey of New South Wales, 1991. Geology of 1:100 000 Penrith Geological Series Sheet 9030 (Edition 1). 2. Bannerman, S. M and Hazelton, P A. Soil Landscapes of the Penrith 1:100 000 Sheet. Soil Conservation Service of NSW, Sydney. 3. Australian Standard AS 2870 – 2011 Residential Slabs and Footings. 4. Fell, R. 1985. Slope Stability in the Wianamatta Group. In P. J. N. Fells (Ed) Engineering Geology of the Sydney Region. Published on behalf of the Australian Geomechanics Society, A. A. Balkema, Rotterdam. 5. Practice Note Guidelines for Landslide Risk Management, Australian Geomechanics Society Landslide Taskforce (2007). 6. Australian Standard AS 3798 – 2007 Guidelines on Earthworks for Commercial and Residential Developments. 7. CSIRO 2003. Foundation Maintenance and Footing Performance: A Homeowner’s Guide. BFT18.

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8. Austroads 2012. Pavement Design – A Guide to the Structural Design of Road Pavements. 9. ARRB – SR41, 1989. A Structural Design Guide for Flexible Residential Street Pavements, Australian Road Research Board, Special Report No 41. 10. NSW Department of Housing, 1998. Managing Urban Stormwater, Soils and Construction. 11. Australian Standard AS 1170 – 2002 Structural Code.

12. Limitations

The scope for work for this investigation/report did not include the assessment of surface or subsurface materials or groundwater for contaminants, within or adjacent to the site. Should evidence of filling of unknown origin be noted in the report, and in particular the presence of building demolition materials, it should be recognised that there may be some risk that such filling may contain contaminants and hazardous building materials.

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The contents of this report do not constitute formal design components such as are required, by Health and Safety Legislation and Regulations, to be included in a Safety Report specifying the hazards likely to be encountered during construction of all works (not just geotechnical components) and the controls required to mitigate risk. This report does, however, identify hazards associated with the geotechnical aspects of development and presents the results of risk assessment associated with the management of these hazards. It is suggested that the developer’s principal design company may wish to include the geotechnical hazards and risk assessment information contained in this report, in their own Safety Report. If the principal design company, in the preparation of its project Design Report, wishes to undertake such inclusion by use of specific extracts from this subject DP report, rather than by appending the complete report, then such inclusion of extracts should only be undertaken with DP’s express agreement, following DP’s review of how any such extracts are to be utilised in the context of the project Safety Report. Any such review shall be undertaken either as an extension to contract for the works associated with this subject DP report or under additional conditions of engagement, with either option subject to agreement between DP and the payee.

Douglas Partners Pty Ltd

Geotechnical Investigation, Land Capability Study Project 76742.00.R.002.Rev1 Lowes Creek / Maryland (Barkers Mill), Bringelly, NSW September 2018