Evidenced by Glenn Ottrey requested by Development

609-621 Burwood Expert opinion on stormwater management strategy for fast track government land service

2 March 2018

V6000_002

EVIDENCED BY GLENN OTTREY REQUESTED BY DEVELOPMENT VICTORIA 609-621

CONTENTS

1. INTRODUCTION ...... 3

2. THE SUBJECT SITE ...... 4 2.1 Subject Site ...... 4

3. REFERENCE DOCUMENTS ...... 5

4. ASSESSMENT ...... 6 4.1 Stormwater quantity management ...... 6 4.2 Stormwater quality management ...... 6 4.3 Flood modelling of Blind Creek ...... 7 4.4 Existing dam ...... 8

5. STATEMENT ...... 10

Appendices

APPENDIX A – GLENN OTTREY DETAILS, CURRICULUM VITAE AND INSTRUCTIONS

APPENDIX B – WETLAND FUNCTIONAL DESIGN PLANS

APPENDIX C – FLOOD MAPS

APPENDIX D – DAM CONDITION ASSESSMENT REPORT

Job No. V6000_002 Page ii : 02/03/2018

EVIDENCED BY GLENN OTTREY REQUESTED BY DEVELOPMENT VICTORIA 609-621 BURWOOD HIGHWAY

1. INTRODUCTION

This report provides expert evidence by Glenn Ottrey as requested by Development Victoria. This report relates to the proposed preliminary stormwater management strategy for 609-621 Burwood Highway in Knoxfield.

The stormwater strategy has been described as a preliminary strategy as the masterplan for the site has not yet been developed. The stormwater management strategy will be further refined once the masterplan is developed, however it is not expected that there would be any significant changes required to the stormwater management strategy.

Details of the report author and contributors are provided in Appendix A.

Job No. V6000_002 Page 3 : 02/03/2018

EVIDENCED BY GLENN OTTREY REQUESTED BY DEVELOPMENT VICTORIA 609-621 BURWOOD HIGHWAY

2. THE SUBJECT SITE

This report is based on information provided to me listed as the reference documents in section 3, as well as a site visit undertaken by me and Andrew Prout on Wednesday 16 November 2016.

2.1 Subject Site

The subject site is located in Knoxfield in the . A locality plan showing the property is provided in Figure 3-1.

Figure 2-1 Locality Plan

Job No. V6000_002 Page 4 : 02/03/2018

EVIDENCED BY GLENN OTTREY REQUESTED BY DEVELOPMENT VICTORIA 609-621 BURWOOD HIGHWAY

3. REFERENCE DOCUMENTS

The following documents and information has been supplied to or sourced by Engeny and has been used to inform the preliminary stormwater management plan.

▪ CSIRO 1999, Urban Stormwater Best Practice Environmental Management Guidelines (BPEMG)

▪ Ecocentric Environmental Consulting 2015, Preliminary Biodiversity Assessment 609- 619 & 621 Burwood Highway Knoxfield

▪ Ecocentric Environmental Consulting 2017 Flora, Fauna and Native Vegetation Assessment 609-619 & 621 Burwood Highway Knoxfield

▪ Engeny, 2017 Dam Condition Assessment Report – 621 Burwood Highway, Knoxfield

▪ Feature and level survey, including dam bathymetry by CRA Survey Pty Ltd version 3 dated 20-07-2017

▪ GHD 2015, 621 Burwood Highway, Knoxfield Development Assessment

▪ GIS asset data of underground drains provided by Water

▪ Knox 5 year MUSIC rainfall template file “Knox City Council - 5 Year 6 Minute Rainfall Template.mlb”

▪ LiDAR data sourced from the Department of Environment Land Water and Planning

▪ Planning Panel’s Victoria “Guide to Expert Evidence”

▪ RORB hydrologic model of Blind Creek provided by Melbourne Water on 22-06-2017

▪ Stormwater drainage guidelines for residential, commercial, industrial and broad acre subdivisional developments, City of Knox, May 2006 (currently available from the City of Knox website https://www.knox.vic.gov.au/Files/Roads/StormwaterDrainageGuidelines.pdf)

▪ The Royal Life Saving Society Australia, 2004, Royal Life Saving Guidelines for Water Safety in Urban Water Developments

Job No. V6000_002 Page 5 : 02/03/2018

EVIDENCED BY GLENN OTTREY REQUESTED BY DEVELOPMENT VICTORIA 609-621 BURWOOD HIGHWAY

4. ASSESSMENT

I have led the preparation of the preliminary stormwater management plan for 609-621 Burwood Highway Knoxfield. This report is titled “621 Burwood Highway Knoxfield, Preliminary stormwater management plan, Revision 7, dated 3 August 2017”. This report details the proposed management of stormwater as the site is developed. A summary of the key points in the report is contained below.

4.1 Stormwater quantity management

A summary of key points regarding to stormwater quantity management is:

▪ A minor (piped) drainage system sized for the 5 year average recurrence interval (ARI) event, in line with the City of Knox stormwater drainage guidelines.

• Since the issue of the preliminary stormwater management strategy, I have spoken to Neils Unger, drainage engineer at the City of Knox, who has requested a 10 year ARI drainage design standard for the piped system. This can be accommodated with no change in the proposed zoning and overlays.

▪ The major stormwater drainage system sized to convey the gap flow between the capacity of the minor drainage design system and flows in the 100 year ARI event.

▪ A RORB hydrologic model was developed to determine the required size of the retarding basin to ensure that peak flows discharging from the site were not increased in the 100 year ARI event in developed conditions compared to existing conditions. The retarding impact of the existing dam was considered as part of the development of this modelling.

• The RORB modelling showed that the current 100 year ARI peak flow from the site is 3.6 m3/s under existing conditions and under the proposed development conditions it would be 3.5 m3/s.

4.2 Stormwater quality management

A summary of the key points relating to stormwater quality management is:

▪ Stormwater will need to be treated to Best Management Practices as required by Clause 56.07-4 of the Victoria Planning Provisions.

▪ Stormwater treatment for the entire site is proposed to be achieved in a single location through a combined sedimentation basin and wetland.

▪ MUSIC modelling of the proposed stormwater treatment system shows that a 1100 m2 sedimentation basin and 4500 m2 stormwater treatment wetland are able to meet the best practice targets for the development area.

Job No. V6000_002 Page 6 : 02/03/2018

EVIDENCED BY GLENN OTTREY REQUESTED BY DEVELOPMENT VICTORIA 609-621 BURWOOD HIGHWAY

• Since the issue of the preliminary stormwater management strategy, I have spoken to Neils Unger, drainage engineer at the City of Knox, who has requested that the MUSIC model be run with the Knox MUSIC rainfall template. I have run the MUSIC model with the Knox MUSIC template and it meets the best practice targets with no changes to any of the other model parameters (apart from the rainfall), including wetland or sedimentation basin sizes.

▪ 10,400 m2 of additional habitat wetland is also provided. Stormwater entering the habitat wetland will first be treated in the sedimentation pond and the stormwater treatment wetland to improve the quality of the stormwater entering the habitat wetland

▪ Construction could be staged so that the habitat wetland is constructed prior to the removal of the existing dam

▪ A functional design of the wetland has been undertaken to demonstrate that the required treatment areas can physically be achieved within the proposed footprint. The functional design plans are shown in Appendix B.

▪ Consideration could be given to utilising the wetland system for stormwater harvesting to provide water for irrigation.

4.3 Flood modelling of Blind Creek

A summary of the key points relating to the flood modelling on Blind Creek is:

▪ Blind Creek is a Melbourne Water managed waterway. At the request of Melbourne Water, Engeny created a two-dimensional hydraulic model (TUFLOW) of Blind Creek adjacent to the development area to assess the impact of the proposed development on flood levels within and adjacent to the creek.

▪ Melbourne Water provided a RORB model of the Blind Creek catchment, which was used to provide inflow hydrographs for the TUFLOW modelling.

▪ Based on the RORB model, the critical duration event for the 100 year ARI storm for Blind Creek adjacent to the development location is the 2 hour duration storm, which has a peak flow rate of 41.8 m3/s.

▪ The TUFLOW model was validated against flood levels provided by Melbourne Water. The results for the existing conditions model were 60 mm and 30 mm higher than the flood levels provided by Melbourne Water at the north west and north east corners of the subject site, which represents a good and slightly conservative match to the information provided by Melbourne Water.

▪ The modelling assumed that the dam was full to spillway level at the time of the storm event as there is no low flow outlet which can be relied upon to drain the dam and provide additional floodplain storage.

Job No. V6000_002 Page 7 : 02/03/2018

EVIDENCED BY GLENN OTTREY REQUESTED BY DEVELOPMENT VICTORIA 609-621 BURWOOD HIGHWAY

▪ The developed conditions were modelled, including the proposed wetland system and filling the development areas at least 600 mm above the 100 year ARI flood levels provided by Melbourne Water (to provide the required freeboard for future dwellings). The developed conditions modelling showed that floodplain storage increases from approximately 21000 m3 on the site to 33600 m3, an increase of 12600 m3.

▪ The modelling shows that there is no increase in flood levels upstream of the development area – See Appendix C for flood maps.

▪ The modelling shows that there is a reduction in the flooding experienced by the properties adjacent to and downstream of the development area. There is some increases in flood levels, however these are contained to the waterway corridor and dissipate within a few hundred meters downstream of the development area.

4.4 Existing dam

A summary of the key points relating to the existing dam is:

▪ The majority of the dam (approximately 75%) is between 1.5 to 2.0 m deep. There is an area in the south west corner of the which is over 4 m deep.

▪ The dam in its current state is not engineered to provide stormwater treatment.

▪ Retrofitting the existing dam to provide stormwater treatment is not considered to be feasible without significant disturbance to the dam as stormwater treatment wetlands require shallow areas with significant vegetation.

▪ There is only approximately 300 mm difference in level between the existing outfall drain from Fairhills High School and the normal water level of the dam. This lack of available grade would make providing stormwater treatment upstream of the dam (between the dam and the outfall) very challenging.

▪ The current edge slopes of the dam do not comply with safety requirements for urban public water bodies from the Royal Lifesaving Society Australia.

I am not an expert in dam engineering, however my colleague, Ben Stark, a geotechnical engineer and dams engineering expert has undertaken a dam condition assessment of the existing dam. A full copy of this report is included in Appendix D. This included visiting the site on 3 July 2017. Ben’s conclusions on the state of the current dam are:

• “The Dam is not currently considered fit for purpose and would only be considered to be suitable for on-going use if the following upgrades / remedial works are completed: • Upgrade the spillway to provide capacity to convey, as a minimum, the 1 % AEP rainfall event plus the 10 % AEP wave freeboard. To provide the recommended spillway capacity will require raising or relocation of the existing dam embankment.

Job No. V6000_002 Page 8 : 02/03/2018

EVIDENCED BY GLENN OTTREY REQUESTED BY DEVELOPMENT VICTORIA 609-621 BURWOOD HIGHWAY

Raising the embankment to ensure that it is not overtopped in a 1 % AEP event may impact on flooding behaviour within Blind Creek and could increase flood levels within the creek in a 1 % AEP event. This would need to be investigated and any increase in flood levels approved by Melbourne Water. • Undertake the following remedial works to repair existing dam embankment defects: o Modify existing uneven embankment surface levels (ruts, depressions, etc) to reduce the likelihood of rill erosion due to concentrated runoff o Repair longitudinal cracks o Repair void in downstream shoulder adjacent to pit o Repair existing erosion on downstream batter in north-west corner of dam and stabilise embankment o Protect the upstream batter slope from further erosion / steepening / slumping. • Develop an operational plan for the Dam which defines roles and responsibilities, surveillance, monitoring and maintenance requirements.”

▪ Based on the points listed above it is my opinion that the dam should be removed and replaced with a new combined stormwater treatment and habitat wetland. This strategy has been adopted in the preliminary stormwater management plan.

Job No. V6000_002 Page 9 : 02/03/2018

EVIDENCED BY GLENN OTTREY REQUESTED BY DEVELOPMENT VICTORIA 609-621 BURWOOD HIGHWAY

5. STATEMENT

I have made all the inquiries that I believe are desirable and appropriate at this time and that no matters of significance which I regard as relevant have to my knowledge been withheld from the Panel.

I have read the Planning Panel’s Victoria “Guide to Expert Evidence” and agree to be bound by it.

Glenn Ottrey

BEnvEng (Hons)

Job No. V6000_002 Page 10 : 02/03/2018

EVIDENCED BY GLENN OTTREY REQUESTED BY DEVELOPMENT VICTORIA 609-621 BURWOOD HIGHWAY

APPENDIX A Glenn Ottrey Details, Curriculum Vitae and Instructions

Job No. V6000_002 Appendix : 02/03/2018

EVIDENCED BY GLENN OTTREY REQUESTED BY DEVELOPMENT VICTORIA 609-621 BURWOOD HIGHWAY

Expert Witness Details

Name and Address

Glenn Ottrey

Suite 15, 333 Canterbury Road

Canterbury, Victoria, 3126

Qualifications

Glenn Ottrey has the following qualifications and professional memberships:

Education

Bachelor of Environmental Engineering (First Class Honours), Monash University, 2007

Registrations/Affiliations

Member, Stormwater Victoria

Experience and Expertise of the Author

I am a senior engineer and associate at the Melbourne branch of Engeny Water Management (Engeny). I have over ten years of experience in the water resources industry working as a consultant. My area of technical expertise is in the fields of drainage design, flood modelling and water sensitive urban design. I have presented at conferences on topics relating to flood modelling and water sensitive urban design.

I have also worked on a range engineering projects in the civil and environmental disciplines, including environmental risk assessments, environmental monitoring and water supply demand strategies. I am proficient in the use of TUFLOW, HEC-RAS, RORB, MUSIC, Mapinfo, QGIS and REALM computer software packages.

I am is familiar with the drainage design standards in Victoria and the standards, policies and other issues related to urban drainage. I am also familiar with Australian Rainfall and Runoff, including the 2016 revision and how it should be applied in practice.

I have visited the site and prepared this report.

I have been supported in the preparation of the preliminary stormwater management plan by Andrew Prout, Ben Stark and Tim O’Brien.

Andrew is a senior principal engineer with over 30 years experience in the water resources field. Andrew has reviewed the preliminary stormwater management strategy for the site prepared in August 2017. Andrew has also visited the site with me in 2016.

Job No. V6000_002 Appendix : 02/03/2018

EVIDENCED BY GLENN OTTREY REQUESTED BY DEVELOPMENT VICTORIA 609-621 BURWOOD HIGHWAY

Ben is principal geotechnical engineer at Engeny and a Chartered Professional Engineer and a Registered Professional Engineer of Queensland. His expertise includes the management, supervision and interpretation of geotechnical investigations; and the analysis and design of water retention structures, water management infrastructure and waste containment facilities including tailings storage facilities. Ben undertook a dam condition assessment of the dam at 609-621 Burwood Highway Knoxfield.

Tim is a senior designer at Engeny. Tim has assisted in the production of functional design drawings of the proposed wetland, which are included in the preliminary stormwater management strategy.

A CV with more details regarding my experience is included in below.

Job No. V6000_002 Appendix : 02/03/2018

EVIDENCED BY GLENN OTTREY REQUESTED BY DEVELOPMENT VICTORIA 609-621 BURWOOD HIGHWAY

INSTRUCTIONS

Instructions were received from Development Victoria. These verbal instructions asked me to document the approach and results of developing the preliminary stormwater management plan for 609-621 Burwood Highway Knoxfield.

Job No. V6000_002 Appendix : 02/03/2018

Glenn Ottrey Senior Water Resources Engineer BEngEng (Hons)

SUMMARY Glenn is senior engineer with ten years of experience in the water resources industry. Glenn is experienced in hydraulic and hydrologic analysis and design and project management. He is an experienced project manager, having managed numerous large and small projects over the past eight years. He has worked on a wide range of projects involving drainage design and Water Sensitive Urban Design (WSUD), from concept level through to detailed design. He has also undertaken numerous flood modelling and mapping projects using both one and two dimensional models. He has also worked on a range engineering projects in the civil and environmental disciplines, including environmental risk assessments, environmental monitoring and water supply demand strategies. Glenn is proficient in the use of TUFLOW, HEC-RAS, RORB, MUSIC, Mapinfo, QGIS and REALM computer software packages.

KEY AREAS OF ◦ Hydraulic flood modelling EXPERTISE ◦ Traditional drainage design ◦ Water sensitive urban design ◦ Integrated stormwater management.

EXPERIENCE 2011 - present Troups Creek Flood Modelling, Melbourne Water and Casey City Council Senior Water Melbourne Water and the engaged Engeny to undertake flood Resources mapping of the Troups Creek Catchment. Glenn project managing this project Engineer, and oversaw its successful delivery within tight deadlines and to a high standard. Engeny, The results from this project will be used to inform planning scheme amendments Melbourne and mitigation assessments. Cranbourne Central Flood Modelling, Melbourne Water Engeny developed a detailed Tuflow flood model of Cranbourne Central for the City of Casey. Melbourne Water had previously flood modelled the key drains within the catchment but wanted to adopt outputs from the full catchment. Glenn led the project to update the flood model to Melbourne Water’s specifications and to create a full set of outputs from the flood model. Wonthaggi North East Drainage Scheme, Council Engeny was engaged to develop a drainage strategy for the future growth areas in the north and east of Wonthaggi. The proposed growth area is subject to significant flooding under current conditions and determining a suitable strategy to manage flooding was key to facilitating development in the area. Glenn led the team at Engeny working on the project and was able to deliver a strategy that could facilitate future urban growth in this area.

Melbourne Office Suite 15 / 333 Canterbury Road (PO Box 452), Canterbury VIC 3126 P: 03 9888 6978 F: 03 9830 2601 E: [email protected] W: www.engeny.com.au

City of Moreland Pilot Study Flood Mapping, Moreland City Council The Moreland City Council undertook a pilot flood mapping study of a small catchment with a known history of flooding. The pilot study will help build confidence in the flood mapping methodologies and also provided Council with a detailed insight into the flooding issues being experienced in the catchment. Murray Street drainage investigation Wonthaggi, Bass Coast Shire Council In a recent storm event flooding was experienced in a dwelling in Murray Street in Wonthaggi. Engeny was engaged by the Bass Coast Shire Council to create a flood model of the catchment which includes approximately one third of the Wonthaggi township. Glenn led the flood modelling project and was able to meet council’s key criteria of being able to establish the magnitude and frequency of flooding likely to be experienced in the catchment. WSUD data collection, Bass Coast Shire Council Engeny was engaged to audit over 200 water sensitive urban design assets in the Bass Coast Shire. Each asset was individually visited and its current condition assessed. Glenn led the project and field work which involved two weeks of field work. Following the field work a capital works and maintenance plan was devised to bring the deficient assets up to a functioning level. as a result of undertaking the project the Bass Coast Shire Council now has a detailed understanding of the current condition of their assets and the tools to be able to assess their condition and bring them back to a functioning level. Camberwell Road development flood modelling, PDS Group Engeny was engaged to PDS Group to create a flood model of a large infill development site in Camberwell. The site was subject to flooding from a local Council catchment and also contained a Council drain which needed to be relocated. Engeny was able to create a flood model and devise a flood mitigation scenario which allowed for the development to proceed and for the drain to be realigned. Kayes Drain flood modelling, SCT Logistics Engeny was engaged by SCT Logistics to undertake flood modelling of a proposed expansion of the rail warehouse adjacent to Kayes Drain. The expansion involved filling a large area which is currently subject to inundation. Multiple development planning flood advice projects, Various Clients Glenn has assisted multiple development clients in obtaining approval for smaller development sites in areas subject to flooding and covered by SBOs and LSIOs. Glenn’s approach is to try to work with the authorities and the developer to reach a position that allows for a feasible development to occur in an appropriate and safe manner. This work will often involve the use of hydraulic models, such as Tuflow, to be able to demonstrate that the development has a minimal impact on the surrounding area.

Curriculum Vitae – GLENN OTTREY Page | 2

Warrnambool citywide flood modelling, Warrnambool City Council: Engeny was engaged to flood map the . The project involved mapping the whole town of Warrnambool using Tuflow and provided the Council with an excellent knowledge of the flooding issues within the municipality. Glenn’s role was to lead the project and provide technical review of the flood modelling. A mitigation assessment was also undertaken to assist council in prioritising future works. Flood modelling and mapping, Frankston City Council: Glenn has project managed and led flood modelling and mitigation assessments with the . Three separate projects have been recently completed including Frankston South, Frankston North and Seaford. Each of these projects involved the creation of a detailed flood model in Tuflow and mitigation assessments. Developer Services Scheme Reviews (Various Locations), Melbourne Water: Melbourne Water undertakes periodic engineering reviews on their developer services schemes. The schemes provide the drainage layout for new developments areas within Greater Melbourne. The reviews have involved both concept and functional design of traditional drainage assets, such as pipe and retarding basin and also of WSUD features such as wetlands and waterways. Sunbury PSP Retarding Basin Analysis, Western Water Engeny worked with E2Designlab to complete the Integrated Water Management Plan for several major catchments in Sunbury on behalf of Western Water and Melbourne Water. Engeny’s scope of works included sub-catchment delineation, identification of suitable locations for combined wetland/retarding basins, hydrological modelling to size retarding basins and determining locations for waterway corridors. As large areas of the catchments are very steep, Engeny followed a functional design procedure to ensure that the proposed wetlands and retarding can actually be built given the site constraints Canterbury Hill Estate, Canterbury Hills Pty Ltd: Engeny has undertaken surface water master planning for this major estate in Sunbury. The work has included assessment of existing waterways, retarding basins, sediment ponds and drains and planning for future development. Engeny developed a drainage layout and plans for waterway rehabilitation, stormwater treatment, main drainage and peak flow control. Work included MUSIC modelling, RORB modelling, HEC-RAS modelling, wetland and waterway rehabilitation concept designs. Engeny produced plans and detailed reports and received approvals from Melbourne Water. Boroondara Flood Modelling and Mapping, Boroondara City Council: Engeny was engaged by the Boroondara City Council to flood map the whole municipality. Glenn was the project manager for this job and led the team through all aspects of the project. A total of 64 km2 of urban area with over 40,000 pipes was flood mapped as part of this project.

Curriculum Vitae – GLENN OTTREY Page | 3

Highton Lane Stormwater Management Plan, Mansfield Shire Council: Engeny created a stormwater management plan for the Highton lane development area, which included the required trunk drainage assets, wetlands and retarding basins for the area. It set the required setbacks from Monkey Gully Creek. The strategy ensures that all stormwater quality and quantity objectives for the development area are met including the Environmental Best Practices Management Guidelines. Eastern Bacchus Marsh Flood Modelling, VicRoads: Engeny assisted VicRoads in flood modelling the eastern interchange of the western freeway at Bacchus Marsh. The interchange is located within the Lerderderg River flood plain and its recent construction had the potential to negative impact some of the surrounding properties. Glenn led the project to find a solution to the flooding issues, which would minimise the need for costly works to alter the existing infrastructure. Surface Water Management Plan, Rookwood Necropolis: Engeny provided surface water advice input to the updated Rookwood Necropolis Landscape Masterplan. The purpose of the project was to identify opportunities and constraints at Rookwood to help to maximise the number of interments that could occur at the historic site. Blackwater Mine Flood Study, BHP Mitsubishi Alliance (BMA): Blackwater Mine is one of Australia’s largest open cut coal mines and is located near Emerald in central Queensland approximately 200 km west of Rockhampton. Seven creeks flow through the mine site along its 80 km length. Engeny was engaged to model the impacts of flooding on mine operations including determining flood immunity of critical infrastructure such as roads and plant and also the open cut pits. Inflows into pits were also quantified for different storm events. The flood models also tested compliance against Department of Environment and Resources Management guidelines for diversion channels. Lower Lerderderg Catchments Flood Mapping, Melbourne Water: The project involved undertaking hydrologic and hydraulic flood modelling and mapping of Melbourne Water Assets in Bacchus Marsh and Darley. The one and two dimensional flood modelling was undertaken using Tuflow. The final outputs were flood and hazard maps which form inputs to planning scheme overlays. Flooding Investigation, Melbourne Water: Following large rainfall events in Melbourne in early 2011 Engeny were asked to investigate flooding in Glen Iris near Gardiners Creek. The project involved creating and calibrating a one and two dimensional Tuflow model to gauged rainfall and flow data and determining mitigation options to reduce future flooding risk. The mitigation options were also assessed against design storms to determine the level of protection they provided. Civic Square Flooding Investigation, Maroondah City Council: This study involved investigating the causes and solutions to flooding in the caused by heavy rainfall events in early 2011. A hydrologic RORB model and a hydraulic Tuflow model were created to assist in determining the effectiveness of the proposed mitigation measures.

Curriculum Vitae – GLENN OTTREY Page | 4

Flood Management Plans, Melbourne Water: Melbourne Water has developed and reviews on a rolling 5 yearly basis Flood Management Plans with every council around Melbourne. Glenn has project managed the development and review of a number of Flood Management Plans for Melbourne Water. The councils Glenn has worked with include Glen Eira, Bass Coast, Moorabool and Manningham. 42-58 Nelson Street, Hantang Taifu: Engeny was engaged by Hantang Taifu to assist in the development of a flood affected site. The site was covered by an LSIO and UFZ, with Melbourne Water objecting to the initially proposed development on the site. Engeny was able to work with our client and Melbourne Water to obtain a removal of the flooding restrictions from the site and to gain Melbourne Water’s support for the removal of the Urban Flood Zone. Moorabool Shire Waterway and Stormwater Management Strategy, Moorabool Shire Council: Engeny worked with Moorabool Shire Council to develop a Stormwater and Waterway Management Strategy. The key focus to examine Moorabool Shire’s current practices for stormwater treatment, stormwater management and protecting waterways and make recommendations on how they could be improved, including identification of water quality works throughout the Shire. This included detailed MUSIC modelling of the Shire to identify opportunities in urban areas for retrofitting the existing stormwater system to provide stormwater treatment using WSUD techniques. Rain Garden Design Reviews and Infiltration Testing, Frasers (formerly Australand): Glenn has led the review of rain garden designs prior to their construction and also undertaken infiltration testing and functionality assessments prior to handover of the assets to council. Flood Investigations, : Engeny was engaged by the City of Ballarat on numerous occasions to investigate and quantify flooding issues at various different areas throughout the council. Tuflow has been used to create a flood model of the areas with known flooding issues and mitigation solutions have been proposed and modelled to test their effectiveness. The outputs from the flood modelling have been used to prepare planning scheme amendment overlays. Rural Flood Investigation, : Engeny created a flood model of a complex rural flood plain to quantify the impact of flooding being reported on a series of properties. The project also involved modelling mitigation options to assess their effectiveness in reducing flooding and also the impact on the receiving waterways. Ballarat West Drainage Scheme: A drainage scheme was required to form part of the precinct structure plan for the Ballarat West Growth Area. This involved setting out the future locations and sizing of the retarding basins, wetlands, major drainage infrastructure and overland flow paths in a large greenfield development area west of Ballarat. Werribee Flood Modelling, DLA Piper: Engeny was engaged to determine if recent works on a drainage channel had worsened flooding conditions for nearby properties following heavy rain in early 2011. The Tuflow model created was able to quantify the negative or positive impact which each property experienced as a result of the works.

Curriculum Vitae – GLENN OTTREY Page | 5

2008 - 2011 Glenn worked across the Water, Water Resources and Environment groups Engineer, while at AECOM. The projects included road drainage and WSRD design, flood AECOM Australia mapping, WSUD detailed design, environmental risk assessments and Pty Ltd (formerly environmental monitoring. Some of the major projects Glenn was involved with Maunsell Aust include the Victorian Desalination project, Victoria Harbour, Geelong Ring Road Pty Ltd) and Melbourne Water main drain flood mapping.

EDUCATION 2007 Bachelor of Environmental Engineering (Hons), Monash University, Melbourne

REGISTRATIONS Member Stormwater Association Australia / AFFILIATIONS

Curriculum Vitae – GLENN OTTREY Page | 6

EVIDENCED BY GLENN OTTREY REQUESTED BY DEVELOPMENT VICTORIA 609-621 BURWOOD HIGHWAY

APPENDIX B Wetland Functional Design

Job No. V6000_002 Appendix : 02/03/2018 NOT FOR CONSTRUCTION

Plot Date: 5 July 2017 - 9:59 AM Plotted by: ---- Cad File No: V:\Projects\V6000 Places Victoria\V6000_002 621 Burwood Highway SWMP\05 Design\AutoCAD\Drawings\V6000-002-C001.dwg NOT FOR CONSTRUCTION

Plot Date: 5 July 2017 - 10:43 AM Plotted by: ---- Cad File No: V:\Projects\V6000 Places Victoria\V6000_002 621 Burwood Highway SWMP\05 Design\AutoCAD\Drawings\V6000-002-C010.dwg NOT FOR CONSTRUCTION

Plot Date: 5 July 2017 - 10:52 AM Plotted by: ---- Cad File No: V:\Projects\V6000 Places Victoria\V6000_002 621 Burwood Highway SWMP\05 Design\AutoCAD\Drawings\V6000-002-C020.dwg NOT FOR CONSTRUCTION

Plot Date: 11 July 2017 - 4:05 PM Plotted by: ---- Cad File No: V:\Projects\V6000 Places Victoria\V6000_002 621 Burwood Highway SWMP\05 Design\AutoCAD\Drawings\V6000-002-C021.dwg NOT FOR CONSTRUCTION

Plot Date: 5 July 2017 - 10:57 AM Plotted by: ---- Cad File No: V:\Projects\V6000 Places Victoria\V6000_002 621 Burwood Highway SWMP\05 Design\AutoCAD\Drawings\V6000-002-C030.dwg NOT FOR CONSTRUCTION

Plot Date: 27 July 2017 - 8:19 AM Plotted by: ---- Cad File No: V:\Projects\V6000 Places Victoria\V6000_002 621 Burwood Highway SWMP\05 Design\AutoCAD\Drawings\V6000-002-C031.dwg NOT FOR CONSTRUCTION

Plot Date: 5 July 2017 - 10:58 AM Plotted by: ---- Cad File No: V:\Projects\V6000 Places Victoria\V6000_002 621 Burwood Highway SWMP\05 Design\AutoCAD\Drawings\V6000-002-C040.dwg

EVIDENCED BY GLENN OTTREY REQUESTED BY DEVELOPMENT VICTORIA 609-621 BURWOOD HIGHWAY

APPENDIX C Flood Maps

Job No. V6000_002 Appendix : 02/03/2018 Legend 1% AEP Peak Flood Depth 0 m 0.2 m 0.4 m 0.6 m 0.8 m 1 m

50 0 50 m 621 Burwood Highway Knoxville Suite 15, 333 Canterbury Rd, Canterbury VIC 3126 PO Box 452 Canterbury VIC 3126 1:2,000 www.engeny.com.au Map Projection: Tranverse Mercator Job Number: V6000_002 P: 03 9888 6978 Horizontal Datum: Geocentric Datum of Australia Revision: 0 F: 03 9830 2601 Vertical Datum: Australia Height Datum Grid: Map Grid of Australia, Zone 55 Drawn: GO E: [email protected] Data Source: DELWP: VicMap - Sep 2016 1% AEP Existing Conditions Checked: SD NearMaps Aerial Photography Dec 2017 Peak Flood Depth Date: 24/7/2017 Legend 1% AEP Peak Flood Depth 0 m 0.2 m 0.4 m 0.6 m 0.8 m 1 m

50 0 50 m 621 Burwood Highway Knoxville Suite 15, 333 Canterbury Rd, Canterbury VIC 3126 PO Box 452 Canterbury VIC 3126 1:2,000 www.engeny.com.au Map Projection: Tranverse Mercator Job Number: V6000_002 P: 03 9888 6978 Horizontal Datum: Geocentric Datum of Australia Revision: 0 F: 03 9830 2601 Vertical Datum: Australia Height Datum Grid: Map Grid of Australia, Zone 55 Drawn: GO E: [email protected] Data Source: DELWP: VicMap - Sep 2016 1% AEP Developed Conditions Checked: SD NearMaps Aerial Photography Dec 2017 Peak Flood Depth Date: 24/7/2017 Legend Change in Flood Level <= -0.09 m -0.09 - -0.07 m -0.07 - -0.05 m -0.05 - -0.03 m -0.03 - -0.01 m -0.01 - 0.01 m 0.01 - 0.03 m 0.03 - 0.05 m 0.05 - 0.07 m 0.07 - 0.09 m > 0.09 m Was flooded, now not flooded Was not flooded, now flooded Flow comparison location

50 0 50 m 621 Burwood Highway Knoxville Suite 15, 333 Canterbury Rd, Canterbury VIC 3126 PO Box 452 Canterbury VIC 3126 1:2,000 www.engeny.com.au Map Projection: Tranverse Mercator Job Number: V6000_002 P: 03 9888 6978 Horizontal Datum: Geocentric Datum of Australia Revision: 0 F: 03 9830 2601 Vertical Datum: Australia Height Datum Grid: Map Grid of Australia, Zone 55 Drawn: GO E: [email protected] Data Source: DELWP: VicMap - Sep 2016 1% AEP Peak Flood Depth Comparison Map Checked: SD NearMaps Aerial Photography Dec 2017 Date: 24/7/2017

EVIDENCED BY GLENN OTTREY REQUESTED BY DEVELOPMENT VICTORIA 609-621 BURWOOD HIGHWAY

APPENDIX D Dam Condition Assessment Report

Job No. V6000_002 Appendix : 02/03/2018

Development Victoria

Dam Condition Assessment Report

621 Burwood Highway, Knoxfield

July 2017

V6000_002

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

DISCLAIMER

This report has been prepared on behalf of and for the exclusive use of Development Victoria and is subject to and issued in accordance with Development Victoria instruction to Engeny Water Management (Engeny). The content of this report was based on previous information and studies supplied by Development Victoria.

Engeny accepts no liability or responsibility whatsoever for it in respect of any use of or reliance upon this report by any third party. Copying this report without the permission of Development Victoria or Engeny is not permitted.

V6000_002 621 Burwood Highway SWMP V:\Projects\V6000 Places Victoria\V6000_002 621 Burwood Highway SWMP\07 Deliverables\Documents\Report\Revisions\Dam Assessment\621 Burwood Highway Knoxfield Dam Condition Assessment Rev 0.docx REV DESCRIPTION AUTHOR REVIEWER APPROVED BY DATE

Rev 0 Client Issue Ben Stark Glenn Ottrey Glenn Ottrey 21/07/2014

Signatures

Job No. V6000_002 Page i Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

CONTENTS

1. INTRODUCTION ...... 1

2. DAM DESCRIPTION ...... 3 2.1 General Description ...... 3

3. FIELD INSPECTION ...... 5 3.1 General ...... 5 3.2 Observations ...... 5

4. DESKTOP FAILURE MODES ASSESSMENT...... 8 4.1 Background Information ...... 8 4.2 Failure Modes ...... 8 4.3 Embankment Stability Assessment ...... 8 4.4 Spillway Capacity Assessment ...... 10 4.5 Flood Immunity Assessment ...... 11

5. DAM CONDITION ASSESSMENT ...... 12

6. CONCLUSIONS AND RECOMMENDATIONS ...... 13

7. QUALIFICATIONS ...... 14

Appendices

APPENDIX A ...... SITE INSPECTION PHOTOS

List of Tables Table 2.1 Dam Details...... 4 Table 3.1 Field Observations ...... 6 Table 4.1 Assumed Material Parameters Adopted for Analysis ...... 9 Table 4.2 Desktop Stability Analysis Results ...... 9

Job No. V6000_002 Page ii Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

List of Figures Figure 1.1 Site Layout ...... 2 Figure 2.1 Dam General Arrangement ...... 3 Figure 3.1 Western Dam Embankment Typical Cross-Section ...... 5 Figure 4.1 Stability Analysis Output – Lower Bound Strength Parameters ...... 10

Job No. V6000_002 Page iii Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

1. INTRODUCTION

Engeny Water Management has been engaged by Development Victoria (previously Places Victoria) to undertake a condition assessment of the existing dam (herein referred to as ‘the dam’) at 621 Burwood Highway, Knoxfield (herein referred to as ‘the site’). The site is the disused Institute of Horticultural Development site. Commercial and industrial properties are located to the west and the DELWP Precinct is located to the site’s immediate south-west. The Fairhills High School and residential properties lie to the east of the site. Figure 1.1 provides an overview of the dam location.

The dam is located in the site’s north-west corner and overflows to the north into the adjacent Blind Creek waterway. Currently the dam provides water storage services with limited treatment. The dam was originally built for agricultural water supply purposes.

This report summarises the findings of the dam site inspection and the outcomes of the dam condition assessment.

Job No. V6000_002 Page 1 Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Blind Creek

Dam

Figure 1.1 Site Layout

Job No. V6000_002 Page 2 Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

2. DAM DESCRIPTION

2.1 General Description

The dam is a combination excavation and earth fill embankment dam with a storage capacity of approximately 31 ML. There is no design or as-constructed documentation available for the dam.

The dam is used to contain stormwater from the upstream catchment which enters the dam via a combination of overland flow and an open drain.

Overflows from the dam are directed to the north into Blind Creek via the spillway pipes.

Details of the existing dam are summarised in Table 2.1. The dam general arrangement is illustrated in Figure 2.1.

Blind Creek

Spillway Pipes Dam Embankment

Dam Impoundment

Inlet Drain

Figure 2.1 Dam General Arrangement

Job No. V6000_002 Page 3 Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Table 2.1 Dam Details

Detail Value

Location North-West corner of Site – 621 Burwood Highway, Knoxfield

Current Function - Stormwater storage Function Previous Function – Water supply for agricultural purposes

Year Constructed Unknown

It appears that a buried pipeline has been retrospectively installed Dam Modifications along the length of the embankment within the downstream shoulder

Design Documentation None available

As-Constructed Documentation None available

Earth fill embankment around north-western perimeter (low side) and Type of Construction excavation within reservoir area

Catchment Area 45 ha

Full Supply Level (FSL) 77.54 m AHD

Storage Capacity 30.8 ML

Ponded Area at FSL 1.6 ha

Dam Crest Level 77.81 m AHD (varies)

Freeboard Between Spillway and Dam Crest 0.27 m (varies)

Maximum Excavation Depth Below Natural 4.8 m Surface

Reservoir Excavation Batter Slope Unknown – under water line during site inspection and survey

Maximum Embankment Height Above 1.5 m Natural Surface

Embankment Length 150 m

Slope of Upstream Embankment Face Varies from 1V:4H to as steep as 2V:1H

Slope of Downstream Embankment Face Varies due to benched profile but as steep as 1V:2H

Spillway 10 x 225 mm diameter concrete pipes

Consequence Category Assessment None available

Job No. V6000_002 Page 4 Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

3. FIELD INSPECTION

3.1 General

A visual inspection of the dam was undertaken and focussed on all aspects of the storage structure necessary for it to perform its required function. The inspections were undertaken by Ben Stark (Chartered Professional Engineer) of Engeny Water Management on 3rd July 2017.

The inspections included visual inspections of the condition of the following aspects of the storage structure:

. Dam crest

. Downstream embankment slope

. Upstream embankment slope (where visible)

. Spillway.

3.2 Observations

Field observations of deficiencies or defects are summarised below in Table 3.1.

Photographs illustrating the observed deficiencies or defects are included in Appendix A.

A typical western dam embankment cross-section is presented below in Figure 3.1

Upstream Downstream

Bench Buried Pipe

Figure 3.1 Western Dam Embankment Typical Cross-Section

Job No. V6000_002 Page 5 Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Table 3.1 Field Observations

Photo Observed Defect or Deficiency Potential Cause Potential Impact Reference (Appendix A)

Uneven crest surface will promote concentrated rainfall runoff and progressive rill erosion / steepening of the Wheel ruts on the dam embankment crest Driving on crest following rain A4 downstream batter which can in time lead to embankment instability and dam breach

Uneven batter slope surface will promote concentrated Longitudinal crack present along the majority of the length rainfall runoff and progressive rill erosion / steepening of of western dam embankment on the downstream batter the downstream batter which can in time lead to A5 bench. The crack alignment is immediately downstream of Poor construction embankment instability and dam breach the inferred location of the buried pipeline.

Settlement of poorly compacted pipeline Water ingress into the longitudinal cracks increasing trench backfill materials. pore pressures in the downstream shoulder which can Depression / settlement of dam embankment downstream lead to embankment instability and dam breach A6 batter bench above inferred location of buried pipeline Progressive loss / erosion of pipeline

trench backfill materials due to open pipe Water ingress into the longitudinal cracks leading to joints progressive erosion of the cracks and steepening of the A void has formed against the concrete pit within the downstream batter which can in time lead to A7 downstream shoulder of the dam embankment embankment instability and dam breach

Progressive erosion / slumping of the upstream batter Erosion / steepening of the visible portion of the upstream slope resulting in reduced embankment crest width Wind generated waves A8 embankment batter slope which can in time lead to embankment instability and dam breach

Job No. V6000_002 Page 6 Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Photo Observed Defect or Deficiency Potential Cause Potential Impact Reference (Appendix A)

Overtopping of dam embankment crest during rainfall events which exceed the Significant erosion (>1 m deep) around the concrete pit spillway capacity. Ground survey located within the downstream shoulder of the dam indicates the north-western corner of the Further erosion / steepening of the downstream batter, embankment at the north-western corner of the dam. A9 dam is the low point of the dam during a single overtopping event or multiple events, A10 embankment crest. leading to embankment instability and dam breach Note: this erosion was not evident during a previous site

inspection in November 2016, Progressive erosion due to open pipe joints upstream of the pit

Increased risk of internal erosion (piping) failure along Medium size tree (~4 m high) on downstream batter slope N/A the root / embankment fill interface particularly if the A11 of dam embankment roots extend to the upstream batter slope

Progressive erosion / slumping of the upstream batter Erosion (undercutting) adjacent to and beneath the spillway slope resulting in failure / partial blockage of the pipes concrete apron. Significant cracking / failure of the Wind generated waves concrete pipes, reduced spillway capacity and increased A12 concrete spillway apron. frequency of embankment overtopping events which could lead to dam breach.

Job No. V6000_002 Page 7 Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

4. DESKTOP FAILURE MODES ASSESSMENT

4.1 Background Information

No dam design or as-constructed documentation is available for the existing dam. As a result, the following is currently unknown:

. Dam embankment zoning / material type and foundation conditions / treatment

. Design factor of safety against dam embankment instability

. Design spillway capacity

. Dam flood immunity.

4.2 Failure Modes

A desktop assessment has been undertaken to understand the likelihood of the following failure modes:

. Embankment Instability

. Overtopping failure (spillway capacity)

. Overtopping failure (flood immunity from Blind Creek).

4.3 Embankment Stability Assessment

Desktop level stability analysis was undertaken for the typical western dam embankment section under steady state conditions with the water level in the dam at full supply (spillway) level. The dam embankment geometry was adopted from recent ground survey data.

Due to the lack of available geotechnical information for the dam the analyses considered a range of assumed material strength parameters (upper and lower bound). The stability analysis assumed that materials excavated from within the dam impoundment would have been used to construct the dam embankment. Assumed seepage parameters adopted for the materials are based on experience. The material parameters adopted for the analysis are summarised below in Table 4.1.

Job No. V6000_002 Page 8 Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Table 4.1 Assumed Material Parameters Adopted for Analysis

Unit Effective Horizontal Friction Permeability Material Weight cohesion Permeability Angle ratio (kv:kh) (kN/m3) (kPa) (m/s)

Dam Embankment – Lower 20 2 22 1 x 10-8 0.1 Bound

Dam Embankment – Upper 20 2 34 1 x 10-8 0.1 Bound

Foundations – Lower Bound 20 2 20 1 x 10-7 0.25

Foundations – Upper Bound 20 2 32 1 x 10-7 0.25

Finite element seepage analysis was undertaken using SEEP/W 2016 software (version 8.16) developed by GEO-SLOPE International. Seepage analysis was undertaken to predict the location of the phreatic surface within the embankment.

Limit equilibrium slope stability analysis was undertaken using SLOPE/W 2016 software (version 8.16) developed by GEO-SLOPE International. All slip failure surfaces and factors of safety (FoS) were optimised in SLOPE/W, and computed using the Morgenstern-Price method.

The steady state embankment stability was assessed under drained conditions with all materials modelled with effective strength parameters. The results of the desktop stability analyses are summarised below in Table 4.2 and the output from the lower bound analysis is presented in Figure 4.1.

Table 4.2 Desktop Stability Analysis Results

Minimum Acceptable Steady State Stability Analysis Factor of Safety Factor of Safety (ANCOLD)

Upper bound strength parameters 2.53 1.50

Lower bound strength parameters (conservative) 1.75 1.50

The results of the desktop analyses suggests the factor of safety (FoS) against dam embankment instability, for even lower bound assumed strength parameters, is greater than 1.50, which is typically considered to be the minimum acceptable FoS for a dam under steady state conditions.

Job No. V6000_002 Page 9 Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

1.751

Figure 4.1 Stability Analysis Output – Lower Bound Strength Parameters

4.4 Spillway Capacity Assessment

The dam was constructed with a spillway comprising 10 x 225 mm diameter concrete pipes. The maximum freeboard between the spillway pipe invert and the dam crest low point (north-west corner of the dam) is only 270 mm.

The existing spillway has a full flow capacity of approximately 0.35 m3/s and it is predicted that the low section of the embankment crest in the north-west corner of the dam will overtop during 63 % AEP rainfall events (1 year ARI event or 1 exceedance per year). Based on the capacity of the existing spillway it is expected that multiple dam crest flood overtopping events have occurred over the life of the dam.

For a dam fetch length of 150 m, the 63 % AEP wave height (wave set-up plus run-up) is predicted to be approximately 300 mm. Based on the existing freeboard of 270 mm it is expected that wind generated waves will overtop the embankment during 63 % AEP wind events. It is expected that multiple dam crest wave overtopping events have occurred over the life of the cam.

An embankment overtopping event has the potential to lead to dam breach dependent on the duration of the overtopping event, downstream tail water levels during the event (head differential) and embankment material properties.

Typically, low consequence category dams of this size would be designed with a spillway capable of conveying the 1 % AEP rainfall event plus 10 % AEP wave freeboard to reduce the likelihood of an overtopping failure of the embankment.

Job No. V6000_002 Page 10 Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

4.5 Flood Immunity Assessment

Flood modelling of the Blind Creek catchment indicates that flood ingress into the dam via the spillway pipes would be expected during a 5 % AEP rainfall event. Flood modelling also indicates that flood ingress into the dam from Blind Creek would occur in the 18 % AEP rainfall event in the north east corner of the dam. During a 2 % AEP event the predicted flood levels in Blind Creek would overtop the dam embankment crest.

A flood ingress embankment overtopping event has the potential to lead to dam breach dependent on the duration of the overtopping event, dam water levels during the event (head differential) and embankment material properties.

In this instance, due to the small dam storage capacity and low spillway capacity (63 % AEP event), dam embankment overtopping (flow from dam to Blind Creek) would be expected to occur prior to any embankment crest overtopping due to flood ingress (2 % AEP event).

Typically, low consequence category dams of this size would be designed with a 1 % AEP flood ingress immunity to reduce the likelihood of an overtopping failure of the embankment and to limit the impacts of tail water flood levels on dam spillway capacity.

Job No. V6000_002 Page 11 Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

5. DAM CONDITION ASSESSMENT

Based on the site inspection observations the dam is currently considered to be in fair to poor condition. A number of existing defects / deficiencies were identified which have the potential to lead to dam failure in time if left to progressively deteriorate without intervention.

The desktop failure modes assessment identified that the existing spillway doesn’t have capacity to pass even the 63 % AEP event. This is significantly lower than the minimum spillway capacity of 1 %AEP recommended by industry guidelines (ANCOLD) for even low consequence category dams. Overtopping of the dam embankment crest would be expected to occur on a regular basis, which significantly increases the likelihood of dam failure.

Job No. V6000_002 Page 12 Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

6. CONCLUSIONS AND RECOMMENDATIONS

The Dam is not currently considered fit for purpose and would only be considered to be suitable for on-going use if the following upgrades / remedial works are completed:

. Upgrade the spillway to provide capacity to convey, as a minimum, the 1 % AEP rainfall event plus the 10 % AEP wave freeboard. To provide the recommended spillway capacity will require raising or relocation of the existing dam embankment. Raising the embankment to ensure that it is not overtopped in a 1 % AEP event may impact on flooding behaviour within Blind Creek and could increase flood levels within the creek in a 1 % AEP event. This would need to be investigated and any increase in flood levels approved by Melbourne Water

. Undertake the following remedial works to repair existing dam embankment defects:

 Modify existing uneven embankment surface levels (ruts, depressions, etc) to reduce the likelihood of rill erosion due to concentrated runoff  Repair longitudinal cracks  Repair void in downstream shoulder adjacent to pit  Repair existing erosion on downstream batter in north-west corner of dam and stabilise embankment  Protect the upstream batter slope from further erosion / steepening / slumping.

. Develop an operational plan for the Dam which defines roles and responsibilities, surveillance, monitoring and maintenance requirements.

Job No. V6000_002 Page 13 Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

7. QUALIFICATIONS

a. In preparing this document, including all relevant calculation and modelling, Engeny Management Pty Ltd (Engeny) has exercised the degree of skill, care and diligence normally exercised by members of the engineering profession and has acted in accordance with accepted practices of engineering principles.

b. Engeny has used reasonable endeavours to inform itself of the parameters and requirements of the project and has taken reasonable steps to ensure that the works and document is as accurate and comprehensive as possible given the information upon which it has been based including information that may have been provided or obtained by any third party or external sources which has not been independently verified.

c. Engeny reserves the right to review and amend any aspect of the works performed including any opinions and recommendations from the works included or referred to in the works if:

(i) Additional sources of information not presently available (for whatever reason) are provided or become known to Engeny; or

(ii) Engeny considers it prudent to revise any aspect of the works in light of any information which becomes known to it after the date of submission.

d. Engeny does not give any warranty nor accept any liability in relation to the completeness or accuracy of the works, which may be inherently reliant upon the completeness and accuracy of the input data and the agreed scope of works. All limitations of liability shall apply for the benefit of the employees, agents and representatives of Engeny to the same extent that they apply for the benefit of Engeny.

e. This document is for the use of the party to whom it is addressed and for no other persons. No responsibility is accepted to any third party for the whole or part of the contents of this report.

f. If any claim or demand is made by any person against Engeny on the basis of detriment sustained or alleged to have been sustained as a result of reliance upon the report or information therein, Engeny will rely upon this provision as a defence to any such claim or demand.

g. This report does not provide legal advice.

Job No. V6000_002 Page 14 Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

APPENDIX A Inspection Photos

Job No. V6000_002 Appendix Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Photo A1 Dam impoundment looking east

Job No. V6000_002 Appendix Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Photo A2 Dam embankment upstream batter slope looking north towards spillway

Job No. V6000_002 Appendix Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Photo A3 Dam embankment downstream batter slope with benched profile - looking north

Job No. V6000_002 Appendix Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Photo A4 Wheel ruts on dam embankment crest

Job No. V6000_002 Appendix Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Photo A5 Longitudinal crack on dam embankment downstream batter slope bench

Job No. V6000_002 Appendix Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Photo A6 Pit located on dam embankment downstream batter slope bench. Visible depression / settlement of embankment bench above inferred pipeline alignment either side of the pit

Job No. V6000_002 Appendix Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Photo A7 A void has formed within the embankment downstream shoulder beneath the pit concrete surround

Job No. V6000_002 Appendix Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Photo A8 Erosion / steepening of the dam embankment upstream batter slope

Job No. V6000_002 Appendix Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Photo A9 Significant erosion around the pit located on the downstream embankment batter slope at the northern end of the dam embankment

Job No. V6000_002 Appendix Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Photo A10 Northwest corner of the Dam embankment 16 November 2016

Job No. V6000_002 Appendix Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Photo A11 Tree on dam embankment downstream batter slope

Job No. V6000_002 Appendix Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Photo A12 Erosion of the upstream batter slope. Undercutting and significant cracking of the concrete spillway structure

Job No. V6000_002 Appendix Rev 0 : 21/07/2014

DEVELOPMENT VICTORIA DAM CONDITION ASSESSMENT REPORT

Photo A13 Dam embankment looking south showing proximity of buildings to the west of the dam

Job No. V6000_002 Appendix Rev 0 : 21/07/2014