Golder Associates

24 February 2015 Project No. 1523668-001-L-Rev1

Mr Adam Garrisson Burnham Beeches Pty Ltd 1 Sherbrooke Road Sherbrooke VIC 3789

PRELIMINARY ASSESSMENT OF EROSION MANAGEMENT OVERLAY

BURNHAM BEECHES ESTATE, SHERBROOKE, VICTORIA

Dear Adam

INTRODUCTION Burnham Beeches Pty Ltd (Burnham Beeches) proposes to develop the Burnham Beeches Estate located at 1 Sherbrooke Road, Sherbrooke, Victoria. The estate is within the bounds of Yarra Ranges Shire Council (Yarra Ranges).

Yarra Ranges' Erosion Management Overlay (EMO) applies to part of the estate. Burnham Beeches has requested that Golder Associates Pty Ltd (Golder) undertake a preliminary assessment of the site, with regards to the requirements of the EMO for the development application.

Authorisation to proceed with this work was provided by Burnham Beeches via email (Garrison/Russell) on 17 February 2015. This letter sets out the results of our assessment and provides guidance on the implications of the EMO to the proposed development.

PROPOSED DEVELOPMENT We have been provided with documents describing the master plan for the proposed development. Based on this information, we understand the development will comprise a mixed use development including:

• Low rise structures, including cabins, villas, sheds a brewery and restaurant.

• New roadways, carparking areas and pedestrian tracks, some of which will be paved.

• Several small market gardens.

Some earthworks are proposed, to accommodate pedestrian tracks, car parks and buildings. However, these are expected to be relatively minor with cut and fill depths generally less than 1 m.

Golder Associates Pty Ltd Building 7, Botanicca Corporate Park, 570 — 588 Swan Street, Richmond, Victoria 3121, Australia (PO Box 6079, Hawthorn West VIC 3122)

Tel: +61 3 8862 3500 Fax: +61 3 8862 3501 www.golder.com Golder Associates: Operations in Africa, Asia, Australasia, Europe, North America and South America

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Mr Adam Garrisson 1523668-001-L-Rev1 Burnham Beeches Pty Ltd 24 February 2015

OBJECTIVES

The objectives of the preliminary assessment are to:

• Assess the impact the proposed development could have on slope stability.

• Identify constraints to the proposed development associated with the Erosion Management Overlay which affects part of the site.

• Provide guidance to Burnham Beeches regarding further works that may be needed to address the requirements of the EMO with respect to the proposed residential development of the site.

GEOLOGY AND GEOMORPHOLOGY

The 1:63,360 geological mapsheet of Ringwood indicates that the site is underlain by Devonian age Ferny Creek Rhyodacite. In its fresh state, this material is a very high strength rock. However, the upper 1 m to 5 m is typically weathered to a residual clay soil. There is a history of landslides occurring within the residual soils developed over the Devonian Rhyodacite rock. Steeper slopes have a greater susceptibility to landslides, which are typically triggered by water infiltration associated with heavy or prolonged rainfall or poor drainage.

OVERLAY Part of the site is subject to an EMO. Figure 1 indicates the part of the site affected (shaded yellow).

Figure 1: Area subject to Erosion Management Overlay shown in yellow (site boundary shown in red)

The area highlighted in Figure 1 is subject to the requirements set out in Amendment C40 to the Yarra Ranges Planning Scheme, attached. There are areas within the Shire of Yarra Ranges that are susceptible to landslide. The intent of the EMO is to manage development such that the risk to life and property from landslide or slope instability is maintained within tolerable limits.

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Mr Adam Garrisson 1523668-001-L-Rev1 Burnham Beeches Pty Ltd 24 February 2015

Areas are included in the EMO on the basis of:

• The underlying geology is Devonian age Rhyodacite and the slope angle is greater than 30%.

• The underlying geology is Tertiary age Basalt and the slope angle is greater than 20%.

• The site has previously been affected by landslides.

The basis for the area shown in Figure 1 being included in the EMO is that it is underlain by Devonian age Rhyodacite and the slope angle is greater than 30%. Slope angle measurements taken during our site visit generally confirm this. The part of the site not included in the EMO is also underlain by Devonian Rhyodacite, however has a slope angle of generally less than 20%.

No landslides have been identified that have previously affected this or adjacent sites.

SITE OBSERVATIONS A Principal geotechnical engineer from Golder visited the site of the proposed development on 19 February 2015. A site walkover was undertaken during which features relevant to slope stability were observed and recorded. The following photographs and text summarise the site observations made.

The general slope angle of the site is relatively gentle, typically between 6° and 10° (10% and 17%). In general, the slope angle steepens towards a gully feature located along the northern boundary of the site. As indicated in Figure 1, this is the general area subject to the EMO. The area subject to the EMO has a slope angle of up to 16° (30%) and is well vegetated as shown in Figure 2.

Figure 2: View towards vegetated gully. This area is subject to the EMO.

There are minor earthworks on the site associated with tracks and levelled areas. The cut and fill batters are generally less than 1 m high. The exception is a 1.8 m to 2.0 m high unsupported cut batter located towards the north east of the site, as shown in Figure 3. This batter is well vegetated and does not show any signs of instability.

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Figure 4: Dry stone retaining wall, north east of site. Wall appears to be in good condition.

Mr Adam Garrisson 1523668-001-L-Rev1 Burnham Beeches Pty Ltd 24 February 2015

Figure 3: Well vegetated cut batter, north east of site.

A cut batter towards the north eastern part of the site is supported by a dry stone retaining wall, as shown in Figure 4. The retaining wall appears to be in reasonable condition.

Mr Adam Garrisson 1523668-001-L-Rey1 Burnham Beeches Pty Ltd 24 February 2015

With the exception of the gully (See Figure 1) vegetation on the site is relatively sparse. However, we note that an orchard has recently been established on cleared areas as shown in Figure 5.

Figure 5: View east towards central part of site. Recently planted orchard visible in centre of photo.

No evidence for slope instability was observed on the site.

LANDSLIDE HAZARDS

Based on the review and site observations, there are no credible landslide hazards that present a risk to life or property associated with the current site conditions.

However, there is potential for future development to create landslide hazards. Good hillside design and construction will be required to avoid creating landslide hazards. This is further discussed in the following section.

DEVELOPMENT CONSTRAINTS

The following development constraints are consistent with the requirements of the Schedule to the Yarra Ranges EMO and are recommended to avoid increasing this risk to life and property on this site.

Golder 5/8 Associates

Mr Adam Garrisson 1523668-001-L-Rev1 Burnham Beeches Pty Ltd

24 February 2015

Table 1: Recommended Development Constraints Geotechnical Assessment

As a requirement of the planning scheme, any proposed structures (including cabins, brewery and sheds) or earthworks greater than 1 m will require a geotechnical assessment. A suitably qualified Chartered (CPEng or RPGeo) practitioner will be required to undertake this assessment. Conceptual or 'town planning' stage drawings will be required to allow the practitioner to undertake the

Planning application assessment. These plans must show all proposed structures, earthworks and a requirements drainage plan. Dimensions of earthworks including cut depths and batter angles

must be shown.

The practitioner must provide a signed geotechnical declaration which specifically refers to the plans for the proposed development and verifies that the risk associated with landslide or slope instability is tolerable.

Design and Construction

Structure Design Use floor plans that minimise the amount of cutting and filling of the site. Use flexible structures which incorporate properly designed brickwork, timber or steel frames, timber or panel cladding. Consider using split-level decking for recreational areas.

Site Clearing Do not indiscriminately clear the site. Retain and supplement natural vegetation wherever possible.

Roads and Pavement

Take advantage of natural site topography to minimise the extent of earthworks required by aligning roads along slope contours. Satisfy all guidelines for cuts, retaining walls and drainage as set out below.

E arthworks

Retain natural land contours wherever possible. Do not make large cuts or fills. Do not block any existing drainage courses by earthworks. Complete all earthworks and retaining walls prior to commencing construction of structures. The existing earthworks observed on the site are relatively minor and well vegetated. Do not remove vegetation from and avoid disturbance to existing cut and fill batters.

Cuts in Soil

Unsupported cut depths should not exceed 1.0 m and maximum batters should not exceed 1V:2H (V = Vertical; H = Horizontal). Steeper and/or higher cuts should be supported with an engineer designed retaining wall. Provide drainage measures and prevent erosion. The existing unsupported batters can remain as is, with no support requirement, provided no structures are built within 2 m of the batter.

Fills

Unsupported fill thickness should not exceed 1.0 m and batters should not exceed 1V:2H (V = Vertical; H = Horizontal). Steeper and/or higher fills should be supported with an engineer designed retaining wall. Remove vegetation and topsoil before placing fill. Use clean fill materials and compact to appropriate Australian Standards. Key the fill into the natural slope. Provide surface and subsurface drainage as appropriate. If seepage from any fill is observed, seek advice. Do not place fills at the crest of cuts, proposed or existing retaining walls.

Rocks and Boulders Rock boulders may be recovered from earthworks. Remove or stabilise rocks or boulders that are potentially unstable.

F oundations Support on rock where practical or on stable ground as identified by a suitably qualified Geotechnical Practitioner. Do not found on topsoil, loose fill or unstable ground. Use rows of piers or strip footings oriented up and down slope. Backfill foundation excavations to prevent the entry of surface water.

er Golder 6/8 Associates

Mr Adam Garrisson 1523668-001-L-Rev1

Burnham Beeches Pty Ltd

24 February 2015

R etaining Walls

Obtain an engineer's design for retaining walls greater than 1 m height, where the ground surface above or below the retaining wall slopes at greater than 1V:4H, or when retaining walls are closer than a distance of twice the maximum wall height apart. Found in rock or competent natural soil. Provide subsurface drainage behind the base of the wall. Provide surface drainage behind and at the toe of the wall. Construct wall as soon as possible after completion of earthworks. Where there is no ready access to replace or repair the retaining wall after construction of a dwelling, the retaining wall should be constructed from durable material with a design life equal to or greater than that of the structure. The existing retaining walls on the site appear to be in a good condition. Do not modify change the loading on the retaining wall by loading the ground at the crest or removing vegetation.

Drainage and Water Management

Surface

Do not impede or channel natural surface water flows unless necessary. If intercepted, collect surface run-off and discharge to street drainage or natural watercourses. Provide drains uphill of structures and cuts and fills. Line drains to minimise infiltration and erosion. Provide generous falls to prevent blockage by siltation and incorporate silt traps. Provide energy dissipation structures where fast flow is possible.

Subsurface

Provide sand or screenings and filter around subsurface drain. Use flexible pipelines with access to allow blockages to be cleared. Prevent direct inflow of surface water to subsurface drains. (e.g. using a capping layer over trench). Pipe discharge to street drainage or natural water course.

Dams Obtain an engineer's design. Line dam and direct spillway to a legal point of discharge.

Water Tanks Support on rock or stable ground. Provide with under drainage and gravity drain outlet directed to a legal point of discharge. Pipe overflow to stormwater.

Septic and Sullage Connect to mains sewer where available. Where not available, use treatment and . . . irrigation systems to disperse waste water (subject to environmental assessment).

During and after construction

Construction

Review of plans with a qualified Geotechnical Practitioner if uncertain of compliance guidelines. Have the Geotechnical Practitioner visit the site as appropriate during construction.

Landscaping

Observe earthworks and drainage recommendations when landscaping. Revegetate cleared areas.

Maintenance

Promptly clean blocked drainage systems, repair broken joins in drains and leaks in supply lines. If seepage is observed, establish the cause and seek advice on consequences and remedial works. Seek advice about any damage observed in structures on your property.

9, Golder 7/8 Associates

Mr Adam Garrisson 1523668-001-L-Rev1 Burnham Beeches Pty Ltd 24 February 2015

SUMMARY AND CONCLUSIONS Our assessment has not identified any credible landslide or slope stability hazards on this site that we expect could influence the proposed development.

We have no general concerns with this land being used for the proposed residential purposes. However, as mentioned previously, any permit application for buildings and works should include a more detailed geotechnical assessment. This could be a condition of any future permit.

To avoid the development creating hazards, development should accord with good hillside practice and the requirements of the Yarra Ranges Erosion Management Overlay.

We trust the advice presented in this letter is suitable for your requirements at this time. If you have any questions, please feel free to contact the undersigned.

Yours Sincerely

GOLDER ASSOCIATES PTY LTD

e MLied Chris Haberfield Principal

DRP/CMH/drp

Attachments: Limitations Hillside Construction Practice (Australian Geoguide LR8)

j: \ geo \2015 \1523668 - burnham beeches, emo assessment, sherbrooke \correspondence out \1523668-001-1-revl burnham beeches report.docx

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Associates

EXAMPLES OF GOOD HILLSIDE CONSTRUCTION PRACTICE 'X*

Vegetation retained

Surface water interception drainage

Watertight, adequately sited and founded roof water storage tanks (with due regard for impact of potential leakage) -

Flexible structure

Roof water piped off site or stored

On-site detention tanks, watertight and adequately founded. Potential leakage managed by sub-soil drains

MANTLE OF SOIL AND ROCK FRAGMENTS (COLLUVIUM)

-Pier footings into rock —Subsoil drainage may be

required in slope Cutting and filling minimised in development

Sewage effluent pumped out or connected to sewer. Tanks adequately founded and watertight. Potential leakage managed by sub-soil drains

Engineered retaining walls with both surface and - subsurface drainage (constructed before dwelling)

Vegetation retained

OFF STREET PARKING

BEDROCK

ROADWAY

AGS (2007) See also AGS (2000) Appendix J

AUSTRALIAN GEOGUIDE LR8 (CONSTRUCTION PRACTICE)

HILLSIDE CONSTRUCTION PRACTICE Sensible development practices are required when building on hillsides, particularly if the hillside has more than a low risk of instability (GeoGuide LR7). Only building techniques intended to maintain, or reduce, the overall level of landslide risk should be considered. Examples of good hillside construction practice are illustrated below.

WHY ARE THESE PRACTICES GOOD?

Roadways and parking areas - are paved and incorporate kerbs which prevent water discharging straight into the hillside (GeoGuide LR5). Cuttings - are supported by retaining walls (GeoGuide LR6). Retaining walls - are engineer designed to withstand the lateral earth pressures and surcharges expected, and include drains to prevent water pressures developing in the backfill. Where the ground slopes steeply down towards the high side of a retaining wall, the disturbing force (see GeoGuide LR6) can be two or more times that in level ground. Retaining walls must be designed taking these forces into account. Sewage - whether treated or not is either taken away in pipes or contained in properly founded tanks so it cannot soak into the ground. Surface water - from roofs and other hard surfaces is piped away to a suitable discharge point rather than being allowed to infiltrate into the ground. Preferably, the discharge point will be in a natural creek where ground water exits, rather than enters, the ground. Shallow, lined, drains on the surface can fulfil the same purpose (GeoGuide LR5). Surface loads - are minimised. No fill embankments have been built. The house is a lightweight structure. Foundation loads have been taken down below the level at which a landslide is likely to occur and, preferably, to rock. This sort of construction is probably not applicable to soil slopes (GeoGuide LR3). If you are uncertain whether your site has rock near the surface, or is essentially a soil slope, you should engage a geotechnical practitioner to find out. Flexible structures - have been used because they can tolerate a certain amount of movement with minimal signs of distress and maintain their functionality. Vegetation clearance - on soil slopes has been kept to a reasonable minimum. Trees, and to a lesser extent smaller vegetation, take large quantities of water out of the ground every day. This lowers the ground water table, which in turn helps to maintain the stability of the slope. Large scale clearing can result in a rise in water table with a consequent increase in the likelihood of a landslide (GeoGuide LR5). An exception may have to be made to this rule on steep rock slopes where trees have little effect on the water table, but their roots pose a landslide hazard by dislodging boulders. Possible effects of ignoring good construction practices are illustrated on page 2. Unfortunately, these poor construction practices are not as unusual as you might think and are often chosen because, on the face of it, they will save the developer, or owner, money. You should not lose sight of the fact that the cost and anguish associated with any one of the disasters illustrated, is likely to more than wipe out any apparent savings at the outset.

ADOPT GOOD PRACTICE ON HILLSIDE SITES

174 Australian Geomechanics Vol 42 No 1 March 2007

Inadequately supported cut fails

Unstabilised rock topples and travels downslope Vegetation removed

Steep unsupported cut fails Discharges of roofwater soak away rather than conducted offsite or to secure storage for re-use

Structure unable to tolerate settlement and cracks

Poorly compacted fill settles

' / 1

unevenly and cracks pool

Inadequate walling unable to support fill

NTLE1OF SOIL; ROCK FRAGMENTS \VCOLLUVIUAN

BEDROCK , Absence of subsoil drainage within fill

- Loose, saturated fill slides and possibly flows downslope

- Ponded water enters slope and activates landslide AGS (2007)

Possible travel downslope which impacts other development downhill See aho AGS (2000)Apixmd.x

Saturated slope fails

Vegetation removed -

Mud flow occurs

RoofiNater introduced into slope

Dwelling not founded in bedrock

AUSTRALIAN GEOGUIDE LR8 (CONSTRUCTION PRACTICE)

EXAMPLES OF POOR HILLSIDE CONSTRUCTION PRACTICE

WHY ARE THESE PRACTICES POOR?

Roadways and parking areas - are unsurfaced and lack proper table drains (gutters) causing surface water to pond and soak into the ground. Cut and fill - has been used to balance earthworks quantities and level the site leaving unstable cut faces and added large surface loads to the ground. Failure to compact the fill properly has led to settlement, which will probably continue for several years after completion. The house and pool have been built on the fill and have settled with it and cracked. Leakage from the cracked pool and the applied surface loads from the fill have combined to cause landslides. Retaining walls - have been avoided, to minimise cost, and hand placed rock walls used instead. Without applying engineering design principles, the walls have failed to provide the required support to the ground and have failed, creating a very dangerous situation. A heavy, rigid, house - has been built on shallow, conventional, footings. Not only has the brickwork cracked because of the resulting ground movements, but it has also become involved in a man-made landslide. Soak-away drainage - has been used for sewage and surface water run-off from roofs and pavements. This water soaks into the ground and raises the water table (GeoGuide LR5). Subsoil drains that run along the contours should be avoided for the same reason. If felt necessary, subsoil drains should run steeply downhill in a chevron, or herring bone, pattern. This may conflict with the requirements for effluent and surface water disposal (GeoGuide LR9) and if so, you will need to seek professional advice. Rock debris - from landslides higher up on the slope seems likely to pass through the site. Such locations are often referred to by geotechnical practitioners as "debris flow paths". Rock is normally even denser than ordinary fill, so even quite modest boulders are likely to weigh many tonnes and do a lot of damage once they start to roll. Boulders have been known to travel hundreds of metres downhill leaving behind a trail of destruction. Vegetation - has been completely cleared, leading to a possible rise in the water table and increased landslide risk (GeoGuide LR5).

DON'T CUT CORNERS ON HILLSIDE SITES - OBTAIN ADVICE FROM A GEOTECHNICAL PRACTITIONER

More information relevant to your particular situation may be found in other Australian GeoGuides:

• GeoGuide LR1 • GeoGuide LR2 • GeoGuide LR3 • GeoGuide LR4 • GeoGuide LR5

- Introduction - Landslides - Landslides in Soil - Landslides in Rock - Water & Drainage

• GeoGuide LR6 • GeoGuide LR7 • GeoGuide LR9

GeoGuide LR10 GeoGuide LR11

- Retaining Walls - Landslide Risk - Effluent & Surface Water Disposal - Coastal Landslides - Record Keeping

The Australian GeoGuides (LR series) are a set of publications intended for property owners; local councils; planning authorities; developers; insurers; lawyers and, in fact, anyone who lives with, or has an interest in, a natural or engineered slope, a cutting, or an excavation. They are intended to help you understand why slopes and retaining structures can be a hazard and what can be done with appropriate professional advice and local council approval (if required) to remove, reduce, or minimise the risk they represent. The GeoGuides have been prepared by the Australian Geomechanics Society, a specialist technical society within Engineers Australia, the national peak body for all engineering disciplines in Australia, whose members are professional geotechnical engineers and engineering geologists with a particular interest in ground engineering. The GeoGuides have been funded under the Australian governments' National Disaster Mitigation Program.

Australian Geomechanics Vol 42 No 1 March 2007 175

Golder Associates

LIMITATIONS

This Document has been provided by Golder Associates Pty Ltd ("Golder") subject to the following limitations:

This Document has been prepared for the particular purpose outlined in Golder's proposal and no responsibility is accepted for the use of this Document, in whole or in part, in other contexts or for any other purpose.

The scope and the period of Golder's Services are as described in Golder's proposal, and are subject to restrictions and limitations. Golder did not perform a complete assessment of all possible conditions or circumstances that may exist at the site referenced in the Document. If a service is not expressly indicated, do not assume it has been provided. If a matter is not addressed, do not assume that any determination has been made by Golder in regards to it.

Conditions may exist which were undetectable given the limited nature of the enquiry Golder was retained to undertake with respect to the site. Variations in conditions may occur between investigatory locations, and there may be special conditions pertaining to the site which have not been revealed by the investigation and which have not therefore been taken into account in the Document. Accordingly, additional studies and actions may be required.

In addition, it is recognised that the passage of time affects the information and assessment provided in this Document. Golder's opinions are based upon information that existed at the time of the production of the Document. It is understood that the Services provided allowed Golder to form no more than an opinion of the actual conditions of the site at the time the site was visited and cannot be used to assess the effect of any subsequent changes in the quality of the site, or its surroundings, or any laws or regulations.

Any assessments made in this Document are based on the conditions indicated from published sources and the investigation described. No warranty is included, either express or implied, that the actual conditions will conform exactly to the assessments contained in this Document.

Where data supplied by the client or other external sources, including previous site investigation data, have been used, it has been assumed that the information is correct unless otherwise stated. No responsibility is accepted by Golder for incomplete or inaccurate data supplied by others.

Golder may have retained subconsultants affiliated with Golder to provide Services for the benefit of Golder. To the maximum extent allowed by law, the Client acknowledges and agrees it will not have any direct legal recourse to, and waives any claim, demand, or cause of action against, Golder's affiliated companies, and their employees, officers and directors.

This Document is provided for sole use by the Client and is confidential to it and its professional advisers. No responsibility whatsoever for the contents of this Document will be accepted to any person other than the Client. Any use which a third party makes of this Document, or any reliance on or decisions to be made based on it, is the responsibility of such third parties. Golder accepts no responsibility for damages, if any, suffered by any third party as a result of decisions made or actions based on this Document.

GOLDER ASSOCIATES PTY LTD GAP Form No. LEG 04 RL 1

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