Draft Elsternwick Park Sustainable Water Management Strategy

Transcription

1 Draft Elsternwick Park Sustainable Water Management Strategy Prepared for Bayside City Council Prepared by EDAW Ecological Engineering Practice Area September 2008 DESIGN, ENVIRONMENTS AND PLANNING WORLDWIDE

2 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y This document has been prepared solely for the benefit of Bayside City Council and is issued in confidence for the purposes only for which it is supplied. Unauthorised use of this document in any form whatsoever is prohibited. No liability is accepted by EDAW or any employee, contractor, or sub-consultant of this company with respect to its use by any other person. This disclaimer shall apply notwithstanding that the document may be made available to other persons for an application for permission or approval to fulfil a legal obligation. Document Control Sheet Report title: Elsternwick park Sustainable Water Management Strategy Suggested Reference: EDAW (2008) Version: Author(s): Approved by: Final Sara Lloyd Peter Breen Signed: Date: September, 2008 Our reference: Distribution: Acknowledgements: P:\ Elsternwick Park Water Strategy\ Elsternwick park\edaw report Naomi Paton, Bayside City Council State Government (funding body) Steering committee: SE Water, Melbourne Water, Department of Sustainability and Environment Involvement of park tenants EDAW is accredited as a 100% Climate Neutral business in the Australian Region. We are committed to reducing our energy consumption and ecological footprint and have neutralised our emissions from travel and utilities.

3 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y Table of Content Chapter 1. Introduction 1.1 Background Council s commitment to sustainable water management practices Sustainable water management targets Purpose of this report Modelling approach adopted...6 Chapter 2. Place Based Model 2.1 Sustainable urban water management Fit for - purpose Cost consideration of alternative water supplies Consideration of alternative water supplies...11 Chapter 3. Elsternwick Park Implementation Plan 3.1 Park description Park stakeholders Demand management strategies Catchment description and stormwater characteristics Stormwater quality Flow management configuration at the site Site water balance Stormwater harvesting schemes and requirements for treatment What harvesting demands can be sustained at Elsternwick Park? Concept design for a treatment wetland Water level fluctuations predicted for Elsternwick Park lake Stormwater quality benefits to Port Phillip Bay associated with a harvesting scheme in Elsternwick Park Estimated costs...29 Chapter 4. Recommendations 4.1 Moving forward Funding opportunities Implementation plan...33

4 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y Introduction 1.1 Background Bayside City Council is committed to conserving water and protecting the beneficial uses of its waterways through integrated urban water management projects. EDAW has been engaged to explore stormwater harvesting opportunities at Elsternwick Park to reduce Council dependence on mains water consumption and enhance the high amenity and recreational values associated with the park This project explores the potential to close the loop on the water balance at Elsternwick Park. A fundamental component to achieve this is to minimize the use of mains water and optimize the use of alternative water resources across the site in a fit-for-purpose capacity. Council has made significant advances towards achieving broad sustainable water objectives across the municipality. This includes both conserving water and protecting receiving environments from the impacts of urban runoff, both in terms of quantity and quality. This includes: Reducing mains water use through efficiency, urban design and behaviour change; Minimising wastewater disposal to sewer through demand management; Treating stormwater to meet water quality objectives for harvesting and reuse and/or discharge to waterways; Protecting groundwater from contaminants and disruption; and Managing catchment hydrology, particularly for the protection of aquatic habitats. This project was made possible with the assistance of state government Drought Relief Community Sport and Recreational Program funding, to help communities develop sustainable approaches to water management of sports grounds and facilities Council s commitment to sustainable water management practices The City of Bayside has the highest per capita residential water consumption in South East Water s service area. Over 90% of Councils water demands is attributed to irrigation of parks, sporting facilities, golf courses and gardens (ICLEI, 2005). South

5 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 5 East Water has identified Elsternwick Park as having the third highest usage of potable water across Council owned assets or controlled facilities (including those under lease arrangements). Its usage is exceeded only by the Brighton Public Golf Course and Sandringham Municipal Golf Links. The Bayside Planning Scheme Municipal Strategic Statement overarching goal is to be an ecologically focused city in which natural resources are valued by all the community, present needs are met, and development is responsibly managed for the benefits of this and future generations. It aims: to provide a drainage system that promotes the on-site retention and re-use of stormwater run-off, regulates overland flow to prevent flooding and improves water quality, particularly in terms of run-off to the Bay. Council Plan ( ) states that the key strategic challenge for council over the coming years is environmental sustainability. The key objectives outlined in the plan are: Reduce the impact of the drought and water restrictions on Council assets and services; Continue to provide a service to the community; and Adopt a strategic service approach in planning for long-term water sustainable facilities. Council s Water Action Plan ( ) provides an action plan to assist council in achieving these objectives Sustainable water management targets Bayside Council has set a goal to reduce water consumption by 30% for Council operations and 20% for the community by 2010/2011 (with 2000/01 used as a base line year). Goals have also been set for improving erosion and sediment control across the municipality, and reduce litter, herbicide and fertilizer entering the stormwater drainage systems and waterways (ICLEI, 2005). Bayside Council s water quality vision (Fisher Stewart, 2001) states the quality of stormwater within Bayside and discharging into Port Phillip Bay will not impact upon the natural environment or human activities. Bayside will strive to achieve the following objectives: All stormwater drains will be free of litter. All stormwater will be pollution free. All outfall drains will discharge clean stormwater. In addition to this, Melbourne Water is committed to reducing nitrogen loading to the Port Phillip Bay. A study of Port Phillip Bay undertaken by CSIRO recommended a reduction in total nitrogen of 1000 tonne per year were critical to maintaining a healthy ecosystem. The target reduction in nitrogen loads from catchment sources (500 t/y) is a shared responsibility (the remaining 500 t/y will be achieved through

6 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 6 upgrade the Western Treatment Plant). The program began in 2000 and aims to achieve a 100 tonne reduction in total nitrogen loads by The reduction in nitrogen loading to Port Phillip Bay achieved through a stormwater harvesting scheme in Elsternwick Park will be therefore strongly support by Melbourne Water. 1.2 Purpose of this report The purpose of this report is to investigate opportunities to develop a sustainable water management strategy for Elsternwick Park to meet community needs and preserve sportsgrounds and facilities under drought conditions. Long term sustainable management of these assets requires reductions in mains water supply through demand management practices and opportunities for stormwater harvesting. Modeling is undertaken to investigate water supply opportunities, reliability of supply, and requirements for treatment, storage and delivery of harvested stormwater. Concept design for treatment measures is provided including storage volumes, and surface area and design characteristics for a treatment wetland. This project is undertaken and reported on at three levels. At the strategic level, the underlying philosophy and guiding principles for water conservation across sportsgrounds and reserves consistent with Council s corporate goals and vision (Chapter 1), At the planning level, a framework for action (place-based model) that provides broad environmental considerations across the park and meet multiple outcomes for sustainable water cycle management, habitat protection/enhancements and improved recreational amenities. This includes a review of alternative water sources and demands with opportunities outside of the park boundary that could contribute to improved benefits at the park identified and incorporated into the strategy (Chapter 2), At the implementation level, the setting of priorities detailing the necessary site works to be undertaken at a conceptual level that details storage and/or treatment requirements (include footprints, storage volume, etc), the calculation of the reliability of a stormwater harvesting scheme (Chapter 3). Recommendations are provided to Council as to moving forward with meeting the park s water demands with consideration for access harvested water to be used elsewhere. 1.3 Modelling approach adopted The Model for Urban Stormwater Improvement Conceptualisation (MUSIC) has been used to model catchment runoff using rainfall data recorded at 6 minute intervals from 1986 to 2006 in Melbourne (BOM Station 86071). This rainfall record incorporates the drought that has occurred over the last decade and therefore provides a sound indication of the performance of the system during extended periods of low rainfall.

7 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 7 Catchment areas potentially available for harvesting and their characteristics have been interpreted from Council and Melbourne Water drainage network plans and Google Earth aerial imagery. More detailed drainage network information will be required to undertake subsequent functional and detail designs of the options proposed in this report.

8 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y Place Based Model 2.1 Sustainable urban water management An emerging challenge for urban communities is to incorporate design strategies that provide resilience to future uncertainty associated with drought and climate change, while catering for increased demands placed on the supply system due to population growth. WSUD is a holistic approach to sustainable and integrated management of the urban water cycle, encompassing the three urban water streams of potable mains water, sewerage and stormwater, within the context of the urban built form and landscape. Sustainable urban water management can be achieved by incorporating the following principles into urban design: 1. Conserve water supplies (mains and alternative sources of water) through demand management strategies, 2. Protect and enhance natural systems by minimising the impact of urban stormwater on the receiving aquatic ecosystem, 3. Integrate stormwater management into the landscape and maximise its use as an alternative water supply, 4. Use available water sources for the most appropriate purposes ( fit-forpurpose ), and 5. Add value while minimising costs. The GHD (2007) provides two key recommendations for the medium to long management of sportsgrounds in a drier climate. They are to: 1. Any rehabilitation works of drought affected ovals should consider as a minimum conversion of grasses to warm season varieties 2. The following plans need to be prepared to work towards a long term solution and be ready to respond to water conservation funding opportunities: Sustainable water use plans; and Water conservation plans.

9 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 9 The recent Prime Minister s Science, Engineering and Innovation Council report states that all cities need to develop a diversified portfolio of water supply options (PMSEIC, 2007). All water management initiatives should be supported through demand management strategies such as the installation of water efficient appliances and fittings to conserve water. Alternative water source options should be explored and include: Pipelines and interlining grids Rainwater tanks Stormwater harvesting Use of groundwater where available Recycling, including: - Recycling at the household scale - Sewer mining with small scale treatment plants - Large scale use of recycled water for industrial/commercial purposes - Third pipe systems to recycle water to households - Injection of purified water back into the drinking water supply Desalination Aquifer storage and recovery Each of the alternative water sources has unique reliability, energy cost, environmental risk and economic profile. 2.2 Fit for - purpose The concept of fit-for-purpose provides a means for prioritising alternative water sources to demands based on a cascading range in quality as shown in Figure 1. With the exception of wastewater, the closer the match in quality of the source and demand the less treatment required and generally the less energy intensive and cheaper the provision of the alternative water source. Alternative sources of water are therefore considered to have a preferred use in the urban environment, if site opportunities and constraints are conducive. However, if the preferred source-demand arrangement is not viable then other source-demand combinations need to be considered in the context of local site conditions.

10 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 1 0 High Quality of water required for urban demands Low High Water cascade Human consumption - kitchen Quality of alternative water source Mains drinking water Shower & bathroom taps Rainwater Hot water runoff (roof) system Clothes Stormwater runoff washing Garden Catchment runoff irrigation Irrigation of sporting Greywater facilities & parks Toilet Wastewater flushing Low Figure 1 Consideration of cascading quality in defining preferred demands for alterative water sources (modified after Holt, 2003) 2.3 Cost consideration of alternative water supplies A recent analysis of capital costs associated with alternative water supplies shows that stormwater reuse on a large scale (precinct or catchment basis) is costed on average at below $1.50 per kl, as shown in Figure 2. As of the 1 st July 2008 mains water provided by South East Water is costed at: $ per kl for the first 440 litres of water used per day. $ per kl for water usage above 440 litres and up to 880 litres per day, and $ per kl for water usage above 880 litres per day. At the current cost for mains water supply a regional or catchment based stormwater harvesting scheme, as proposed for Elsternwick Park, is similar in cost of supply to that for mains water. The Essential Services Commission has warned that the cost of mains water is likely to double when the desalination plant is constructed in Victoria to cover the cost of this new infrastructure. Energy requirements for the production of desalinated water and the governments commitment to a carbon tax is likely to drive prices even higher. Figure 2 shows the long term sustainability of stormwater harvesting from urban catchments and its relatively cheap supply cost compared to that for wastewater, desalination or use of rainwater tanks.

11 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 1 1 $12.00 $12.30 $10.00 $9.30 $8.00 $/kl $6.00 $5.00 $6.00 $4.00 $2.61 $3.00 $3.50 $4.00 $2.00 $0.00 Catchment thinning $1.30 $1.45 $1.50 $1.58 $2.15 $1.68 $0.25 $1.15 $0.30 $1.30 $0.63 $0.00 $0.10 $0.20 $0.15 $0.06 $0.08 $0.22 Purchase irrigation water Demand management Stormwater reuse Groundwater Indirect potable reuse Dams and surface water Seawater desalination BASIX Loss reduction Nonpotable water recycling Long distance pipelines Rainwater tanks Figure 2 Cost of alternative water supplies (Source: ( Marsden Jacon Associates, 2006) 2.4 Consideration of alternative water supplies Further consideration was given to a range of criteria for potential use of a range of alternative water supplies for Elsternwick Park. Table 1 summarises the advantages, challenges and recommendations associated with the use mains water and alternative water sources including: Rainwater and stormwater harvesting (local catchments) Stormwater harvesting from Elster Creek/Elwood Canal (stormwater/catchment runoff) Sewer mining and grey water reuse > high energy demand The recommended alternative water supply for Elsternwick Park is harvesting stormwater from Elster Creek/Elwood canal because it is in plentiful supply and offers multiple benefits for water conservation and minimising stormwater discharge to the environment thereby reduce pollutant loads to Port Phillip Bay. In addition, the cost of supply is likely to be similar or less than mains water supply.

12 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 1 2 Table 1 Advantages and challenges associated with alternative water w sources Water source Advantages Challenges Recommendations Mains water Inexpensive supply Reliant on single source of Demand management to (because externalities supply that is venerable to reduce water use remain unaccounted drought Harvest alternative sources for and supply was Population growth and urban of water to conserve mains heavily subsidised by consolidation across the water government in its municipality, and beyond, are establishment phase) placing greater pressure on Existing infrastructure mains supply is accessible and Climate change will result in regulations/approval less runoff due to higher process are well temperatures and lower soil understood moisture levels (irrespective of rainfall conditions) No ecological protection 1. issues associated with environmental flows downstream of water supply reservoirs, and 2. no means to reduce stormwater or wastewater discharges to the environment Roof runoff Multiple water cycle Volume of supply to meet Decentralised system benefits (mains water competing demands requiring minimal conservation and Reliability of supply infrastructure and reducing stormwater Potentially higher pollutant maintenance. Greatest volumes and pollutant concentrations conveyed to water conservation and loads discharged to receiving waters from other ecosystem protection the environment ) landuse practices across benefits achieved when used Minimal treatment catchment because runoff is for indoor demands such as required as roof runoff not diluted with cleaner roof toilet flushing and/or hot is considerably cleaner runoff (treatment of water than other alternative stormwater quality from Also viable for other sources of supply sources, such as roads, is purposes such as garden Provides resilience to important to counteract this irrigation when other climate change potential issue) sources are not a practicable supply option

13 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 1 3 Water source Advantages Challenges Recommendations Stormwater Multiple water cycle Land uptake for treatment and Plentiful supply for open /catchment benefits (drinking storage requirements space irrigation and toilet runoff water conservation and flushing. minimising stormwater Provides landscaping and discharge to the aesthetic values environment thereby reduce pollutant loads to receiving waters) Elster Creek/Elwood Canal offers Provides resilience to climate change Wastewater Multiple water cycle High energy expenditure for Broader sustainability benefits (water treatment to meet end use impacts should be conservation and water quality requirements considered (such as, energy) minimising wastewater Limit direct pathway for especially if water is not discharges to receiving ingestion to minimise health sourced from Carrum waters) risk Treatment Plant Provides resilience to Storage requirements if climate change supply-demand profile does Constant supply not match Possible increase in salt and nutrient levels in supply, irrigation rates need to be well managed to ensure excess runoff does not enter waterways and impact ecological health

14 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y Elsternwick Park Implementation Plan 3.1 Park description Elsternwick Park is 35 ha in area divided in to a northern and southern section by Bent Avenue as shown in Figure ha of the site is allocated to sporting and ancillary infrastructure use such as pavilions and carparks. The remaining 16 ha of parkland is used for passive recreational activities. Bayside Council Elsternwick Park Strategy Plan states the vision for the Park is that it be developed as: a high quality regional park; a valuable resource for the residents of Bayside; a home for sporting and recreation activities; an outdoor venue for public events and activities; Elsternwick Park is Crown land permanently reserved for public park and recreational purposes in For any change in use Council requires Ministerial sign-off under Crown Land (reserves) Act The northern precinct consists of: Sportsground #1 accessed under a seasonal tenancy agreement with the Victorian Amateur Football Association (VAFA) and Elsternwick Cricket Club. The VAFA have a community lease in the administration office/change rooms and social rooms. Sportsground #2 accessed under a seasonal tenancy agreement with Elsternwick Cricket Club and Elsternwick Amateur Football Club. Elsternwick Public Golf Course: a nine-hole golf course and pro-shop operating under a commercial lease (course management and operations). Elsternwick Park Tennis Centre: an eight en-tout-cas court tennis centre and clubhouse operating under a commercial lease. Elsternwick Park Sports Club with two lawn bowls greens and a clubhouse operating under a community lease. Elster Creek/Elwood Canal flows east to west through the reserve dissecting the golf course and sustains a dam. The dam supplies water to the golf course and Council s street tree watering program. Rakali (native water rat) have been recorded along the canal at Elsternwick Park Golf Course (Melbourne Water, 2007).

15 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 1 5 The southern precinct features two sportsgrounds for cricket, football and soccer. It is accessed under a seasonal tenancy agreement with Elsternwick Cricket Club, Cluden Cricket, Brighton Union Cricket clubs, and on occasions, Elsternwick Auskick. Other uses of the southern precinct include playgrounds, half basketball court, public toilets, barbecue facility, a skate facility consisting of two bowls, and provides for a dog off leash area.. The southern precinct also features a lake, 1.4ha in surface area which was constructed in 1998.

16 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 1 6 Tennis Centre Playground Sportsground #1 Glen Huntly Road Bowling Club Sportsground #2 Elsternwick Public Golf Course St Kilda Street Elster Creek/Elwood Canal New Street Skate facility Bent Avenue Elsternwick Park lake Playground Sportsground #4 Sportsground #3 Playground Head Street Figure 3 Layout of Elsternwick Park

17 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 1 7 The remainder of this report is directed at developing a stormwater harvesting schemes that satisfies stakeholder s recreational, landscape and cultural values at the site. A stormwater harvesting scheme provides the following multiple benefits: Reduced demand for potable water by substitution with stormwater, providing a fit for purpose source for appropriate uses in accordance with WSUD principles, state planning guidelines (Clause 56) and current best practice, Increased resilience against drought and climate change by providing cost effective alternate water supply, Enhancing recreational (passive and active park uses) and landscaping values at the site, Improving habitat value for rakali (native water rat), and Reduced pollutant loads, particularly nitrogen loads to Port Phillip Bay Park stakeholders A number of activities were undertaken to engaged with park stakeholders, including two presentations given during the development of the projects: the first when some preliminary results were available the second once the results of the finalised. Stakeholder s included: Council representatives from Bayside Council Council representatives from Port Phillip Council Sport club tenants and commercial tennis and golf facility operators SouthEast Water Melbourne Water Department of Sustainability and Environment 3.2 Demand management strategies Actions to manage and reduce the water demand across Elsternwick Park are an integral part to the development of a sustainable water management strategy for the site. The following demand management options are being considered and a summary of the reduction in mains water use are summarised in Table 3: Improve irrigation system efficiencies through the installation of sub-surface and moisture controlled irrigation systems where practical, Landscape changes with drought tolerant plant selection (e.g. warm season grasses) and mulching on garden beds, Converting en-tout-cas tennis courts and lawn bowls greens to synthetic surfaces,

18 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 1 8 Passive irrigation diverts runoff from hard surfaces onto garden beds and trees, Indoor water conservation fittings, fixtures and appliances, and Leakage repair. These demand management strategies implemented are likely to reduce the annual demand at Elsternwick Park by 27%, from 28 ML/yr to 20.4 ML/yr (excluding golf course demands). Section 3.5 describes the water balance at the site further. 3.3 Catchment description and stormwater characteristics Melbourne Water is responsible for Elster Creek/Elwood Canal, which drains an area of approximately 40 square kilometres (4,010 ha) of metropolitan Melbourne s inner southeast. Catchment and waterway responsibility is shared between Kingston, Glen Eira, Pot Phillip, Bayside and Melbourne Water. Elster Creek/Elwood Canal is about 18 km in length and five major subcatchment that discharge predominantly untreated stormwater directly to it and then out to Port Phillip Bay. The landuse is predominantly residential (78%) with an additional 7% public open space, 7% commercial and public use, 4 % roads, 4% industrial (WBM, 2005). Average annual stormwater flow volume for Elster Creek/Elwood Canal is 9,260 ML/yr (9,260,000 kl/yr) at Elsternwick Park. Baseflow occurs for 66% of the time and the mean flow is 0.3 m 3 /s and peak flow is 26m 3 /s. The majority of flows are diverted to a box culvert structure from Elster Creek/Elwood Canal to Head Street main drain (as described in Section 3.4) Stormwater quality Stormwater quality conveyed along Elster Creek/Elwood Canal was modelled using MUSIC (assumptions described in Section 1.3) and the results are shown in Table 2. Approximately 26,700 kg of Total Nitrogen is discharged to Port Phillip Bay from the catchment; a key pollutant Melbourne Water actively targets for the long term protection of the ecological health of the system. These large loads of suspended solids and nutrients indicate that it is important to provide water quality treatment to the harvested stormwater to protect long term integrity of Elsternwick Park lake, and the harvesting and irrigation system. In 2001 Melbourne Water found elevated levels of faecal contaminants in the Elster Creek during wet weather, and the source was likely to be non-human (Coleman 2001). It is therefore recommended that a VU disinfection unit is included in the treatment of stormwater prior to use as an irrigation supply. Further consideration of treatment issues are given in Section 3.6. It should be noted that comparison of results to previous investigation undertaken by WBM (2005) shows a variation in results up to 11% different for the generation of Total

19 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 1 9 Suspended Solids, as shown in Table 2. This is due to the WBM investigation using an earlier version of MUSIC (V2) and one year of rainfall data (1959). Table 2 Summary of water quality characteristics for Elster Creek/ Elwood Canal Parameter Results for this study (rainfall data Melb, ) WBM 2005 (rainfall data Melb 1959) % difference Flow (ML/yr) Total Suspended Solids (kg/yr) Total Phosphorus (kg/yr) Total Nitrogen (kg/yr) 9,260 1,890,000 1, 688,100 11% 3,840 3,500 9% 26,700 24,880 7% 3.4 Flow management configuration at the site The 1.4 ha lake is fed by the Elster Canal. The lake forms part of the local flood mitigation infrastructure with overflow from the lake discharging into the Head Street main drain. Figure 4 to Figure 7 shows photos of key design elements for flow management at Elsternwick Park. Melbourne Water provided the following information regarding flow management at the site. A flow diversion structure is located upstream of New St with a passing base flow of unknown quantity (these details need to be addressed as part of the functional design stage). Tailwater from the existing dam on the golf course extends to the diversion structure from Elster creek/elwwod canal to Head Street (as shown in Figure 4). Runoff from adjacent residential catchments discharge to the canal at various locations through the Elsternwick Park. The canal downstream of Elsternwick Park has the capacity to carry about 30 cumecs of flow. A culvert structure at the western/downstream end of the park retards any flow that exceeds this downstream carrying capacity of the canal. Retarded flow initially accumulates in the retarding basin located to the north of Bent Avenue. A series of culverts constructed under Bent Avenue discharges cumulated water to retarding basin to the south of Bent Avenue. A series of large box drains operate under Elsternwick Park which crosses the park diagonally from intersection of Bent Avenue and New Street to

20 Elstern wic k Park Sus tainable W ater Ma nage men t Strateg y 20 intersection of St. Kilda Street and Head Street. Some inlet structures have been constructed on the top of these drains within Elsternwick Park. Depending upon the flow in these drains, water cumulated in Elsternwick Park flows into these drains and gets discharged into the Port Phillip Bay via Head Street. Figure 4 Diversion structure from Elster Creek/Elwood Canal to Head Street main drain Figure 5 Elster Creek/Elwood Canal dissecting the golf course and the dam EDAW DESIGN, PLANNI NG AND ENVIRONMENT S W ORLDW IDE

21 Elstern wic k Park Sus tainable W ater Ma nage men t Strateg y 21 Figure 6 Culverts constructed under Bent Avenue that connect the northern precinct and southern precinct when operating as a retarding basin Figure 7 Elsternwick Park lake and inlet structure to Head Street main drain box drains 3.5 Site water balance Calculations of land uptake, treatment effectiveness, storage characteristics, reliability of supply, etc will be summarized for each opportunity identified. These considerations are required to help facilitate a closed loop water management strategy for the site. Recent data provided by SouthEast Water and summarised in Table 3 indicate an average annual water demand for Elsternwick Park is 19 ML/yr with a maximum use over the last 6 years of 28 ML/yr (excluding water harvested from Elster Creek for irrigation of the Elsternwick Park Public Golf Course). No reliable data was provided for golf course irrigation demands and an estimate of ML/yr of supply was estimated to maintain the course to a desirable standard (Pers. Comm. Leisure Management Services - current lease holders). Demands of the adjacent Elwood Park (City of Port Phillip) are 17.8 ML/yr. Maximum demand for Elsternwick Park and Elwood Park is 85.7 ML/yr. EDAW DESIGN, PLANNI NG AND ENVIRONMENT S W ORLDW IDE

22 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 2 2 Table 3 Water demands for Elsternwick Park

23 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y Stormwater harvesting schemes and requirements for treatment To minimise risk to end users, and ecological and aesthetic values of the water bodies at the site consideration is given to treatment requirements for the proposed stormwater harvesting scheme. Guidelines for water quality requirements for alternative water sources have been recently produced by EPHC (2008) in draft form for comment. They are currently focused on public health and safety, as opposed to the protection of the long term sustainability of storage facility or protection of receiving waters. Nevertheless, treatment of harvested stormwater is also necessary to minimise the risk of deterioration of the water supply infrastructure. The level of treatment required depends on its source, storage arrangement, end use and method of delivery (i.e. drip or spray irrigation) and where public access is unrestricted as shown in Figure 8. Harvesting stormwater from Elster Creek/Elwood Canal would required pre-treatment to reduce suspended solids, nutrients and other associated stormwater pollutants (such as metals) using a wetland. Elsternwick Park lake could be used for a dual function of a storage facility for the harvested stormwater resulting in a considerable cheaper stormwater harvesting scheme for the site, compared to incurring the costs to provide another storage (lake or underground tank systems). Figure 8 Schematic representation of treatment considerations for the protection of storage infrastructure and receiving waters

24 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y What harvesting demands can be sustained at Elsternwick Park? Demand is not the limiting factor to a stormwater harvesting scheme at Elsternwick Park. A catchment area of 4000 ha results in the smallest rainfall events generating considerable volumes of flow downstream. Based on achieving best practice targets of a 80% reduction in annual Total Suspended Solids load and a 45% reduction in annual Total Phosphorus and Total Nitrogen load a wetland 1.4ha in area would be required (this is considered a standard design approach, Victorian Stormwater Committee 1999). However, to sustain this demand a wetland 1.4 ha in surface area would be required. This area of land uptake is considered to be unacceptable by the stakeholders of the park. The area of land around the existing dam on the golf course is used to establish what is considered available for a treatment wetland (not impeding on the current layout of the golf course s greens and fairways). This area of land is equivalent to 0.46 ha (further details of the assumptions for the concept design of the wetland system are discussed in Section 3.6.2). A larger wetland would enable a greater volume of water to be harvested at 100% reliability of supply. Figure 9 shows the results for the analysis undertaken to determine the reliability of supply. The results demonstrates that diverting as little as 10 l/s baseflow into a treatment wetland 0.46 ha in surface area (land uptake is shown in Figure 10) with storage provided by Elsternwick Park lake will provide 100% reliability for reuse demands up to 100 ML/yr. Given that current maximum water demand across Elsternwick Park and Elwood Park is 85.7 ML/yr there is ample supply to meet these demands. 140% 120% 100% Reliability (%) 80% 60% 40% 20% 0% Demand (ML/yr) Figure 9 Reliability lity of supply of stormwater to meet increasing demands across Elsternwick Park

25 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 2 5 Figure 10 Comparison of land uptake for a stormwater treatment wetland Concept design for a treatment wetland Figure 11 shows the typical design components of a stormwater treatment wetland. The constructed wetland system should include the following design features at the functional design phase: a deep inlet pond with fringing vegetation to collect coarse sediment and regulate flow at a rate of 10 l/s through the rest of the system. a macrophyte zone 0.46 ha in area with extensive vegetation that filters sediment, nutrients and metals from the stormwater. Lots of microscopic organisms, known as biofilms, grow on the plants and help to clean the water. This will protect the long term sustainability of the Elsternwick Park lake (which will serve the dual function of storage for the harvested stormwater), minimise the risk of algal blooms through reduced nutrient loading and will reduce the current high turbidity levels in the lake. Design for a detention time of 120 hr to maximise the opportunity for background pollutant levels for suspended

26 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 2 6 solids and nutrients (C* in MUSIC) to be achieved for the proportion of flows diverted into the system. Average depth below normal water level assumed is 0.4 m with an extended detention depth of 0.5 m. The existing diversion to Head Street main drain will provide the bypass system to divert excess flows away from the wetland to protect the vegetation during large storm events. Depending on its final location arrangement through gravity or pumping to transfer the treated runoff from the wetland to Elsternwick Park lake for storage. Figure 11 Schematic layout l of a typical stormwater treatment wetland Consideration is given to the long term water level fluctuation within the wetland system. Figure 12 shows that for the majority of the time (more than 75% of the time) the depth of water will be above the normal water level (of 400 mm), ranging between 0 m and 300 mm This is because the system is treating predominantly baseflow from a large catchment and the detention time of the system is 120 hrs. For less than 5% of the time the water level will recede to 250 mm below the normal water level. The hydraulic behaviour of the system needs to be taken into account for the selection of vegetation during the functional design phase of the treatment wetland. To maximise vegetation growth the wetland system could accommodate significant areas of deep marsh to account for water levels typically between 400 mm and 700 mm deep. Alternatively, the permanent pool depth could be reduced to lower the water level in the system to those typical of systems with extensive marsh and shallow marsh areas.

27 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 2 7 Figure 12 Water level fluctuation in the proposed wetland system Some discussion with stakeholders was directed at the possibility of realigning Elster Creek/Elwood Canal through the northern precinct of Elsternwick Park so that the canal and wetland could run adjacent to Bent Avenue. Further consideration should be given to this opportunity during the functional design phase of the project Water level fluctuations predicted for Elsternwick Park lake Investigation in to the water level fluctuations in Elsternwick Park lake associated with different harvesting demands in shown in Figure 13 for annual demands of 25 ML, 50 ML, 125 ML and 200 ML. The maximum water demand across Elsternwick Park and Elwood Park is 69.5 ML/yr and therefore the water level fluctuation in the lake is closely represented by the 50 ML/yr demand line shown in Figure 13. The results show that for 75% of the time the water level in the lake will be at its normal water level (current water level). Less than 5% of the time the water level will drop to below 500 mm of the normal water level. This occasional drop in water level can be managed in a number of ways. Firstly it is recommended the batter slope of the lake are reconfigured and vegetated to minimise the impact of wave erosion on the shore line and help stabilise the embankment and reduce turbidity level in the lake (albeit some of the turbidity issues are likely to be attributed to the pumping arrangement currently in place). Operating rules could also be developed during the functional design phase of the harvesting scheme to accommodate both the aesthetic requirements of the system and the demands of supply for the 5% of time when water level recede to below 500 mm of the normal water level.

28 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 2 8 Figure 13 Water level fluctuation in Elsternwick Park lake with demand options of 25 ML/yr, 50 ML/yr, 125 ML/yr and 200 ML/yr Stormwater quality benefits to Port Phillip Bay associated with a harvesting scheme in Elsternwick Park The proposed wetland and harvesting scheme provides significant water quality benefits to stormwater discharged from Elster Creek /Elwood Canal to Port Phillip Bay. MUSIC modelling demonstrates that for annual demands of between 50 ML and 100 ML per year nitrogen loads to the bay will be reduced by up 575 kg/yr and suspended solids will be reduced by up to 73,000 kg/yr, as shown in Table 4. The slight increase in pollutant load reduction associated with doubling the volume of water harvested from 50 ML to 100 ML is because it is the wetland system that predominantly provides improvements in water quality (not the storage lake only clean water is discharged to the lake). Melbourne Water should strongly support this project as it will provide significant benefits to its nitrogen load reduction program for the protection of Port Phillip Bay. One potential funding source is their Nitrogen Offsets Program currently provides $800 per 1 kg/yr of Total Nitrogen removal from urban stormwater. This may provide up to $460,000 in capital funding for the stormwater treatment wetland component of the harvesting scheme.

29 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 2 9 Table 4 Water quality Improvement and flow reduction attributed to a stormwater harvesting scheme Estimated costs It is estimated that the capital cost of the wetland, lake reconfiguration and UV disinfection unit is $830,000. The following cost assumptions have been made: 1. Wetland construction: Capital Cost Annual Maintenance Upper $749,642 $19,610 Expected $468,450 $10, Cost associated with lake for the regrading of edges and planting Civil works for the regrading of edges: $5.50 per m 2 Spread topsoil over batters: $7.25per m 2 Planting: $15 - $30 per m 2 3. Assume 1500m of edge reconfiguration would need occur about $50,000 in lake works 4. Cost for UV disinfection unit and installation $25,000-30,000 It is likely the existing pumping system could be used to transfer flows from the wetland to the lake. As a conservative estimate it is likely that $1M capital expenditure would cover the cost of the entire system. It is likely holding tanks for the temporary storage of supply of harvested stormwater from the lake would be required to provide sufficient pressure for irrigation systems located across the different areas of Elsternwick Park. These preliminary cost estimates need to be refined during the functional design phase of the project.

30 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y Recommendations 4.1 Moving forward The City of Bayside has the highest per capita residential water consumption in SouthEast Water s service area. Over 90% of Bayside City Councils water demands on council managed land is attributed to irrigation of parks, sporting facilities and gardens (ICLEI, 2005). Elsternwick Park is the third highest water use across the municipality with a maximum use over the last 6 years of 28 ML/yr (excluding water harvested from Elster Creek for irrigation of the Elsternwick Public Golf Course). Elsternwick Public Golf Course irrigation demands are estimated to be ML/yr. Actions to manage and reduce the water demand across Elsternwick Park are an integral part to the development of a sustainable water management strategy for the site. Actions indentified by Council for implementation include: Improve irrigation system efficiencies through the installation of sub-surface and moisture controlled irrigation systems where practical, Landscape changes with drought tolerant plant selection (e.g. warm season grasses) and mulching on garden beds, Sport surface conversions to synthetic (tennis and bowls) Passive irrigation diverts runoff from hard surfaces onto garden beds and trees, Indoor water conservation fittings, fixtures and appliances, and Leakage repair. These demand management strategies implemented are likely to reduce the annual demand at Elsternwick Park by 27%, from 28 ML/yr to 20.4 ML/yr (excluding golf course demands). The catchment area for Elster Creek/Elwood Canal at Elsternwick Park is 4000 ha results in the smallest rainfall events generating considerable volumes of flow downstream. As a result the irrigation demands of the site are not the limiting factors to a stormwater harvesting scheme but rather the available area of land for the construction of a treatment wetland. The results demonstrate that diverting as little as 10 l/s baseflow into a treatment wetland 0.46 ha in surface area with storage provided by Elsternwick Park lake will provide 100% reliability for reuse demands up to 100 ML/yr.

31 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 3 1 This means there is plenty of supply available for other opportunities such as continuous street tree irrigation program and transfer for other irrigation needs, as well as the provision of supply to the neighbouring Elwood Park in the City of Port Phillip. Figure 14 shows a schematic representation of the stormwater treatment and harvesting scheme presented in this report. The location of key elements (wetland, pumps, holding tanks etc) of the water management scheme could be located. There is no reason why these elements can not be located elsewhere during the detailed/functional design stages of work. It is recommended that the concept design for a stormwater harvesting scheme presented in this report is used to apply for funding and taken through to a functional/detailed design phase, then implementation. The following design features of the wetland are recommended: a deep inlet pond with fringing vegetation to regulate flow at a rate of 10 l/s through the rest of the system. a macrophyte zone 0.46 ha in area with extensive deep marsh vegetation and a detention time of 120 hr to maximise the opportunity for background pollutant levels for suspended solids and nutrient. average depth below normal water level of 0.4 m with an extended detention depth of 0.5 m. The existing Elsternwick Park lake provides an ideal opportunity to provide a dual function as a storage facility. Investigations into water level fluctuations show that for 75% of the time the water level in the lake will be at its normal water level (current water level). Less than 5% of the time the water level will drop to below 500 mm of the normal water level. Melbourne Water should strongly support this project as it will provide significant benefits to its nitrogen load reduction program for the protection of Port Phillip Bay. MUSIC modelling demonstrates that for annual demands of between 50 ML and 100ML per year nitrogen loads to the bay will be reduced by up 575 kg/yr and suspended solids will be reduced by up to 73,000 kg/yr. It is estimated that the capital cost of the wetland, lake reconfiguration and UV disinfection unit is $830,000. As a conservative estimate it is likely that $1M capital expenditure would cover the cost of the entire system (including pumping and irrigation supply infrastructure). These preliminary cost estimates need to be refined during the functional design phase of the project. This project should be developed in conjunction with an education / broader community awareness through some sort of community engagement strategy so that the community/facility operators understand that we can still provide sustainable and safe facilities while using less mains water. With state government indicating some level of commitment to water restrictions for at least the next 8 years, then long-term behaviour change is necessary across all community sectors.

32 E l s t e r n w i c k P a r k S u s t a i n a b l e W a t e r M a n a g e m e n t S t r a t e g y 3 2 pump to transfer water pump with UV disinfection unit temporary holding tanks from which irrigation supply lines draw from Treatment wetland Storage of harvested stormwater Figure 14 Schematic representation of the proposed stormwater harvesting scheme at Elsternwick Park