REPORT - Planning...Golder's letter dated 15 September 2017 (ref: 1787175-001-L-Rev0) APPENDIX C Site photographs (2 & 3 October 2017) APPENDIX D Important information relating to

1 November 2017

LANDSLIDE RISK ASSESSMENT

Apollo Bay Resort 275-305 Barham River RoadApollo Bay

REPO

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Report Number. 1787175-002-R-Rev1 Distribution: Irwinconsult Pty Ltd - 1 copy Godfrey Spowers (Victoria) Pty Ltd - 1 copy Golder Associates Pty Ltd - 1 copy

Submitted to:Irwinconsult Pty Ltd Level 3, 289 Wellington Parade South EAST MELBOURNE VIC 3002

APOLLO BAY RESORT - LANDSLIDE RISK ASSESSMENT

1 November 2017 Report No. 1787175-002-R-Rev1

Executive Summary

Irwinconsult Pty Ltd (Irwinconsult) has engaged Golder Associates Pty Ltd (Golder) to perform a landslide risk assessment (LRA) associated with the proposed Apollo Bay Resort located at 275 – 305 Barham River Road, Apollo Bay.

The proposed development is located about 3.5 km southwest of Apollo Bay in southwest Victoria. The site covers an area of approximately 100 hectares and is bound to the north by Barham River Road and Old Hordern Vale Access and to the east, west and south by private property. The Barham River is located to the north of the site. The proposed development comprises a hotel building with up to three above ground levels, several one to two level villa units and associated site access roads and services.

The geological history of the site appears complex with the main topographical features inferred to have developed over geological time as a result of tectonic activity (uplift and faulting), coastal inundation and erosion and more recent erosion and flooding associated with the Barham River. There are ridges with inferred shallow rock to the north, west and south of the central part of the site. The central part of the site is inferred to comprise relatively deep (more than 5 m deep) soil deposits. Historically, the central part of the site may have been inundated as a result of water impounded by a landslide dam or other temporary blockage of the Barham River northeast of the site.

Where soil slopes are steeper than about 18° and unfavourable drainage conditions are present (e.g. groundwater seepage or toe saturation/erosion) there are numerous examples of rotational landslides or earthflows. There does not appear to be evidence of significant recent instability on slopes shallower than about 15°, particularly where slopes are vegetated or have good drainage. The following landslide hazards have been identified that in the absence of risk mitigation measures pose intolerable risk levels to property and/or life:

Debris runout from the very steep slopes near the northern and southern site boundaries.

Rotational landslides or earthflows within the soil deposits in the central part of the site.

Rock fall and rotational landslides associated with the old access road near the northern site boundary.

Lateral spreading associated with a recurrence of a landslide dam/extreme flooding event.

We consider there to be three main approaches available to reduce risk to tolerable levels, as follows:

Relocate the elements at risk. This will require revision of the current development plan. A plan showing approximate landslide risk zones is included in this report to assist with planning for future development.

Engineering works including restrictions on earthworks, supporting buildings on piled footings, the provision of surface and subsurface drainage and revegetation of slopes (where practical given bushfire management considerations).

Development and implementation of a formal monitoring and response plan to help identify and respond to slope stability issues should they arise over the design life of the development.

Development of the mitigation measures (e.g. engineering design requirements and the development and implementation of a formal monitoring and response plan) will require additional investigation and assessment/analysis, which should be done as part of detailed design for the proposed development. This LRA should be revised and updated once these additional works have been performed and details of the proposed development are confirmed.

Subject to the implementation of the remedial measures in accordance with our recommendations, we consider it practical and feasible to reduce the landslide risk level to meet the tolerable risk set out in the Colac Otway Planning Scheme, Schedule 1 to the Erosion Management Overlay.


1 November 2017 Report No. 1787175-002-R-Rev1 i

Table of Contents

1.0 ENGAGEMENT ............................................................................................................................................................. 1

2.0 PROPOSED DEVELOPMENT ...................................................................................................................................... 1

3.0 OBJECTIVES ................................................................................................................................................................ 1

4.0 GEOTECHNICAL PRACTITIONER DETAILS ............................................................................................................. 1

5.0 EXISTING INFORMATION ........................................................................................................................................... 2

6.0 SITE OBSERVATIONS ................................................................................................................................................. 6

7.0 CONCEPTUAL GEOTECHNICAL MODEL ................................................................................................................. 9

8.0 METHOD OF LANDSLIDE RISK ASSESSMENT ..................................................................................................... 10

9.0 HAZARD IDENTIFICATION........................................................................................................................................ 11

10.0 RISK TO PROPERTY ................................................................................................................................................. 14

11.0 RISK TO LIFE ............................................................................................................................................................. 17

12.0 RISK MITIGATION ...................................................................................................................................................... 21

13.0 SOCIETAL RISK ......................................................................................................................................................... 25

14.0 CONCLUSIONS .......................................................................................................................................................... 26

15.0 REFERENCES ............................................................................................................................................................ 26

16.0 IMPORTANT INFORMATION ..................................................................................................................................... 26

TABLES Table 1: Assessment of risk level to property (current conditions) ...................................................................................... 17

Table 2: Assessment of risk to life (current conditions) ....................................................................................................... 21

Table 3: Proposed risk mitigation measures ........................................................................................................................ 24

PLATES Plate 1: Geological map of the site from the GeoVic website (1:50 000 scale seamless geology) ...................................... 2

Plate 2: Hillshade imagery of the site and surrounding areas derived from LiDAR (provided by ASMG). Examples of linear features are highlighted. .......................................................................................................................... 4

Plate 3: Larger scale hillshade image of the site derived from LiDAR (image provided by ASMG)...................................... 4

Plate 4: Annual rainfall totals for Apollo Bay (Bureau of Meteorology) .................................................................................. 5

Plate 5: Monthly rainfall records for Apollo Bay (Bureau of Meteorology) ............................................................................. 6

Plate 6: Cross-section A-A (vertical exaggeration of 2:1) showing indicative hazards (Hazards 3 and 4 relevant to the old access road are not shown) .................................................................................................................... 12

Plate 7: Chart representing 'tolerable' societal risk for landslides (graph based on ANCOLD, 2003) ................................ 25


1 November 2017 Report No. 1787175-002-R-Rev1 ii

FIGURES

Figure 1 – Site topography

Figure 2 – Development plan

Figure 3 – Site observations

Figure 4 – Slope angle

Figure 5 – Elevation

Figure 6 – Indicative landslide risk zones (risk to buildings)

APPENDICES APPENDIX AColac Otway Planning Scheme Schedule 1 to the Erosion Management Overlay

Résumé for Dr Stuart Colls

AGS 2007 Landslide risk management guidelines – Appendix C

APPENDIX BGolder's letter dated 15 September 2017 (ref: 1787175-001-L-Rev0)

APPENDIX CSite photographs (2 & 3 October 2017)

APPENDIX DImportant information relating to this report (LEG04, RL2)


1 November 2017 Report No. 1787175-002-R-Rev1 1

1.0 ENGAGEMENT Irwinconsult Pty Ltd (Irwinconsult) has engaged Golder Associates Pty Ltd (Golder) to provide geotechnical consulting services associated with the proposed Apollo Bay Resort located at 275 – 305 Barham River Road, Apollo Bay. We understand that Irwinconsult are the structural engineers engaged by the developer (Oceans United Investments), with architectural services provided by Godfrey Spowers (Victoria) Pty Ltd (Spowers).

The landslide risk assessment (LRA) set out in this report has been undertaken in general accordance with the ‘Stage 2’ scope set out in our proposal dated 6 September 2017. Approval to proceed was provided by Irwinconsult in an email dated 11 September 2017. We have revised our report in response to discussion at a project meeting on 31 October 2017.

2.0 PROPOSED DEVELOPMENT The proposed development is located about 3.5 km southwest of Apollo Bay in southwest Victoria as indicated on Figure 1. The main topographical features referred to in this report are also highlighted on Figure 1. The site covers an area of approximately 100 hectares and is bound to the north by Barham River Road and Old Hordern Vale Access and to the east, west and south by private property.

Figure 2 shows the proposed development plan based on information provided by Irwinconsult (Spowers drawing SK_MP.01 dated 15 June 2017). The proposed development comprises a hotel building with up to three above ground levels, several one to two level villa units and associated site access roads and services. The majority of the proposed development is within the northern half of the site, although future expansion is planned in the southern half of the site. Other information provided by Irwinconsult (Spowers drawings SK_MP.02 and SK_MP_A.06 dated June 2017) indicates earthworks including retaining walls (maximum height about 7 m but typically less than 3 m high) beneath the proposed hotel building and villa units.

Based on discussions at a site meeting between the developer, Golder, Spowers and Irwinconsult on 3 October 2017, we understand that the proposed building layout and earthworks will be revised taking into consideration the information presented in this report. For the purpose of this report we have assumed that new earthworks associated with the development will typically be minor, i.e. cut and fill typically less than 1 m depth. We understand there will be local areas (e.g. lift overrun pits) where deeper excavation (which will require permanent excavation support) is required.

3.0 OBJECTIVES The objectives of the LRA are to:

Estimate the risk to life and property for the proposed development.

Compare the assessed risks with the tolerable risk criteria set out in the Colac Otway Planning Scheme, Schedule 1 to the Erosion Management Overlay (EMO1, copy included in Appendix A).

Recommend landslide risk mitigation measures, where required.

Prepare a map of indicative landslide risk zones to assist in the planning of future development.

4.0 GEOTECHNICAL PRACTITIONER DETAILS This LRA has been prepared by Dr Stuart Colls (BSc, BE(Hons), PhD, MIEAust CPEng) based on field observations made during a site visit performed on 2 and 3 October 2017 and review of publically available information and reports of intrusive investigations at the site made available by Irwinconsult (refer Section 5).



Dr Colls has over 15 years of geotechnical engineering experience including slope stability assessments relating to natural and man-made slopes in and around Melbourne and more widely within parts of Victoria and Queensland. Recent experience near Apollo Bay includes assessments relating to redevelopment of the Wye River and Separation Creek townships following the December 2015 bushfires, and assessments at specific locations on the Great Ocean Road between Kennett River and Anglesea. A brief résumé for Dr Colls is included in Appendix A of this report.

5.0 EXISTING INFORMATION A copy of Golder’s geotechnical desktop assessment (letter dated 15 September 2017, ref: 1787175-001-L-Rev0) is included in Appendix B of this report. The desktop assessment was performed based on a review of available information including Bruce Hollioake Consulting & Civil Engineers (BH) report dated 26 June 2017 (ref: 17310) titled ‘Geotechnical assessment and land stability assessment report’. The general concepts and background information presented in the desktop assessment are relevant to this LRA. However, we have updated the conceptual geotechnical model (Section 7.0) based on observations from the site visit including discussions with A.S. Miner Geotechnical Consulting Engineers (ASMG), geotechnical consultant to Colac Otway Shire (COS).

In addition to the information referred to in our desktop assessment, we have reviewed information shown on hillshade images for the site derived from LiDAR (provided to us by ASMG), published geological information accessed via the Victorian Department of Economic Development, Jobs, Transport and Resources ‘GeoVic’ website1 and Bureau of Meteorology (BoM) rainfall data. A copy of the GeoVic geological map (1:50 000 scale seamless geology) is presented in Plate 1. The geological units shown on this map are discussed below Plate 1.

Plate 1: Geological map of the site from the GeoVic website (1:50 000 scale seamless geology)

1 http://er-info.dpi.vic.gov.au/sd_weave/anonymous.html

Koe

Koe

Koe

Koe

Qa1

Qc1

Qc1

Pww

Pww

Pww

Qdl1

Qdl1

‘Skenes Creek’ shear displacement structure

Approximate site location



The GeoVic website provides the following information regarding the geological units shown on Plate 1:

Koe: Early Cretaceous age Eumeralla Formation predominantly comprising sandstone, mudstone, conglomerate and siltstone.

Pww: Late Cretaceous to Paleocene age Wiridjil Gravel fluival deposits predominantly comprising gravel, sand and clay.

Qc1: Quaternary (Pliocene to Holocene) age colluvium comprising rubble, clay, silt sand and gravel.

Qa1: Quaternary (Pleistocene to Holocene) age alluvium predominantly comprising silt and gravel.

Qld1: Quaternary (Holocene) age coastal dune deposits predominantly comprising silt, sand and clay.

The GeoVic website also indicates the presence of an inferred fault (Skenes Creek displacement structure) close to the northern boundary of the site.

As will be discussed in Section 7.0, our site observations indicate the geology of the site is more complex than indicated on the published information. Other than on ridges, the Eumeralla Formation materials do not outcrop at the ground surface at the site.

Annotated copies of the hillshade images derived from LiDAR (provided by ASMG) are presented in Plates 2 and 3.

A review of the imagery on Plate 2 indicates the presence of several linear valley and ridgeline features that are inferred to be surface expressions of fault/shear zones. These linear features are typically oriented either WNW-ESE or NE-SW. However, there also appear to be some NW-SE oriented features, particularly in the Barham River/Barham River West Branch valleys to the west of the site. There is evidence for offset across some of these linear features which indicates different episodes of faulting. The site appears to be located close to the intersection of several of these shear zones. Quigley et al. (2010)2 indicate that there has been ongoing tectonic activity in the Otway Ranges over the last 5 to 10 million years with an average uplift rate in the order of 100 m per 1 million years. This uplift rate suggests that the western boundary of the site may have been at an elevation close to current sea level about 1 million years ago.

It is also important to note from Plate 2 that the geomorphology of the proposed development site is different to the typical steep sided valleys and ridgelines that characterise the landscape away from the coast and Barham River mouth in the Apollo Bay region.

2 Quigley, M., Clark, D. & Sandiford, M. (2010). ‘Tectonic geomorphology of Australia’ in Australian Landscapes, Geological Society (London) Special Publication 346, pp. 243-265.



Plate 2: Hillshade imagery of the site and surrounding areas derived from LiDAR (provided by ASMG). Examples of linear features are highlighted.

Plate 3: Larger scale hillshade image of the site derived from LiDAR (image provided by ASMG).

Approximate site location

North

N

Approximate site boundary

Colluvium eroded by Barham River

Proposed hotel site

Apollo Bay township

Linear features (upper/west and lower/east)

Conical shaped hill to the east of the site

Steep slopes on the north flank of the south ridge



The following observations are provided following a review of the hillshade image presented as Plate 3. These observations relate to site features discussed in more detail in Section 6.0. Refer to Figure 1 for the locations of key topographic features such as the main dam, north and south ridge, and north and south watercourses.

There are two linear features that cross the central part of the site. The upper/west feature (which extends beneath the proposed hotel site) is oriented roughly WNW-ESE. The lower/east feature is oriented roughly NNW-SSE. There may be a third linear feature west of the main dam/site boundary but it is less distinct.

Within the site boundaries, the ground surface between the south ridge and south watercourse appears more hummocky than the ground to the north of the watercourse that flows out of the main dam.

There is a conical shaped hill of unusual geomorphological appearance to the east of the site boundaries. Inferred colluvial deposits to the north of this hill appear to have been eroded by the Barham River and we consider it is possible that colluvial materials have historically blocked/dammed the Barham River to the north of this hill.

The steep slopes on the north flank of the south ridge are inferred to represent the headscarp of a former landslide or landslides. The inferred scarp appears to extend to the west and east of the subject site, and may rotate towards the north on the west flank of the conical shaped hill.

The north watercourse (south of the north ridge) appears to be more deeply incised than the south watercourse.

Plate 4 shows the total annual rainfall recorded at the BoM’s Apollo Bay monitoring station (opened in 1898, noting there are some years with data gaps). Plate 5 shows the mean and median monthly rainfall totals for Apollo Bay including monthly rainfall totals recorded for 2017.

Plate 4: Annual rainfall totals for Apollo Bay (Bureau of Meteorology)

90th percentile (approx.)



Plate 5: Monthly rainfall records for Apollo Bay (Bureau of Meteorology)

We provide the following comments relating to the BoM data for Apollo Bay.

The mean annual rainfall total is 1058 mm (the median total is 1042 mm). An annual rainfall total of 1273 mm represents the 90th percentile (i.e. 10% of rainfall records are above 1273 mm). The highest annual rainfall on record was 1600 mm in 1952.

Rainfall totals above the mean were recorded in six of the last eight years. The annual rainfall totals in 2010 (1367 mm), 2013 (1280 mm) and 2016 (1271 mm) were close to or above the 90th percentile. The total rainfall recorded to September 2017 (994 mm) is 122% of the mean to the end of September.

The rainfall data indicates that the last eight years in Apollo Bay have been relatively wet. Furthermore, the September 2017 rainfall total (223 mm) is the highest September total on record for Apollo Bay and more than double the mean September rainfall. Hence, the site visit was performed following what appear to have been unusually wet conditions. However, we note that there were periods in the 1920s to 1930s and early 1950s in particular that have been wetter.

6.0 SITE OBSERVATIONS The location and topography of the site is shown on Figure 1. Observations made during our site visit, including the approximate locations of the site photographs included in Appendix C, are shown on Figure 3. Figures 4 and 5 illustrate the variation in slope angle and elevation respectively, based on feature survey and contour information provided to us by Spowers and Irwinconsult. The following observations were made during the site visit:

At the time of our visit the weather was dry and generally partly cloudy. Ground surface conditions were typically wet and boggy, particularly near watercourses. These conditions likely reflect the recent unusually wet conditions in September 2017.

The proposed hotel site straddles the northwest end of the upper/east linear features described in Section 5.0. Slopes below the proposed hotel are typically down towards the northwest at about 15° to 20° below the horizontal. Slopes are gentle (typically about 5° to 8°) above (west of) and below (east of) this linear feature. With reference to Photographs 1 to 4 there are undulations in the slope beneath the



proposed hotel site that may represent soil creep or evidence of previous (not recent) erosion or rotational failure. Some areas with rushes (long grass) were observed that may indicate poor drainage. We understand that rushes are often found near fresh water.

The main dam was full at the time of our site visit (Photographs 5 to 10), with water overflowing via a channel at the south end of the dam wall. Water from this channel eventually flows into the south watercourse. The dam does not appear to have a formal spillway. Some evidence of erosion was observed at the upstream crest (Photograph 6). The downstream face of the dam wall slopes down at about 22°.

Evidence of shallow slumping and wet ground was observed on the slopes to the west of the dam, near the west boundary of the site (Photographs 11 and 12). The slopes in the area to the west of the dam are steeper than in the areas immediately north, south and east of the dam. Water was observed in the watercourse flowing through this area into the dam from the west. The flow rate in this watercourse appeared to be slightly less than the rate of water flowing out of the dam.

Evidence of shallow slumping was also observed in the slopes above the dam located within the north watercourse, northeast of the proposed hotel site (Photograph 13). Similar shallow slumping was observed above the water level in dams elsewhere on the site (e.g. Photograph 44).

The watercourse east of the main dam wall has eroded a steeply incised gully where it crosses the upper/east linear feature south of the proposed hotel site (Photographs 14 to 16). Evidence of ongoing erosion and shallow slumping was observed in the banks of this gully.

The area of the proposed hotel expansion/conference centre on the north side of the south watercourse is (other than where it is crossed by the linear feature) generally characterised by gentle slopes incised by drainage features (Photographs 30 to 33).

Trees observed in gullies to the north and south of the proposed hotel site generally appear to have vertical trunks (e.g. Photograph 17). Bowed trunks can indicate ongoing slope movement or soil creep – some bowed or tilting trees were observed within areas where tree planting appears to have taken place as part of remedial measures for landslides (e.g. above wet ground in Photograph 18). Site fences and powerlines did not appear to have been displaced by slope movement. Review of aerial photographs (refer Appendix B) indicates the majority of revegetation works took place after 1993.

An inferred relict headscarp was observed near the northwest corner of the site (Photographs 21 and 22). The slope of the headscarp is very steep (about 35°) down towards the north. Gentle slopes immediately below this headscarp are inferred to represent landslide debris. The relict headscarp appears to extend west towards the driveway to 105 Old Hordern Vale Access (Photographs 23 and 24) and there appear to be additional relict scarps and debris down towards the Barham River West Branch below Old Hordern Vale Acccess. Boulders were observed on and near the base of the headscarp. Rock is inferred to be present at a relatively shallow depth below the scarp surface.

The north ridge (Photographs 20 and 26) comprises a broad ridge that slopes down towards the east at between about 12° and 14°, with steeper slopes down towards the north watercourse on the south side of this ridge, and the Barham River/Barham River West Branch on the north side of this ridge. There are some boulders exposed at the ground surface level along this ridge (Photograph 26). Weathered sandstone is exposed at about 1.5 m depth in cut batters uphill of the old access road on the north side of the north ridge (Photographs 65 and 66). The BH report indicates this road was built in 2002 by excavating into weathered sandstone at its base, with minimal filling to build the road. Weathered sandstone is exposed in what we understand to be a former quarry near the intersection of Barham River Road and Old Hordern Vale Access (Photographs 69 and 70). A fault was observed in the sandstone exposed in the quarry – this inferred fault trends approximately east-west (strike approximately 86° relative to magnetic north), i.e. it is roughly parallel to the north ridge. No rock outcrop was observed at the base of the watercourses within the central part of the site.



An unsurfaced track has been cut along part of the north ridge extending west of the old access road. There is evidence for shallow slumping at some locations, particularly close to the entrance of culverts that pass under the track (Photograph 25).

The south ridge (e.g. Photograph 36) is characterised by very steep slopes on its north flank (typically 30° to 32°) which slope down to meet a series of gently sloping ‘terraced’ areas separated by moderate to steep batter slopes above the south watercourse.

There is frequent evidence for rotational landslides and earthflows within the steep batter slope below the uppermost terrace below the south ridge. Photographs 37 to 40 show a rotational landslide located near the intersection of this steep slope and the south watercourse. This landslide is inferred to be less than about 10 years old and measures about 30 m wide by 40 m long by 3 m deep (volume of about 3600 m3). The maximum debris run-out distance is estimated to be about 10 m. Some boulders were observed within the debris along with groundwater seepage. The boulders are inferred to be colluvial materials from earlier landslides (e.g. much older landslides on the north flank of the south ridge). We note that the landslide is not apparent in the 1991 aerial photograph (Appendix B), which shows that there was formerly a dam located within the south watercourse near the toe of the landslide.

Other (generally older) rotational landslides observed within this steep batter slope below the uppermost terrace include those shown in Photographs 41 and 42, 54, 56 to 60 and 64. Some areas re-vegetated with trees on this batter slope are inferred to represent relict landslides. The largest of these landslides appears to be that shown in Photographs 56 and 59, which has estimated dimensions of about 150 m wide by 100 m long is inferred to be about 3 m deep (volume approximately 45 000 m3). However, it is difficult to identify if this area represents a single landslide or several adjacent landslides. The driveway to the homestead crosses the landslide debris and headscarp (Photograph 59) and there is an area of standing water above the landslide (Photograph 58). The driveway and arcuate landslide headscarp features can be identified in the 1978 aerial photograph (refer Appendix B). By 1983 vegetation can be observed at this location. The 1952 photograph is not sufficiently clear to assess if the landslide was present earlier.

The lowest ‘terrace’ above the south watercourse is generally characterised by gentle slopes incised by drainage features (Photographs 47 to 50). The presence of rushes indicates wet ground within these drainage paths. The wall of a former dam within the south watercourse appears to have been breached by erosion (Photograph 51). This former dam can be observed in the 1991 aerial photograph.

There appear to be numerous examples of rotational landslides, earthflows and creep on the slopes below the south ridge to the east of the site boundary (Photograph 54), including features on the west flank of the conical shaped hill to the east of the site (Photograph 74). We note that the toe of these slopes intersect the flood plain of the Barham River. Photograph 52 shows the meeting of the flood plain and the slopes that lead up to the hotel site (and north ridge).

Photographs 71 and 72 show the typical slopes above the Barham River and Barham River West Branch to the north of the site. These photographs indicate the presence of a flat floodplain above the river (which is located within an eroded channel within the floodplain), meeting slopes that appear to comprise colluvium below very steep hillsides. Slopes on the north side of the Barham River, east of the site (Photographs 73 and 75 to 77) are steep to very steep with some exposed rock (it is unclear if the rock represents boulders or outcrop). A review of historic aerial photographs indicates the trees on the east side of the Barham River visible in Photographs 75 and 76 were planted between 1952 and 1978. Revegetation may have been done to reduce erosion/improve the stability of this east bank of the river.

Discussions with the property owner (Mr Frank Buchanan) and ASMG indicated that Barwon Water had at one time planned to build a water storage facility near the base of the conical shaped hill to the east of the site. Anecdotal records from a current Golder employee employed by GHD Pty Ltd when geotechnical investigations for this water storage facility were underway indicated that the investigation encountered variable subsurface materials including a deep (greater than 6 m) soil profile that included normally consolidated soils, and rock at variable elevations that was inferred to be indicative of faulting. Mr Buchanan indicated that excavation for the main dam encountered a soil profile at least 6 m deep.



From discussions with Mr Buchanan we understand the homestead in the southeast corner of the site was completed in about 2010. This indicates that the date of the aerial photograph presented as Figure A5 of our geotechnical desktop assessment is later than 2005 as indicated on the Nearmap website.

7.0 CONCEPTUAL GEOTECHNICAL MODEL We consider the indicative block diagram presented as Figure 6 of our geotechnical desktop assessment (Appendix B) to be broadly accurate, in that the north ridge and south ridge are inferred to comprise shallow rock and the central part of the site comprises relatively deep soil deposits. There is also a ridge of inferred shallow rock to the west of the site, typically more than 250 m west of the boundary fence. The very steep slopes to the south and west represent potential locations of rotational landslides and earthflows into the central part of the site. However, slopes on the south flank of the north ridge are more moderate (slopes on the north flank of the north ridge are very steep). Plate 6 (Section 9.0) presents a cross-section drawn through the central part of the site to illustrate the typical slopes.

The gentle slopes within the central part of the site are atypical of slopes at the same elevation in the Otway Ranges, which are typically very steep and likely to have beenformed by a combination of toe erosion (e.g. by the Barham River or other watercourses) in combination with erosion and instability of the resulting oversteep slopes. Periods of high rainfall and episodic seismicity are also likely to be factors contributing to landslides in the Otway Ranges.

Site observations suggest that where rock is present at a shallow depth the slope angle is up to about 35°. The absence of steep slopes within the central part of the site, together with the lack of rock outcrop in watercourses or at the toe of the linear features and anecdotal evidence regarding subsurface conditions, suggests the soil profile within the central part of the site is at least 5 m deep. Where soil slopes are steeper than about 18° and unfavourable drainage conditions are present (e.g. groundwater seepage or toe saturation/erosion) there are numerous examples of rotational landslides or earthflows. There does not appear to be evidence of significant recent instability on slopes shallower than about 15°, particularly where slopes are vegetated or have good drainage.

The geological history of the site appears complex. In particular, the origin of the deeper soil profile within the central part of the site may remain unclear until further geotechnical investigation has been performed as part of detailed design for the proposed development. It appears unlikely that these soils comprise Eumeralla Formation materials (e.g. residual soils) as indicated on the geological map. Based on the available information and our site observations, we provide the following interpretation of the relevant geological history:

Tectonic activity over the last 5 to 10 million years has uplifted and faulted the Eumeralla Formation materials. The site appears to be located near the intersection of several faults and the overall rock mass may have been weakened as a result of this faulting, leading to preferential erosion compared to surrounding areas. In geological times (over the past 1 million years), the area may have been inundated by the sea exacerbating the erosion. The central part of the site may have been a coastal embayment or inlet when it was at sea level. The orientation and elevation of key topographic features such as the north and south ridges is likely to have been controlled by faulting.

When the central part of the site was inundated or close to sea level, erosion from wave action or the proto-Barham River may have led to instability of the rock slopes surrounding the inferred inlet/embayment. Siltstone beds may also have been present that were preferentially eroded in comparison to higher strength sandstone. Relatively high groundwater levels at this time, and episodic seismicity, may also have led to large to very large landslides on the rock slopes surrounding the inlet/embayment, e.g. the north flank of the south ridge. The deeper soil deposits within the central part of the site are likely to be predominantly colluvial in origin near the base of the very steep slopes but may include alluvial, lacustrine or marine deposits within the central part of the site.

The linear features observed on the slopes within the central part of the site are inferred to have been formed by the impoundment of water within the central part of the site/lower reaches of the Barham



River. The clear definition of these linear features on soil slopes suggests they post-date the period when the central part of the site was close to sea level (note the average rate of tectonic uplift ignores sea level changes due to climate impacts). We estimate that these features are in the order of 10,000 to 100,000 years old. With reference to Plate 2, the conical shaped hill and colluvial slopes north of the Barham River appear to provide a natural restriction to the river east of the site. If this restriction point was blocked, water levels within the central part of the site could potentially have risen to about RL 50 m (an elevation similar to the toe of the upper/west linear feature) before water could flow downstream past the conical shaped hill or slopes on the north side of the Barham River. Blockage could potentially have been a result of very large landslide to the north or south of the river (i.e. a valley-blocking landslide dam), or an accumulation of debris from landslides upstream within the Barham River catchment. The morphology of the linear features is generally consistent with lateral spreading towards the eastern outlet to this central part of the site. Lateral spreading is often observed in sediments as landslide dams are breached and water levels within the ‘dam’ recede. However, it is also possible the linear features (particularly the lower/east feature at approximately RL 30 m) were formed by extreme flooding of the Barham River. A key inference from our understanding of the geological history is that the processes which formed the upper/east linear feature beneath the proposed hotel site do not appear to be active.

We infer there to be ongoing erosion by the Barham River to the northeast of the site, noting that the 1:100 year flood level extends over the northeast corner of the site. Slopes at elevations close to the flood level (e.g. the east end of the south ridge) are expected to be more prone to slope instability due to the impact of higher groundwater levels and toe erosion during flooding. There is also ongoing erosion associated with the watercourses that cross the central part of the site. Recent revegetation of the watercourses is likely to help reduce the rate of erosion.

8.0 METHOD OF LANDSLIDE RISK ASSESSMENT The LRA presented in this report has been undertaken in general accordance with the Australian Geomechanics Society (AGS) landslide risk management guidelines (AGS 2007) and in particular the practice note guidelines for landslide risk management contained within that document (AGS 2007c). We consider the AGS 2007 guidelines to represent current best practice in landslide risk management in Australia.

A quantitative assessment of the risk to life and qualitative assessment of the risk to property has been undertaken based on our understanding of the proposed development and likely practical risk mitigation measures.

The process followed to undertake the risk assessment is set out below.

1) Identification of hazards that could impact property and people on site.

2) Assessment of the likelihood that the hazard, should it occur, could impact assets or persons at the site.

3) Assessment of the likelihood, that if the hazard occurs (for example reactivation of a landslide), that property or a person could be impacted.

4) Assessment of the likelihood that if a person is impacted, it would result in loss of life and an estimate of the level of damage to which property is likely to be subject if impacted by a landslide.

5) Comparison with the criteria for tolerable risk set out in EMO1.

6) If required, management recommendations to reduce the estimated risks to tolerable levels.



The quantitative risk assessment as set out in AGS 2007 estimates the annual probability of loss of life in accordance with the following equation:

R(LOL) = P(H) x P(S:H) x P(T:S) x V(D:T)

Where:

R(LOL) = the risk or annual probability of loss of life of an individual

P(H) = the annual probability that a landslide occurs

P(S:H) = the probability of impacting property (assets) or a person taking into account the scale and location of the landslide event

P(T:S) = the temporal spatial probability (e.g. of there being a person in a location at risk) given the spatial probability and allowing for evacuation if there is warning of the landslide event

V(D:T) = the vulnerability, or likelihood of death or permanent injury of the individual given they are impacted

Our assessment of risk to life includes an assessment of societal risk associated with the proposed hotel development (refer to Section 13.0). Societal risk is defined in AGS 2007 as ‘the risk of multiple fatalities or injuries in society as a whole: one where society would have to carry the burden of a landslide causing a number of deaths, injuries, financial, environmental and other losses.’

Risk to property has been assessed based on a qualitative assessment in accordance with Appendix C of AGS 2007c, which is included in Appendix A of this report. This assessment requires identification of hazards that could affect property or assets and provides a qualitative estimation of the likelihood and consequence of the hazard. Note that the likelihood parameter takes into account the probability that a landslide occurs and the probability of the landslide impacting property if it occurs.

We have interpreted the ‘tolerable’ risk criteria set out in EMO1 to be those set out in Tables 1 and C10 of AGS 2007, i.e. tolerable risk to life of 10-5 per annum for the person most at risk and tolerable risk of low for property with a structure importance level of 3.

‘Acceptable’ risks are generally considered to be one order of magnitude lower than ‘tolerable’ risks.

9.0 HAZARD IDENTIFICATION Based on the conceptual site model we have identified five landslide hazards at the site. A description of each hazard identified is provided below. Example locations for the hazards are indicated on Figure 3 (Hazards 1 to 5) and Plate 9 (Hazards 1, 2 and 5 only). Note we have not assessed soil creep or erosion of the watercourses as landslide hazards. Other than at locations affected by landslide (e.g. Hazard 1), no significant evidence of soil creep was observed. We recommend that potential erosion hazards are addressed during detailed design and siting of the proposed development, in accordance with the recommendations presented in Section 12.0.

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Hazard 1 – Rotational landslide/earthflows Evidence of numerous rotational landslides and earthflows were observed within steep soil slopes (slope angle more than about 18°), particularly where unfavourable drainage conditions were present at the base of the uppermost terrace below the south ridge. Similar landslide mechanisms could potentially occur on moderate soil slopes (slope angle about 10° to 18°) given sufficiently adverse drainage conditions. Rotational landslides/earthflows originating on gentle site slopes (i.e. the typical slope angle of about 5° in the central part of the site) do not appear to be a feasible hazard however regression of these landslides, or landslide debris, could potentially impact gentle slopes above or below moderate or steeper slopes.

A recent (less than about 10 years old) rotational landslide with an estimated volume of about 3600 m3 was observed south of the south watercourse, near the west boundary of the site, and is considered to be typical of Hazard 1. The displacement of the landslide debris was estimated to be about 10 m, and the rate of movement is estimated to have been moderate (nominally between 2 m per hour and 10 m per month). Detachment on this steep slope would likely have been triggered by heavy rainfall (say a 1 in 10 year event). Larger landslides (e.g. of similar volume to the inferred landslide on the homestead driveway) could potentially occur on steep slopes with more intense rainfall (say a 1 in 100 year event).

For the moderate slopes at the proposed hotel site our observations (indicate the trigger mechanism would likely require extreme rainfall (say a 1 in 1000 year event). Where the depth to rock is shallow and slopes are moderate (e.g. on the north ridge) we estimate the detachment probability to be one order of magnitude lower than for the circumstance where there is a deep soil profile.

Hazard 2 – Debris runout from very steep ridges The evidence of rock blocks in the colluvial terraces below the north flank of the south and ridge (and the west end of the north flank of the north ridge) indicates the potential for landslide debris originating from these very steep slopes to run-out onto the gently sloping terraces below.

The trigger event for debris run-out on this scale is inferred to be extreme rainfall, possibly in conjunction with a seismic event (e.g. earthquake) as the scale of the landslide and the potential runout distance increases. We estimate an annual detachment probability of 1 in 100 for debris volumes up to about 10 m3 (including individual rock blocks) that could travel up to about 20 m from the toe of the very steep slopes. For very large landslides with a run-out distance of about 50 m we estimate an indicative annual detachment probability of 1 in 10,000 years.

Hazard 3 - Detachment of boulders from old access road rock cutting It is unclear how the old access road (north boundary of the site) will be used as part of the proposed development. Notwithstanding this, we have considered rock fall from the cutting on the upslope part of the road as Hazard 3. Rock blocks up to about 0.15 m minimum dimension were observed to have travelled up to about 1 m beyond the toe of the cut batter onto the road carriageway. We estimate an indicative annual probability of 1 in 5 years for the detachment of similar blocks from the cutting, with the trigger likely to be heavy rainfall. We estimate that about 1 in 10 detached rock blocks would travel sufficiently far onto the road carriageway to potentially impact vehicles.

Hazard 4 – Rotational landslide below the old access road We consider there to be the potential for rotational failure within the steep slopes below the old access road (north flank of the north ridge). There is a retaining wall below this road near where it intersects with Old Hordern Vale Access that does not appear to be engineer designed. However, the BH report indicates that the old access road was primarily built by excavation to expose weathered sandstone and that minimal fill was placed to build the road.

The trigger for Hazard 4 is likely to be erosion at the toe of the slope due to flooding of the Barham River West Branch during or shortly after an extreme rainfall (say 1 in 1000 year event). If the Hazard 4 event occurs it would likely undermine the lower half of the old access road.



Hazard 5 – Lateral spreading of central soil deposits due to landslide dam event Based on the inferred geological history of the site we have considered the potential for a very large valley blocking landslide, leading to the formation of a landslide dam, as Hazard 5. The impoundment and/or draining of water from the dam could lead to lateral spreading (and flooding which is not considered in this landslide risk assessment) that could potentially affect the eastern (lower) half of the development site.

The trigger mechanism for Hazard 5 is inferred to be extreme rainfall combined with a large earthquake. We have assumed an annual probability of 1 in 100,000 years for this hazard.

10.0 RISK TO PROPERTY Risk to property has been assessed in accordance with Appendix C of AGS 2007c, as reproduced in Appendix A of this report. We have considered the following property types/locations in this assessment, based on the development plan presented as Figure 2. Our assessment of the hazards relevant to each of these locations is presented below.

1) Hotel Villas on the north flank of the north ridge.

Hazard 2: The proposed villas are located on or at the toe of the very steep north flank of the north ridge. For relatively small landslide volumes (i.e. less than about 10 m3) we have assessed the likelihood as ‘likely’ based on the estimated detachment probability for Hazard 2 and a probability of 1 that debris originating on the very steep slopes will impact the villas. For this volume we assess the consequence as ‘medium’, i.e. one or more of the villas would likely be damaged and stabilisation works would be required. For large to very large landslides we have assessed the likelihood as ‘possible’ and the consequence as ‘major’, given that landslide debris would likely destroy the villas and could potentially travel down to and across Old Hordern Vale Access resulting in offsite impact. In either scenario the assessed risk level to property is ‘high’.

2) Hotel Villas on the north ridge more than 15 m south of the crest of the very steep slope.

Hazard 1: Slopes in this area are moderate (typically less than 14°), rock is anticipated at a shallow depth and drainage conditions generally appear good. The depth to rock may increase to the south of the main ridge. We have assessed the likelihood of Hazard 1 as ‘unlikely’ in areas of shallow rock, increasing to ‘possible’ as the depth to rock increases, and the consequence to property as ‘medium’. The assessed risk level to property is ‘low’ where shallow rock is present increasing to ‘moderate’ in areas with a deep soil profile.

3) Hotel Villas on the gentle slopes north and south of the main dam.

Hazard 1: Development in areas with gentle slopes could potentially be impacted by regression of Hazard 1 failures on moderate or steeper slopes. For the proposed hotel villas north and south of the dam we have assessed the likelihood of Hazard 1 as ‘unlikely’, based on an annual detachment probability of 10-3 for landslides originating in nearby moderate slopes and a travel probability of 10-1 for the villas closest to the moderate slopes. We have assessed the consequence as ‘minor’ taking into consideration our expectation that remedial stabilisation measures could be implemented before villas are damaged. The assessed risk level to property is ‘low’.

4) Hotel Villas on the steep slope west of the main dam.

Hazard 1: We have assessed the likelihood of Hazard 1 as ‘almost certain’ in this area based on the observed evidence of instability, and our assessment that if a landslide occurs it will impact development in this area. We have assessed the consequence as ‘major’ taking into consideration our expectation that any villas built in this area would be destroyed if a Hazard 1 landslide occurs. The assessed risk level to property is ‘very high’.



5) Hotel.

Hazard 1: We have assessed the likelihood of Hazard 1 as ‘possible’ based on the estimated detachment probability for Hazard 1 on moderate slopes and a probability of 1 that if a landslide occurs it will impact part of the hotel. We have assessed the consequence as ‘major’ taking into consideration that if a Hazard 1 landslide occurs, the hotel is not expected to be completely destroyed but would be shut for some period with consequent economic impacts. The assessed risk level to property (in the absence of mitigation measures) is ‘high’.

Hazard 5: We have assessed the likelihood of Hazard 5 as ‘barely credible’ based on the estimated detachment probability for this hazard and a travel probability of 10-1 (if this hazard occurs it is unlikely to immediately impact the hotel site which is at a relatively high elevation). We have assessed the consequence as ‘catastrophic’. The assessed risk level to property is ‘low’.

6) Hotel car park.

Hazard 1: The assessed risk level to property for the proposed hotel car park is ‘low’ based on the justification provided for the hotel villas on the gentle slopes north of the dam.

7) Proposed hotel expansion, conference centre, chapel and yoga retreat.

Hazard 1: The risk associated with Hazard 1 will depend on the slope at the locations of proposed structures.

For buildings on gentle slopes more than about 15 m from the crest or toe of moderate or steeper slopes we have assessed the risk level to property as ‘low’ based on the justification presented for villas on gentle slopes north and south of the main dam.

For buildings located on or within about 15 m of the crest or toe of moderate to steep slopes we have assessed the likelihood as ‘likely’ (we note the linear feature is steeper to the south of the proposed hotel site, and evidence for rotational failure was observed in some places on this slope) and the consequence as ‘medium’. The assessed risk level to property is ‘high’.

Hazard 5: We have assessed the likelihood of Hazard 5 as ‘barely credible’ based on the estimated detachment probability for this hazard and a travel probability of 10-1. We have assessed the consequence as ‘catastrophic’. The assessed risk level to property is ‘low’.

8) New access road.

Hazard 1: The risk associated with Hazard 1 will depend on the slope beneath different parts of the proposed road.

Where the road is located on gentle slopes we have assessed the likelihood as ‘unlikely’ and the consequence as ‘minor’. The assessed risk level to property is ‘low’.

Where the road is located on or within about 15 m of the crest or toe of moderate to steep slopes we have assessed the likelihood as ‘likely’ and the consequence as ‘minor’. The assessed risk level to property is ‘moderate’.

Hazard 5: We have assessed the likelihood of Hazard 5 as ‘rare’ based on the estimated detachment probability for this hazard and a travel probability of 1 (for the part of the access road close to Barham River). We have assessed the consequence with respect to the access road as ‘medium’. The assessed risk level to property is ‘low’.

9) Old access road.

Hazard 3: We have assessed the likelihood as ‘almost certain’ and the consequence as ‘insignificant’. The assessed risk level to property is ‘low’.

Hazard 4: We have assessed the likelihood as ‘unlikely’ (assuming a travel probability of 10-1) and the consequence as ‘major’ given that if Hazard 4 occurs the old access road would be closed. The assessed risk level to property is ‘moderate’.



10) Staff accommodation.

Hazard 1: The assessed risk level to property for the proposed staff accommodation is ‘low’ based on the justification provided for the hotel villas on the gentle slopes north of the dam.

Hazard 5: We have assessed the likelihood as ‘barely credible’ based on the estimated detachment probability for this hazard and a travel probability of 10-1. We have assessed the consequence as ‘catastrophic’. The assessed risk level to property is ‘low’.

11) Resort villas and future villas on the north flank of the south ridge and uppermost terrace below the south ridge.

Hazard 1: We have assessed the likelihood as ‘likely’ and the consequence as ‘major’ based on the observed evidence of this hazard on the uppermost terrace and our assessment that buildings would be destroyed if this hazard occurs. The assessed risk level to property is ‘very high’.

Hazard 2: Based on the same justification as was provided for hotel villas on the north flank of the north ridge we have assessed the risk level to property as ‘high’.

Hazard 5: We have assessed the likelihood as ‘rare’ based on the estimated detachment probability for this hazard and a travel probability of 1 (for buildings close to the level of the Barham River near the east boundary of the site). We have assessed the consequence as ‘catastrophic’. The assessed risk level to property is ‘moderate’.

12) Resort villas and future villas on the lowermost terrace to the south of the south watercourse.

Hazard 1: The assessed risk level to property is ‘low’ based on the justification provided for the hotel villas on the gentle slopes north of the dam. This assumes structures will be located at least 15 m from the crest or toe of moderate or steep slopes.

Hazard 5: We have assessed the likelihood as ‘rare’ based on the estimated detachment probability for this hazard and a travel probability of 1 (for buildings near the east boundary of the site). We have assessed the consequence as ‘catastrophic’. The assessed risk level to property is ‘moderate’.

Summary of risk to property assessment The results of our assessment of risk level to property are summarised in Table 1. A risk level of more than moderate (i.e. high and very high risk) does not comply with the EMO1 tolerable risk criteria. Mitigation measures are required to reduce these risks to tolerable levels. Recommended risk mitigation measures are presented in Section 12.0.



Table 1: Assessment of risk level to property (current conditions) Element at risk Hazard 1 Hazard 2 Hazard 3 Hazard 4 Hazard 5 1. Villas north of the north ridge N/A High N/A N/A N/A

2. Villas on the north ridge Shallow rock: Low

N/A N/A N/A N/A Deep soil: Moderate

3. Villas on gentle slopes near the Main Dam Low N/A N/A N/A N/A

4. Villas west of the Main Dam Very high N/A N/A N/A N/A 5. Hotel High N/A N/A N/A Low 6. Hotel car park Low N/A N/A N/A N/A

7. Proposed hotel expansion, conference centre and chapel/yoga retreat

Gentle slopes: Low N/A N/A N/A Low Moderate or steeper

slopes: High

8. New access road Gentle slopes: Low

N/A N/A N/A Low Moderate or steeper slopes: Moderate

9. Old access road N/A N/A Low Moderate N/A 10. Staff accommodation Low N/A N/A N/A Low 11. Villas on the uppermost terrace below the south ridge Very high High N/A N/A Moderate

12. Villas on the lowermost terrace south of the south watercourse Low N/A N/A N/A Moderate

11.0 RISK TO LIFE We have estimated the risk to life of the individual most at risk from the hazards described above based on persons being present within the different parts of the development described in Section 10.0. Comments on societal risk (the risk associated with the loss of multiple lives in a single event) are presented in Section 13.0.

Refer to Sections 9.0 and 10.0 for information relating to our estimation of the landslide detachment and travel probability values.

We have made the following assumptions when estimating temporal probability values:

For Hazard 5 (all elements at risk) we have adopted P(T:S) = 10-2 assuming that formation of a landslide dam or other extreme flooding would result in the development being evacuated before a flood occurs.

For the other hazards:

Hotel villas and the hotel are occupied 80% of the time (P(T:S) = 8 x 10-1).

The staff accommodation building is continuously occupied (P(T:S) = 1).

The old and new access roads are used by 300 vehicles per day travelling at 20 km/hr. For Hazard 1 we have assumed the length of road that could be impacted by a landslide is 30 m (P(T:S) = 2 x 10-

2 based on the procedures outlined in Appendix CA of AGS 2007). For Hazard 3 we have assumed that the length of road that could be impacted by rockfall is 5 m (P(T:S) = 3 x 10-3). For Hazard 4 we have assumed the length of road that could be impacted by landslide is 10 m (P(T:S) = 6 x 10-3).

The hotel car park is occupied 10% of the time (P(T:S) = 10-1).



In our estimation of vulnerability we have made the following assumptions based on the example vulnerability values presented in Appendix D of AGS 2007.

Person in a building that collapses as a result of landslide or impact by landslide debris (e.g. relatively large scale Hazard 2): V(D:T) = 1.

Person in a building impacted by Hazard 1 (building is unlikely to collapse and there is a high chance of survival): V(D:T) = 3 x 10-1.

Person in a building that is struck by debris only (e.g. small scale Hazard 2 event): V(D:T) = 5 x 10-2.

Person in a vehicle damaged by rockfall or landslide debris (e.g. Hazard 1/Hazard 3): V(D:T) = 3 x 10-1.

Person in a vehicle impacted by Hazard 4 (e.g. vehicle rollover due to collapse of road): V(D:T) = 1.

Person in open space impacted but not buried by landslide (e.g. within car park): V(D:T) = 1 x 10-1.

1) Hotel Villas on the north flank of the north ridge.

Hazard 2: For relatively small landslide volumes (i.e. less than about 10 m3) we have assessed the following probability values:

P(H) = 10-2; P(S:H) = 1; P(T:S) = 8 x 10-1; V(D:T) = 5 x 10-2

R(LOL) = 10-2 x 1 x (8 x 10-1) x (5 x 10-2) = 4 x 10-4

For large to very large landslide volumes we have assessed the following probability values:

P(H) = 10-3; P(S:H) = 1; P(T:S) = 8 x 10-1; V(D:T) = 1

R(LOL) = 10-3 x 1 x (8 x 10-1) x 1 = 8 x 10-4

2) Hotel Villas on the north ridge more than 15 m south of the crest of the very steep slope.

Hazard 1:

P(H) = 10-3 to 10-4 depending on rock depth; P(S:H) = 1; P(T:S) = 8 x 10-1; V(D:T) = 5 x 10-2

R(LOL) (shallow rock) = 10-4 x 1 x (8 x 10-1) x (5 x 10-2) = 4 x 10-6

R(LOL) (deep soil) = 10-3 x 1 x (8 x 10-1) x (5 x 10-2) = 4 x 10-5

3) Hotel Villas on the gentle slopes north and south of the main dam.

Hazard 1:

P(H) = 10-3; P(S:H) = 10-1; P(T:S) = 8 x 10-1; V(D:T) = 5 x 10-2

R(LOL) = 10-3 x 10-1 x (8 x 10-1) x (5 x 10-2) = 4 x 10-6

4) Hotel Villas on the steep slope west of the main dam.

Hazard 1:

P(H) = 10-1; P(S:H) = 1; P(T:S) = 8 x 10-1; V(D:T) = 5 x 10-2

R(LOL) = 10-1 x 1 x (8 x 10-1) x (5 x 10-2) = 4 x 10-3

5) Hotel.

Hazard 1:

P(H) = 10-3; P(S:H) = 1; P(T:S) = 8 x 10-1; V(D:T) = 5 x 10-2



R(LOL) = 10-3 x 1 x (8 x 10-1) x (5 x 10-2) = 4 x 10-5

Hazard 5:

P(H) = 10-5; P(S:H) = 10-1; P(T:S) = 10-2; V(D:T) = 1

R(LOL) = 10-5 x 10-1 x 10-2 x 1 = 1 x 10-8

6) Hotel car park.

Hazard 1:

P(H) = 10-3; P(S:H) = 10-1; P(T:S) = 10-1; V(D:T) = 10-1

R(LOL) = 10-3 x 10-1 x 10-1 x 10-1 = 1 x 10-6

7) Proposed hotel expansion, conference centre, chapel and yoga retreat.

Hazard 1:

P(H) = 10-3 (gentle slopes) to 10-2 (moderate to steep slopes); P(S:H) = 10-1 (gentle slopes) to 1 (moderate to steep slopes); P(T:S) = 8 x 10-1; V(D:T) = 5 x 10-2

R(LOL) (gentle slopes) = 10-3 x 10-1 x (8 x 10-1) x (5 x 10-2) = 4 x 10-6

R(LOL) (moderate to steep slopes) = 10-2 x 1 x (8 x 10-1) x (5 x 10-2) = 4 x 10-4

Hazard 5:

P(H) = 10-5; P(S:H) = 10-1; P(T:S) = 10-2; V(D:T) = 1

R(LOL) = 10-5 x 10-1 x 10-2 x 1 = 1 x 10-8

8) New access road.

Hazard 1:

P(H) = 10-3 (gentle slopes) to 10-2 (moderate to steep slopes); P(S:H) = 10-1 (gentle slopes) to 1 (moderate to steep slopes); P(T:S) = 2 x 10-2; V(D:T) = 3 x 10-1

R(LOL) (gentle slopes) = 10-3 x 10-1 x (2 x 10-2) x (3 x 10-1) = 6 x 10-7

R(LOL) (moderate to steep slopes) = 10-2 x 1 x (2 x 10-2) x (3 x 10-1) = 6 x 10-5

Hazard 5:

P(H) = 10-5; P(S:H) = 1; P(T:S) = 10-2; V(D:T) = 3 x 10-1

R(LOL) = 10-5 x 1 x 10-2 x (3 x 10-1) = 3 x 10-8

9) Old access road.

Hazard 3:

P(H) = 2 x 10-1; P(S:H) = 10-1; P(T:S) = 3 x 10-3; V(D:T) = 3 x 10-1

R(LOL) = (2 x 10-1) x 10-1 x (3 x 10-3) x (3 x 10-1) = 1.8 x 10-5

Hazard 4:

P(H) = 10-3; P(S:H) = 10-1; P(T:S) = 6 x 10-3; V(D:T) = 1

R(LOL) = 10-3 x 10-1 x (6 x 10-3) x 1 = 6 x 10-7



10) Staff accommodation.

Hazard 1:

P(H) = 10-3; P(S:H) = 10-1; P(T:S) = 1; V(D:T) = 5 x 10-2

R(LOL) = 10-3 x 10-1 x 1 x (5 x 10-2) = 5 x 10-6

Hazard 5:

P(H) = 10-5; P(S:H) = 10-1; P(T:S) = 10-2; V(D:T) = 1

R(LOL) = 10-5 x 10-1 x 10-2 x 1 = 1 x 10-8

11) Resort villas and future villas on the north flank of the south ridge and uppermost terrace below the south ridge.

Hazard 1:

P(H) = 10-1; P(S:H) = 10-1; P(T:S) = 8 x 10-1; V(D:T) = 5 x 10-2

R(LOL) = 10-1 x 10-1 x (8 x 10-1) x (5 x 10-2) = 4 x 10-4

Hazard 2: For relatively small landslide volumes (i.e. less than about 10 m3) we have assessed the following probability values:

P(H) = 10-2; P(S:H) = 1; P(T:S) = 8 x 10-1; V(D:T) = 5 x 10-2

R(LOL) = 10-2 x 1 x (8 x 10-1) x (5 x 10-2) = 4 x 10-4

For large to very large landslide volumes we have assessed the following probability values:

P(H) = 10-3; P(S:H) = 1; P(T:S) = 8 x 10-1; V(D:T) = 1

R(LOL) = 10-3 x 1 x (8 x 10-1) x 1 = 8 x 10-4

Hazard 5:

P(H) = 10-5; P(S:H) = 1; P(T:S) = 10-2; V(D:T) = 1

R(LOL) = 10-5 x 1 x 10-2 x 1 = 1 x 10-7

12) Resort villas and future villas on the lowermost terrace to the south of the south watercourse.

Hazard 1 (assumes structures are at least 15 m from the crest or toe of moderate or steep slopes):

P(H) = 10-3; P(S:H) = 10-1; P(T:S) = 8 x 10-1; V(D:T) = 5 x 10-2

R(LOL) = 10-3 x 10-1 x (8 x 10-1) x (5 x 10-2) = 4 x 10-6

Hazard 5:

P(H) = 10-5; P(S:H) = 1; P(T:S) = 10-2; V(D:T) = 1

R(LOL) = 10-5 x 1 x 10-2 x 1 = 1 x 10-7

Summary of assessment of risk to life The results of our assessment of risk to life are summarised in Table 2. Assessed risk levels above EMO1 tolerable criteria are highlighted. Mitigation measures are required to reduce these risks to tolerable levels. Recommended risk mitigation measures are presented in Section 12.0.



Table 2: Assessment of risk to life (current conditions) Element at risk Hazard 1 Hazard 2 Hazard 3 Hazard 4 Hazard 5 1. Villas north of north ridge N/A 8 x 10-4 N/A N/A N/A

2. Villas on north ridge Shallow rock: 4 x 10-6

N/A N/A N/A N/A Deep soil: 4 x 10-5

3. Villas on gentle slopes near Main Dam 4 x 10-6 N/A N/A N/A N/A

4. Villas west of Main Dam 4 x 10-3 N/A N/A N/A N/A 5. Hotel 4 x 10-5 N/A N/A N/A 1 x 10-8 6. Hotel car park 1 x 10-6 N/A N/A N/A N/A


Gentle slopes: 4 x 10-6 N/A N/A N/A 1 x 10-8 Moderate or steeper

slopes: 4 x 10-4

8. New access road Gentle slopes: 6 x 10-7

N/A N/A N/A 3 x 10-8 Moderate or steeper slopes: 6 x 10-5

9. Old access road N/A N/A 1.8 x 10-5 6 x 10-7 N/A 10. Staff accommodation 5 x 10-6 N/A N/A N/A 1 x 10-8 11. Villas on the uppermost terrace below the south ridge 4 x 10-4 8 x 10-4 N/A N/A 1 x 10-7

12. Villas on the lowermost terrace south of the south watercourse 4 x 10-6 N/A N/A N/A 1 x 10-7

12.0 RISK MITIGATION Our risk assessment has identified elements of the proposed development where the assessed landslide risk levels are above COS EMO1 tolerable risk criteria. Remedial works are required to achieve tolerable risk in these areas. We consider there to be three main approaches available to reduce risk to tolerable levels, as follows:

Relocate elements at risk Based on discussions during our site meeting (3 October 2017) we understand that there is the potential to relocate some elements of the development away from locations with intolerable risk levels.

We recommend no villas or hotel buildings are located within the area north of the north ridge, west of the Main Dam or on the uppermost terrace below the south ridge. Avoiding building/development in these areas will eliminate the risk to property and persons associated with the current development proposal. We recommend that buildings associated with the proposed hotel expansion, conference centre and chapel/yoga retreat are located on the gentle slopes at least 15 m above the crest of, and at least 15 m below the toe of moderate to steep slopes associated with the linear features and the watercourses, to avoid building on or close to the steeper slopes. Siting of the proposed Hotel Villas on the north ridge should be subject to further geotechnical investigation to confirm buildings are located where shallow rock is present.

Approximate landslide risk zones, based on the results of our assessment of risk to property, are indicated on Figure 6. This information is provided to assist with relocation or siting of buildings and should be considered as large scale preliminary zoning. Further investigation and risk assessment works will be required once the layout and type of buildings proposed is confirmed. On Figure 6 we have used the qualitative risk to property terminology in AGS 2007 to define the risk zones, based on current conditions (i.e. no mitigation measures). As discussed below there are some locations (e.g. the hotel site) where we



expect it to be practical and feasible to reduce the risk level shown on Figure 6. These risk zones are based on buildings similar to the proposed villas and may not apply to roads or other structures.

We have not commented on landslide risk on the south side of the south ridge, or the Barham River floodplain, based on our understanding that no development is proposed in these areas.

Engineering works We understand that relocation of the proposed hotel building away from the moderate slope is not desirable given the intent to make use of the slope to provide views from hotel rooms. If it is practical to do so, relocating the hotel onto gentle slopes will reduce the landslide risk. However, we expect it to be practical and feasible to achieve compliance with tolerable risk criteria at this location through engineering design.

Our site observations indicate that slope and drainage are key contributing factors to observed instability at the site. Detailed design of the proposed hotel building (and other proposed structures) should aim to minimise earthworks as far as practical and to incorporate surface and subsurface drainage into the design. Revegetation of slopes should be undertaken where practical to help mechanically control erosion and to reduce soil moisture, reducing the likelihood of landslide initiation.

We recommend that the proposed earthworks associated with the hotel building are redesigned to reduce their extent. We recommend that earthworks associated with buildings are avoided where practical and otherwise generally limited to a maximum cut and fill depth of 1 m. Localised excavations deeper than 1 m (e.g. for lift overrun pits) will require detailed design based on the results of geotechnical investigation(s) and the recommendations of a suitably qualified geotechnical engineer and are expected to require permanent excavation support. All earthworks and earthwork support measures should be accompanied by engineering design (e.g. engineer designed retaining walls or stability analysis of batter slopes). Long excavations that are parallel to contours should be avoided as they could introduce a plane of weakness into the slope.

We recommend that the proposed buildings are supported on piles founded on or within weathered rock (where practical). Further intrusive geotechnical investigation is required within the proposed building areas to identify a suitable founding stratum for piles and to inform detailed design of buildings. Other than on the north ridge we anticipate pile founding depths will be at least 5 m.

Further investigation is also required to inform design requirements for the proposed new access road and upgrades to the existing (old) access road. The new access road is typically expected to traverse gentle slopes and we do not expect significant earthworks to be required in these areas. Where the new access road crosses moderate or steep slopes including the watercourse channels the proposed earthworks should be based on design recommendations from a suitably qualified geotechnical engineer. For preliminary purposes we suggest the adoption of a maximum unsupported batter slope of 3H:1V for cut and fill batters, based on our observations of an increased likelihood of instability for batters steeper than about 18° (3H:1V). Design of the new access road should also incorporate drainage provisions. Further assessment of the old access road will be required depending on how this road is intended to be used – construction of slope stabilisation measures such as retaining walls, scaling or rock fall netting may be required at targeted locations on slopes above or below the road. Road drainage provisions will also need to be upgraded and maintained.

Upgrades to the main dam will be required prior to development works downstream. For example, the dam should be provided with a formal spillway. Depending on the final location of structures downstream of the dam, dam break analysis may need to be performed by a suitably qualified hydrologist to assess the potential impact on structures of failure of the dam wall.

We consider that the provision of drainage works and engineer design of building footings/earthworks will reduce the probability of landslide detachment for Hazards 1, 3 and 4 by at least one order of magnitude for the relevant elements at risk.



Formal monitoring and response plan Assuming that buildings are relocated away from areas of relatively high landslide risk, Hazard 2 is not relevant to buildings. Hazard 1 is typically expected to move at a moderate rate in response to periods of extreme rainfall. We expect it to be practical to identify evidence of potential slope instability before the hazard impacts people or structures, allowing remedial stabilisation measures or evacuation and reducing the vulnerability of persons and consequence of landslides. If Hazard 5 occurs, the initial damming of the Barham River is expected to provide ample warning of instability further upslope in the central part of the site. Hence, we recommend that a formal slope monitoring and response plan is implemented as part of the proposed development. Such a plan would also assist with the management of Hazards 3 and 4 and would assist in identifying and responding to slope instability issues should they arise over the design life of the development.

Further work would be required to develop this plan, which we expect would include the establishment of survey reference points to assess rates of slope movement at key locations, the setting of rainfall thresholds to alert workers/residents to an increase in the risk of instability, and regular visual assessment of key areas to monitor changes in site conditions. The plan should also set out requirements for maintenance (e.g. of drains) and response protocols (i.e. requirements ranging from say further geotechnical assessment to evacuation). We expect it to be practical and feasible to implement a plan of this nature, which would reduce the estimated risk to life by at least one order of magnitude compared to the circumstances where there is no plan in place (i.e. a reduction in the temporal probability value). Warning signs could also be installed on the access roads to alert drivers to rockfall and other landslide hazards.

SummaryA summary of the proposed risk mitigation measures is set out in Table 3 for the elements at risks/hazards that were assessed as intolerable in the absence of mitigation measures. We consider that the proposed mitigation measures will also reduce the risk associated with hazards assessed as meeting the tolerable risk criteria without additional mitigation measures and should be implemented across all parts of the development.

Development of the mitigation measures (e.g. engineering design requirements and the development and implementation of a formal monitoring and response plan) will require additional investigation and assessment/analysis, which should be done as part of detailed design for the proposed development. This LRA should be revised and updated once these additional works have been performed and details of the proposed development are confirmed.



Table 3: Proposed risk mitigation measures

Element at risk Intolerable risk Proposed mitigation measures Estimate of residual risk

1. Villas north of north ridge Hazard 2 (property and life) Avoid building in this area N/A - element at risk is eliminated by

relocation.

2. Villas on north ridge

Hazard 1 (life) where there are moderate slopes and a

deep soil profile

Locate buildings where the rock profile is shallow. Engineering measures including drainage. Formal monitoring and response plan.

Risk reduced to shallow rock conditions or better (Property: Low; Life: 4 x 10-7 with monitoring plan)

4. Villas west of Main Dam Hazard 1 (property and life) Avoid building in this area N/A - element at risk is eliminated by

relocation.

5. Hotel Hazard 1 (property and life)

Engineering measures to improve drainage. Minimal earthworks. Formal monitoring and response plan.

Reduction by at least one order of magnitude (Property: Moderate

Life: 4 x 10-7 with monitoring plan)


Hazard 1 (property and life) where slopes are moderate

or steeper

Do not locate buildings on moderate/steep slopes or within 15 m of these slopes. Engineering measures including drainage.

N/A - element at risk is eliminated by relocation.

8. New access road

Hazard 1 (life) where slopes are moderate or

steeper

Engineering measures to improve drainage. Minimal earthworks. Formal monitoring and response plan and warning signage.

Reduction by at least one order of magnitude (Life: 6 x 10-7 with

monitoring plan)

9. Old access road Hazard 3 (life)

Engineering measures. Formal monitoring and response plan and warning signage.

Reduction by at least one order of magnitude (Life: 1.8 x 10-7 with

monitoring plan)

11. Villas on the uppermost terrace below the south ridge

Hazards 1 and 2 (property and life) Avoid building in this area N/A - element at risk is eliminated by

relocation.



13.0 SOCIETAL RISK Based on the acceptance criteria described in AGS 2007 and referred to in EMO1, the ‘tolerable’ risk for loss of life of an individual is 1 x 10-5 per annum. Given the potential for hotel buildings impacted by landslide to contain multiple occupants we have assessed societal risk to life. We have used the Australian National Committee on Large Dams ‘Guidelines on Risk Assessment’ (ANCOLD, 2003) as a guide the tolerable risk to life criteria for societal risk (Plate 7).

Plate 7: Chart representing 'tolerable' societal risk for landslides (graph based on ANCOLD, 2003)

The following comments relate to our assessment of societal risk (risk to life):

At this stage of the proposal, the total occupancy of the proposed development including potential future expansions is not yet known. Our assessment assumes that development is in accordance with our recommended risk mitigation measures, including relocation of some elements, engineering design of new structures and the implementation of a formal monitoring and response plan.

For Hazard 1 we have assumed a maximum tolerable probability for societal risk to life of 1 x 10-6 per annum based on the inferred landslide intensity and the information presented in Plate 7 (i.e. we expect only part of the hotel building would be affected). With reference to Table 3 we assess the residual risk associated with Hazard 1 to have a probability of less than 1 x 10-6 per annum.

Hazard 2 is not relevant to the assessment of societal risk if elements of the development are relocated away from the areas at risk in accordance with our recommendations.

For Hazards 3 and 4 we have assumed a maximum tolerable probabilty of societal risk to life of 1 x 10-6 per annum based on the inferred landslide intensity and the information presented in Plate 7. With reference to Tables 2 and 3 we assess the residual risk associated with Hazards 3 and 4 to have a probability of less than 1 x 10-6 per annum.

For Hazard 5 we have assumed a maximum tolerable probability of societal risk of 1 x 10-7 based on the inferred landslide intensity and the information presented in Plate 7 (i.e. the entire hotel building could potentially be affected). With reference to Table 2 we assess the residual risk associated with Hazard 5 once risk mitigation measures are implemented to have a probability of less than 1 x 10-7 per annum.

Based on the above comments we expect it to be practical and feasible to implement risk mitigation measures to achieve tolerable societal risk levels.

‘Tolerable’ societal risk curve for a new development (AGS LRM, 2007)



14.0 CONCLUSIONS Landslide hazards have been identified that in the absence of risk mitigation measures pose intolerable risk levels. Subject to the implementation of the remedial measures in accordance with our recommendations, we consider it practical and feasible to reduce the landslide risk level to meet the tolerable risk criteria set out in the COS EMO1.

Although demonstrating ‘Moderate’ risk to property complies with the requirements of EMO1, it is higher than the risk level considered to be tolerable by some other regulators in Victoria, including Yarra Ranges Council (where tolerable risk to property is defined as no more than ‘Low’). It is important that the developers and owners of the hotel are aware that a ‘Moderate’ risk of property damage due to landslide remains relatively high compared to ‘typical’ development sites that are not subject to significant landslide hazards, even if (based on the schedule to EMO1) it can be tolerated by COS.

Further investigation works will be required as part of the detailed design of the proposed development. This landslide risk assessment should be reviewed and updated (if required) once further investigation works are performed and details of the proposed development are confirmed.

If requested to do so, we would be pleased to provide a ‘geotechnical declaration’ form in accordance with the requirements of the COS EMO1 once plans show development in accordance with our recommendations.

15.0 REFERENCES 1) ANCOLD (2003). Australian National Committee on Large Dams, Guidelines to Risk Assessment, 2003

2) AGS LRM (2007). Australian Geomechanics Society, Landslide Risk Management Concepts and Guidelines, Australian Geomechanics, Vol. 42, No.1 March 2007.

3) Bruce Hollioake Consulting & Civil Engineers (2017) report dated 26 June 2017 (ref: 17310) titled ‘Geotechnical assessment and land stability assessment report’.

4) EMO1 (2013). Colac Otway Planning Scheme, Schedule 1 to the Erosion Management Overlay.

5) Golder Associates Pty Ltd (2017) letter dated 15 September 2017 (ref: 1787175-001-L-Rev0) titled ‘Stage 1 – Desktop Review of Bruce Hollioake Report’.

6) Quigley, M., Clark, D & Sandiford, M. (2010). ‘Tectonic geomorphology of Australia’ in Australian Landscapes, Geological Society (London) Special Publication 346, pp. 243-265.

16.0 IMPORTANT INFORMATION Your attention is drawn to the document titled - “Important Information Relating to this Report”, which is included in Appendix D. The statements presented in that document are intended to inform a reader of the report about its proper use. There are important limitations as to who can use the report and how it can be used. It is important that a reader of the report understands and has realistic expectations about those matters. The Important Information document does not alter the obligations Golder has under the contract between it and its client.



Report Signature Page

GOLDER ASSOCIATES PTY LTD

Stuart Colls Associate

SC/DRP/sc

A.B.N. 64 006 107 857 Golder, Golder Associates and the GA globe design are trademarks of Golder Associates Corporation.

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APPENDIX A Colac Otway Planning Scheme Schedule 1 to the Erosion Management Overlay

Résumé for Dr Stuart Colls

AGS 2007 Landslide risk management guidelines – Appendix C

COLAC OTWAY PLANNING SCHEME

EROSION MANAGEMENT OVERLAY – SCHEDULE 1 PAGE 1 OF 5

SCHEDULE 1 TO THE EROSION MANAGEMENT OVERLAY

Shown on the planning scheme map as EMO1.

1.0 Land susceptible to landslip and erosion

The Shire contains areas which are susceptible to landslip, including land throughout theOtway Ranges.A number of geotechnical studies have been undertaken, in various forms and scope, withinColac Otway by various public agencies.Colac Otway Shire Council has adopted updated landslip and erosion data for the wholeShire and subsequent reviews of selected areas displaying a greater complexity of landslipand erosion issues.All land included in the Erosion Management Overlay has been identified as having asufficiently high risk of potential instability to warrant specific review of these risks prior tothe construction of buildings, commencement of works and the removal of vegetation asoutlined below.

2.0 Definitions

AGS Guidelines 2007 means including all Practice Notes Guidelines (Part C) andCommentary (Part D).Geotechnical Practitioner means a specialist Geotechnical Engineer or EngineeringGeologist who is degree qualified, is a member of a professional institute, with experiencein the management of slope stability problems and landslip risk management as a corecompetence.Landslide, as defined by the AGS Guidelines 2007, or “landslip”, as defined by the VPPs,means the movement of a mass of rock, debris or earth down a slope. This includes debrisflow, which is the rapid flow of water saturated soil or rock debris.Acceptable Risk – A risk for which, for the purposes of life or work, we are prepared toaccept as it is with no regard to its management. Society does not generally considerexpenditure in further reducing such risks justifiable. An acceptable risk level for newdevelopment or changes to existing development a risk to life and/or risk to property is inaccordance with the AGS Guidelines 2007. It reflects a combination of the slope and typeof development proposed.Tolerable Risk – A risk within a range that society can live with so as to secure certain netbenefits. It is a range of risk regarded as non-negligible and needing to be kept underreview and reduced further if possible. Tolerable Risk for new development or changes toexisting development a risk to life and/or risk to property is in accordance with the AGSGuidelines 2007.

3.0 Guidance for users

This schedule;Requires at a minimum a Geotechnical Assessment to be prepared by a suitablyqualified professional; andPotentially requires a Landslip Risk Assessment to be prepared where required by aGeotechnical Assessment or where the site is located within the slope thresholdscontained in Clause 6.0 of this schedule by a suitably qualified professional.

4.0 Objectives

To manage the risk of landslip.

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To ensure that development can be carried out in a manner which will not adverselyincrease the landslip risk to life or property affecting the subject land or adjoining ornearby land.To ensure that development is not carried out unless the risk associated with thedevelopment is a Tolerable Risk or lower.To ensure that applications for development are supported by adequate investigationand documentation of geotechnical and related structural matters.To ensure that development is only carried out if identified geotechnical and relatedstructural engineering risks to life and property are effectively addressed.

5.0 Exemptions from permit requirements

A permit is not required to construct or carry out the following:Earthworks that do not exceed 1m in depth or fill exceeding 1m in height; orA retaining wall that does not exceed 1m in height that is replacing an existing retainingwall with the same form of construction and dimensions and/or materials of improveddurability and is not associated with other building construction work and does notprovide landslip protection for any adjoining land; orExtension to the floor area of an existing building, including decks and verandahsprovided that there is no increase in the ground surface area covered by roofed buildingsand the floor area of the extension does not exceed 20m2; orRoad works undertaken by a public authority; orMinor structures ancillary to an existing dwelling where the floor area of the structuredoes not exceed 20m2; orThe removal, destruction or lopping of any vegetation providing the roots below groundlevel are retained; orTimber production where all timber production activities comply with the Code ofForest Practices for Timber Production (Revision No.2 November 1996) or as amendedfrom time to time in accordance with section 55 of the Conservation, Forests and LandsAct 1987, and/or the Timber harvesting Prescriptions for Environmental Protection –Otway Region Private Land Native Forests and Plantations, where details ofmanagement of landslip risk have been provided to the satisfaction of the ResponsibleAuthority; orIn the Farming Zone, the construction of an outbuilding with a floor area less than150m2 for non habitable agricultural purposes.

6.0 Application requirements

An application for a planning permit must be accompanied by a Geotechnical Declarationand Verification Form (Form A) and include the information set out below, to thesatisfaction of the Responsible Authority.

Development Plans

Development plans drawn to scale and dimensioned, showing as appropriate:The proposed development, including a site plan and building elevations, access, anyproposed cut and fill, retaining wall or effluent disposal system.Any existing development, including buildings, water tanks and dams on both thesubject lot and adjacent land (as appropriate).Any existing development on the subject lot, including cut and fill, stormwaterdrainage, subsurface drainage, water supply pipelines, sewerage pipelines or effluentdisposal installations and pipelines and any otherwise identified geotechnical hazard.Details and location of existing vegetation, including any vegetation to be removed.

Geotechnical Assessment

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A written Geotechnical Assessment must be prepared by a suitably qualified andexperienced Geotechnical Practitioner in accordance with the methodology described belowand with reference to the AGS Guidelines 2007. The Geotechnical Assessment must be forthe development proposed in the application and include, to the satisfaction of theResponsible Authority:

Details of the Geotechnical Practitioner and their qualifications and experienceincluding but not limited to experience in the management of slope instability problemsand landslip risk management.A statement that the assessment is based on field survey measurements which have beenundertaken not more than 12 months prior to the relevant application for development.A detailed site description.Site assessment plans and cross-sections of the subject lot within the landslip impactzone and related land form survey and field measurements with contours and groundslopes as measured shown and drawn to scale and dimensioned.A detailed assessment of subsurface conditions, including the underlying geology.A statement indicating whether there are natural slopes on or immediately adjacent tothe subject lot which exhibit evidence of possible or past landslip.Details of all site investigations and any other information used in preparation of thegeotechnical report.A statement indicating whether site investigation requires subsurface investigation ormay involve boreholes and/or test pit excavations or other methods necessary toadequately assess the geotechnical/geological model for the subject lot and details of allsuch investigations, boreholes, test pits or other methods.Include a statement indicating that the risks for all slope instability hazards identified,are of an acceptable risk level (as defined above) and will remain at an acceptable risklevel over the design life of the development such that a Landslip Risk Assessment (asdescribed in the following section) is not required.Where it is considered that a Landslip Risk Assessment is not required, state that, in theopinion of the Geotechnical Practitioner, the development can be carried out in amanner which will not adversely increase the landslip risk to life or property affectingthe subject lot or adjoining or nearby landA statement as to whether the subject lot/s are suitable for the proposed development, orcan be made suitable for the proposed development, and that the subject lot/s and theproposed development can meet the tolerable risk criteria, as defined in this schedule.A statement indicating whether or not development should only be approved subject toconditions, and if so state recommendations of what conditions should be requiredincluding but without limitation conditions relating to:

The determination of appropriate footing levels and foundation materials in anystructural works, including all footings and retaining walls.The location/s of and depth/s of earth and rock cut and fill.The construction of any excavations and fill and the method of retention of suchworks.Any details of surface and sub-surface drainage.The selection and design of a building structure system to minimise the effects of allidentified geotechnical hazards.Retention, replanting and new planting of vegetation.Any drainage and effluent discharge.Any necessary ongoing mitigation and maintenance measures and any recommendedperiodic inspections, including performance measures.The time within which works must be completed after commencement and thelocation/s and period in which materials associated with the development can bestockpiled.



Any requirements for geotechnical inspections and approvals that may need to beincorporated into a construction work plan for building approval.

A statement on whether or not a Landslip Risk Assessment is required.

Landslide/Landslip Risk Assessment

A written Landslip Risk Assessment of the proposed development must be included in theapplication for a planning permit if the Geotechnical Assessment or other landform data (adetailed site survey) indicates natural slopes on or immediately adjacent to the subject lotwhich:

are steeper than 9 degrees (15.8%) in Gellibrand Marl Narrawaturk Marl & the YaugherVolcanic Group the unnamed coastal lagoon deposits and lake and swamp deposits; orare steeper than 14 degrees (25%) in all other geologies including the spatially extensiveEumeralla Formation (Otway Group); orexhibit evidence of possible or past landsliding on or immediately adjacent to the site;orwhere, in the opinion of the Responsible Authority, the Geotechnical Assessment is notsufficient to determine that the development can be carried out in a manner which willnot adversely increase the landslip risk to life or property affecting the subject lot oradjoining or nearby land.

A written Landslip Risk Assessment must be prepared by a suitably qualified andexperienced Geotechnical Practitioner in accordance with the methodology detailed in theAGS Guidelines 2007. The Landslip Risk Assessment must be for the developmentproposed in the application and include, to the satisfaction of the Responsible Authority:

A copy of the Geotechnical Assessment prepared for the subject land and proposal and,if not prepared by the Geotechnical Practitioner preparing the Landslip RiskAssessment, contain a response by the Geotechnical Practitioner preparing the LandslipRisk Assessment that the finding and conclusions of the Geotechnical Assessment areagreed with.Contain all the requirements of a Geotechnical Assessment if the need for an LRA istriggered by the LRA slope thresholds above.If the Geotechnical Practitioner preparing the Landslip Risk Assessment does not agreewith the findings and conclusions of the Geotechnical Assessment for the subject landand proposal, another Geotechnical Assessment must be prepared by that GeotechnicalPractitioner.An assessment underpinned by field survey and measurements which have beenundertaken not more than 12 months prior to the lodgement of the application for aplanning permit.A full assessment of the risk posed by all reasonably identified geotechnical hazardswhich have the potential to either individually or cumulatively impact upon people orproperty on the subject lot or related land, in accordance with the AGS Guidelines 2007.A full assessment of the risk posed by future vegetation removal for bushfire protectionif undertaken to the maximum extent permissible under the conditions of any planningpermit and under permit exemptions in the Planning Scheme, in accordance with theAGS Guidelines 2007.A conclusion as to whether the subject lot/s are suitable for the proposed development.This must be in the form of a specific statement that the subject lot/s are suitable, or canbe made suitable, for the proposed development and that the subject lot and/or theproposed development can meet the tolerable risk criteria, as defined in this schedule.The report must specify all conditions required to achieve this objective.

7.0 Independent review

The Responsible Authority may require a Geotechnical Assessment and any Landslip RiskAssessment that has been submitted with an application to be reviewed by an independentGeotechnical Practitioner.

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8.0 Transitional requirements

Any planning permit application that was lodged with Council prior to the approval datedoes not need to meet the requirements of the new schedule.

9.0 Decision Guidelines

Before deciding on a planning permit application the Responsible Authority must consider,as appropriate:

Whether the risk to property and the risk to life measured against the tolerable risk asdefined in the AGS Guidelines 2007 is acceptable.Geotechnical reports greater than one year old from the time of application will not beaccepted unless accompanied by a letter from the Geotechnical Practitioner confirmingreport conclusions are still applicable.Whether the proposed subdivision, building or works or the removal of vegetation canbe carried out in a manner which will not increase to an unacceptable level thepossibility of landslip affecting the site or adjoining or nearby land.The recommendations of the Geotechnical Assessment and any Landslip RiskAssessment and any other information accompanying the application.The recommendations of any Independent Review of the Geotechnical Assessment andany Landslip Risk Assessment.Whether the proposed removal of vegetation is required to facilitate a permitted use ordevelopment of the land, and if there is any practical alternative form of developmentwhich would result in less disturbance to the existing vegetation.The impact of future vegetation removal for bushfire protection and whether any suchvegetation removal would result in an increase to the risk to property and/or the risk tolife as measured against the tolerable risk criteria defined in the AGS Guidelines 2007.The risks associated with the development requiring ongoing monitoring andmaintenance of all mitigation measures.The risks associated with non-compliance with any conditions of any permit which maybe subsequently issued.Effluent disposal considerations including any Environment Protection Authorityrequirements for on-site disposal in unsewered areas.

10.0 Permit conditions

Any permit issued must also contain the following condition:The approved development must be carried out on the site in accordance with therecommendations of the Geotechnical Assessment (title/date/author) or, whereapplicable, the Landslip Risk Assessment (title/date/author) or any GeotechnicalPractitioner engaged to review those assessments submitted with the application.

11.0 Reference Documents

Practice Note Guidelines for Landslide Risk Management 2007, Journal of AustralianGeomechanics Society, Vol. 42: No 1, March 2007.Commentary on Practice Note Guidelines for Landslide Risk Management 2007,Journal of Australian Geomechanics Society, Vol. 42: No 1, March 2007.Guideline for Development of Sites Prone to Landslide Hazard, Final draft submitted toAustralian Building Codes Board, prepared by Australian Geomechanics Society, 2004.Miner A S & Dalhaus P 2011, Revision of Colac Otway Shire’s Erosion ManagementOverlay, A.S. Miner Geotechnical, Manifold Heights, Victoria, Australia.

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31/01/2013C68

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Résumé STUART COLLS

EducationBachelor of Engineering (Civil, Hons 1) , University of Melbourne , 2001

Bachelor of Science (Geology), University of Melbourne , 2001

Doctor of Philosophy, Department of Infrastructure Engineering, University of Melbourne, 2014

AffiliationsMember, Engineers Australia

Member, Australian Geomechanics Society

Certifications CPEng

Certified Geoxchange Designer (in training)

RMS Slope Risk Assessor

Relevant Experience Infrastructure

Land Development

Slope Stability

Power

Mining

Geothermal Energy

Golder Associates Pty Ltd – Melbourne Principal Geotechnical Engineer Stuart Colls has over fifteen years of experience in providing geotechnical consulting services for projects in Australia and overseas.

Stuart has extensive experience in the performance and management of geotechnical site investigations, construction phase assessments and earthworks for infrastructure, land development, power and mining projects.

Relevant project experience includes:

Infrastructure. Participated in and managed geotechnical investigations, tender and construction phase consulting services for a variety of infrastructure projects in Victoria. Major projects include the Melbourne City Link tunnels, Victorian Desalination Plant, Dandenong Revitalisation Project, Melbourne Cricket Ground resurfacing, Southern Cross Station, Melbourne-Ballarat Fast Rail Project and Eastlink.

Land Development. Participated in and managed geotechnical investigations, construction phase consulting services and earthworks supervision for a variety of land development projects. Major projects include Yarra’s Edge and Freshwater Place buildings in Melbourne, Nakheel Tower in Dubai and bulk earthworks and subsequent development of the Valley Lake, Metro 3175 and Burwood Brickworks developments in Melbourne.

Slope Stability. Participated in a variety of studies related to slope stability in soil and rock. These studies include slope stability assessments and review of planning applications for Yarra Ranges Council, stability assessments for various coastal sites in Victoria including work associated with the 2016 Victorian Bushfires Clean-up project in Wye River and Separation Creek, and qualitative and quantitative mapping of soil and rock face stability in various Victorian quarries for the purpose of assessing stability. Accredited to perform risk assessments on RMS assets in New South Wales.

Power. Managed projects and participated in feasibility studies, geotechnical investigations and construction phase consulting services for wind farm projects including Waubra Wind Farm, Lexton Wind Farm and Waubra North Wind Farm in western Victoria.

Mining. Participated in geotechnical investigation for the Goro Nickel Project in New Caledonia. Participated in a variety of studies at mine sites including Prominent Hill in South Australia and Marandoo and Yandicoogina Mines in Western Australia.

Geothermal Energy. Experience in the design and construction of ground heat exchangers for ground-source heat pump systems, including energy piles and borehole heat exchangers. PhD research work included extensive field experiments aimed at in situ assessment of the ground’s thermal properties.

Stuart Colls can be contacted on +61 3 8862 3576 or [email protected].



APPENDIX B Golder's letter dated 15 September 2017 (ref: 1787175-001-L-Rev0)

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

A.B.N. 64 006 107 857 Golder, Golder Associates and the GA globe design are trademarks of Golder Associates Corporation.

Dear Phil

1.0 ENGAGEMENT Irwinconsult Pty Ltd (Irwinconsult) has engaged Golder Associates Pty Ltd (Golder) to provide geotechnical consulting services associated with the proposed Apollo Bay Resort located at 275 – 305 Barham River Road, Apollo Bay.

This letter presents the results and findings of our desktop review including a preliminary geotechnical model and comments regarding key slope instability constraints relevant to the proposed development, in general accordance with the ‘Stage 1’ scope set out in our proposal dated 6 September 2017. Approval to proceed was provided by Irwinconsult in an email dated 11 September 2017.

2.0 PROPOSED DEVELOPMENT Drawings provided by Irwinconsult (Spowers drawings SK_MP.01, SK_MP.02 and SK_MP_A.06 dated June 2017) indicate that the proposed Apollo Bay Resort comprises a hotel building with up to three above ground levels, several one to two level villa units, and associated site access roads and services. Proposed earthworks include retaining walls (maximum height about 7 m but typically less than 3 m high) beneath the proposed hotel building and villa units, which are proposed to be cut into the hillside of the sloping site. A copy of Spowers drawing SK_MP.01 is presented as Figure 1 for reference. The majority of the proposed development is within the northern half of the site, although future expansion is planned in the southern half of the site.

15 September 2017 Reference No. 1787175-001-L-Rev0

Mr Phil Gardiner Irwinconsult Pty Ltd Level 3, 289 Wellington Parade South EAST MELBOURNE VIC 3002

APOLLO BAY RESORT, 275 – 305 BARHAM RIVER ROAD, APOLLO BAY STAGE 1 – DESKTOP REVIEW OF BRUCE HOLLIOAKE REPORT

Mr Phil Gardiner 1787175-001-L-Rev0Irwinconsult Pty Ltd 15 September 2017

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Figure 1: Spowers drawing SK_MP.01 showing the proposed development

3.0 DESKTOP REVIEW METHODOLOGY As part of the desktop review we have considered the Spowers drawings and the following documents:

1) Bruce Hollioake Consulting Civil & Structural Engineers (BH) report dated 26 June 2017 (ref: 17310) titled ‘Geotechnical assessment and land stability assessment report’. A copy of this report was provided to us by Irwinconsult.

2) Colac Otway Shire (COS) schedule to the erosion management overlay (EMO1).

3) Geological Survey of Victoria (GSV) 1:250 000 scale ‘Colac’ mapsheet.

4) Historic aerial photographs dated 1952, 1978, 1983, 1991, 2005 and 2015. Copies of the aerial photographs are attached to this letter.

5) Publically available information on the Corangamite Catchment Management Authority (CCMA) ‘erosion and landslide resources in the CCMA region’ website1 including COS landslide inventory mapsheets for Apollo Bay and Cape Otway, and A.S. Miner Geotechnical Consulting Engineers (ASMG) report no. 356.3/01/06 titled ‘Case study for erosion and landslides – Barham Valley Road, Apollo Bay.’

1 http://www.ccma.vic.gov.au/soilhealth/resource/index.htm


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4.0 REVIEW COMMENTS 4.1 Site location The location and topography of the site is shown on Figure 2. The site covers an area of approximately 100 hectares and is bound to the north by Barham River Road and Old Hordern Vale Access and to the east, west and south by private property. The site typically slopes down towards the east from about RL 140 m in its southwest corner to about RL 20 m in its northeast corner. The BH report indicates that site slopes typically vary between 5 degrees and 15 degrees below the horizontal.

Major drainage features near the site include the Barham River and Barham River West Branch to the north and Beauty Gully to the south. The Barham River flows towards the coast which is about 3 km east of the site. There are also several near-parallel watercourses which drain from west to east across the site, and a dam near the west boundary of the site.

Figure 2: Site location and topography (image from land.vic.gov.au website)

4.2 Published geology and subsurface conditions The GSV ‘Colac’ mapsheet indicates the site is underlain by Quaternary age colluvial deposits that likely overlie Cretaceous age Eumeralla Formation materials. The BH report includes the results of thirteen boreholes drilled to maximum depths ranging from about 1.2 m to 2.0 m. The results of these boreholes are summarised as follows:

Boreholes drilled north of the watercourse near the northern boundary of the site typically encountered firm to stiff silty or sandy clay overlying weathered sandstone below about 1.2 m depth.

Boreholes drilled within the footprint of the proposed hotel (northwest part of the site) typically encountered firm to stiff silty clay to the maximum borehole depth (2 m). The BH report presents anecdotal evidence of clay to at least 6 m depth in the vicinity of the existing farm dam.


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Boreholes drilled within the area to the east of the farm dam (close to the alignment of the proposed hotel access road) typically encountered firm to stiff silty clay to the maximum borehole depth of 1.5 m to 2.0 m.

There do not appear to have been any boreholes drilled within the southern half of the site. The presence of a ridgeline near the southern boundary of the site may indicate the presence of relatively shallow rock along this boundary.

Information from the COS online maps (reproduced as Figure 3) indicates the presence of mapped landslide features at the site. Limited information is available regarding the mapped landslide features however it appears they have been interpreted from aerial photographs rather than reports of slope movements.

Figure 3: Mapped landslides recorded in the COS online mapping portal

Figure 3 indicates that the proposed hotel site is located on a mapped landslide. However, the extent of this landslide does not appear to be consistent with the site topography. Our ground model interpretation based on the topographic features, borehole information and anecdotal evidence of a deep soil profile near the farm dam, is that the east-facing slope represents colluvium (landslide debris) and that the ridgelines to the north, west and south represent the scarps of previous landslides. Note these features may result from a series of smaller landslides rather than a single very large landslide. The colluvial deposits may also have affected the course of the Barham River to the east of the site. The depth to groundwater at the site is unknown. However, we note there appear to be several watercourses that originate near the inferred landslide headscarp near the western part of the site, and the farm dam is also located in this part of the site. Groundwater in the vicinity of the watercourses is expected to be relatively shallow and may vary seasonally.

We note there are also mapped landslide features on and adjacent to the site that generally appear to be parallel to ridge or valley lines.

The BH report appears to reach similar conclusions regarding the colluvial origin of the materials encountered in boreholes near the proposed hotel. However, we disagree with the inference from BH that the age of the colluvium means it can be treated as a ‘natural soil’ (we infer BH to mean a soil not affected by landslide given it has been emplaced by natural processes). The presence of deep colluvium requires careful

Geomorphological interpretation of historic landslide debris (green shading) and potential head and side scarps (dashed line)

Mapped landslide features (COS database) indicated by red lines or dots

Mapped landslides (COS database) indicated by red shading

Proposed hotel site (approximate)


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consideration because of the potential to reactivate instability with inappropriate earthworks, particularly deep excavation parallel to the slope. As will be discussed we consider the depth of earthworks proposed (up to 7 m) to be inappropriate given the apparent history of instability at the site.

The ASMG case study report presents a relatively detailed summary of a landslide that occurred in about 1986 on the north side of the Barham River, about 1 km north of the site. Although the geomorphology of the case study site differs from the proposed resort site (the landslide occurred on a steep slope above the Barham River), it provides an indication of the scale and typical characteristics of rotational landslides in the vicinity of Apollo Bay. The ASMG report indicates that the landslide measured about 50 m wide by 125 m long and travelled about 40 m. The depth of the slide and its volume is not known. There was heavy rainfall during April 1986 (two days of more than 60 mm in a 24-hour period between 17 and 28 April 1986) that may have triggered the landslide. A photograph of the landslide is presented in Figure 4.

Figure 4: Photograph of the Barham River landslide dated 1998 (from ASMG report)

4.3 Aerial photographs Other than the general hummocky nature of the ground and the geomorphological features discussed above, the aerial photographs do not appear to show evidence of recent landslide events at the site. The main change evident over time is an increase in vegetation cover within gullies at and adjacent to the site. In general terms, revegetation reduces the likelihood of landslide by lowering the moisture content of the soil. The large dam near the western boundary of the site appears to have been built between 1991 and 2005.

4.4 COS EMO1 requirements Figure 5 indicates that other than a small area in the northwest corner the site is covered by an erosion management overlay (EMO1). The schedule to EMO1 requires a landslide risk assessment (LRA) to be performed where there is evidence of past landslides on a site. EMO1 sets out the required contents of an LRA and provides decision guidelines which include an assessment as to whether the LRA demonstrates tolerable risk as defined in the Australian Geomechanics Society Practice Note Guidelines and Commentary

Approximate extent of the Barham River landslide


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for Landslide Risk Management, 20072 (AGS 2007). EMO1 requires that an LRA is undertaken in accordance with the methodology outlined in AGS 2007.

Figure 5: Extent of erosion management overlay (image from land.vic.gov.au website)

With reference to Section 3.5 of AGS 2007, the regulator (i.e. COS) is responsible for setting the tolerable risk criteria for life and property loss. Hence, defining ‘tolerable risk’ in EMO1 as that defined in AGS 2007 raises uncertainty. From discussions with COS’s geotechnical consultant (ASMG) we expect the following tolerable risk criteria to apply to the proposed hotel development, assuming a building importance level of 3 as defined in AGS 2007 (buildings or structures that may contain people in crowds):

Risk to property of no more than ‘Moderate’.

Annual risk to life of no more than 1 x 10-5 for the person most at risk and an assessment of societal risk given the potential for buildings to have a high number of occupants.

Although demonstrating ‘Moderate’ risk to property is expected to comply with the requirements of EMO1, it is higher than the risk level considered to be tolerable by some other regulators in Victoria, including Yarra Ranges Council (where tolerable risk to property is defined as no more than ‘Low’). It is important that the developers and owners of the hotel are aware that a ‘Moderate’ risk of property damage due to landslide remains relatively high compared to ‘typical’ development sites that are not subject to significant landslide hazards, even if (based on the schedule to EMO1) it can be tolerated by COS. This level of landslide risk may have implications for requirements for ongoing monitoring and maintenance of the property.

4.5 Bruce Hollioake LRA We provide the following comments regarding the risk assessment presented in the BH report:

The level of detail in the discussion of the landslide history of the site and justification for the probability values presented in the LRA is less than what we consider to be required given the mapped landslide

2 Australian Geomechanics Society, Practice Note Guidelines for Landslide Risk Management, Australian Geomechanics, Vol. 42, No 1, March 2007.


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features at the site and the nature of the proposed development. For example, no geological section is presented to illustrate the hazards identified and their inferred mechanism of instability.

The LRA appears to consider only the proposed hotel building, new access road and existing access road as elements at risk. The proposed development (Figure 1) includes hotel villa units, staff accommodation buildings and other structures within the EMO1 area that should also be considered in the LRA.

The outcome of the BH LRA indicates risk to property and life that complies with the above tolerable risk criteria. However, the BH report does not consider the societal risk associated with the proposed hotel.

While we do not agree with aspects of the BH LRA, based on the available information we expect mitigation of landslide risk to ‘tolerable’ levels to be practical for both life and property. This is subject to confirmation following our proposed LRA (see further works below) and will likely require the implementation of mitigation measures including controls on building layout, minimal earthworks, engineered design of retention, drainage and effluent disposal systems. A formal monitoring program may also need to be developed to mitigate risk to life.

5.0 PRELIMINARY GEOTECHNICAL MODEL AND KEY LANDSLIDE CONSTRAINTS

The preliminary geotechnical model and key constraints to development related to landslide hazards are summarised on Figure 6. We provide the following preliminary comments relating to the proposed development:

Rotational landslides present a landslide hazard for structures built on the steeper sides of the valley. However, the proposed development is generally on the flatter colluvial slopes. Given the relatively flat slopes, rotational landslides in these colluvial materials are not expected to pose a significant constraint to development provided development is in accordance with good construction practice on hillsides. For reference, a copy of AGS’s ‘Australian Geoguide LR8 (Construction Practice)’ is attached to this letter. Note the presence of relatively deep colluvium may have an impact on footing design requirements.

Debris run-out from rotational landslides on the steeper valley sides presents a hazard to structures below the steeper slopes. However, the proposed buildings generally appear to be located beyond the run-out distance of debris from rotational landslides (assuming a similar runout distance as observed for the Barham River landslide). The location of the proposed villa units in the northwest corner of the site may require further assessment with respect to debris flow hazards.

Colluvial materials within the flatter valley base area are likely to have variable strength properties including relict failure planes. Reactivation of previous failure planes in the colluvium could occur with inappropriate earthworks. The scale of earthworks proposed (retaining walls up to about 7 m high) appears excessive for the site conditions and we recommend reducing the extent and volume of earthworks proposed. Where practical, earthworks should be avoided and structures built up above the existing ground surface (e.g. on piers or posts). This approach will also help limit the impact of development on surface drainage.

The condition of the dam wall in the western part of the site should be assessed if this has not already been done, as instability of this dam wall could adversely impact structures built downstream. Consideration may need to be given to re-routing the proposed access road immediately below the dam wall if construction of the road at this location could adversely affect wall stability or spillway provisions.

It is important that the location of future development or expansion of the hotel is confirmed so that landslide issues associated with future development can be assessed as part of the LRA for the overall site.

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6.0 FURTHER WORKS In accordance with our Stage 1 scope of services we propose to meet with Irwinconsult to discuss the information presented in this letter before proceeding with the proposed Stage 2 scope of works (including a site visit and meeting with COS and their geotechnical consultant, followed by the performance of a LRA).

Further targeted geotechnical investigation will be required to inform geotechnical design of the proposed development. Depending on observations from the planned site visit, further geotechnical investigation may also be required to inform the LRA. From a landslide perspective, potential factors for consideration in the scoping of future geotechnical investigation works include:

Assessment of the variability in the depth to rock across the site, and the strength of the colluvial and residual soil materials. This would help with the assessment of potential landslide volume as well as practical constraints on earthworks and the retention of cut and fill batters.

Assessment of groundwater levels and their seasonal variability.

The potential to install an inclinometer or inclinometers for monitoring purposes. Regular monitoring including visual assessment of the site may need to be considered as a mitigation measure to demonstrate tolerable risk to life (in particular societal risk).

Assessment of the condition of the dam wall and other existing site earthworks.

7.0 IMPORTANT INFORMATION Your attention is drawn to the document titled - “Important Information Relating to this Report”, which is attached to this letter. The statements presented in that document are intended to inform a reader of the report about its proper use. There are important limitations as to who can use the report and how it can be used. It is important that a reader of the report understands and has realistic expectations about those matters. The Important Information document does not alter the obligations Golder has under the contract between it and its client.

Please contact Stuart Colls on 8862 3576 should you have any queries regarding the information presented in this letter.

Yours sincerely,

GOLDER ASSOCIATES PTY LTD

Stuart Colls Associate

SC/DRP/sc

Attachments: Appendix A – Historical aerial photographs Australian Geoguide LR8 (construction practice) Important information relating to this report (LEG04, RL2)

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AUSTRALIAN GEOGUIDE LR8 (CONSTRUCTION PRACTICE)

174 Australian Geomechanics Vol 42 No 1 March 2007

HILLSIDE CONSTRUCTION PRACTICE

Sensible development practices are required when building on hillsides, particularly if the hillside has more than a lowrisk of instability (GeoGuide LR7). Only building techniques intended to maintain, or reduce, the overall level of landsliderisk 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 thehillside (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 includedrains to prevent water pressures developing in the backfill. Where the ground slopes steeply down towards the highside 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 soakinto the ground.Surface water - from roofs and other hard surfaces is piped away to a suitable discharge point rather than being allowedto infiltrate into the ground. Preferably, the discharge point will be in a natural creek where ground water exits, ratherthan 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. Foundationloads have been taken down below the level at which a landslide is likely to occur and, preferably, to rock. This sort ofconstruction is probably not applicable to soil slopes (GeoGuide LR3). If you are uncertain whether your site has rocknear 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 ofdistress and maintain their functionality.Vegetation clearance - on soil slopes has been kept to a reasonable minimum. Trees, and to a lesser extent smallervegetation, take large quantities of water out of the ground every day. This lowers the ground water table, which in turnhelps to maintain the stability of the slope. Large scale clearing can result in a rise in water table with a consequentincrease in the likelihood of a landslide (GeoGuide LR5). An exception may have to be made to this rule on steep rockslopes 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 constructionpractices are not as unusual as you might think and are often chosen because, on the face of it, they will save thedeveloper, or owner, money. You should not lose sight of the fact that the cost and anguish associated with any one ofthe disasters illustrated, is likely to more than wipe out any apparent savings at the outset.

ADOPT GOOD PRACTICE ON HILLSIDE SITES

AUSTRALIAN GEOGUIDE LR8 (CONSTRUCTION PRACTICE)

Australian Geomechanics Vol 42 No 1 March 2007 175

WHY ARE THESE PRACTICES POOR?

Roadways and parking areas - are unsurfaced and lack proper table drains (gutters) causing surface water to pond andsoak into the ground.Cut and fill - has been used to balance earthworks quantities and level the site leaving unstable cut faces and addedlarge surface loads to the ground. Failure to compact the fill properly has led to settlement, which will probably continuefor 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 applyingengineering 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 becauseof 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 watersoaks into the ground and raises the water table (GeoGuide LR5). Subsoil drains that run along the contours should beavoided 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, youwill need to seek professional advice.Rock debris - from landslides higher up on the slope seems likely to pass through the site. Such locations are oftenreferred to by geotechnical practitioners as "debris flow paths". Rock is normally even denser than ordinary fill, so evenquite modest boulders are likely to weigh many tonnes and do a lot of damage once they start to roll. Boulders havebeen 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 PRACTITIONERMore information relevant to your particular situation may be found in other Australian GeoGuides:

GeoGuide LR1 - Introduction GeoGuide LR2 - Landslides GeoGuide LR3 - Landslides in Soil GeoGuide LR4 - Landslides in Rock GeoGuide LR5 - Water & Drainage

GeoGuide LR6 - Retaining Walls GeoGuide LR7 - Landslide Risk GeoGuide LR9 - Effluent & Surface Water Disposal

GeoGuide LR10 - Coastal Landslides GeoGuide LR11 - 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 anexcavation. They are intended to help you understand why slopes and retaining structures can be a hazard and what can be done withappropriate professional advice and local council approval (if required) to remove, reduce, or minimise the risk they represent. TheGeoGuides have been prepared by the Australian Geomechanics Society, a specialist technical society within Engineers Australia, thenational peak body for all engineering disciplines in Australia, whose members are professional geotechnical engineers and engineeringgeologists with a particular interest in ground engineering. The GeoGuides have been funded under the Australian governments’National Disaster Mitigation Program.

IMPORTANT INFORMATION RELATING TO THIS REPORT

The document (“Report”) to which this page is attached and which this page forms a part of, has been issued by Golder Associates Pty Ltd (“Golder”) subject to the important limitations and other qualifications set out below.

This Report constitutes or is part of services (“Services”) provided by Golder to its client (“Client”) under and subject to a contract between Golder and its Client (“Contract”). The contents of this page are not intended to and do not alter Golder’s obligations (including any limits on those obligations) to its Client under the Contract.

This Report is provided for use solely by Golder’s Client and persons acting on the Client’s behalf, such as its professional advisers. Golder is responsible only to its Client for this Report. Golder has no responsibility to any other person who relies or makes decisions based upon this Report or who makes any other use of this Report. Golder accepts no responsibility for any loss or damage suffered by any person other than its Client as a result of any reliance upon any part of this Report, decisions made based upon this Report or any other use of it.

This Report has been prepared in the context of the circumstances and purposes referred to in, or derived from, the Contract and Golder accepts no responsibility for use of the Report, in whole or in part, in any other context or circumstance or for any other purpose.

The scope of Golder’s Services and the period of time they relate to are determined by the Contract and are subject to restrictions and limitations set out in the Contract. If a service or other work is not expressly referred to in this Report, do not assume that it has been provided or performed. If a matter is not addressed in this Report, do not assume that any determination has been made by Golder in regards to it.

At any location relevant to the Services conditions may exist which were not detected by Golder, in particular due to the specific scope of the investigation Golder has been engaged to undertake. Conditions can only be verified at the exact location of any tests undertaken. Variations in conditions may occur between tested locations and there may be conditions which have not been revealed by the investigation and which have not therefore been taken into account in this Report.

Golder accepts no responsibility for and makes no representation as to the accuracy or completeness of the information provided to it by or on behalf of the Client or sourced from any third party. Golder has assumed that such information is correct unless otherwise stated and no responsibility is accepted by Golder for incomplete or inaccurate data supplied by its Client or any other person for whom Golder is not responsible. Golder has not taken account of matters that may have existed when the Report was prepared but which were only later disclosed to Golder.

Having regard to the matters referred to in the previous paragraphs on this page in particular, carrying out the Services has allowed Golder to form no more than an opinion as to the actual conditions at any relevant location. That opinion is necessarily constrained by the extent of the information collected by Golder or otherwise made available to Golder. Further, the passage of time may affect the accuracy, applicability or usefulness of the opinions, assessments or other information in this Report. This Report is based upon the information and other circumstances that existed and were known to Golder when the Services were performed and this Report was prepared. Golder has not considered the effect of any possible future developments including physical changes to any relevant location or changes to any laws or regulations relevant to such location.

Where permitted by the Contract, Golder may have retained subconsultants affiliated with Golder to provide some or all of the Services. However, it is Golder which remains solely responsible for the Services and there is no legal recourse against any of Golder’s affiliated companies or the employees, officers or directors of any of them.

By date, or revision, the Report supersedes any prior report or other document issued by Golder dealing with any matter that is addressed in the Report.

Any uncertainty as to the extent to which this Report can be used or relied upon in any respect should be referred to Golder for clarification.

GAP Form No. LEG04RL2July 2015 1/1



APPENDIX C Site photographs (2 & 3 October 2017)

APPENDIX C Site photographs, 2 & 3 October 2017

1 November 2017 Reference No. 1787175-002-R-Rev1 1/39

Photograph 1: View of the escarpment below the proposed hotel site, from the north ridge

Photograph 2: View of the escarpment below and to the south of the proposed hotel, from the north ridge

Proposed hotel site (approx.)



Photograph 3: View to the south along the upper/west linear feature at the proposed hotel site

Photograph 4: View to the south along the upper/west linear feature at the proposed hotel site



Photograph 5: View of the main dam wall from the north

Photograph 6: View of the upstream dam wall



Photograph 7: View of the downstream dam wall

Photograph 8: View downstream (east) from the dam wall. The route of the proposed hotel access road crosses this gully.



Photograph 9: Overflow on the south side of the dam wall

Photograph 10: Discharge of overflow on the south side of the dam wall



Photograph 11: Shallow slumping of the slopes to the west of the main dam. The proposed hotel parking area is on the flatter slopes beyond this area of shallow slumping.

Photograph 12: Damp ground to the west of the main dam

Proposed hotel parking (approx.)



Photograph 13: Dam to the north of the proposed hotel site. Note minor slumping above the far bank. The proposed hotel parking area is on the flatter slopes beyond (south of) this dam.

Photograph 14: View to the east of the upper/west linear feature along the farm track (the route of the proposed hotel access track is to the north (right) of the farm dam in the top right of this photograph)

Proposed hotel parking (approx.)

Hotel access road route (approx.)



Photograph 15: Erosion and slumping on the banks of the incised watercourse through the upper/west linear feature

Photograph 16: Erosion and slumping of the watercourse through the upper/west linear feature to the south of the proposed hotel



Photograph 17: Trees in the gully to the southwest of the main dam

Photograph 18: Trees planted on the upper/west linear feature to the southeast of the proposed hotel site. Note some bowing of tree trunks at the toe of the slope



Photograph 19: Powerlines to the northwest of the main dam

Photograph 20: View to the east along the north ridge.



Photograph 21: Historic rotational failure within the northwest corner of the site. Approximate scarp location indicated by dashed line.

Photograph 22: Northwest corner of the site. Note occasional boulders on the slope and hummocky ground.



Photograph 23: Inferred landslide headscarp with boulder debris to the west of the northwest corner of the site (from Old Hordern Vale Access).

Photograph 24: Inferred landslide headscarp at 105 Old Hordern Vale Access).



Photograph 25: Shallow slumping above a culvert entry on the north ridge access track.

Photograph 26: View from the north ridge towards the proposed hotel site.




Photograph 27: View from the north ridge to the area west of the vineyard.

Photograph 28: View from the north ridge to the area east of the vineyard




Photograph 29: Watercourse to the north of the proposed hotel site (view towards the west).

Photograph 30: View towards the east towards the proposed staff accommodation building. The approximate route of the proposed hotel access road is indicated by the dashed line.




Photograph 31: View towards the north from the area of the proposed hotel expansion/conference centre. The proposed hotel access road crosses this area.

Photograph 32: View towards the north from the area of the proposed hotel expansion. The proposed hotel access road crosses this area.



Photograph 33: Area to the southwest of the proposed staff accommodation. Proposed access road passes to the left of the group of trees on the right of the photograph.

Photograph 34: View from the southwest boundary of the site towards the inferred headscarp feature to the northwest (this feature continues around to 105 Old Hordern Vale Access, refer Photograph 24)

Headscarp feature West boundary fence

Proposed access road route



Photograph 35: View towards the main dam and proposed hotel site from the south ridge

Photograph 36: View towards the east along the south ridge.

Proposed hotel site (approx.) Main dam



Photograph 37: View towards the main dam and proposed hotel site from the high point on the south ridge. Note the headscarps of landslides on the terrace below the south ridge (indicated by dashed lines).

Photograph 38: Landslide to the south of the south watercourse. Note transverse cracking of the debris. Approximate headscarp indicated by dashed line.

See photographs 41 & 42

See photographs 38 to 40



Photograph 39: Landslide to the south of the south watercourse. Note boulders and water seepage within the debris.

Photograph 40: Landslide to the south of the south watercourse. View towards the toe of the debris (estimated maximum movement about 10 m). Approximate toe of debris indicated by dashed line.



Photograph 41: Landslide within the uppermost terrace below the south ridge (headscarp indicated by dashed line)

Photograph 42: Groundwater seepage through landslide area pictured in Photograph 41



Photograph 43: View towards the northeast from the high point on the south ridge

Photograph 44: Dam to the east of the high point on the south ridge. Note minor slumping on the far bank.



Photograph 45: View to the west from below the homestead. Note ‘terracing’ at the toe of the steeper south ridge.

Photograph 46: Low hills near the Barham River, east of the homestead.

Uppermost terrace below the south ridge

Barham River



Photograph 47: View towards the west on the lower terrace below the south ridge.

Photograph 48: View towards the east on the lower terrace below the south ridge.



Photograph 49: View towards the east on the lower terrace below the south ridge.

Photograph 50: Watercourse on the lower terrace below the south ridge.



Photograph 51: Breached dam wall within the south watercourse.

Photograph 52: View towards the west from the proposed access road intersection with Barham River Road (route follows the farm access track on the left of the photograph).



Photograph 53: View towards the west from the driveway to the homestead. The upper/west linear feature (south of the proposed hotel) and farm access track can be observed at the top right of the photograph

Photograph 54: View from Barham River Road towards the east boundary of the site (fence-line). Note there are frequent arcuate headscarps near the toe of this slope. Photograph 60 shows further detail of the scarp indicated by the dashed line.

East boundary fence

Farm access track



Photograph 55: View towards the southwest from Barham River Road, towards the homestead.

Photograph 56: Vegetated area east of the driveway to the homestead. The trees are inferred to cover an old landslide.

Homestead



Photograph 57: Landslide headscarp within the vegetated area shown in Photograph 56.

Photograph 58: Water ponding in the area above the landslide shown in Photographs 56 & 57.



Photograph 59: Driveway through the vegetated former landslide.

Photograph 60: View of landslide near the east boundary of the site. Headscarp indicated by dashed line.



Photograph 61: View towards the west and north from the south ridge, near the east boundary of the site.

Photograph 62: View towards the north and east from the south ridge, near the east boundary of the site.



Photograph 63: View to the east along the south ridge, near the east boundary of the site.

Photograph 64: Inferred old landslide covered by vegetation, west of the driveway to the homestead. The approximate toe of the landslide debris is indicated by a dashed line.



Photograph 65: Old access road from near its intersection with Old Hordern Vale Access.

Photograph 66: Cut batter on the old access road, north side of the north ridge.



Photograph 67: Old access road, view towards the east.

Photograph 68: Cut batter and retaining wall on Old Hordern Vale Access, below the old access road.



Photograph 69: Former quarry/exposed rock near the intersection of Barham River Road and Old Hordern Vale Access.

Photograph 70: Quarried face near the intersection of Barham River Road and Old Hordern Vale Access. Note displacement of siltstone bed along inferred fault (LHS photo is an enlargement of the inferred fault)

Inferred fault



Photograph 71: Barham River (West Branch) below Old Hordern Vale Access.

Photograph 72: Typical slopes above the Barham River. Note the apparent landslide debris from steep ridge and eroded alluvial terrace.



Photograph 73: Slopes on the east side of the Barham River opposite the site.

Photograph 74: Conical shaped hill on the south side of the Barham River, east of the site.








j:\2017\1787175 - irwinconsult, 310 barham river road, apollo bay\correspondence out\1787175-002-r-rev1 appendix c.docx



APPENDIX D Important information relating to this report (LEG04, RL2)

IMPORTANT INFORMATION RELATING TO THIS REPORT

The document (“Report”) to which this page is attached and which this page forms a part of, has been issued by Golder Associates Pty Ltd (“Golder”) subject to the important limitations and other qualifications set out below.

This Report constitutes or is part of services (“Services”) provided by Golder to its client (“Client”) under and subject to a contract between Golder and its Client (“Contract”). The contents of this page are not intended to and do not alter Golder’s obligations (including any limits on those obligations) to its Client under the Contract.

This Report is provided for use solely by Golder’s Client and persons acting on the Client’s behalf, such as its professional advisers. Golder is responsible only to its Client for this Report. Golder has no responsibility to any other person who relies or makes decisions based upon this Report or who makes any other use of this Report. Golder accepts no responsibility for any loss or damage suffered by any person other than its Client as a result of any reliance upon any part of this Report, decisions made based upon this Report or any other use of it.

This Report has been prepared in the context of the circumstances and purposes referred to in, or derived from, the Contract and Golder accepts no responsibility for use of the Report, in whole or in part, in any other context or circumstance or for any other purpose.

The scope of Golder’s Services and the period of time they relate to are determined by the Contract and are subject to restrictions and limitations set out in the Contract. If a service or other work is not expressly referred to in this Report, do not assume that it has been provided or performed. If a matter is not addressed in this Report, do not assume that any determination has been made by Golder in regards to it.

At any location relevant to the Services conditions may exist which were not detected by Golder, in particular due to the specific scope of the investigation Golder has been engaged to undertake. Conditions can only be verified at the exact location of any tests undertaken. Variations in conditions may occur between tested locations and there may be conditions which have not been revealed by the investigation and which have not therefore been taken into account in this Report.

Golder accepts no responsibility for and makes no representation as to the accuracy or completeness of the information provided to it by or on behalf of the Client or sourced from any third party. Golder has assumed that such information is correct unless otherwise stated and no responsibility is accepted by Golder for incomplete or inaccurate data supplied by its Client or any other person for whom Golder is not responsible. Golder has not taken account of matters that may have existed when the Report was prepared but which were only later disclosed to Golder.

Having regard to the matters referred to in the previous paragraphs on this page in particular, carrying out the Services has allowed Golder to form no more than an opinion as to the actual conditions at any relevant location. That opinion is necessarily constrained by the extent of the information collected by Golder or otherwise made available to Golder. Further, the passage of time may affect the accuracy, applicability or usefulness of the opinions, assessments or other information in this Report. This Report is based upon the information and other circumstances that existed and were known to Golder when the Services were performed and this Report was prepared. Golder has not considered the effect of any possible future developments including physical changes to any relevant location or changes to any laws or regulations relevant to such location.

Where permitted by the Contract, Golder may have retained subconsultants affiliated with Golder to provide some or all of the Services. However, it is Golder which remains solely responsible for the Services and there is no legal recourse against any of Golder’s affiliated companies or the employees, officers or directors of any of them.

By date, or revision, the Report supersedes any prior report or other document issued by Golder dealing with any matter that is addressed in the Report.

Any uncertainty as to the extent to which this Report can be used or relied upon in any respect should be referred to Golder for clarification.

GAP Form No. LEG04RL2July 2015 1/1

Golder Associates Pty Ltd Building 7, Botanicca Corporate Park 570 – 588 Swan Street Richmond, Victoria 3121 Australia T: +61 3 8862 3500