Melbourne Park – Stormwater Harvesting System
Authors
Niruma Akhter, Rhys Anderson and Michael O’Neil
OVERVIEW
Melbourne and Olympic Park - Australia's premier sport and entertainment precinct, hosts around 600 events annually, attracting over two million visitors. The precinct is a large scale user of potable water and is on City West Water's top 200 water users list.
Delivered as an integral s part of the Melbourne and Olympic Park Redevelopment Project which aims to enhance the precinct’s status as a world class sporting and entertainment precinct, the construction of the $6.9 M Stormwater Harvesting project at Melbourne Park began in 2010 and was completed by the end of 2011.
The project was designed by Arup, managed by Major Projects Victoria (MPV) and constructed by Bovis Lend Lease (LL).
The stormwater harvesting project was also successful in obtaining a $2.9M Federal Government Grant through the National Urban Water and Desalination Plan, under the Water for the Future initiative (DSE 2012).
This paper describes the basis of design including catchment analysis, water quality and quantity monitoring, site constraints and construction challenges and achieved treated water quality. It also provides a broader picture of how the project evolved from a feasibility study and progressed through to construction.
OBJECTIVES
This project aims to reduce the overall potable water demand of the Melbourne Park facilities shown in Figures 1 and 2 by approximately 70% through the diversion of stormwater from the existing local stormwater drainage network, followed by treatment, storage and distribution to Rod Laver Arena, Hisense Arena and other areas for non-potable water uses such as irrigation and wash down.
1 The scheme forms an integral part of ensuring the overall sustainability of the area and the events which take place onsite. This is achieved through reduced potable water usage for irrigation and toilet flushing and reducing the environmental impact of runoff to the adjacent Yarra River.
METHOD
Project Feasibility
In 2008, Arup conducted a feasibility study into the potential development of an integrated water recycling scheme at the Melbourne Sports Precinct (MSP) with the aim of sourcing alternative water supplies for non-potable uses in the precinct, such as for irrigation, toilet flushing and wash down.
The study included the entire sporting precinct including the Melbourne Cricket Ground (MCG), Yarra River, Richmond Oval AAMI Park and Gosch’s Paddock. Figure 1 shows the various facilities at MSP before the redevelopment and Figure 2 shows the master plan for the redevelopment works.
Figure 1 The various facilities at Melbourne Sports Precinct, as they were before the redevelopment works.
2 Figure 2 The early master plan vision for the precinct.
The feasibility study included the determination of feasibility of the system, capital and operating costs, requirements for implementation of the system (including timeframes and indicative costs, etc.), operational and management requirements and potential partners/models for project delivery (including financing options).
At this feasibility stage both rainfall dependent and non-rainfall dependent sources were considered, black water from precinct venues and nearby sewer mains being the non-rainfall dependent source.
Non-potable water use data was obtained from all the sites at the sports precinct. Refer to Figure 3 which shows a demand summary. The blue curve represents demand from all the facilities north of the Yarra River and the green curve represents demand from all the facilities south of the Yarra River.
3 Figure 3 Graphical presentation of non-potable water demands.
The southern part of the precinct is more heavily built up with a very high percentage of impermeable area and large networks of stormwater drains to convey and remove the surface runoff. Comparatively, the northern part of the precinct has more permeable and grassed area, Yarra Park occupying a large portion of the catchment. Thus most of the rainfall infiltrates through to the ground and cannot be captured for re-use.
A nearby City West Water (CWW) trunk sewer main in Wellington Parade was found to be a reliable source of wastewater that could be treated and reused. This eventually led to the MCG sewer mining scheme, which became a separate project with a 600 kL/d underground sewage treatment plant located north of the MCG, in Yarra Park, to supply MCG, Yarra Park and Richmond Oval with Class A recycled water for irrigation, toilet flushing and wash down. The sewer mine, now known as the Yarra Park Water Recycling Facility, is currently being commissioned and is expected to be fully operational by the end of 2012 (Water Recycling Facility 2012).
4 Water Balance
Based on historical rainfall data obtained from the Bureau of Meteorology (BOM), a rainfall reliability analysis was carried out for a range of rainfall scenarios for the southern part of the precinct. These scenarios formed the basis of a system reliability analysis. Additionally, a recent very low rainfall year (2006) has been inputted into the reliability model to demonstrate scheme viability should current weather patterns continue. The scenarios are shown in Figure 4.
Figure 4 Generated scenarios monthly rainfall (mm).
For the northern part of the precinct, sewage flow/ quantity and quality data was obtained from CWW. These data, along with the non-potable water demand data, were then used to produce a water balance.
Altogether, a diverse suite of rainfall dependent and independent options and combinations of these options were considered including the option of extracting and treating water from Yarra River; extraction of groundwater from the City Link tunnels as part of the drawdown of the water table caused by the underground structures which effectively act as a sink of groundwater; stormwater harvesting and sewer mining.
5 One of these rainfall dependent options included an isolated stormwater harvesting scheme for the Melbourne Park catchments. For this particular option, Figure 5 shows the reliability of the scheme based on four different rainfall years. Based on historical rainfall data obtained from Bureau of Meteorology, one very low, one low and two typical rainfall years were selected and modelled against actual water demand throughout the year to predict the reliability of the scheme. Figure 5 illustrates that 64%-80% of the total non-potable water demands at Melbourne Park could be met by an isolated stormwater harvesting scheme within the Melbourne Park catchments, depending on the actual rainfall pattern in a given year.
Figure 5 Preliminary reliability graphs for one of the Melbourne Park Stormwater Harvesting option (Very Low, Low, Typical and Typical 2).
The outcomes of this feasibility study led to three separate alternative water projects, including the MCG sewer mining scheme mentioned earlier, a stormwater harvesting scheme to be located in Gosch’s Paddock fed by the Yarra Main Drain, and the Melbourne Park Stormwater Harvesting Scheme, which is the focus topic and is discussed in detail throughout the rest of this paper. The Melbourne Park site boundary is shown in Figure 6.
6 Figure 6 The Melbourne Park Site.
Detailed Site Investigation and Concept Design
Catchment analysis
Melbourne Park, with an area of 18.3 ha is divided into four sub-catchments, as shown in Figure 7. The Western Courts already have a stormwater harvesting system in place.
The Melbourne Park – Stormwater Harvesting System harvests runoff from the remaining three catchments namely: Rod Laver catchment, Forecourt catchment and the Oval (Old Scotch Oval) catchment. The blue lines in the catchment plan represent the drainage networks
7 Figure 7 Melbourne Park sub-catchment areas.
Two major stormwater networks operate at Melbourne Park, excluding the Western Courts sub- catchment. One system collects all stormwater runoff (including roof water) from Rod Laver Arena (RLA), Café Arena, the Show Courts and an adjacent function building. This water is then directed to a pit located in the berm in front of RLA. This pit, (referred to as the existing pump station from this point onwards), contains two pumps that pump stormwater from the pit before discharging to the Yarra. The single point of discharge into this pump station was considered highly advantageous for tapping, requiring minimal retrofitting to capture the entire stormwater runoff from the areas it services (including the roofs).
Similarly, the second network collects run off from the Oval and Forecourts sub-catchments catchments, which are also directed to a single pit before discharging out to the Yarra River. These two sub-catchments include the Oval, Hisense Arena and the Melbourne Park Function Centre.
8 Quantity Monitoring
Arup engaged ADS Flow Monitoring to monitor the stormwater flows though the two trunk drains mentioned earlier to verify our initial modelling. The flow monitors were initially installed inside the drains near at the outfall end, where the drains discharge to the Yarra River. It was soon evident from the results that during high tides water from the river travels up these drains and the meters were repositioned.
The actual measured flow monitoring was compared with the predicted rainfall and existing design discharge flowrate of the stormwater pump station and the model verified.
Water quality sampling
Stormwater samples were taken from the two largest contributing catchments to determine treatment requirements. Results of analyses are presented in Table 1. The stormwater quality from the Forecourts is understood to be of a similar quality to the Rod Laver catchment with similar activities taking place in the area.
Due to the dry weather at the time of sampling and intended timelines for the completion of the concept design of the system, and the large variability in stormwater quality, operating experience from the existing Western Courts stormwater harvesting scheme and rainwater reuse system at Rod Laver was integrated in the design of the treatment system. From these existing systems, it was noted that court runoff had the potential to add colour to the water. Likewise the rainwater system encountered significant sediment volumes despite the restricted catchment area.
9 Parameter Units Oval Rod Laver
pH pH units 7.71 7.15
Total Dissolved Solids mg/L 1200 586
Suspended Solids mg/L 50 5
Turbidity NTU 34.3 3.9
Total Hardness mg/L 290 108
Chloride mg/L 480 288
Calcium mg/L 36 11
Sodium mg/L 319 159
Magnesium mg/L 48 20
Iron mg/L 0.9 0.27
TN mg/L 0.5 <0.1
TP mg/L 2.23 1.46 Table 1 Stormwater analysis results
The stormwater treatment plant was required to be capable of treating water of the quality described in Table 1 and be capable of producing the quality of water specified in Table 2 below. The treated stormwater is intended for use in irrigation, toilet flushing and wash down.
AGWR Concentration Parameter KPI Target Limit Limit
Suspended Solids <50mg/L <5mg/L
Coarse Particles <2mm diameter -
Iron (total) <9.6mg/L -
Phosphorus (total) <0.8mg/L -
Hardness (CaCO3) <350mg/L -
10 <25 NTU max <5NTU without Turbidity <10 NTU 95th percentile chemical dosing
COD - <5mg/L
E. Coli <10 CFU/100mL
Tolerable AGWR Required Pathogens concentrations Reduction (infectious units per L)
Rotavirus 0.0037 99.60% 2.4 log
Cryptosporidium 0.024 98.70% 1.9 log
Campylobacter jejuni 0.057 99.60% 2.4 log
Table 2 Treated stormwater quality requirements (adapted from Australian Guidelines for Water Recycling (July 2009))
Based on the catchment analysis, stormwater flow monitoring and water quality sampling data, the preliminary/concept design was completed in early 2010. Detailed design progressed quickly when the decision was made to include the stormwater harvesting project in the early works package of the redevelopment.
During detailed design the original concept design had to go through a number of changes due to site constraints and difficulties which became evident as more information was made available through survey, geotechnical assessment and discovery of different site conditions during construction, including unmapped services. These are discussed in more details in the following sections.
Detailed Design and Construction
Stormwater is diverted from discharging to the Yarra from the existing stormwater infrastructure at two key points, detained in a detention structure before passing through a flow-limiting structure and gross pollutant trap. The stormwater is then pumped to a 4.5ML underground storage tank. From here the raw water is pumped to a buffer tank located within the treatment plant room. The treatment plant treats raw stormwater through coagulation and direct media filtration followed by granular activated carbon and UV disinfection, prior to storing the treated water in three new tanks located within the treatment plant room and in another three existing tanks located next to Hisense Arena. Finally, the treated water is distributed for use to various locations on as required basis. The figure below summarises the
11 stormwater capture, treatment and reuse process as stormwater travels though the various components of the system.
Figure 8 Stormwater capture, treatment and reuse process diagram
Design Constraints and Other Consideration
Stormwater extraction/diversion - Stormwater is diverted from two key locations in the existing network. The first point of extraction is downstream of an existing stormwater pump station into which most of the Rod Laver Arena catchment drains. This is a very important pump station as it prevents some very significant areas from flooding including the Rod Laver Arena. Due to natural ground levels and the water level in the tidal Yarra River, the existing drains from this catchment are not able to drain by gravity into the Yarra. The pump station lifts the stormwater well above the highest river tide and discharges into a 600mm diameter gravity outlet/drain.
12 Flow monitoring data recorded for this particular drain indicated flow rates of up to 375L/s. Investigation of original design drawings from the 1980’s found that the pump station was designed for a total combined capacity of up to 800L/s (400L/s capacity of each pump) under high flow conditions. At a later date, due to a flooding incident at the RLA, the pump station was fitted with an adjacent overflow structure pit with two 900mm diameter overflow pipes that drain into the Yarra, to cater for extreme weather events or malfunction of the pumps.
A concrete pit (1.8m x 1.8m) with a concrete weir to divert flows was installed immediately downstream of this pump station. The pit was founded on a new pile cap to prevent it from settling with the adjacent Coode Island Silt (CIS) which was estimated to be subsiding by a few millimetres each year. The existing pump station was also founded on piles. During excavation for construction, it was discovered that the outlet pipe from this drain had failed at the pump station wall. This was a result of the approximately 35m long outlet pipe subsiding with the surrounding CIS.
To prevent similar pipe failure in the future, over the short distance between the existing pump station and the new diversion pit, which were both designed to be founded on piles and were bridged with an 800mm steel pipe with rigid connection. The connection between the diversion pit and the downstream 600mm concrete drain was designed to be flexible with a combination of stainless steel mechanical coupling and a rocker pipe arrangement with short length rubber ring jointed steel pipes.
The second diversion pit is an existing stormwater pit retrofitted with a stainless steel weir to divert the flow. The stainless steel weir was made of multiple smaller components to allow it to be taken inside the pit, through the smaller lid and assembled into place. This pit was originally constructed on a basalt base.
The top of the weir levels in both of the diversion pits were designed to be above the highest recorded tide in this region. In the event that the stormwater harvesting system’s storage capacity is exceeded, stormwater simply overflows over the weir and out to the Yarra River.
Detention structure – Flows from both of the diversion pits are diverted into a detention structure, which after a number of redesigns due to site constraints, was specified to be a Humes ReserVault which is essentially made up of 2m diameter pipes. The purpose of the detention system is to temporarily store stormwater prior to transferring it to the main storage tank which had to be located in a different place due to site constraints. The existing and new infrastructure levels meant stormwater could not be transferred to the storage tank by gravity. A 25L/s pump station was designed to allow for slow but efficient transfer of stormwater. An inline GPT, a Rocla CDS PL0506, was installed upstream of the new pump station. The GPT is most efficient at a flow rate of up to 25L/s. While it allows a greater flow to pass through, its treatment efficiency is reduced. Thus a flow limiting device, Rocla Hydro-brake, was installed prior to the GPT to limit the flow to the optimum rate.
13 The flow from the detention structure flows into a junction pit before entering the Hydro-brake and passing though the GPT and then on into the pump station. Due to lack of space, a separate oil and grease trap could not be installed. As such the inlet into the new pump station was fitted with an oil and grease interceptor basket that hangs just under the inlet pipe and is chained to the top of the pump station to allow for it to be removed and maintained.
The pump station is a pre-fabricated FRP structure, approximately 6 m deep and came with a built in intermediate platform. The pump station is also fitted with hydrocarbon and salinity sensors.
Due to the ground water table and the relative depth of the flow limiting device, the GPT and the pump station were designed for anti-flotation.
The pump station pumps the raw water to the 4.5ML raw water storage tank via a 200m rising main. The tank, shown in Figure 9, is 50m long, 25m wide and 4m high. An assessment was carried out to determine the optimum storage tank capacity versus economic viability before choosing this particular size.
The tank is buried under the Old Scotch Oval, with a topsoil cover that varies between 1 – 1.5m in depth. The tank has a 750mm high sedimentation weir inside it to limit the accumulation of sedimentation to a small area and make maintenance easier.
The tank has three access shafts that rise to the ground level. One of the shafts is located directly above the pump sump inside the tank and is provided to allow pump maintenance. The other access shafts are fitted with stainless steel ladder, cage and an intermediate platform where the depth is greater than 6m.
Figure 9 Raw water storage tank nears completion
14 The pump inside the raw water storage tank transfers the raw water at 12L/s via a 320m long rising main to a buffer tank in the treatment plant room, which is a new extension of the Rod Laver Arena basement car park. The treatment plant room is 80m long and only 6m wide.
The treatment process consists of dosing polyaluminium chloride, direct media filtration, activated carbon and UV disinfection. Due to the varying quality of stormwater, particularly relating to suspended solids concentration, a conservative approach to the filtration system was taken. This included utilising low filtration rates of 8m/h and an empty bed contact time of 10 minutes for the activated carbon filters. However, conservative filtration rates impacted on the footprint of the plant which was restricted to 40m2 . Subsequently, the flow was split between two trains of filter vessels to balance the footprint and size of each vessel.
Activated Filtration Media (AFM) was nominated for use as the sole media for the media filtration process. AFM is manufactured from reprocessed glass, but is separated from basic crushed glass filter media and has been used for applications such as drinking water, swimming pool filtration. Three grades of the AFM media were selected for the media filters:
150mm of Grade 3 with effective size of 2-5mm for covering of filter laterals 150mm of Grade 2 with effective size of 1.2-1.8mm for substrate support 700mm of Grade 1 with effective size of 0.5-0.7mm filter material.
Based on the physical properties of the three grades of media, the clean filter head loss was calculated to be less than 1.45m.
A coal based activated carbon with an Iodine no. of 1000mg/g min was selected for colour and organics removal (see water quality results below).
To increase the overall efficiency of the treatment system, the backwash of the filters incorporated additional air scouring, allowing lower flow rates and shorter backwash times. The backwash system was designed to allow individual filters to be backwashed at a rate of 15L/s for 10 mins in combination with an air scour rate of 1.5m3/m2.min. This provided water savings of approximately 40% when compared with the typical backwash rates employed for water only backwashing systems.
In addition to the treatment plant the remaining area is occupied by the three clear water storage tanks which were designed to fit within an approximate footprint of 6m x 80m while still meeting the relevant code requirements for OH&S and access around the plant. This meant the sewer pump station (into which the backwash water drains as well as temporary toilets, and tents that are set up on the roof level for special events) had to be cast in and suspended from the treatment plant room’s concrete slab.
15 To allow for a movement joint in the treatment plant room floor the three treated water storage tanks were sized to avoid the joint and provide the required storage volumes for processes such as backwashing of filters and irrigation requirements.
The clear water storage tanks within the treatment plant room, shown in Figure 10, have a capacity of 0.5ML. Clear water is also transferred and stored within the three existing tanks adjacent to Hisense Arena, with a combined capacity of 0.5ML.
Figure 10 Inside one of the clear water storage tanks during construction
Distribution and Reuse – Treated water is distributed from the two storage locations on an as required basis to various locations around the site for irrigation and wash down. The next stage of the project will also allow for this water to be used for toilet flushing at Rod Laver Arena when it is upgraded.
Instrumentation and Controls
The entire stormwater harvesting system is operated by means of a fully functional control system which effectively and reliably interfaces with the existing Building/Site Management System.
The supervisory control and data acquisition (SCADA) is a Citect system and includes an UPS unit. The SCADA Alarm outputs are able to interface with existing BMS (Building Management System). The BMS is able to incorporate an alarm mimic screen for the water treatment plant, however, the control, data, acquisition, and treatment plant are monitored via the SCADA system
16 The programmable logic control (PLC) and a human machine interface (HMI) are located at the treatment plant room, enabling the plant to be monitored or controlled by the operator from within this room. However, the stormwater harvesting system and its operation, including all its field devices, can be also be monitored from the Utility Managers Office i.e. the existing building management control room. Figure 11 illustrates how the pre-programmed SCADA system enables the water level in one of the treated water storage tank to be controlled automatically.
Figure 11 Instrumentation for one of the clear water storage tanks.
Construction Issues
The construction of the stormwater harvesting system faced a number of challenges due to the previous and existing use of the site and prevailing site conditions, including:
Difficult soil conditions due to the presence of Coode Island Silt (CIS) and hard rock. Initial geotechnical survey information indicated that the 4.5ML underground raw water storage tank could be installed entirely on basalt. After excavation had commenced it was evident that the geotechnical boreholes had hit floating basalt rock with Coode Island Silt (CIS) around and under the rock. Changes in the expected ground conditions required prompt redesign that allowed the tank to partially sit on basalt and the subsiding CIS An excess amount of Category C soil was found in the area of the below-ground raw water storage tank, this required additional handling and disposal Lack of space - Finding room both in-ground, above ground and within building structures to fit in each of the elements of the Stormwater Harvesting System was testing The area was heavily built up with many existing known, unknown, abandoned underground services and structures. In addition to this, the need to tie into existing and new infrastructure at the site boundaries resulted in a number of difficulties during construction requiring trench shield, scaffolding, ladders and other temporary structures.
17 The stormwater detention structure, gross pollutant, trap and pump station had to be relocated and redesigned a number of times as excavation commenced and multiple adverse latent conditions were discovered. The structural complexity of the system components was greatly increased, affecting piled foundations, bridging over the underground services, protection of existing trees etc. Rectification works and redesign due to discovery of a damaged pipe at an existing stormwater pump station, which were uncovered during excavation Deep excavation particularly for the detention system and underground storage tank High voltage electricity cables and a gas line running parallel on either side of the detention structure/ReserVault resulted in delay until one of the services were relocated and the old service abandoned. Vegetation - The scheme was designed and constructed to avoid impacts on native vegetation. Various components of the stormwater harvesting system were re-arranged to fit in between significant trees. Weather - Inclement weather resulted in time delays, due to excavators not being able to work on the saturated soil. Tight timeframe - Finishing the project and certain components on time was very critical to ensure that the Australian Tennis Open, held early in 2012, was not impacted by the construction program.
Risk
In 2010, a risk assessment on using stormwater at the Melbourne and Olympic Park was carried out by Atura. This included an Environmental and Human Health Risk Workshop for the stormwater harvesting scheme.
A HAZOP workshop with attendance from relevant stakeholders was also run by Arup, to identify and address any hazard and operational issues at the start of the construction phase.
Stakeholders and Coordination
Due to the sensitivity of the site and the complexity of the overall project a very high level of coordination was required between various stakeholders for the implementation of the Melbourne Park Stormwater Harvesting System, right from the planning stage through to design, constructing and commissioning. The various stakeholders for the stormwater harvesting system included:
Arup – Consulting Engineer Atura – Urban Risk Assessor BKB – Pump and Treatment Plant sub-contractor Bovis Lend Lease – Managing Contractor City of Melbourne City West Water
18 Department of Health Victoria – Regulatory Authority Environmental Protection Authority, Victoria (EPA Vic) – Regulatory Authority LADDs - Electrical Contractor Major Projects Victoria – Client Melbourne & Olympic Parks Trust – End user HWM – Civil Contractor NSG Plumbing – Hydraulics Contractor Cox Populous – Architect Rush Wright Associates – Landscape Architect Ten Buuren – Irrigation consultant
Validation & Verification
At commissioning the treatment and disinfection effectiveness was validated with a number of in situ and laboratory samples. Table 3 summarizes the water quality results achieved with the aid of chemical dosing, in the form of poly aluminium chloride (PAC). Additional microbiological tests were undertaken to further validate the effectiveness of the UV disinfection system.
Parameter Units Result
Suspended Solids mg/L <1
Turbidity NTU 0.2
COD mg/L 3
Total Phosphorus mg/L 0.14
Calcium mg/L 29
Magnesium mg/L 23
Total Hardness as CaCO3 mg/L 170
Total Iron as Fe mg/L <0.01 pH 8.1
Median Particle Size μm 7.7
E. coli per 100mL <1
19 Giardia cyst / 50L <1.0
Cryptosporidium oocysts / 50L <1.0
Campylobacter spp1 per 100mL ND1
Table 3 Treated water quality
The following graph indicates the typical particle size of the suspended solids after filtration. The results indicate a mean particle size of 7.7μm and a filter passing size of approximately 30μm.
Figure 12 Typical particle size distributions of the suspended solids after filtration.
The treated water quality results indicate excellent clarity (as observed by the low turbidity and suspended solids) and effective disinfection. The water quality results meet or exceed the requirements from the Australian Guidelines for Water Recycling: Stormwater Harvesting and Reuse (AGWR).
20 Further validation of the disinfection system included weekly E. coli testing. The results of this testing is summarized in Table 4 below.
Date Parameter Result
02/11/11 E. coli <1 / 100mL
10/11/11 E. coli <1 / 100mL
22/11/11 E. coli <1 / 100mL
29/11/11 E. coli <1 / 100mL
Table 4 Weekly E. coli tests from commissioning and validation period.
Arup, with the consent of MOPT and Major Projects Victoria, is undertaking a 12 month verification study that will investigate the performance of the scheme to its design specification and provide real operating cost data for future use in costing future schemes.
Verification of the stormwater harvesting model was undertaken for the period of November 2011 to May 2012, over which approximately 480mm of rain fell over the Melbourne Sports Precinct. Based on the monthly rainfall figures, the stormwater system was capable of supplying over 70ML of water over the period. This is relative to the demand on the system (i.e. a tank needs to be emptied to allow future storm events to refill the tank).
To May, approximately 8ML of treated stormwater had been used for irrigation, representing approximately 25% of the estimated irrigation demand over the same period.
During the time from commissioning through to May 2012, Melbourne experienced significantly higher volumes of rainfall than in previous years (particularly during the Millennium drought). Additionally, due to the frequent and large rainfall events over the summer period, irrigation demand was expected to be reduced compared with past estimates, thereby reducing the volume of water used, and in so doing, reducing the total amount of water which could be captured.
The stormwater harvesting system is also designed to provide a baseline water supply for toilet flushing within Rod Laver Arena and other buildings. As this has not yet been connected, the volume of treated water used is also significantly less than expected over this period and indicates a positive opportunity to optimize the system and utilize more of the stormwater for alternative demands.
21 RESULTS
The new water recycling system is expected to save 45 ML or 18 Olympic swimm ing pools worth, of drinking water each year and reduce the precinct’s annual mains water use by an average of 70 per cent.
These improvements, worth $6.9 million excluding the costs associated with handling and disposing of contaminated soil encountered during the construction of the 4.5 ML underground storage tank, will help deliver the greenest sports and entertainment precinct in the world.
Costs associated with handling and disposing of the contaminated land were $1.3 million. The Commonwealth Government provided $2.9 million in funding under the Water for the Future Program.
With recent rainfall events, the new infrastructure has been tested and shown to divert and capture raw stormwater effectively. All components of the stormwater harvesting system are now fully operational.
The treatment process has proved to be producing high quality treated water. Commissioning data indicates the filters are removing suspended solids up to a 30μm particle size, and high level of COD and colour removal. Validation and ongoing tests have shown the UV disinfection meeting requirements for E. Coli removal in accordance with recycled water guidelines.
From a wider perspective, the Melbourne Park St ormwater Harvesting had a range of impacts and benefits which include:
Environmental
Expected potable water saving of 45 ML/year was achieved. Recycled water was provided for a number of uses including irrigation, toilet flushing and wash down There were benefits to the Yarra River from reducing pollutant loads from a catchment partially contaminated due to past use Heritage trees and other vegetation were retained. Carbon impacts are fully offset - The project sources part of its energy requirements from renewable sources and fully offsets the carbon impact of the project’s operations. A Greenhouse Gas Assessment for the scheme’s power usage has been conducted , indicating usage of 83332.6 kWh/per annum producing 101,666 kg CO2 -e. The Melbourne Olympic Parks Trust purchases carbon offsets from recognized sources in addition to any green power purchased. The project complements, and in many cases exceeds, existing government initiatives and policies regarding water reuse, urban water management and river health
22 Social
Public use of facility for sporting and recreational purposes is maintained and enhanced The project is located in high profile venues and facilities and provides multiple opportunities to engage and educate the public regarding water conservation. It also provides the ability to continue to maintain high quality sporting facilities independent of water restrictions
Economic
The precinct is insulated from future water restrictions and the potential need to truck in recycled water at significant expense
Other
The supply of recycled water attracting points under sustainability rating schemes . There were multiple beneficiaries of the project, particularly tenants of Melbourne Park, including Tennis Australia The project enhances the overall sustainability credentials of Melbourne Park and the Australian Tennis Open Ongoing management, ownership and responsibility of the scheme is held by the Melbourne and Olympic Parks Trust a statutory body with significant experience in the management of major infrastructure
CONCLUSIONS
Despite facing numerous inherent challenges in designing and constructing the new stormwater harvesting infrastructure within a built up and urban environment with particularly difficult soil conditions, the Melbourne Park Stormwater Harvesting Scheme has proved successful in diverting, capturing and treating stormwater.
The scheme will play a significant role in insulating the precinct from ever increasingly stringent future water restrictions and regulatory requirements to conserve a limited and precious resource - potable water. Stormwater harvesting at such an iconic venue will raise the profile of alternative water use and support the overall sustainability of the precinct.
23 REFERENCES
Department of Sustainability, Environment, Water, Population and Communities (DSE) 2012, National Urban Water and Desalination Plan, Department of Sustainability, Environment, Water, Population and Communities (DSE), Australian Government, viewed 26 September 2012, < http://www.environment.gov.au/water/policy-programs/urban-water-desalination/index.html>
Arup 2010, Melbourne Park and Olympic Park – Stormwater Harvesting Schemes, Water for the Future, Grant application, Arup, Melbourne
Arup 2008, Melbourne Sports Precinct – Integrated Water Recycling Scheme, Feasibility Study, Arup, Melbourne
Arup 2008, Melbourne Sports Precinct – Water Reuse, Underground Water Storage Location Assessment for the Department of Planning and Community Development
Water Recycling Facility 2012, Melbourne Cricket Club, Melbourne, Victoria, viewed 26 September 2012,
Natural Resource Management Ministerial Council, Environment Protection and Heritage Council, National Health and Medical Research Council 2009, Australian Guidelines 23 for Water Recycling (AGWR): Managing Health and Environmental Risks (Phase 2) - Stormwater Harvesting and Reuse July 2009, Canberra, Australia
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