Mar 7, 2008 - additional capacity in the Greater Melbourne water supply. ...... Warrnambool rail line and there is the possibility of a future railway station in the vicinity) ...... water uses from the Yarra Valley Water area reported by Roberts24 ...
Analysis of Integrated Water, Stormwater and Wastewater Options
7 March 2008
BONACCI WATER
50 Hoddle Street Abbotsford 3067 Australia Telephone 03 9418 4000 Facsimile 03 9418 4001
RESPONSIBLE WATER USE AT THE ARMSTRONG CREEK DEVELOPMENT
RESPONSIBLE WATER USE AT THE ARMSTRONG CREEK DEVELOPMENT
Authors The principal authors of this study were Dr. Peter Coombes and Geoff Foster from Bonacci Water Pty Ltd. 50 Hoddle Street Abbotsford Victoria 3067.
Acknowledgement The authors gratefully acknowledge the contributions from the City of Greater Geelong, Barwon Water, ABC Project Management, Greg Bryant (Geelong Airport Group), Villawood, Dennis Family, Richardson Group, Casey Group, Lockwood Group, Carter Group, Coomes Consulting, EarthTech, Watson’s, St. Quentin Consulting, Jazz Water, Plains Water, Sirex, Forest Resort and Alfasi Water.
i
EXECUTIVE SUMMARY
Findings 1. This study has provided a compelling argument for innovation at the Armstrong Creek land release area that will incorporate a precinct based infrastructure planning philosophy. It has utilised an integrated systems analysis to examine the water cycle management options for the Armstrong Creek land release area. This has allowed an understanding of the reduced requirements for infrastructure generated by different options. 2. A wide range of options for providing water cycle management services for the Armstrong Creek area were assessed against the objectives of the City of Greater Geelong that included development of a green suburb and a range of community sustainability goals. 3. An integrated water cycle management (Option 7b) that includes the use of rainwater tanks, water efficient appliances and gardens, and wastewater reuse from treatment plants located within the Armstrong Creek area provided the greatest benefits. These benefits included the best net present value, a 75% reduction in mains water demand, a 63% reduction in wastewater discharges to the Black Rock outfall and the greatest reductions in greenhouse gas emissions. 4. This strategy will also improve the security of water supplies in the greater Geelong region allowing the avoidance or deferral of some local and regional augmentation strategies. 5. This study has incorporated feed back from land developers, infrastructure providers and the City of Greater Geelong. 6. Considerable effort was required to separate misinformation, myths and agendas from the important facts associated with water related sustainability issues. Importantly, the wastewater reuse market can best be described as containing water speculators, system providers and component manufacturers. It is also fair to comment that the market is not fully informed Introduction The proposed Armstrong Creek Development is an important strategic project for the City of Greater Geelong. This development will concentrate the majority of the future urban growth of Geelong into a ‘comprehensive community’ in the area south of the railway line at Grovedale and Marshall. This study has employed integrated systems analysis approaches to examine water cycle management options to achieve responsible water use at the Armstrong Creek Development. An integrated water cycle management strategy should combine best practice stormwater management with reductions in mains water use and wastewater discharges. The analysis also considered greenhouse gas emissions, costs and benefits, and timing of the development. Options investigated include wastewater reuse from a wastewater treatment plant at Black Rock (12.5km away) or from wastewater treatment plants located within the Armstrong Creek development, to supply toilet flushing, garden watering and open space irrigation. Rainwater tanks, water sensitive urban design and water efficient appliances and gardens were also investigated. All options were compared to the assumption that desalinated seawater from Wonthaggi will allow additional capacity in the Greater Melbourne water supply. Transfer of some of Melbourne’s water i
supply capacity to Geelong via the Melbourne to Geelong pipeline will allow additional capacity in Geelong’s water supply which can be used to supply the Armstrong Creek development. In this situation, the cost of desalination is an accurate proxy for the cost of supplying water to Armstrong Creek. Similarly, the energy use of desalination is an adequate proxy for the energy impacts of supplying potable water to Armstrong Creek. Note that this study has not counted the additional energy impacts and costs of transporting water to Geelong. Objectives A wide range of stakeholders were interviewed to determine objectives for responsible water use at the Armstrong Creek development. The City of Greater Geelong highlighted objectives relating to the control of flooding, management of receiving water quality and aspirational targets for reductions in mains water use and waste water discharges by 70% and 50% respectively. The infrastructure system that delivers these services should feature, where possible, reduced greenhouse gas emissions and low operating and maintenance costs. Council has a responsibility for land use planning and stormwater management and aims to encourage the development of a smart and green community. Council planners see the Armstrong Creek development as an opportunity to raise sustainability standards across the entire community. The City of Greater Geelong was keen to have a third pipe distribution system for wastewater reuse in the development. Land developers were prepared to support the use of internal wastewater treatment plants to supply treated wastewater via a third pipe distribution system. They were prepared to form consortiums to facilitate the early delivery of trunk sewerage infrastructure and wastewater treatment plants within the Armstrong Creek development. The strategic provision of wastewater treatment plants within Armstrong Creek will allow early development in the central and western areas of Armstrong creek and facilitate wastewater reuse via a third pipe system. Nevertheless, land developers were looking for certainty and infrastructure strategies that will minimise delays. Barwon Water was hesitant about provision of a third pipe wastewater reuse strategy. However, they would strongly prefer to operate any third pipe wastewater reuse system and capture the resulting income stream. There was some reluctance from Barwon Water about the financial merits of introducing alternative water treatment measures. They believe that if the Melbourne Geelong pipeline is constructed there will be an abundance of water supplied to the Greater Geelong region. Private infrastructure providers have developed various business models for a wastewater reuse scheme for the supply of Class A treated wastewater from Black Rock. There were also proposals to deliver treated wastewater to Torquay from a Black Rock wastewater treatment plant. Other private infrastructure providers were willing to finance, build, own, operate and maintain a wastewater treatment and reuse system for the Armstrong Creek development. State government legislation will allow a range of business models to deliver a third pipe wastewater reuse strategy at Armstrong Creek. The potential strategies range from a mandated third pipe wastewater reuse strategy delivered and managed by Barwon Water to delivery of a wastewater reuse strategy by private water authority. Approval for a wastewater reuse strategy will ultimately be provided by the EPA and the Minister for Water.
ii
Options This study examined six alternative options for water cycle management at Armstrong Creek.
Option 1 is the base case (BAU) which assumes that mains water will be the sole source of water supply to the Armstrong Creek development. The BAU case assumes that potable water will be freed up in the Greater Melbourne water supply system by construction of the Wonthaggi desalination plant and the Food Bowl Modernisation project. This water will be delivered to Geelong via the Melbourne to Geelong connector pipeline.
Options 2 – 6 considers the use of rainwater tanks (2a and 2b), Water Sensitive Urban Design (WSUD) (3a and 3b), wastewater reuse from Black Rock (4a) and Armstrong Creek (4b), water efficient appliances and gardens (5) and rainwater tanks plus water efficient appliances (6a and 6b) and gardens.
Option 7 is an integrated water cycle management strategy incorporating all of the above elements. This strategy meets all of the City of Greater Geelong objectives for a whole of community perspective. Two variations of option 7 have been analysed. Option 7a includes treated effluent from a wastewater treatment plant at Black Rock, 12.5km away, used for toilet flushing, garden watering and open space irrigation. Option 7b includes treated effluent from wastewater treatment plants within the Armstrong Creek development used for toilet flushing, garden watering and open space irrigation. Class A+ treated effluent will be distributed to households and commercial users via a third pipe distribution network.
Results The best options reduce demand on mains water supplies, minimise sewerage discharges and has a positive net present value, while reducing greenhouse gas emissions in comparison to the Business As Usual (BAU) Option. The global water demands for the Armstrong Creek development from each Option are shown below.
Water demand (ML/day)
25
20
Reduced water demand by 73%
15
10
5
7b
7a
6b
6a
5
4b
4a
3b
3a
2b
2a
1
0
Option
Figure i: Average annual water demand for the Armstrong Creek development.
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The highest water savings are achieved by the integrated water cycle management Options 7a and 7b, generating a 73% reduction in mains water demands. Importantly, this Option has reduced average annual water demands to a level that would avoid or defer the need to augment the water supply for the Greater Geelong region. Options 4a, 4b, 5, 6a, 6b, 7a and 7b also produced considerable reductions in the requirement for trunk water infrastructure within the Armstrong Creek development. The sewerage discharges from the Armstrong Creek development to the Black Rock trunk sewerage main from each Option is shown below. 16
Sewage discharge (ML/day)
14
Sewerage discharges reduced by 63%
12
10
8
6
4
2
7b
7a
6
5
4b
4a
3b
3a
2b
2a
1
0
Scenario
Figure ii: Average daily sewerage discharges from the Armstrong Creek Development to Black Rock. The greatest reduction in sewerage discharges to Black Rock was achieved in Option 7b which uses wastewater treatment plants within the Armstrong Creek development to supply treated wastewater for toilet, outdoor and open space uses and water efficient appliances and gardens. Sewerage discharges from the Armstrong Creek development were decreased by 65%. Option 4b that employs wastewater treatment plants within the Armstrong Creek area to supply treated wastewater to the development reduces sewerage discharges by 57%. Options that do not include water efficient appliances or wastewater reuse from treatment plants located at Armstrong Creek did not reduce sewerage discharges from the Armstrong Creek development.
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The relative net present values of each of the Options is summarised below. 15
Achieves City of Greater Geelong objectives with positive NPV
NPV ($M)
10
5
0 2a
2b
3a
3b
4a
4b
5
6a
6b
7a
7b
-5
-10
Option
Figure iii: Relative Net Present Values of the alternative Options. The use of rainwater tanks as part of a water sensitive urban design “treatment train” in Options 3a and 3b produces combined stormwater benefits that overwhelm the costs. Use of water efficient appliances and gardens (Option 5) was found to have a net present benefit. The integrated water cycle management strategies (7a and to a greater extent 7b) provide combined water savings, stormwater benefits, and considerable reductions in the requirement for water and sewerage infrastructure that overwhelm the costs of providing and operating the infrastructure. The costs of providing and operating the wastewater reuse infrastructure in Options 4a and 4b overwhelm the benefits derived from water savings and reductions in the requirement for water and sewerage infrastructure. The net present losses in Option 4a are higher due to the additional costs for wastewater treatment, storage and transfer across 12.5 km distance to the Armstrong Creek development from a treatment plant at Black Rock.
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The greenhouse gas emissions from the alternative Options are compared to emissions from the BAU Option below.
Greenhouse gas emissions (%)
5
Increased greenhouse gas emissions by wastewater reuse from Black Rock
Minimum greenhouse gas emissions
0 2a
2b
3a
3b
4a
4b
5
6a
6b
7a
7b
-5 -10 -15 -20 -25 -30 -35 -40 -45
Option Figure iv: Relative difference in greenhouse gas emissions for each Option from a BAU Option that is reliant on desalinated water supply. The supply of treated wastewater from Black Rock for toilet, outdoor and open space uses at Armstrong Creek (Option 4a) will increase greenhouse gas emissions. The increased emissions are caused by the additional energy required to pump treated wastewater from Black Rock to Armstrong Creek. The options using water efficient appliances and gardens (5), combinations of rainwater tanks, water efficient appliances and gardens (6a and 6b), and integrated water cycle management (7a and 7b) produce large reductions in greenhouse gas emissions. Conclusions The Armstrong Creek urban growth area provides Council with a unique opportunity to create a sustainable ‘extension’ of Geelong’s urban area to accommodate the population expansion proposed for the area. By adopting a progressive and innovative approach to planning and design, Armstrong Creek can be a smart, green community with enhanced lifestyle and amenity, meeting a range of community sustainability goals. This study makes a compelling argument for innovation at the Armstrong Creek land release area that will incorporate a precinct based infrastructure planning philosophy. It has utilised an integrated systems analysis to examine the water cycle management options for the area to optimise the mix of water, sewer and stormwater infrastructure required to service the area and to understand the impact of the development on the regional water supply, along with existing or planned regional infrastructure. Option 7b that includes the use of rainwater tanks, water efficient appliances and gardens, and wastewater reuse from treatment plants located within the Armstrong Creek area provided the greatest benefits against the whole of community objectives. These benefits included combined water savings of 75%, a decrease in sewerage discharges from the Armstrong Creek area to Black Rock by 65%, and considerable reductions in the requirement for water and sewerage infrastructure that overwhelm the costs of providing and operating the infrastructure. This option also provided the greatest reduction in greenhouse gas emissions. vi
In addition, the inclusion of wastewater reuse within the Armstrong Creek development in this option provides a more reliable water source than BAU and meets Council’s objective for a development that is not subject to water shortages. It will also allow timely allocation of financial resources and infrastructure to the project. This strategy will also have improved the security of water supplies in the Greater Geelong region allowing the avoidance or deferral of some regional augmentation strategies because the majority of population will be at Armstrong Creek. Armstrong Creek can be developed as a green and inviting suburb free from water shortages with a minimised carbon footprint by adopting infrastructure planning and design principles that make use of all available water sources from within the development area before relying on large external infrastructure upgrades. A localised infrastructure solution also provides increased flexibility in the timing and rate of development. Both Council and Barwon Water will need, however, to adopt an open minded approach to the results arrived at from the use of the progressive and innovative analysis techniques contained in this report for these benefits to be realised.
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TABLE OF CONTENTS i
EXECUTIVE SUMMARY…………………………………………………………………………….……………………………………i
1
INTRODUCTION ...........................................................................................................................1
2
BACKGROUND ..............................................................................................................................5
3
4
2.1
Regional water supply...........................................................................................................5
2.2
Regional water demands .......................................................................................................6
2.3
Regional water supply augmentation strategies .......................................................................6
2.4
The Armstrong Creek context ................................................................................................7
SETTING OBJECTIVES ...................................................................................................................9 3.1
Workshop outcomes .............................................................................................................9
3.2
Council discussions ...............................................................................................................9
3.3
Developer discussions ...........................................................................................................9
3.4
Barwon Water .................................................................................................................... 10
3.5
Infrastructure providers ...................................................................................................... 10
3.6
Legislation and regulations for wastewater reuse .................................................................. 11
OPTIONS ................................................................................................................................... 13 Option 1: Business As Usual (BAU) .................................................................................................... 13 Option 2: Business As Usual Plus Rainwater Tanks (BAU + RWT)......................................................... 16 Option 3: Business As Usual Plus Rainwater Tanks Plus Water Sensitive Urban Design (BAU + RWT + WSUD) ........................................................................................................................................... 17 Option 4: Business As Usual Plus Wastewater Reuse (BAU + WWR) ..................................................... 18 Option 5: Business As Usual Plus Water Efficient Appliances And Gardens (BAU + WEA ......................... 21 Option 6: Rainwater Tanks Plus Water Efficient Appliances And Gardens (RWT + WEA) ......................... 22 Option 7: Business As Usual Plus All Of The Above (BAU + RWT + WSUD + WWR + WEA) ................... 22
5
6
METHODS AND ASSUMPTIONS .................................................................................................... 24 5.1
Water use .......................................................................................................................... 24
5.2
Lot scale analysis ............................................................................................................... 26
5.3
Compiling regional water demand ........................................................................................ 27
5.4
Regional analysis of water and wastewater flows .................................................................. 28
5.5
Analysis of stormwater peak discharges................................................................................ 28
5.6
Analysis of stormwater quality ............................................................................................. 29
5.7
Additional infrastructure costs ............................................................................................. 30
RESULTS .................................................................................................................................... 31 6.1
Water ................................................................................................................................ 31
6.2
Wastewater ....................................................................................................................... 35
6.3
Wastewater reuse .............................................................................................................. 37
6.4
Stormwater........................................................................................................................ 39
6.5
Economic analysis .............................................................................................................. 41
6.6
Greenhouse gas emissions .................................................................................................. 45 viii
7
DISCUSSION .............................................................................................................................. 46 7.1
Multi-criteria analysis .......................................................................................................... 46
7.2
Development timing ........................................................................................................... 47
7.3
Business models for the timely delivery of infrastructure ........................................................ 47
7.4
Establishing competition for wastewater reuse markets at Armstrong Creek............................. 51
7.5
Avoiding or deferring the need for regional infrastructure ...................................................... 52
7.6
Assumptions ...................................................................................................................... 52
8
CONCLUSIONS AND RECOMMENDATIONS ................................................................................... 55
9
APPENDICES .............................................................................................................................. 56
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1
INTRODUCTION
The Armstrong Creek urban growth area is proposed as a mixed use development covering 2,350 hectares, and is located approximately 10 kilometres south of Geelong’s CBD (Figure 1.1).
Figure 1.1: Plan showing the location of the proposed Armstrong Creek development. The project will be one of the largest and most important strategic developments that the City of Greater Geelong will undertake. A ‘comprehensive community’ has been planned that will be the location where the majority of Geelong’s foreseeable growth will be concentrated. The site characteristics include:
normal, medium and high density residential development. Ultimately, the area will accommodate 22,000 dwellings
employment precincts
activity centres
mixed use corridors
active parkland sites
passive open spaces
1
The Armstrong Creek urban growth plan requires a holistic review of water sustainability. The City of Greater Geelong engaged Bonacci Water to provide advice on the development and implementation of a Responsible Water Use Plan which meets Council’s objectives for the area. Bonacci Water’s brief will address the following issues:
A review of the regional linked water-drainage-wastewater systems, and Barwon Water’s five year plan, to establish the context, critical issues and design Options for the Armstrong Creek development
A critique of existing water-drainage-wastewater concept plans in the Urban Growth Plan for Armstrong Creek
A conceptual design and feasibility study for both local precinct and development wide wastewater reuse options
A cost benefit and multi-criteria analysis for recommended solutions
A review of major providers of wastewater reuse solutions
Identification of drivers, barriers and thresholds for establishing competition in wastewater reuse markets at Armstrong Creek
Development of an implementation plan and timing for the chosen option(s)
The location of the Armstrong Creek and surrounding features is shown in Figure 1.2.
Figure 1.2: The Armstrong Creek location with respect to railway lines, major roads, community facilities and other land uses.
2
The Armstrong Creek urban growth area provides a unique opportunity to create a sustainable ‘extension’ of Geelong’s urban area to accommodate growing population, through progressive and innovative approaches. This study aims to assist Council to clarify its responsible water use aspirational objectives which include:
Setting high standards for sustainable design throughout the area to provide enhanced lifestyle and amenity and to encourage the development of a smart, green community Control of flooding and enhancement of Armstrong Creek riparian zone (for example by limiting retarding basins by use of integrated design solutions) Management of receiving water quality Reduction of potable water use and of wastewater discharge by testing the feasibility of wastewater treatment and reuse and rainwater harvesting. Reductions greenhouse gas emissions, operating and maintenance costs associated with provision of stormwater, water and wastewater infrastructure Development of Armstrong Creek as a drought proof precinct Selection of innovative infrastructure solutions that provide flexibility in the order of precinct development.
A structure plan of the proposed development site and precincts is shown in Figure 1.3.
Figure 1.3: Structure plan depicting the current plan for the Armstrong Creek site and the planned uses of the land.
3
There are several significant factors why the Armstrong Creek area has been designated as Geelong’s primary growth corridor. These include:
its proximity to the Geelong CBD
the potential for excellent public transport access (the site is adjacent to the MelbourneWarrnambool rail line and there is the possibility of a future railway station in the vicinity)
the immediate access to both the Surf Coast and Princes highways
the development is adjacent to established urban areas which may allow for incremental servicing in line with the rate of development
environmental constraints are reduced because the site is gently undulating
Figure 1.4: Proposed staging plan for the development of Armstrong Creek showing the spatial and timing aspects of development. The development of the Armstrong Creek area is the key site to meet projected growth in Geelong region over the next 10 to 20 years. This study explores multiple options for delivery of infrastructure to meet water demands, dispose of sewerage and manage stormwater runoff. The areas indicated for early development shown in the staging plan above assumes consolidation of adjoining fragmented land ownership and availability of trunk infrastructure, particularly for sewerage infrastructure. This study will investigate a more flexible approach to infrastructure delivery that may allow development on simultaneous fronts driven by developer readiness and market forces.
4
2
BACKGROUND
Australian capital cities have been historically dependent on rainfall runoff collected in dams for the majority of water supply. In recent times, the combined effects of drought, climate change and considerable population growth have raised concerns about the reliability of urban water supplies.1 Relatively small decreases in average annual rainfall have resulted in large reductions in runoff entering water supply reservoirs. The reason for the large decreases in runoff into rivers supplying dams is not clear. A combination of small reductions in annual rainfall, changing rainfall patterns and increased temperatures is believed to have led to decreases in the efficiency of water supply catchments to translate rainfall into runoff. Changes in catchment management practices, including logging and back burning, increased use of farm dams and higher frequency of bush fires will also reduce runoff. In any event, the reliability of urban water supplies is uncertain. A diverse portfolio of water management options that includes wastewater reuse, rainwater harvesting, demand management and larger regional strategies is required to provide certainty about future urban water supplies. 2.1
Regional water supply
Combined water storage levels of dams supplying Greater Melbourne have been below 60% of capacity since 2000, reaching a low level of about 26% in 2006 and are currently at 36% of capacity. Water storage levels in dams supplying the Greater Geelong region have declined to a low of 15% in 2007 and are currently at 31% of capacity. The Greater Geelong region is also dependent on groundwater to supplement water supplies from dams. Annual rainfall in the Thompson catchments supplying Melbourne was about 10% less than average during the period 2001 to 2006 whilst 35% to 60% reductions in runoff into dams was experienced. Annual rainfall on the Barwon catchments supplying Greater Geelong was 3% less than average rainfall during the period 2001 to 2006 that corresponded to a 39% to 53% reduction in runoff to streams. Note that in 2006 annual rainfall was 35% less than the average. During 2007, both the Thompson and Barwon catchments experienced a return to higher rainfall depths. Both regions have experienced considerable reductions in runoff into dams that has had considerable impact on the security of the regions’ water supplies. The expected changes in climate for the central region of Victoria shown in Table 2.12 will increase uncertainty about the reliability of future water supplies in the regions. Table 2.1: Expected impacts of climate change on temperature and rainfall Parameter Expected change by 2030 for a given season Spring Summer Autumn Winter Temperature (°C) 0.3 – 1.6 0.2 – 1.3 0.2 – 1.3 0.2 – 1.3 Rainfall (%) 0 to -20 -15 to +10 -15 to 0 -15 to 0
1
PMSIEC (2007). Water for our cities – building resilience in a climate of uncertainty. A report by the Prime Minister’s Science, Engineering and Innovation Council working group. The Australian Government. Canberra. 2 DSE (2006). Climate change in Victoria: a summary. Department of Sustainability and Environment. Victoria. Australia.
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2.2
Regional water demands
The Greater Melbourne and Greater Geelong regions have been subject to severe water restrictions since 2006. Average household water use in the Greater Geelong region has varied from 206 to 219 kL/hh/yr during the period 2002/03 to 2005/06. During the period January 2004 to December 2006 households in the Barwon Water service area were subject to periodic water restrictions up to level 2. Permanent water restrictions were introduced in July 2006. The application of level 4 water restrictions since December 2006, which bans outdoor water use, has reduced average household water use to 169 kL/hh/yr in the 2006/07 year. Note that level 4 water restrictions do not allow irrigation of sporting ovals and open space areas.
700
60
650
55
Water demand (GL/yr)
Water demand (GL/yr)
The efficiency of a water supply strategy is dependent on water sources and demands generated by population growth. The population in the region serviced by Barwon Water has grown from 251,535 people in 2002/03 to 275,433 people in 2006/07.3 The population in the Greater Geelong region is expected to grow from 246,000 people to 314,000 people in 2030.4 As shown in Figures 2.1 and 2.2 the Greater Melbourne and Greater Geelong regions will be subject to considerable growth in water demands.
600 550 500 275 ML/day increase in water demand
450 400 350 300 1980
1990
2000
2010
2020
2030
2040
2050
Year
Figure 2.1: Expected water demands from Greater Melbourne
50 45 34 ML/day increase in water demand
40 35 30 25 1994
2004
2014
2024
2034
2044
2054
Year
Figure 2.2: Expected water demands from Greater Geelong
Figure 2.1 shows that water demands from Greater Melbourne are expected to increase by 275 ML/day by 2030 and water demands from Greater Geelong are expected to increase by 34 ML/day by 2030. A fully developed Armstrong Creek area will provide most of the growth in water demand from the Greater Geelong region to 2030. 2.3
Regional water supply augmentation strategies
The Greater Geelong region currently has an estimated water supply surplus of 6,000 ML/yr whilst the Greater Melbourne water supply is considered to be in deficit with water demands exceeding sustainable yields from the system. In response to growing water demands in the regions a range of water supply augmentation strategies have been proposed. The augmentation strategies that may have some influence on the security of water supply to Greater Geelong are discussed below. The Victorian government have made a commitment to construct a seawater desalination plant at Wonthaggi by 2012 to supply 400 ML/day of water into the eastern portion of the Greater 3 4
Barwon Water (2007). Sustainability report 2006/07 Barwon Water (2007). Water supply demand strategy.
6
Melbourne water system. This plant is expected to cost more than $3 billion. The project is subject to review by the Victorian Auditor General and by the federal government Department of Environment, Water, Heritage and Arts in accordance with the Environment Protection and Conservation Act (1999). A “Food Bowl Modernisation” project is also supported by the Victorian government that includes a pipeline to Sugarloaf Reservoir that will facilitate extractions from the Goulburn River for urban water supply to Greater Melbourne. This project is expected to cost more than $1.5 billion, may deliver 200 ML of water per day and is promised for 2012. The project is dependent on improving the efficiency of irrigation in the Goulburn Murray Irrigation District (GMID) which may result in excess water being available for the environment and Greater Melbourne. Farmer’s groups are concerned that the project may transfer water to Melbourne from the GMID ahead of establishing water efficiency measures and environmental flows will not be made available to streams in the district. Given that both the GMID and streams in the district are subject to serious deficits in water supply, preferential supply to Melbourne would have profound impacts on the GMID. It has been argued that water efficiency in rural areas should be matched by water efficiency in urban areas and Melbourne currently does not utilise the water available within the city and, therefore, water should not be transferred from rural areas to Melbourne. A pipeline with a capacity of 44 ML/day connecting the Greater Melbourne water system to the Greater Geelong system is proposed for 2012 at a cost of $142 million. This connection is dependent on agreements for bulk water transfers between the Victorian government, Melbourne Water and Barwon Water. It is claimed in a number of publications that this connection will deliver desalinated seawater from Wonthaggi to Geelong. However, it is improbable that desalinated seawater can be delivered from Wonthaggi to Geelong via the current Greater Melbourne water distribution system. A bulk water agreement will include the full costs of transfer of water to Geelong and of water supply in Melbourne. The Northern Water Plant is supported by the Victorian government and is planned to supply 5.5 ML/day of treated wastewater to the Shell Geelong Refinery from 2012. This project will reduce water demands on the Greater Geelong water supply and decrease sewerage flows to the Black Rock outfall. The Central Region Sustainable Water Strategy has set targets to reduce per capita water use by at least 25%, in comparison to the 1990s average, in 2015 and by 30% in 2020. Barwon Water has committed to these targets.5 It is assumed that this strategy includes adoption of water efficient appliances and gardens. Barwon Water has also set a target for replacement of 25% mains water demand with treated wastewater reuse in 2015. The Victorian Planning Provisions have been changed to allow for mandate of dual pipe reticulation systems in new subdivisions. Barwon Water have budgeted $11.7 million for the delivery of the Armstrong Creek sewerage scheme and $11 million to upgrade the Bellarine transfer main in 2014. These proposed expenditures are related to the development of the Armstrong Creek area. 2.4
The Armstrong Creek context
The proposed Armstrong Creek development will include over 22,000 dwellings, employment precincts, shopping centres, sporting fields and open space areas. Development of the site over a 10 to 20 year period will ultimately generate water demands in excess of 18 ML/day. As such, the
5
Barwon Water (2007). Annual report 2006/07.
7
Armstrong Creek development will produce the majority of Greater Geelong’s growth in water demand over the next 20 years. The Armstrong Creek development will be supplied with mains water from the Pettaval Basin located in the Barwon headworks system via the Bellarine transfer system. The Greater Geelong region is supplied from Barwon and Moorabool headworks systems. Sewerage will discharge from the Armstrong Creek development into the Black Rock trunk sewerage system. The proposed Melbourne to Geelong pipeline will be connected to the Lovely Banks basins in the Moorabool system. The Moorabool system may not facilitate transfer of water from Melbourne into the Barwon system that will supply Armstrong Creek. Instead, the supply of water from Melbourne is expected to reduce the requirement to transfer water from the Barwon system to the Moorabool system thereby providing additional capacity for water supply from Pettaval Basin to Armstrong Creek. Similarly, desalinated seawater from Wonthaggi will not be supplied to Geelong but will, instead, allow transfer of water supply capacity from the eastern regions to the western regions of Greater Melbourne that will supply Geelong. The indirect nature of the transfer of water supply from Melbourne to Geelong requires that this supply has a high energy use and is dependent on runoff that will be affected by droughts and climate change. A more effective water supply strategy for Armstrong Creek should use local strategies including water efficient appliances and gardens, rainwater harvesting and wastewater reuse. The Bellarine transfer system that will supply water from Pettaval Basin has sufficient capacity to supply the early stages of the Armstrong Creek development. Augmentation of the Bellarine transfer system may ultimately need augmentation. The City of Greater Geelong would prefer that Armstrong Creek is supplied with treated wastewater to replace mains water consumption for toilet and outdoor water demands via a third pipe system.6 Barwon Water argues that treating wastewater with high concentrations of salt at Black Rock and transfer across a distance of 12.5 km to Armstrong Creek would be more expensive than the current price of mains water. It is noteworthy that the Victorian government intends to increase the price of mains water. Interception of wastewater with a lower salt content using treatment plants located within the Armstrong Creek development will eliminate the transport and treatment costs associated with providing wastewater reuse from Black Rock. Both City of Greater Geelong and Barwon Water agree that water efficient appliances and gardens, rainwater tanks and Water Sensitive Urban Design (WSUD) approaches should be used at Armstrong Creek.
6
City of Greater Geelong (2006). Armstrong Creek Urban Growth Plan.
8
3
SETTING OBJECTIVES
This study included a workshop with staff from the City of Greater Geelong, interviews with land developers, Barwon Water and infrastructure providers, ongoing discussions with Council and a review of legislation relating to water cycle management. These discussions are summarised in this Section as part of the process of setting objectives for the Armstrong Creek development. 3.1
Workshop outcomes
The preliminary objectives of the City of Greater Geelong for the Armstrong Creek development include control of flooding, management of receiving water quality and aspirational targets for reductions in mains water use (70%) and wastewater discharge (50%). The infrastructure system that delivers these services should feature, where possible reduced greenhouse gas emissions and low operating and maintenance costs. The City of Greater Geelong seeks to provide enhanced amenity and lifestyle facilities to encourage the development of a smart and green community. Council has a responsibility for land use planning and stormwater management. 3.2
Council discussions
The Council seeks to develop robust economic methods of evaluation and design standards for stormwater infrastructure. They would also like a clearer understanding of the ability, progress and organisation of the land developers involved. This understanding will facilitate a final analysis of water supply and sewerage treatment options for the development. Council planners see the Armstrong Creek development as an opportunity to raise sustainability standards across the entire community. To this end they would like to investigate the costs associated with high level sustainability principles. The expected housing demand during the next 3 years is for 200 to 300 hectares of new land releases and as a result there is pressure to make progress with the development of the Armstrong Creek area. The use of innovative solutions that allow multiple and simultaneous development fronts, and the possibility of decentralised options for wastewater treatment and reuse were welcomed by the Council. Council engineers have outlined the catchment scale features relevant to the development. This includes the Parks Victoria managed Reedy Lake and State game reserve (RAMSAR listed wetland), the levee bank at Sparrowvale Farm and the breakwater located downstream in Armstrong Creek. Council managers also wish to ascertain the long term technical ability, ownership and management of potential suppliers of treated wastewater for reuse. 3.3
Developer discussions
The interviewed land developers included Greg Bryant (Geelong Airport Group), Villawood, Dennis Family, Richardson Group, Casey Group, Lockwood Group and Carter Group. In addition consultants from Coomes Consulting, EarthTech, Watson’s and St. Quentin Consulting attended interviews. The level of preparedness of land developers ranged from those with assembled consolidated land parcels ready to proceed subject to resolution of rezoning and planning issues, to those who are still in development or negotiations for joint ventures. Further consolidation of holdings may occur but some developers are willing and able to produce lots as soon as infrastructure support and market forces allow. 9
A clear majority of developers were prepared to support the use of internal wastewater treatment plants to supply treated wastewater via a third pipe system. There was also a perceived misunderstanding of WSUD and IWCM design approaches. Some of the developers have had problems previously with poorly designed, constructed or maintained vegetated swales. Land developers sought assurances about stormwater planning measures and associated land use allocation. They agreed that appropriate reductions in requirement for the size and extent of infrastructure and related land area should be allowed should they provide effective local WSUD solutions. Land developers were also willing to consider forming consortia to fund early delivery of infrastructure if service authorities were unable to provide infrastructure to facilitate timely development on multiple fronts. 3.4
Barwon Water
Barwon Water indicated that they will be duplicating the main sewer to meet EPA flow regulations regardless of any flow reduction associated with an integrated water cycle management strategy. Therefore they maintain that cost deferrals from reduction of sewerage flows from Armstrong Creek development would need to be justified. Barwon Water were interested in the use of pressure sewers but are yet to be convinced of the merits of such a system and are concerned about who will be responsible for operation and maintenance of this infrastructure. They would also consider alternative sites to Black Rock for the construction of wastewater treatment plants. They would also accept more detailed demographic inputs for water demands and network modelling results as input for design of sizing of trunk infrastructure. They have expressed hesitancy over private ownership of any third pipe distribution system and will not cross-subsidise a third pipe wastewater reuse scheme. They would strongly prefer to operate any third pipe system to capture the possible resulting income stream. Private providers would need to deliver a viable business case and submit to end user contracts before Barwon Water will commit to supply Class A treated effluent under a “heads of agreement”. There is hesitancy from Barwon Water about the financial merits of introducing alternative water treatment measures as they believe that if the Melbourne-Geelong pipeline is constructed there will be an abundance of potable water supplied to the area. Further, there is an expectation that current water restrictions will be relaxed in 2013 if water supply of 16 GL/yr is provided by this pipeline. Barwon Water would be prepared to consider developer consortium funding models for earlier than normal provision of trunk infrastructure. They need approval from the Department of Treasury and Finance for any project costing in excess of $5 million. Barwon Water would not guarantee supply of wastewater beyond an initial contract. Finalising a contract for supply of treated wastewater for reuse will be subject to approval from the Department of Sustainability and the Environment (DSE), Department of Human Services (DHS) and the Environment Protection Authority (EPA). 3.5
Infrastructure providers
Jazz Water has developed a “business model” for a South Barwon wastewater reuse scheme for the supply of Class A treated wastewater from Black Rock. The initial agreement would be for 10 ML/day expanding to 25 ML/day in the future. They have approached several major developers in the Armstrong Creek area about supplying a third pipe distribution system and expect to generate 10
income from selling treated wastewater purchased from Barwon Water. Jazz Water currently operates a pilot WWTP at Torquay Sands. Plains Water plan to deliver treated wastewater to Torquay from a Black Rock wastewater treatment plant; however they believe Barwon Water will resist the reuse of wastewater. They plan to use a consortium of major companies to deliver an Ultra-Filtration and Reverse Osmosis (UFRO) system, and are presently preparing estimates for Council for facilities catering for both 20,000 and 3,000 people. They claim to have a market to supply 11.5 ML/day or treated wastewater to Torquay. The Plains Water business model is to own the third pipe delivery infrastructure and charge for headworks, connection and plumbing, and sewer rates. This will result in a predicted charge of $2,500 per lot with an ongoing sewer rate in line with current Barwon Water charges of $368 rising soon to $512 per annum. Sirex finance, build, own, operates and maintains wastewater treatment and reuse systems. They draw income from charging headworks, sewer rates, volumetric rates and treatment costs. They currently operate a number of wastewater treatment plants across the country, mostly in the resort industry, and believe their model can also be applied to new residential developments on the fringes of established areas. The Sirex system utilises pressure sewers and thus minimises wet weather infiltration. Their system involves pre-treatment, which allows the membranes to be almost self cleansing, ultra-filtration and an activated sludge process which results in minimal waste production. They established Victoria’s 14th water utility, the first that is privately owned, Forest Resort Utilities Pty Ltd. They worked in conjunction with engineering consultants URS to gain approval for an Environmental Improvement Plan (EIP) and EPA works approval. Sirex built the pilot plant that is operating at Torquay Sands. Alfasi Water provides services for the management, maintenance and operation of water related infrastructure. They specialise in the water treatment, reuse of wastewater and desalination. Alfasi Water provided a quote to fully install wastewater treatment plants with capacities of 0.36 ML/day, 1.2 ML/day and 6.6 ML/day to provide class A quality water. They proposed a batch treatment process that includes activated sludge processes in Membrane Bio-reactors followed by Ultra-filtration, chlorination and then Electrodialysis Reversal for salt reduction. The quotes for the solutions ranged from $3.5m to $30m. The quote from Alfasi Water is provided in Appendix D.
3.6
Legislation and regulations for wastewater reuse
The provision of new wastewater treatment plants at Armstrong Creek would require a works approval from the EPA in accordance with the Planning and Environment Act (1987). Supply of treated wastewater via a third pipe system for non-potable use requires approval from the Department of Human Services. Approval for a third pipe system supplying treated wastewater will require the submission of a Health and Environmental Management Plan (HEMP) and a Recycled Water Quality Management Plan (RWQMP) to the EPA. Important regulations and guidelines that should be considered include: Guidelines for Environmental Management – dual pipe water recycling schemes; A guide to the sampling and analysis of water and wastewater (EPA publication 441); Guidelines for wastewater irrigation (EPA publication 168); Guidelines for wastewater reuse (EPA publication 464); Guidelines for environmental management – disinfection of reclaimed water (EPA publication 730). Legislation exists in the Water Act (1989), Section 6 that deals with water authorities. The water minister may constitute a new water authority by order published in the Government Gazette. 11
Application to establish a new water authority can be made to the water minister. The powers of the new authority can include the transfer of works owned by local council or other public statutory authority that are used to perform functions governed under the Water Act. The minister will issue a Statement of Obligations for the term of the new authority’s operation. This includes a water plan, governance and risk management, planning and service delivery, environmental management, payment schemes and contributions, and compliance. If the new authority wants to extend its existing water, sewerage or waterway management district than a proposal must be given to the minister. The Victorian Planning Provisions managed by the Department of Sustainability and Environment outlines requirements for drinking water supply, wastewater management, wastewater reuse and stormwater runoff. The integrated water management provisions of Clause 56 – residential subdivision sets out the integrated water management requirements that must be met for residential subdivision proposals in an urban area. It describes the adequate provision of drinking water, wastewater and urban stormwater systems. The reticulated water supply must be supplied to the boundary of all lots maximising the use of shared trenches. There must also be a letter from the water authority demonstrating that submissions to them from the design process are compliant with these guidelines. A detailed plan for a wastewater reuse system must be prepared by a suitably qualified person in accordance with guidance from the EPA, showing how the recycled water system will be implemented and managed. The process for approval is can be outlined by the relevant water authority and the EPA. The EPA handles referrals for the approval of systems to the Department of Human Services. The compliance requirements for wastewater management include design, construction and management to the satisfaction of the relevant water authority and the EPA. A wastewater management proposal must also be compliant with any relevant approved domestic wastewater management plan.
12
4
OPTIONS
In accordance with the objectives of the City of Greater Geelong, this study has focused on the opportunities to reduce mains water demands and sewerage discharges from the Armstrong Creek development. It is a key objective to minimise the impacts of droughts and climate change on the development and that to minimise the likelihood of water restrictions being applied to the development. Six alternative options for water cycle management at Armstrong Creek have been examined. The performance of each Option was compared to the performance of the Business as Usual (BAU) Option.
Option 1: Business As Usual (BAU) Option 1 is the base case which assumes that mains water will be the sole source of water supply to the Armstrong Creek development. The BAU case assumes that potable water will be freed up in the Greater Melbourne water supply system by construction of the Wonthaggi desalination plant and the Food Bowl Modernisation project. This water will be delivered to Geelong via the Melbourne to Geelong connector pipeline. All water demands from the Armstrong Creek development will supplied from the Pettavel Reservoir. The availability of water from the Melbourne to Geelong pipeline will provide additional capacity in the water supply from Pettavel Reservoir which could be used to meet water demands from the Armstrong Creek development. The magnitude of water flows within the development was assessed using the indicative water network shown in Figure 4.1.
Figure 4.1: Indicative trunk water distribution system used for the analysis of water flows at Armstrong Creek. 13
In the BAU Option stormwater runoff from the Armstrong Creek development will be controlled by use of a series of regional detention basins and stormwater quality will be addressed by provision of end of line wetlands and Gross Pollutant Traps (GPTs). The detention basins were designed to ensure a no worsening of stormwater peak discharges from the fully developed Armstrong Creek area in comparison to existing conditions for all design storm events from a 1 year to 100 years Average Recurrence Intervals (ARI). Wetlands and Gross Pollutant Traps (GPTs) were designed to ensure that stormwater runoff from the Armstrong Creek area was compliant with “best practice” stormwater quality guidelines that require an 80% reduction in suspended solids, 45% reduction in Phosphorus and 45% reduction in Nitrogen. The stormwater catchments used in the analysis are shown in Figure 4.2
Figure 4.2: Stormwater catchments used for analysis of the Armstrong Creek area. The stormwater catchments shown in Figure 4.2 have been sub-divided into locations that best represent the proposed development framework. Indicative distributions of various land uses within each location are shown in Table 4.1. The area denoted as not developed indicates land within the catchment that is outside of the current planning scheme, the open space category assigns additional open space that may be located under stormwater management facilities or in stream corridors, and the categories Con, MD and HD refer to conventional, medium and high density housing respectively.
14
Table 4.1: Indicative land use allocations for each location used in the study Location
A1 A2 A3 A4 A5 Sparrow Sparrow Nth Marshall
Total Area 152 495 531 771 593 500 224
Not developed 25 120 213 270 540 360 100
Employment 53 87 0 0 0 0 0
Land use (ha) Open Road space Reserve 12.5 26 32.6 14 31.1 0 26.3 0 12.5 0 15 0 15.3 0
371
90
130
18.3
0
Activity Centre 0 20 20 20 0 0 20
Con 28.7 179 215.7 367.6 32.8 101 71.7
Residential MD 5.3 32.9 39.7 67.6 6 18.6 13.2
HD 1.5 9.5 11.5 19.5 1.7 5.4 3.8
0
104
19.2
9.5
All sewerage from the Armstrong Creek development will be directed to the existing Black Rock Treatment Plant and ocean outfall. The magnitude of sewerage flows within the development was assessed using the indicative sewerage network shown in Figure 4.3.
Figure 4.3: Indicative trunk sewerage distribution system used for the analysis of sewerage flows at Armstrong Creek. In the BAU Option it has been assumed that the availability of desalinated water and the Melbourne to Geelong pipeline will allow additional capacity in Geelong’s water supply which can be used to supply the Armstrong Creek development. In this situation, the cost of desalination is an accurate proxy for the cost of supplying water to Armstrong Creek. Water supplied from the desalination plant at Wonthaggi is expected to cost $1,200/ML to $2,400/ML.7 Previous studies have estimated that the average cost of desalinated water to be $1,900/ML. 8 This value is used as the cost of mains water supply for this study. 7
Department of Sustainability and Environment (2006). Sustainable water strategy for the central region. Our Water Our Future. Victoria. 8 Coomes Consulting Group (2008). Caroline Springs and Environs Servicing Strategy – sewer mining review.
15
The energy demand from the desalinated water supply is estimated to be 4,900 kWh/ML. This study has not assumed that the energy demands from desalination are neutralised by green power. Lower carbon energy sources should be utilised to reduce our existing carbon footprint rather than to neutralise new water sources that have a high energy demand. In addition, the provision of green energy is not usually included in the costs for provision of water projects. The installation costs of detention basins, constructed wetlands and Gross Pollutant Traps (GPTs) used in this study were $35/m3, $95/m3 and $2,000/m3/s respectively. Annual operation and maintenance costs employed in this study sourced from a range of industry publications for detention basins, wetlands and GPTs were 4% of installation cost, $11,000/ha and 5% of installation cost respectively.910 This study has defined net land value as the sale price of a fully serviced conventional allotment less the land and infrastructure costs. Net land values were considered to be $100,000 per conventional allotment. Results from the BAU Option are used as the reference for assessment of the remaining alternative strategies. Option 2: Business As Usual Plus Rainwater Tanks (BAU + RWT) In Option 2, rainwater collected from 100 m 2 area of roofs in conventional and medium density housing and used for toilet flushing, laundry and for garden watering. It was also assumed that 10,000 L rainwater tanks would collect rainwater from 300 m 2 roof areas of high density buildings to supply clusters of 6 dwellings. Each rainwater supply system will include a small first flush device (20 L) and a mains water bypass system for backup during period when water levels in tanks are low. There are two variants of Option 2; Option 2a employs 3,000 L rainwater tanks and Option 2b employs 5,000 L rainwater tanks to supply conventional and medium density housing. The rainwater tanks would be compulsory for all houses and their connection and maintenance would be controlled by use of a Section 173 agreement such as has been adopted by Whittlesea Council for the project “The Groves in Plenty Valley”. 11 A long term annual rainfall sequence (Figure 4.4) and a monthly distribution of rainfall (Figure 4.5) from Portarlington suggests that rainwater tanks will provide a reliable source of water in the Armstrong Creek area.
9
Bayley M.L., and D. Newton (2007). Water quality and maintenance costs of constructed water bodies in urban areas of South East Queensland. Rainwater and Urban Design Conference. Engineers Australia. Sydney. 10 Taylor A.C., (2005). Work undertaken to develop a lifecycle costing module for the CRC for Catchment Hydrology’s MUSIC model. CRC for Catchment Hydrology. Melbourne. Victoria. 11 Coombes P.J., C. Jayakody, C. Anson and G. Foster (2006). Development, analysis and monitoring of a WSUD and IWCM strategy for The Groves project in Mernda Victoria. 30 th Hydrology and Water Resources Symposium. Engineers Australia.
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900
160
800
140
700
120
Rain (mm/mth)
Rain (mm/yr)
Median
600 500 400 300
25%-75%
Non-Outlier Range
100 80 60 40
200
20 100
0 0 1886 1896 1906 1916 1926 1936 1946 1956 1966 1976 1986 1996 2006
Year
Figure 4.4: Annual rainfall in the Geelong area
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month
Figure 4.5: Monthly distribution of rainfall in the Geelong area
Figure 4.4 shows that the Geelong area has been subject to a number of droughts since 1886 and the current drought may not be the worst on record. Importantly, sufficient annual rainfall is available, even during droughts, to support the reliable annual yields from rainwater tanks. Similarly, Figure 4.5 reveals that the pattern of rainfall in the Geelong area has even distribution throughout the year which will facilitate a generally reliable seasonal supply of rainwater. Investigations into the impacts of climate change on the performance of water resources in Australia has revealed that the future yields from Thompson Dam supplying Melbourne are subject to increasing uncertainty and decline. In contrast the certainty and magnitudes of rainwater yields from tanks in Melbourne were subject to marginal change because the roof surfaces in urban areas are impervious and are, therefore, not subject to the considerable losses that reduce runoff from water supply catchments.12 The average costs to install 3,000 L and 5,000 L rainwater tanks to supply laundry, toilet and outdoors uses of $2,765 and $3,055 respectively was sourced from recent research into the rainwater industry.13 This research has established that the use of the most common rainwater pumps (0.45 kWh) in a mains water bypass configuration will consume 1,068 kWh/ML of rainwater supply. On average, rainwater pumps will have a design life of 10 years and a replacement cost of $550. Option 3: Business As Usual Plus Rainwater Tanks Plus Water Sensitive Urban Design (BAU + RWT + WSUD) Option 3 includes a combination of rainwater tanks and accepted water sensitive urban design (WSUD) approaches in a treatment train philosophy. Elements of this approach would include swales and bio-retention systems along appropriate areas of arterial roads such as the medians within dual carriageways. The solution would also include bio-retention systems and rain gardens in appropriate suburban streets and public open space. It is assumed that the WSUD systems with storage volumes of 42 m3/ha will be strategically located to reduce the effective impervious areas of the Armstrong Creek
12
Coombes P.J., and M.E. Barry (2007). Climate change, efficiency of water supply catchments and integrated water cycle management in Australia. Rainwater and Urban Design Conference. Engineers Australia. 13 Coombes P.J (2007). Energy and economic impacts of rainwater tanks on the operation of regional water systems. Australian Journal of Water Resources. 11(2). 177-191
17
development. Two variants of the WSUD option were evaluated that incorporate 3,000 L rainwater tanks (Option 3a) and 5,000 L rainwater tanks (Option 3b). The installation costs of the bio-retention strategies were assumed to be $150/m 3 of storage. Operation and maintenance costs of 4% of installation costs were adopted. Incremental renewal and adaptation expenses of 2% of installation costs were used in this study. Option 4: Business As Usual Plus Wastewater Reuse (BAU + WWR) Analysis of this Option considers two main variants (4a and 4b) for the delivery of wastewater reuse at the Armstrong Creek development. The treated wastewater will be used to supply toilet, outdoor, commercial, industrial and open space uses. This study has assumed that 50% of nonresidential water demand can be supplied with treated wastewater. Several sub-variants of options 4a and 4b should also be considered. 4a: New Wastewater Treatment Plant at Black Rock: Construct a wastewater treatment plant at the Black Rock sewerage outfall and treat effluent to Class A+ standard. Transfer the treated effluent to Armstrong Creek via a system of pumps, 12.5 km of rising mains, a pressure reservoir and distribute to households and commercial users via a third pipe distribution network (see Figure 4.6).
Figure 4.6: Schematic of the Black Rock wastewater reuse scheme. Barwon Water expects the cost of this plant to be offset by the $10 million committed for its construction during the recent federal election campaign. The plant could be delivered in the following ways: 1. The WWTP plant with associated transfer and distribution network could be built and operated by Barwon Water to provide class A+ recycled effluent to households and commercial users at Armstrong Creek. 2. The WWTP plant only could be built and operated by Barwon Water to produce class A+ treated effluent which would be provided under a long term contract with a private 18
infrastructure provider. The private infrastructure provider could build and maintain the transfer and distribution network necessary to provide class A+ recycled effluent to households and commercial users in Armstrong Creek. The magnitude of treated wastewater flows within the development was assessed using the indicative wastewater reuse network shown in Figure 4.7.
Figure 4.7: Indicative trunk treated wastewater distribution system used for the analysis of wastewater reuse flows at Armstrong Creek. 4b: New Wastewater Treatment Plants within the Armstrong Creek area: This study has examined placement of 2 wastewater treatment plants in strategic locations within the proposed green corridors at Armstrong Creek to provide treated effluent to Class A+ standard (see Figure 4.8). Treated effluent will be distributed to households and commercial users via a third pipe distribution network. It was assumed that this Option will include the use of pressure sewers that will reduce wet weather discharges. The pressure sewers would collect sewerage from urban clusters serviced by gravity sewers in an optimum configuration. A two-way connection to Black Rock trunk sewer will supply additional wastewater during shortages and dispose of excess sewerage thereby minimising requirement for “wet weather” storages. The Armstrong Creek WWTP(s) could be provided by one of the following means: 1. Armstrong Creek Treatment plants and associated infrastructure could be built and operated by Barwon Water. 2. Armstrong Creek Treatment plants and associated infrastructure could be built by a developer consortium with negotiated infrastructure and headworks offsets and operated by Barwon Water.
19
3. Armstrong Creek Treatment plants and associated distribution infrastructure could be built by a private infrastructure provider with negotiated offsets for infrastructure reduction and deferral. Financial offsets would also be negotiated for headworks and sewerage service charges. Barwon Water would bill households and commercial users for treated effluent. 4. Armstrong Creek Treatment plants and associated distribution infrastructure and all minor sewers, could be built by a private infrastructure provider with negotiated offsets for infrastructure reduction and deferral, headworks and sewerage service charges. The private infrastructure provider would become the sewer authority for the Armstrong Creek area.
Figure 4.8: Indicative locations of the wastewater treatment plants within green corridors at Armstrong Creek. The magnitude of treated wastewater flows from wastewater treatment plants within the development was assessed using the indicative wastewater reuse network shown in Figure 4.9.
20
Figure 4.9: Indicative trunk treated wastewater distribution system for wastewater treatment plants located at Armstrong Creek used for the analysis of wastewater reuse flows. In each of the options the costs of installing the third pipe within the development was assumed to be $1,500 per dwelling. It was envisaged that planning controls will be used to ensure dwellings are built to accept recycled wastewater thereby reducing the costs of plumbing connections to $250 per dwelling. The costs of trunk infrastructure and wastewater treatment plants will be dependent on the sewerage and wastewater reuse flow rates in each Option. The sources of revenue counted in this study were:
Option 4a: Black Rock o o
$530/dwelling headworks charge $420/dwelling connection fees
Option 4b: Armstrong Creek o o o
$530/dwelling headworks charge $420/dwelling connection fees $371/dwelling annual service charge
The costs of wastewater treatment using membrane bioreactors and ultra-filtration was estimated to be $328/ML. Additional treatment and distribution costs were assumed to be 1% of installation costs. The energy use to supply treated wastewater from Black Rock was calculated to be 5,220 kWh/ML and wastewater reuse from the Armstrong Creek treatment plants was 3,780 kWh/ML. Option 5: Business As Usual Plus Water Efficient Appliances And Gardens (BAU + WEA) This Option includes the use of water efficient clothes washers, shower heads and gardens. Water efficient clothes washers are currently adopted in about 8% of Melbourne’s households and are expected to reduce laundry water use by 50%. The small proportion of water efficient clothes washers impacting on current water demand trends indicates that adoption in a demand
21
management strategy should produce maximum water savings. Installation of water efficient clothes washers is expected to reduce energy use by 3.5 kWh/ML of water saved. 14 Water efficient shower roses have a 52% adoption in Melbourne and are expected to reduce bathroom water use by 20% from current water use patterns. Energy savings of 6.4 kWh/ML of water saved area expected. It is expected that the incorporation of water efficient gardens in the Armstrong Creek area with support from Council planning policies and a local plant nursery will reduce garden water use by 50%. This strategy has been successfully employed in Multiplex projects in Perth and in Stocklands Projects in Queensland (for example at the Jacobs Ridge development). The water efficient appliances have design lives of about 10 years. This study estimated the residual cost of installing a water efficient clothes washer to be $300 and $60 for a water efficient shower head. The residual cost is the difference between purchasing a non-water efficient and water efficient appliances. Current water use patterns will include the water savings from Water efficient 6/3 L flush toilets that are installed in over 85% of Melbourne households. Additional water savings from 6/3 flush toilets have not been counted in this study. Option 6: Rainwater Tanks Plus Water Efficient Appliances And Gardens (RWT + WEA) This option combines the use of rainwater tanks to supply household laundry, toilet and outdoors uses (Options 2a and 2b) with the use of water efficient appliances and gardens. Option 6a includes 3,000 L rainwater tanks and Option 6b includes 5,000 L rainwater tanks. Option 7: Business As Usual Plus All Of The Above (BAU + RWT + WSUD + WWR + WEA) Option 7 provides an integrated water cycle strategy incorporating all of the above elements. Two variations of option 7 have been analysed. Both options include the water sensitive design strategy described in Option 3 and the use of the water efficient appliances outlined in Option 5. Option 7a includes the use of 3,000 L rainwater tanks for household laundry and hot water uses with treated effluent from a wastewater treatment plant at Black Rock used for toilet flushing, garden watering and open space irrigation. Option 7b includes the use of 3,000 L rainwater tanks for laundry and hot water uses with treated effluent from wastewater treatment plants within the Armstrong Creek development used for toilet flushing, garden watering and open space irrigation. Option 7 is similar to the strategies employed at the Aurora project by VicUrban, at the Pimpama Coomera Water Futures Strategy by Gold Coast City Council and in the Yarrabilba project by Delfin Lendlease. Analysis of these types of projects that contain integrated infrastructure solutions reveal considerable additional infrastructure savings and benefits at the local scale that has not been considered in this study.15 The significant opportunities imbedded in these types of
14
PMSIEC (2007). Water for Our Cities: building resilience in a climate of uncertainty. Section by Coombes on household energy use. Report by the Prime Minister’s Science, Innovation and Engineering Council working group. The Australian Government. Canberra. 15
WBM (2005). Strategic stormwater study for the Pimpama Coomera Water Futures Strategy. Report for Gold Coast City Council with assistance from Dr. Peter Coombes.
22
integrated water cycle management are only revealed by detailed and integrated systems analysis of the entire water cycle. These opportunities are often, unfortunately, overlooked by the use of traditional assumptions and more simplistic analysis processes. The author’s investigations for these projects have established that use of rainwater in hot water services was a safe and efficient use of rainwater. The rainwater treatment train of a small first flush device, processes of settlement and flocculation in the rainwater storage, the cleansing processes of biofilms on the walls (slime) and on the bottom (sludge) of tanks, and heat death processes in the hot water services form a robust mechanism to deliver rainwater of acceptable quality for household consumption.16,17
16
Spinks A.T., R.H. Dunstan, P.J. Coombes, T. Harrison, G. Kuczera, (2006). Heat Inactivation of Pathogenic Bacteria in Water at Sub-boiling Temperatures. Water Research. 40(6). 1326–1332. 17 Coombes P.J., Hugh Dunstan, Anthony Spinks, Craig Evans and Tracy Harrison (2006). Key Messages from a Decade of Water Quality Research into Roof Collected Rainwater Supplies. 1st National HYDROPOLIS Conference, Perth, Western Australia 23
5
METHODS AND ASSUMPTIONS
This study has taken an integrated systems approach to analysing the performance of a range of water cycle management options for the Armstrong Creek development. This type of analysis is dependent on detailed inputs, such as water demands, and linked systems analysis that accounts for water supply, sewerage, stormwater, environmental considerations. This section outlines the key assumptions and methods used in this analysis. 5.1
Water use
Average residential water demand in the City of Greater Geelong area was 165 kL per household during the 2006/2007 water year.18 However this average household water demand was recorded during a year when the Geelong area was subject to Level 4 water restrictions that banned outdoor water use. The City of Greater Geelong has been subject to water restrictions for a number of years which have substantially reduced residential water use. Average residential water use has reduced from 216 kL/hh/yr (22%) from the previous water year. 19,20 It is prudent that planning of water resource allocation for new urban areas utilise urban water demands that are not modified by water restrictions and accounts for the likely demographics of the new area. This water demand is then used as the base case which is modified by a range of water management options. It is likely that the Armstrong Creek area will attract new residents from both the Geelong and Melbourne regions that may create a different demographic profile with a different water use to the existing local trends. As such, the average household water demand from Barwon Water service area was not used in the planning of Armstrong Creek water management, in this study, for two key reasons; the unrestricted average water demands from the Geelong area may not represent that actual water use behaviour of the incoming population and the average household water demand from Barwon Water includes a wide range of demographics that may not be represented at Armstrong Creek. Actual water household water demands from the Greater Geelong Pt. C Statistical Local Area (SLA) from the 2005/06 water year were adopted for this study. Although this area is located within the Melbourne metropolitan water supply region, it is subject to urban growth that has been fed from both Melbourne and Geelong. Importantly this area is also physically close to Geelong and has a record of relatively unrestricted water demands (Level 1 water restrictions applied during the 2005/06 water year) that were representative of a new urban area. Note that the actual water use that will occur at Armstrong Creek is unknown. However, adoption of the water demand from Greater Geelong Pt. C. was considered by the authors to be more robust assumption that some variation of the average water demand from the Barwon Water service area. However, average water demands at any location are dependent on the distribution of household sizes and dwelling types. Importantly, the distribution of household sizes does not take the form of a normal distribution and is skewed toward smaller households. As a consequence of the skewed distribution of household sizes, average water demands for an area cannot represent the water demands of an average household. Importantly, this type of average assumption cannot distinguish between the behaviour of different households and the performance of decentralised water management strategies in each of the households. Using methods described in a recent
18
Barwon Water (2007). Annual report 2006/07. Barwon Water (2007). 2008 Water plan. 20 WSAA and NWC (2007). National performance report 2005-06: Major Urban Water Utilities. Australian Government National Water Commission. 19
24
briefing note to the Department of Sustainability and Environment 21, water demands were derived for different household sizes. The distributions of household sizes from the Greater Geelong Pt. C area used in this study are shown in Table 5.1. Table 5.1: Distribution of household sizes Proportion of households (%) by household size (people) 1 2 3 4 5+ 24.4 38.7 13.3 14.8 8.8 This study has adopted the distribution of dwelling densities provided by the City of Greater Geelong.22 The adopted distribution of dwelling densities for Armstrong Creek is compared to actual distribution of dwellings from the Greater Geelong Pt. C area in Table 5.2. Table 5.2: Distribution of housing types Proportion of dwellings (%) Conventional Medium Density High Density Greater Geelong Pt. C 68 28 4 Armstrong Creek reports 80 15 4
Location
Table 5.2 highlights that a greater proportion of conventional density housing is expected for the Armstrong Creek development. The distributions of household size and dwelling types were combined with the quarterly average household water demands provided by the Department of Environment and Sustainability to derive the likely distribution of household water demands for use in this study (Table 5.3). Table 5.3: Values for indoor and outdoor water use for the Greater Geelong Pt. C SLA Month Outdoor Indoor water use (L/day) water use versus household size (L/day) 1 2 3 4 5+ January 450 179 388 598 808 1018 February 476 166 376 586 795 1005 March 426 177 386 596 806 1016 April 300 193 403 612 822 1032 May 194 202 412 622 832 1041 June 86 216 425 635 845 1055 July 76 208 418 628 838 1048 August 104 218 428 637 847 1057 September 150 229 439 649 859 1068 October 236 225 435 644 854 1064 November 304 195 404 614 824 1034 December 387 186 396 605 815 1025 The distribution of water use shown in Table 5.3 was used in the continuous simulation model PURRS (Probabilistic Urban Rainwater and wastewater Simulator) to evaluate dwelling scale inputs to both regional water distribution and stormwater runoff models. It is important to note that the water demand algorithms in the PURRS model allow for climate generated daily and diurnal variation of water demands that use information from Table 5.3 as conditioning variables. The PURRS demand algorithms allow for daily and diurnal variation of water use whilst maintaining the
21
Urban Water Cycle Solutions. Rainwater Tank Evaluation Study for Metropolitan Melbourne Briefing note on methods and results relating to Stages 1 and 2. DSE. Melbourne. Victoria. 22 City of Greater Geelong (2006). Armstrong Creek Urban Growth Plan. Version 16.
25
expected long term monthly volumes of water use. 23 Simulation of daily indoor uses in the PURRS model are based on the values estimated using values from Table 5.3, diurnal patterns provided and distribution of household indoor water uses into kitchen, laundry, toilet, bathroom and hot water uses. In this study the distribution of indoor water uses from the Yarra Valley Water area reported by Roberts 24 were modified for use in PURRS as shown in Figure 5.1. Kitchen 10% Hot water 27%
Laundry 21%
Bathroom 24%
Toilet 18%
Figure 5.1: Distribution of household indoor water uses. It is acknowledged that the use of a water use distribution from the Yarra Valley Water service area may not represent the distribution of household water use at Armstrong Creek. As discussed by the authors in a recent report to the Department of Sustainability and Environment, there is a paucity of measurements of actual household water use patterns throughout Australia. Nevertheless the distribution of household water demands shown in Figure 5.1 were adopted in this study allowing the household water use to be accurately targeted by the various water management measures in the study. It is recommended that City of Greater Geelong consider the use of smart metering in Armstrong Creek development to allow an understanding of actual water demands, the performance of various water management measures and to send a water conservation signal to residents. 5.2
Lot scale analysis
This study has undertaken a systems analysis of the Armstrong Creek development using linked models. The PURRS model was used to continuously simulate household water demands and the performance of lot scale measures (such as water efficient appliances and rainwater tanks) at 6 minute time steps over a 122 year period.
23
Coombes P.J., (2006). Integrated Water Cycle Modeling Using PURRS (Probabilistic Urban Rainwater and wastewater Reuse Simulator). Urban Water Cycle Solutions. 24 Roberts P., (2006). End use research in Melbourne suburbs. Water. Australian Water Association. 51-55.
26
The long daily rainfall record from Portarlington was converted to a long 6 minute rainfall record using the using a non-parametric nearest neighbourhood scheme developed by Coombes.25 Note that the nearest available rainfall record from Geelong Airport was not available during this study due to the Victorian Bureau of Meteorology moving office and that rainfall record was of insufficient length to allow a full evaluation of all possible climate sequences. Figure 4.4 show that the Portarlington rainfall record includes 8 drought sequences including some which are worse than the current drought, and a number of high rainfall years. Continuous simulation using long rainfall records that contain wet and dry periods with a range of expected rainfall sequences is very important for understanding peak water demands and stormwater peak discharges. The recent industry practice of using a repeated sequence of the last 5 years of rainfall due to concerns about climate change can produce very misleading results because the full range of natural climate variation and rainfall patterns has not been considered in an analysis. The choice of the long Portarlington rainfall record has avoided this problem. The short rainfall record at Geelong Airport (19 years) is reported to have an average annual rainfall depth of 536 mm whilst the long term average rainfall record from Portarlington has an average annual rainfall depth of 601 mm. Importantly, this study has not used average values in the modelling and the difference in average rainfall was expected to have marginal influence on the results of this study. Nevertheless, a comparison between rainfall records will be undertaken as some as the Geelong Airport record becomes available. Average daily minimum and maximum temperatures from Geelong Airport were used in the analysis. All of the options described in Section 4 were analysed for five different household sizes and for three different dwelling types. As such 15 demand records with lengths of 122 years at a daily time step were generated for each option. 5.3
Compiling regional water demand
The regional scale analysis combined the water demand records for each location (for example A1, A2 and so on) within the Armstrong creek area (see Table 4.1) from each dwelling type using the expected number of dwellings. The proportion of dwelling types (from Table 5.2) and the number of people occupying the dwellings (Table 5.1) was used to combine the water demands at each location. Non-residential water demands were assigned to each location that included employment or activity centre land as a proportion of residential water demand and land area assigned to employment or activity centres. Historical records show that non-residential water use ranges from 30% to 40% of total water demand for the Geelong region. This study adopted a non-residential water demand of 34% of total water demand for Armstrong Creek. It is envisaged that non-residential water demand at Armstrong Creek will include industrial and commercial uses at employment centres, commercial use in shopping precincts within activity centres, water use from schools and open space irrigation.
25
Coombes P.J., (2004). Development of Synthetic Pluviograph Rainfall Using a Non-parametric Nearest Neighbourhood Scheme. WSUD2004 conference. Adelaide. 27
5.4
Regional analysis of water and wastewater flows
Regional water demand data for Armstrong Creek was combined with daily rainfall from Portarlington and evaporation from the Geelong area in the WATHNET model26. Performance of the water supply, sewerage disposal and wastewater reuse systems at the different catchments within Armstrong Creek was simulated at a daily time step. The WATHNET model is a network linear program for water supply headworks simulation that is a variant of the WASP model originally developed for Melbourne Board of Works and is similar to the REALM model currently used for systems analysis by Melbourne Water. The distribution of water, sewerage and recycled water throughout the Armstrong Creek development was simulated for a 122 year period. This allowed analysis of peak flows in trunk infrastructure and assessment for regional sewerage discharges and water demands. The schematics of the various networks used in this study are shown in Appendix A. 5.5
Analysis of stormwater peak discharges
It is assumed in this study that the development should not significantly change the stormwater runoff and quality aspects of the existing stormwater catchments. The assessment of the stormwater runoff characteristics of the site in the existing and developed states was undertaken using WUFS (Water Urban Flow Simulator) developed at the University of Newcastle.27 The WUFS program is the only reliable analysis tool available to industry that can compare traditional drainage solutions to water sensitive urban design solutions or analyse combinations of both. The WUFS software was until recently freely available to industry from the website www.eng.newcastle.edu.au/~cegak in a similar mode to the availability of ILSAX. Note that both ILSAX and WUFS are freeware that are recommended for research and investigation purposes. WUFS has been developed from the ILSAX algorithms. Using the WUFS model, the stormwater catchments shown in Figure 4.2 (details in Table 4.1) and design storm parameters from Australian Rainfall and Runoff 28 the performance of the stormwater catchments was analysed. After establishing the peak discharges for all storm events with ARIs ranging from 1 year to 100 years for the catchments in their existing state, the various developed Options were simulated and detention basins were designed to reduce peak stormwater discharges to existing levels. In the developed Options the stormwater catchments were represented as clusters of 100 dwellings. The stormwater networks used in WUFS are shown in Appendix B. The likely storage volumes in rainwater tanks prior to storm events of a given ARI were derived using continuous simulation in accordance with the methods described in scientifically peer reviewed publications by the authors. 29 Available storage volumes in 3,000 Litre rainwater tanks 26
Kuczera, G. (1994). Water supply headworks simulation using network linear programming.
Advances in Engineering Software. Vol. 14. 55-60. 27
Kuczera, G., Williams, B., Binning, P. and Lambert, M., (2000). An education web site for free water engineering software. 3rd International Hydrology and Water Resources Symposium. Institution of Engineers Australia. Perth. Western Australia. 1048 – 1053. 28 IEAust., (1987). Australian rainfall and runoff: a guide to flood estimation. Vols. 1 and 2. The Institution of Engineers, Australia. 29 Coombes P.J., and M.E. Barry (2008). Determination of Available Storage in Rainwater Tanks Prior to Storm Events. Water Down Under. 31st International Hydrology and Water Resources Symposium. Engineers Australia. Adelaide. 28
ranged from 1 m3 to 2 m3, and the available storage in 5,000 L rainwater tanks ranged from 1.5 m3 to 3.5 m3 for storm events with 1 year to 100 year ARIs. 5.6
Analysis of stormwater quality
The MUSIC (Model for Urban Stormwater Improvement Conceptualisation) software developed by the Cooperative Research Centre for Catchment Hydrology was used to continuously simulate flow regimes and stormwater quality from the existing and developed catchments at Armstrong Creek. Potential evapotranspiration and pluviograph (6 minute) rainfall data from Werribee for the period 1968 to 1979 was used in the MUSIC simulations (See Appendix C). The long simulation used in the MUSIC modelling, in comparison to the industry practice of using a single year, has been undertaken to enable a more detailed understanding of the likely catchment behaviour in response to different climate sequences. Climate data from Werribee was utilised for the analysis of water quality because local data was not available due to the relocation of the Victorian Bureau of Meteorology. Nevertheless, the annual average rainfall depth at Werribee of 586 mm was considered to be reasonably close to the annual average rainfall depth of 536 mm at Geelong Airport. Differences in climate regime at the Armstrong Creek location may produce marginal difference in the results. However, the important relative differences between existing and developed catchment states in the simulation are likely to be robust. Further analysis in a subsequent report by the authors will conduct analysis using local climate information. Simulation of the stormwater runoff from the existing conditions in the catchments has determined the annual average stormwater discharge volumes and quality shown in Table 5.4. Table 5.4: Stormwater volumes and quality results for the catchments in the existing state Catchment Flow SS P N (ML/yr) (kg/yr) (kg/yr) (kg/yr) Armstrong 759 104,000 306 2,190 Sparrowdale 357 5,220 147 1,080 Sparrowdale North 84 13,400 229 13,400 Marshall 283 46,700 114 826 Note that SS denotes suspended solids, P denotes Phosphorus and N denotes Nitrogen. Contributing stormwater areas were considered be from existing urban areas outside of the proposed Armstrong Creek development and from pasture areas. The MUSIC network used to simulate the performance of existing catchments is shown in Appendix C. The fully developed catchment was then simulated and the results used to determine “best practice” values for stormwater quality from the catchments as shown in Table 5.5. Table 5.5: Target “best practice” values for each catchment Catchment SS P N (kg/yr) (kg/yr) (kg/yr) Armstrong 194,400 1117 7,810 Sparrowdale 26,800 169 1,199 Sparrowdale North 16,200 93 660 Marshall 48,400 273 1,909 All options were then designed to meet the “best practice” stormwater quality guidelines values defined in Table 5.5. Additional MUSIC networks used in the study are shown in Appendix C. 29
5.7
Additional infrastructure costs
The indicative costs to provide pump stations and conduits in trunk water, sewerage and wastewater reuse infrastructure used in this study are shown in Table 5.6. Note that various costs and benefits are also discussed in Section 4. Table 5.6: Indicative costs for trunk infrastructure Flow rate Pump Conduits (L/s) Stations ($M) ($M/km) 50 0.5 0.318 175 1.3 0.467 640 1.8 1.17 860 2.6 1.25 The values in Table 5.6 were used with flow rates in the indicative trunk infrastructure from each option to derive relative costs of proving trunk infrastructure. Costs of providing storage reservoirs and wastewater treatment plants to deliver Class A treated wastewater that include membrane bio-reaction and salt removal was assumed to be $0.2M/ML and $2.1M/ML/day. These indicative 30 costs were derived from the Caroline Springs and Environs Servicing Strategy. Urban development can increase the nutrient loads discharging to receiving environments. In the case of Armstrong Creek the receiving waters include a RAMSAR wetland that will require protection. This study has, therefore, adopted a value for reduction in discharges of nitrogen of 31 $47.55/kg of Nitrogen from recent studies . This approach is consistent with the approach employed by Melbourne Water Corporation to value the benefits of reduced discharges of Nitrogen 32 to the environment.
30
Coomes Consulting (2008). Caroline Springs and Environs Servicing Strategy – sewer mining review 31 Gray S., and N. Booker (2002). Contaminant flows in urban residential water systems. Urban Water. 4. 331-346. 32 Melbourne Water (2006). Stormwater quality offsets – a guide to developers
30
6
RESULTS
The results of the household water balance and the global (whole of Armstrong Creek) modelling are presented in this section. 6.1
Water
The global water demands for the Armstrong Creek development from each Option are shown in Figure 6.1.
Water demand (ML/day)
25
20
15
10
5
7b
7a
6b
6a
5
4b
4a
3b
3a
2b
2a
1
0
Option Figure 6.1: Average annual water demand for the Armstrong Creek development. Figure 6.1 reveals that significant mains water savings can be achieved by use of an integrated water cycle management strategy. The options using 3,000 L (2a and 3a) and 5,000 L (2b and 3b) rainwater tanks to supply laundry, toilet and outdoor uses reduced average annual mains water demands by 17% and 19% respectively. Options 4a and 4b involving use of recycled wastewater for household toilet and outdoor uses, and open space irrigation reduced mains water demands by 40%. Whilst the use of water efficient washing machines, shower heads and gardens reduced average annual water demands by 27%. The use of combined strategies produces considerable reductions in average annual mains water demands. A combination of 3,000 L rainwater tanks, water efficient appliances and gardens (6a) provides a 44% reduction in mains water demands whilst the use of 5,000 L rainwater tanks with water efficient appliances and gardens reduces mains water demands by 45%. Integrated water cycle management Options (7a and 7b) that includes 3,000 L rainwater tanks used to supply household laundry and hot water uses, wastewater reuse for toilet, outdoor and open space uses, and water efficient appliances and gardens generates a 73% reduction in mains water demands. 31
Importantly, this Option has reduced average annual water demands to a level that would avoid or defer the need for augmentation of regional water supplies 33. It is also noteworthy that Barwon Water plan to replace the Bellarine Basin with a smaller closed tank and increase the storage at Pettavel by 100 ML within the next 10 years to service new water demands. 34 An integrated water cycle management strategy at Armstrong Creek will have significant impact on reducing the sizing and timing of this infrastructure. In order to understand the likely impact of the different water management options on provision of water distribution infrastructure within the Armstrong Creek development water flows in an indicative trunk water distribution system (shown in Figure 6.2) were evaluated in the global modelling. W1
W6
W5
W3
W1
From Reservoir
W8 W4 W2
Marshall W9
A1
A2
Sparrow North
W12
W7
A3
Sparrow W10
A4
W11
A5
Figure 6.2: Indicative trunk water distribution network used to evaluate water flows within the Armstrong Creek development. The peak daily water flows in the water distribution network were determined to be the 95 percentile daily flows and are shown in Table 6.1. Table 6.1: Peak (95 percentile) daily water flows in the trunk water distribution network Conduit Length Peak flows (ML/day) for each Option (km) 1 2a 2b 3 4 5 6 7 W1 30.5 30.4 30.3 30.4 14.6 20.4 19.8 8.6 W2 1.5 1.1 1.1 1.1 1.1 0.2 0.7 0.7 0.3 W3 1.88 29.4 29.3 29.2 29.3 14.5 19.7 19.1 8.3 W4 2.25 23.3 22.6 22.5 22.6 11.3 15.5 14.7 6.4 W5 1.5 6.7 6.7 6.7 6.7 3.2 4.2 4.3 1.9 W6 3 6.7 6.7 6.7 6.7 3.2 4.2 4.3 1.9 W7 2.63 12 11.7 11.6 11.7 5.9 8 7.6 3.3 W8 0.5 6.1 6.7 6.7 6.7 3.2 4.2 4.3 1.9 W9 2.26 2.1 2.7 2.7 2.7 1.4 1.6 1.8 0.8 W10 0.8 10.2 9.9 9.9 9.9 5 6.8 6.5 2.8 W11 1.5 0.8 0.8 0.8 0.8 0.4 0.5 0.5 0.2 W12 2.63 17.6 17.1 17.1 17.1 8.7 11.7 11.1 4.9
33 34
Barwon Water (2007). 2008 Water Plan SKM (2008). Armstrong Creek Water and Sewerage System Design
32
Note that the indicative lengths of trunk water mains will remain constant for all Options unless advised otherwise. The Options 2a and 2b with rainwater tanks revealed small reductions in peak water flows by 0.5% and 0.8% respectively that are unlikely to reduce the requirement for trunk water distribution infrastructure within the development. A similar result was observed for Options 3a and 3b that involve water sensitive urban design and rainwater tanks. Options with wastewater reuse (4a and 4b) reduced peak water flows in the water distribution system by 51% and are likely to significantly reduce the requirement for trunk water distribution infrastructure within the Armstrong Creek development. The use of water efficient appliances and gardens reduced peak water flows by 33% that will lead to a significant decrease in the requirement for trunk water distribution infrastructure. Options 6a and 6b with rainwater tanks, water efficient appliances and gardens reduced peak water flows by 35% that will also reduce the requirement for trunk water infrastructure. The integrated water cycle management Options (7a and 7b) with rainwater tanks, water efficient appliances and gardens, and wastewater reuse decreased peak water flows by 72% that will generate a considerable reduction in the requirement for trunk water distribution infrastructure. There is an important difference between the analysis of peak flows in this study and standard water industry design practice. This study employed climatic and behavioural water demand methods35 at realistically small spatial clusters in a simulation using 122 years of climate records that account for the climate dependent variation in the performance of the different measures (such as rainwater tanks, wastewater reuse for outdoor use and water efficient measures). Traditional estimation of peak daily demands using 1.5 multiplied by average water demand (for the demand nodes at this site) cannot account for the expected variations in peak water demands in response to climate variables and a range of alternative management methods (such as rainwater tanks, water efficient appliances and wastewater reuse). This fact regularly leads to incorrect claims that the size of water distribution infrastructure cannot be changed. It is also commonly argued by water utilities that there is uncertainty about the performance of alternative water management measures and the impacts of these measures on reducing water demands should be ignored in the design of trunk water infrastructure. This argument implies that there is a significant impact from trunk water distribution not conveying all of the peak water demand on rare occasions and seems to stem from analysis that does not account for the variation in the performance of alternative water management measures. This study has accounted for the variation in the performance of alternative water management measures and, therefore, provides a more robust estimation of system performance. However, the impact of not fully conveying peak water demands from time to time deserves critical analysis. It is expected that occasional small to moderate excesses in peak water demands will simply lead to reductions in water pressure. This result will reduce water demand resulting in the desired level of water conservation. It would take a considerable increase in peak water demand above the design peak water demand to create a water deficit in a household. It is noted that the probability of not fully supplying peak water demands is likely to be rare and is unrelated to the probability of a fire event. It is therefore expected that the fire fighting capability of the water systems examined in this study will not be diminished. Nevertheless, the integrated nature of the various water supply Options can lead to more certainty in availability of water to fight fires. For example, provision of fire fighting hydrants in the wastewater reuse system that is 35
Coombes (2002). Rainwater tanks revisited: new opportunities for urban water cycle management. PhD Thesis. The University of Newcastle. Callaghan NSW.
33
backed up by the mains water system or provision of a fire truck with water storage and capacity to draw water from local storages or mains (such as rainwater tanks, stormwater ponds, water and treated wastewater mains) should provide additional security. The weighted average water demands from households using rainwater tanks and water efficient practices are shown in Figure 6.3. Weighted average water demands were derived by using the proportion of household size and water demands for households that have 1 to 5 residents.
Mains water demand (kL/hh/yr)
250
200
150
100
50
0 1
5
Option
2a
2b
6a
Figure 6.3: Weighted average conventional household water demands at Armstrong Creek. Figure 6.3 shows that the use of water efficient appliances and gardens can reduce mains water demands by 30%. The use of 3,000 L and 5,000 L rainwater tanks will reduce mains water demands by 19% and 20% respectively. A strategy combining 3,000 L rainwater tanks, water efficient appliances and gardens will reduce mains water demands by 46%. Lot scale measure can produce considerable reductions in mains water demands.
10
Median
25%-75%
Non-Outlier Range
8
6
4
2
Main water savings (kL/mth)
Rainwater yield (kL/mth)
The monthly distribution of rainwater yields from 3,000 L tanks and mains water savings generated by use of 3,000 L rainwater tanks, water efficient appliances and practices are shown in Figures 6.4 and 6.5 respectively. 18
Median
25%-75%
Non-Outlier Range
16 14 12 10 8 6 4 2 0
0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month
Figure 6.4: Monthly distribution of rainwater yields from 3,000 L tanks
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month
Figure 6.5: Monthly distribution of mains water savings from 3,000 L tanks and water efficient practices 34
Figure 6.4 show that 3,000 L rainwater tanks provide a fairly consistent level of service of 2 kL to 6 kL of rainwater in each month throughout the year. A combination of 3,000 L and water efficient practices is expected to provide monthly mains water savings ranging from 4.5 kL to 10 kL. 6.2
Wastewater
The sewerage discharges from the Armstrong Creek development to the Black Rock trunk sewerage main from each Option is shown in Figure 6.6. 16
Sewage discharge (ML/day)
14 12 10 8 6 4 2
7b
7a
6
5
4b
4a
3b
3a
2b
2a
1
0
Option Figure 6.6: Average daily sewerage discharges from the Armstrong Creek Development to Black Rock. Figure 6.6 reveals that use of water efficient appliances in Options 5 and 6 (6a and 6b) will reduce sewerage discharges from the Armstrong Creek area to Black Rock by 20%. Option 4b that employs wastewater treatment plants within the Armstrong Creek area to supply treated wastewater to the development reduced sewerage discharges by 57%. Use of wastewater reuse from Black Rock water efficient appliances and gardens in Option 7a decreases sewerage discharged from Armstrong Creek by 33%. In contrast, the use of wastewater treatment plants at Armstrong Creek to supply treated wastewater for toilet, outdoor and open space uses and water efficient appliances and gardens in Option 7b decreases sewerage discharges from the Armstrong Creek area by 65%. Options that do not include water efficient appliances or wastewater reuse do not reduce sewerage discharges from the Armstrong Creek area and the use of wastewater treatment plants located within the Armstrong Creek development produces considerable additional reductions in sewerage discharges to the Black Rock sewerage main.
35
In order to understand the likely impact of the different water management Options on provision of sewerage disposal infrastructure within the Armstrong Creek development sewerage flows in an indicative trunk sewerage disposal system (shown in Figure 6.7) were evaluated in the global modelling.
S4
Marshall
S1
S5
A1
A2
Sparrow North
S2
S6
S3
A3
Sparrow S6
A4
S7
A5 S8
To Black Rock
Figure 6.7: Indicative trunk sewerage distribution network used to evaluate sewerage flows within the Armstrong Creek development. The peak daily sewerage flows in the water distribution network were determined to be the 95 percentile daily flows and are shown in Table 6.2. Table 6.2: Peak daily (95 percentile) discharges in the trunk sewerage infrastructure Conduit Length Peak sewerage discharges (ML/day) for each Option (km) 1 2 3 4a 4b 5 6 7a 7b S1 0.56 0.5 0.5 0.5 0.5 0.5 0.4 0.4 0.3 0.3 S2 1.69 3.4 3.4 3.4 3.4 3.4 2.7 2.7 2 2.2 S3 1.58 6.5 6.5 6.5 6.5 1.3 5.2 5.2 4 2 S4 1.13 3 3 3 3 2 1.5 1.5 1.1 1.3 S5 1.88 2.9 2.9 2.9 2.9 2.9 2.3 2.3 1.8 1.9 S6 0.75 4.4 4.4 4.4 4.4 4.4 3.5 3.5 2.7 1.9 S7 1.5 16.1 16.1 16.1 16.1 0.5 12.9 12.9 9.8 0.3 S8 12.5 16.6 16.6 16.6 16.6 11.1 13.2 13.2 10.1 8.3 Note that the indicative lengths of trunk sewerage mains will remain constant for all Options unless advised otherwise. The calculated peak daily flows in the Black Rock sewer (Conduit S8) are the additional discharges from Armstrong Creek. This study has assumed that the existing peak daily flow in the Black Rock sewer is 40 ML/day. Table 6.2 shows that the use of treated wastewater from treatment plants within the Armstrong Creek development (Option 4b) for toilet, outdoor and open space uses will reduce peak daily sewerage discharges from the Armstrong Creek area by 51%. Options 5 and 6 (6a and 6b) that include use of water efficient appliances will generate a 21.9% decrease peak daily sewerage discharges from the Armstrong Creek development.
36
Reuse of wastewater from a treatment plant at Black Rock, water efficient appliances and gardens (Option 7a) decreases peak daily sewerage discharges from Armstrong Creek by 40.5%. The use of wastewater treatment plants at Armstrong Creek to supply treated wastewater for toilet, outdoor and open space uses, use of water efficient appliances and gardens (Option 7b) decreases peak daily sewerage discharges from the Armstrong Creek area by 65%. Wastewater plants located within the Armstrong Creek development decrease peak sewerage discharges by 51% to 20% and will result in significant reductions in the sizing of sewerage disposal infrastructure. In the case of the existing Black Rock sewer these reductions add value to the infrastructure by allowing additional capacity to be utilised elsewhere in Greater Geelong. 6.3
Wastewater reuse
The likely impact of the different water management options on provision of wastewater reuse infrastructure within the Armstrong Creek development and at Black Rock was evaluated using an indicative trunk water supply system (shown in Figure 6.8) in the global modelling to determine peak daily flows.
Marshall WR10
Sparrow North
WR4
A1
A2
WR3
WR9
Sparrow
WR5
WR2
A3
Pressure Reservoir
WR6
WR8 WR7
WR1
A4
A5
Black Rock WWT P
Figure 6.8: Indicative trunk wastewater reuse distribution network used to evaluate wastewater reuse flows within the Armstrong Creek development using a wastewater treatment plant at Black Rock. The peak daily flows in the wastewater reuse network were determined to be the 95 percentile daily flows and are shown in Table 6.3.
37
Table 6.3: Peak flows in the trunk infrastructure providing treated wastewater from Black Rock Option Length Peak flows (ML/day) (km) for each Option 4a 7a WR1 12.5 16.4 9.1 WR2 16.4 9.1 WR3 0.85 3.7 2 WR4 0.56 0.7 0.3 WR5 0.85 12.7 7.1 WR6 1.48 9.6 5.4 WR7 2.63 0.5 0.2 WR8 1.13 3.9 2.2 WR9 1.13 2.9 1.7 WR10 1.13 2.2 1.2 Table 6.3 reveals that supply of treated wastewater from Black Rock for toilet, outdoor and open space water demands within the Armstrong Creek development (Option 4a) will require a wastewater treatment plant, a pump station and a rising main that will deliver 16.5 ML/day. Supply of treated wastewater from Black Rock for toilet, outdoor and open space demands in the Armstrong Creek development that includes water efficient appliances and gardens (Option 7a) will require design of a wastewater treatment plant, a pump station and a rising main that will deliver 9.1 ML/day. The use of water efficient appliances and gardens at the Armstrong Creek development will reduce peak daily flows of treated wastewater by 44.5%. The likely impact of the different water management Options on provision of wastewater reuse infrastructure and treatment plants within the Armstrong Creek development was evaluated using an indicative trunk water supply system (shown in Figure 6.9) in the global modelling to determine peak daily flows.
Marshall WR10
Sparrow North
WR4
A1
A2
WR9
WR3
A3 WR2
Sparrow WR8
WR5
WR7
WWTP WR1
A4
A5
WWTP TopUp1 TopUp2 From existing sewer
Figure 6.9: Indicative trunk wastewater reuse distribution network used to evaluate wastewater reuse flows within the Armstrong Creek development using wastewater treatment plants within the Armstrong Creek development. 38
The peak daily flows in the wastewater reuse network were determined to be the 95 percentile daily flows and are shown in Table 6.4. Table 6.4: Peak (95 percentile) flows in the trunk wastewater reuse infrastructure Option Length Peak flows (ML/day) (km) for each Option 4b 7b WR1 7 4.3 WR2 9.4 5.2 WR3 1.68 3.6 2.0 WR4 0.56 0.8 0.3 WR5 0.85 3.4 2.3 WR6 WR7 1.5 0.5 0.2 WR8 2.63 3.9 2.2 WR9 1.13 2.9 1.7 WR10 1.13 2.1 1.2 TopUp1 1.88 1.3 0 TopUp2 1.88 0.4 0 Table 6.4 shows that supply of treated wastewater from treatment plants within the Armstrong Creek development for toilet, outdoor and open space water demands (Option 4b) will require wastewater treatment plants that will deliver 7 ML/day and 9.4 ML/day. A connection to the Black Rock trunk sewer that will allow top up of the wastewater treatment plants of 1.3 ML/day and 0.4 ML/day will be required to cope with summer peak outdoor demands. It is envisaged that this would be two-way delivery system that allows discharge of excess wastewater to the Black Rock sewerage in winter. Supply of treated wastewater from treatment plants in the Armstrong Creek development for toilet, outdoor and open space water demands that include water efficient appliances and gardens (Option 7a) will require design of a wastewater treatment plants that will deliver 4.3 ML/day and 5.2 ML/day. A wastewater top up main was not required. The use of water efficient appliances and gardens at the Armstrong Creek development (Option 7a) will reduce peak daily flows of treated wastewater by 45% from Option 4b. The use of treatment plants within the Armstrong Creek development will reduce peak daily wastewater reuse flows by 49% from the wastewater reuse peak flows generated by use of a wastewater treatment plant at Black Rock. Use of wastewater treatment plants and water efficient appliances within the Armstrong Creek development significantly reduces the requirement for wastewater treatment and distribution infrastructure. 6.4
Stormwater
Each Option was designed to meet the stormwater quality “best practice” standards 36 and to ensure that peak discharges from all storm events do not increase in comparison to existing conditions. The global volume of stormwater discharges from the Armstrong Creek development for each Option is shown in Figure 6.10.
36
Engineers Australia (2006). Australian Runoff Quality
39
Stormwater runoff volumes (ML/yr)
The developed option shows the stormwater runoff volumes from the fully developed Armstrong Creek catchments without any stormwater management and the existing Option shows the expected stormwater runoff volumes from the Armstrong Creek catchment in the current state. 8000 7000 6000 5000 4000 3000 2000 1000
3b
3a
2b
2a
1
Developed
Existing
0
Option Figure 6.10: Average annual stormwater runoff volumes from the Armstrong Creek development. Figure 6.10 shows that the developed option without stormwater mitigation produces substantial increases in stormwater runoff in comparison to existing conditions. The Options using 3,000 L (2a) and 5,000 L (2b) rainwater tanks reduce stormwater runoff volumes from the developed case by 16% and 17% respectively. The options that employ bio-retention systems with 3,000 L (3a) and 5,000 L (3b) rainwater tanks reduce stormwater runoff volumes from the developed Option by 23% and 25% respectively. Although the options using rainwater tanks and bio-retention were designed in accordance with best practice guidelines substantial increases in stormwater runoff volumes in comparison to the stormwater runoff volumes discharging from the catchments in the existing states. This result shows that the rainwater tanks and bio-retention systems will not reduce the environmental flows in the catchments to less than existing flows. However further reductions in stormwater runoff volumes may be required to meet environmental requirements for protection of Armstrong Creek and the downstream RAMSAR wetlands. The excess of stormwater volumes may provide an opportunity for stormwater harvesting for additional open space irrigation. These issues will be the subject of more detailed studies in a subsequent report on stormwater management in the Armstrong Creek catchments. Design storms were used to evaluate stormwater peak discharges from the catchments in the Armstrong Creek area and to design stormwater detention basin to ensure that stormwater peak discharges do not increase from the existing conditions. The reduced requirement for stormwater detention basins, the land under that basins and related costs are shown in Table 6.5.
40
Option 1 2a 2b 3a 3b
Table 6.5: Results from analysis using design storms Basin Land Residual Equivalent Basin volume area Land area allotments Costs (m3) (ha) (ha) ($m) 872,000 87.2 30.54 834,000 83.4 3.8 54 29.19 809,500 80.95 6.25 88 28.33 560,000 56 31.2 439 19.6 535,000 53.5 33.7 475 18.73
Avoided costs ($m) 8.08 13.2 54.88 71.12
Table 6.5 shows that the use of rainwater tanks reduces the basin volumes, land areas and costs required to manage stormwater peak discharges from the developed catchments. A combination of rainwater tanks and bio-retention provides substantial reductions in the costs of stormwater mitigation. The performance of the stormwater catchments in the Armstrong Creek area were continuously simulated using MUSIC to meet stormwater quality “best practice” standards for each Option. The reduced requirement for constructed wetlands, gross pollutant traps (GPTs), land under the wetlands and related costs are shown in Table 6.6. Option
1 2a 2b 3a 3b
Table 6.6: Results from analysis using continuous simulation Wetland Land Residual Equivalent Wetland volume area Land allotments costs (m3) (ha) area ($m) (ha) 107,500 10.75 10.2 67,000 6.7 4.05 57 6.37 59,500 5.95 4.8 68 4.56 6,500 0.65 10.1 142 0.62 5,000 0.5 10.25 144 0.48
in MUSIC GTP Avoided costs costs ($m) ($m) 2.9 2.68 2.65 2.37 2.31
10.78 16.88 54.05 69.61
Table 6.6 reveals that the use of rainwater tanks will almost halve the requirement for constructed by wetlands generating considerable reductions in costs to met stormwater best practice guidelines. The combined use of rainwater tanks and bio-retention almost eliminates the requirement for constructed wetlands to meet best practice stormwater quality guidelines. 6.5
Economic analysis
The economic performance of each option was evaluated from a whole of society perspective. A net present value of each option was determined using a 30 year horizon that commenced from the 11th year of the development to accommodate City of Greater Geelong’s accelerated growth strategy and a 5% discount rate. As the net difference to the BAU Option was investigated, the asset values and deterioration of infrastructure has not been included. It is acknowledged that this analysis may under-estimate the value of the alternative Options. Installation, operation, maintenance and replacement costs for the majority of assets in the alternative Options have been counted in this analysis and are summarised in previous Sections. The replacement costs of assets that were expected to have an operational life of less than 30 years that were different to the BAU Option were included in this analysis. For example, it has been assumed that rainwater pumps and water efficient appliances will have a 10 year operational life. The economic analysis, therefore, counts the full cost of installing the rainwater harvesting systems and includes a cost of $550 for the replacement of rainwater pump in each household every 10 years. 41
Water efficient shower heads and washing machines were installed and replaced at the net cost of $60 and $300 every 10 years respectively. The net cost is the difference between purchasing a “non-water efficient” product and the water efficient product. This analysis has not made any assumptions about the phasing out of non-water efficient appliances although the authors believe this will occur during the development period of the Armstrong Creek development. It is acknowledged that considerable progress has been made with the WELS scheme for the labelling of appliances. The lifecycle costs of bio-retention systems was accounted for as renewal and adaptation costs of 2% of installation cost per year37 that realise that the life of these types of assets is continued by recurring renewal. This cost was considered to be different to the annual operational and maintenance cost (4% of asset cost) of a bio-retention system. It is assumed that the BAU Option will source water from the Barwon Water’s supply system that has been made available by access to desalinated water from Wonthaggi. Clearly, the Armstrong Creek development and, indeed, the Geelong region will not have access to desalinated water, rather the availability of desalinated water in the eastern regions of Greater Melbourne may reduce demand on water from sources closer to Geelong thereby allowing transfer of that excess to Geelong. Thus the expected cost of desalinated water is assumed for the BAU Option in this analysis. The maintenance and operational costs including energy costs of alternative water sources used in this analysis are assessed as the net difference to the costs of desalinated water. However, this analysis has not counted the transfer costs associated with using desalinated water throughout the Greater Melbourne region. These costs are currently unknown and are the subject of the author’s current work with the Victorian Government. 38 The net installation and lifecycle costs used in this study are summarised in Table 6.7. Note that a net negative cost (eg; -2.9) indicates a net benefit. Option 2a 2b 3a 3c 4a 4b 5 6a 6b 7a 7b
Table 6.7: Net installation and lifecycle costs for each Option Net installation costs ($M) Net lifecycle costs ($M) Water Sewer Reuse SW Water Sewerage Reuse SW 0 -18.9 -1.30 44.6 0 0 0 -0.16 0 -30.1 -1.69 51.4 0 0 0 -0.25 0 -101.8 -1.30 44.4 0 0 0 -0.21 0 -133.6 -1.69 51.4 0 0 0 -0.46 0 0 -6.36 -12 -0.2 0 1.64 0 118.2 0 -6.36 -12 -7.9 0 -0.65 0 104.9 0 -8.35 -3.8 -4.1 0 0 0 0 -18.9 -7.68 62.4 -4.1 0 0 -0.16 0 -30.1 -7.75 67.9 -4.1 0 0 -0.25 0 -101.8 -11.4 48.2 -8.2 0 -0.04 -0.21 91.5 -133.6 -11.4 48.8 -11.3 0 -3.48 -0.46
Note that the installation costs of rainwater tanks and water efficient appliances are included in the water category in Table 6.7. The indicative net costs of water and wastewater reuse trunk infrastructure were derived by 37
Taylor A.C., (2005). Work undertaken to develop a life cycle costing module for the CRC for Catchment Hydrology’s MUSIC model. CRC for Catchment Hydrology. Melbourne. Victoria. 38 Coombes (2008). Rainwater Tank Evaluation Study for Metropolitan Melbourne. Report by Urban Water Cycle Solutions for the Department of Sustainability and Environment. 42
transforming the peak daily demands (ML/day) into peak hourly demands (L/s) as follows:
PeakHourDemand 2( PeakDayDemand *1000000 / 86400)
(1)
Using this relationship the costs for water and wastewater reuse transfer infrastructure was derived using the cost information provided in earlier sections of this report. Similarly the cost of trunk sewerage transfer infrastructure was derived using peak hourly demands as follows:
PeakHourDemand 6( PeakDayDemand *1000000 / 86400)
(2)
Costs of wastewater treatment plants and storages were derived using the values for peak daily demands. The relative performance of each of the Options is summarised as Net Present Values in Figure 6.11. 15
NPV ($M)
10
5
0 2a
2b
3a
3b
4a
4b
5
6a
6b
7a
7b
-5
-10
Option Figure 6.11: The relative Net Present Values of the alternative Options. Figure 6.11 shows that the Options 2a, 2b, 6a and 6b using rainwater tanks are subject to net present losses whereas those Options that include rainwater tanks in a combined strategy (3a, 3b, 7a and 7b) produce net present benefits. This result highlights the importance of the economic evaluation of Options that include portfolios of measures in preference to isolated evaluation of each measure. In Options 2a and 2b the installation costs of the rainwater tanks combine to negate the economic benefits provided by the tanks. Similarly, in Options 6a and 6b the combined installation costs of the rainwater tanks and the water efficient appliances have negated the economic benefits. In contrast, the use of rainwater tanks as part of a water sensitive urban design “treatment train” Option that includes bio-retention strategies as in Options 3a and 3b produces combined stormwater benefits that overwhelm the costs. Use of water efficient appliances and gardens (Option 5) was found to have a net present benefit. Figure 6.11 also reveals that wastewater reuse for toilets, outdoor and open space uses in Options 4a and 4b were subject to net present losses whereas the Options that include wastewater reuse in combined strategies (7a and 7b) produce net present benefits. The considerable difference between the net present losses in Options 4a and 4b is also significant. 43
The costs of providing and operating the wastewater reuse infrastructure in Options 4a and 4b overwhelm the benefits derived from water savings and reductions in the requirement for water and sewerage infrastructure. The net present losses in Option 4a are higher due to the additional costs for wastewater treatment, storage and transfer across 12.5 km distance to the Armstrong Creek development from a treatment plant at Black Rock. In contrast, the integrated water cycle management strategies (7a and 7b) provide combined water savings, stormwater benefits, and considerable reductions in the requirement for water and sewerage infrastructure that overwhelm the costs of providing and operating the infrastructure. Some additional insight provided by this study is also important; there is an optimum size, location and target water demands for a wastewater reuse strategy. The location of two smaller wastewater treatment plants within the Armstrong Creek development reduces installation costs by 35% in comparison to a single wastewater treatment plant located at Black Rock. In addition the placement of wastewater treatment plants at strategic locations within the development reduces the costs of water transport and for the provision of water, wastewater reuse and sewerage infrastructure by considerable amounts. Indeed the benefits of infrastructure savings from locating two wastewater treatment plants within the Armstrong Creek development, in comparison to a single wastewater treatment plant at Black Rock, are greater than the costs of installing the wastewater treatment plants. Use of net present values, in isolation, can be misleading for the assessment of water related alternatives. The magnitude of water savings also needs to be considered in the economic analysis. The “levelised cost” of each Option was evaluated as the net present value divided by the accumulated water savings over the 30 year period used in the economic analysis and shown in Figure 6.12. 0.4
Levelised benefit ($/kL)
0.3
0.2
0.1
0 2a
2b
3a
3b
4a
4b
5
6a
6b
7a
7b
-0.1
-0.2
Scenario Figure 6.12: Relative levelised benefits for each Option. Figure 6.12 reveals that the combination of rainwater tanks and bio-retention systems in water sensitive urban design (WSUD) strategies (Options 3a and 3b) produce a significantly greater relative levelised benefit. The integrated water cycle management strategies (Options 7a and 7b) produce the next most significant benefits. Use of water efficient appliances and gardens also produces a small levelised benefit. 44
Wastewater reuse from a treatment plant located at Black Rock for toilet, outdoor and open space uses at the Armstrong Creek development produced the greatest levelised cost (Option 4a). The remaining Options produced small levelised costs. Importantly, the results of the analysis of levelised costs are narrowly bound between a net increases in costs of $0.18/kL of water supply to a net reduction in costs of $0.32/kL of alternative water supply. Additional issues will need to be considered to clearly define an optimum strategy for the Armstrong Creek development. 6.6
Greenhouse gas emissions
The greenhouse gas emissions from the alternative Options are compared to emissions from the BAU Option in Figure 6.13.
Greenhouse gas emissions (%)
5 0 2a
2b
3a
3b
4a
4b
5
6a
6b
7a
7b
-5 -10 -15 -20 -25 -30 -35 -40 -45
Option Figure 6.13: Difference in greenhouse gas emissions for each Option from a BAU Option that is reliant on desalinated water supply. Figure 6.13 reveals that the supply of treated wastewater from Black Rock for toilet, outdoor and open space uses at Armstrong Creek (Option 4a) will increase greenhouse gas emissions. The increased emissions are caused by the additional energy required to pump treated wastewater from Black Rock to Armstrong Creek. The importance of this issue is highlighted by the relative reduction in greenhouse gas emissions generated by the use of wastewater treatment plants within the Armstrong Creek development to supply toilet, outdoor and open space uses (Option 4b). The remainder of the Options produce significant reductions in greenhouse gas emissions in comparison to the BAU Option. The Options using water efficient appliances and gardens (5), combinations of rainwater tanks, water efficient appliances and gardens (6a and 6b), and integrated water cycle management (7a and 7b) produce large reductions in greenhouse gas emissions.
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7
DISCUSSION
This study has utilised a detailed systems analysis to explore water cycle management options for the Armstrong Creek development. This process has involved the integration of water balance, water cycle network, hydrology and water quality models at sufficient detail to reveal the wide range of opportunities available for whole of water cycle management in the Armstrong Creek area. Interviews were also conducted with stakeholders in the development of the Armstrong Creek area to assist with assigning objectives. 7.1
Multi-criteria analysis
A selection of key results from this study were combined in a rudimentary multi-criteria analysis that utilises the percentage changes in mains water demand, sewerage discharges, stormwater runoff volumes and greenhouse gas emissions, and the net present values of each Option. Given that the comparative ranges of the criteria approximate the importance placed on the related issues by the City of Greater Geelong no attempt was made to place weights on the criteria. This decision was also consistent with the author’s concerns that the subjective application of weights in multi-criteria analysis can add considerable bias to the results. The multi-criteria analysis is shown in Table 7.1. It can be seen by the range of the criteria shown in Table 7.1 that reductions in mains water demands and sewerage discharges have the highest natural weighting that appears to adequately represent City of Greater Geelong’s desire for the development to achieve independence from regional water shortages. The slightly lower natural weightings for greenhouse gas emissions and stormwater runoff volumes represent the objective for global and local sustainability at the Armstrong Creek development. Option 2a 2b 3a 3b 4a 4b 5 6a 6b 7a 7b
Table 7.1: Multi-criteria analysis of Water Sewerage Stormwater 17.3 0 15.9 18.6 0 17.3 17.3 0 23.5 18.6 0 35.1 40.4 0 0 40 57.8 0 26.8 20.4 0 43.6 20.4 15.9 44.9 20.4 17.3 72.6 33.7 23.5 72.6 64.9 23.5
modelling results NPV GHG -4 13.5 -3.2 14.5 9.9 13.5 14.1 14.5 -8.5 -2.6 -4.1 9.1 3 26.9 -5 40.1 -4 39.6 3.2 29.6 6.5 41.5
Total 42.7 47.2 64.2 82.3 29.3 102.8 75.1 115 118.2 162.6 209
Rank 9 10 8 6 11 5 7 4 3 2 1
Table 7.1 shows that the integrated water cycle management option that utilises wastewater treatment plants for wastewater reuse within the Armstrong Creek development has the highest ranking (Option 7b). This option includes use of water efficient appliances and gardens, rainwater tanks to supply laundry and hot water uses, wastewater reuse for toilet, outdoor and open space water use, and a water sensitive urban design strategy. This option integrates a high level of stormwater management, reduction in water demands and sewerage discharges with a reduced requirement for infrastructure. This solution is consistent with the infrastructure strategies developed for the Aurora project by VicUrban, the Gold Coast Pimpama Coomera Water Futures Strategy and the Yarrabilba development. 39 39
Barry M.E., A. McAlister and P.J. Coombes (2004). A Three-Tier Approach to Urban Water Cycle Modelling in South East Queensland. Municipal and Local Government Engineers Association. Warwick. Queensland.
46
Option 4a that employs wastewater reuse at Armstrong Creek from a wastewater treatment plant at Black Rock achieved the lowest rank. The high cost and energy use of transferring treated wastewater from Black Rock to Armstrong Creek across a distance of 12.5 km contributed to the low ranking of this Option. Discharge of all sewerage to Black Rock that did not reduce the requirement for sewerage infrastructure also contributed to the low rank. 7.2
Development timing
The timing and spatial aspect of development at Armstrong Creek will be limited by the availability of sewerage infrastructure. Areas adjacent to the Block Rock trunk sewer can commence early. However, it is unlikely that key western and central precincts, remote from the Black Rock trunk sewer can be developed in a timely fashion without early delivery of trunk sewerage infrastructure. Provision of western and central wastewater treatment plants within the Armstrong Creek development will allow early development of the Sub-regional Centre and the western employment precincts. These areas can also be subject to timely development with the early delivery of trunk sewerage infrastructure. However, this strategy may involve substantial initial costs and a requirement to subsidise the cost of full sized infrastructure that may preclude more sustainable alternatives at Armstrong Creek in the future. A process for provision of infrastructure that allows flexible options, timing and financial strategies is preferred. A strategy that employs wastewater reuse from treatment plants within the development will allow the gradual and timely construction of infrastructure at preferred locations throughout the development. The flexibility of this strategy will allow a range of finance and business strategies. The timing of the development may also be influenced by the availability of water. It appears that there is sufficient capacity in the Pettavel Basin and Bellarine transfer main to support the early stages of the development. The western and northern areas of the site adjacent to existing water mains are well placed, spatially, to commence early development. Again, the proposed Sub-regional Centre is remote from existing water infrastructure and will require early delivery of trunk water infrastructure. Adoption of strategies with water conservation, rainwater harvesting and wastewater reuse will reduce the magnitude and cost of the required early delivery of trunk water infrastructure. The ultimate water demands from Business as Usual (BAU) development at Armstrong Creek are likely to generate a requirement for additional water sources to supply the Greater Geelong region, and for augmentation of the Pettavel Basin and Bellarine transfer main. This may also impact on the timing of the Armstrong Creek development. Importantly, the options for development of Armstrong Creek that include integrated water cycle management approaches (such as water efficient appliances and gardens, rainwater tanks and wastewater reuse) will reduce mains water demands to a level that avoids or significantly defers the requirement for additional water sources and augmentation of trunk water infrastructure. 7.3
Business models for the timely delivery of infrastructure
This study has evaluated the alternative options from a whole of community perspective and found that Options 3a, 3b, 5, 7a and 7b have positive net present values. These Options include rainwater tanks, Water Sensitive Urban Design, water efficient appliances and gardens, and wastewater reuse. The costs and benefits of these Options are provided by different elements in 47
the community. It is noteworthy that the community, developers and Council have a high value for their gardens and the prospect of a green suburb. In addition land developers and Council have a high value for flexible and timely delivery of infrastructure. Delays and uncertainty of about delivery of infrastructure generate considerable holding costs in the land development industry which are passed on to homeowners. These values have not been captured in the economic analysis.
7.3.1
Rainwater tanks and Water Sensitive Urban Design
In Options 3a and 3b, rainwater tanks will be provided by homeowners and the bio-retention facilities will be provided by land developers. The benefits from installing rainwater tanks and bioretention facilities, derived from reducing the requirement for detention basins, constructed wetlands and land area, accrue to the land developer. However, utilisation of these benefits is dependent on City of Greater Geelong accepting that decentralised WSUD approaches can down size the requirement for regional stormwater facilities. The operating benefits of rainwater tanks accrue to both the homeowner (water savings and lifecycle costs), the Council (improved stormwater regime and reduced maintenance of stormwater infrastructure) and to Barwon Water (reduced costs of treating and delivering mains water). The operating benefits of the bio-retention facilities accrue to Council. These benefits are derived from reducing the maintenance requirements for detention basins, constructed wetlands and GPTs. An equitable business model for provision of rainwater tanks and bio-retention facilities will be dependent on the transfer of a proportion of the benefits from the land developer to the home owner and the Council. Part of the avoided costs of providing stormwater infrastructure can be contributed to the Infrastructure Contribution Plan that will fund provision of rainwater tanks and early maintenance of bio-retention facilities. The avoided costs of purchasing mains water can be a proxy for transferring benefits of mains water savings from Barwon Water to the homeowner. Rainwater tanks can be mandated using a Section 173 agreement that could release funds to homeowners or builders for approved rainwater harvesting designs. Alternatively, rainwater tanks could be provided by the developer as a part of the required stormwater infrastructure solution. Bio-retention facilities will be provided by the land developer and can be required in Council’s stormwater planning documents.
7.3.2
Water efficient appliances and gardens
The costs to installing water efficient appliances and gardens (Option 5) accrue to the homeowner whilst the benefits accrue to Barwon Water (reduced requirement for trunk water and sewerage infrastructure). Transfer of benefits from this strategy is dependent on Barwon Water allowing a reduced requirement for water and sewerage trunk infrastructure that will benefit the land developer. This benefit will need to be transferred to the homeowner from the land developer. There are two mechanisms for this transfer of benefit to the homeowner; the developer can provide water efficient appliances and gardens to each homeowner, or the benefits can be delivered as a reduced cost of land in the development. It is preferable that the land developer makes a contribution to an Infrastructure Contribution Plan that benefits homeowners who install water efficient appliances and gardens. Lifecycle benefits of the use of water efficient appliances and gardens accrue to Barwon Water. The avoided costs of purchasing mains water can be a proxy for transferring these benefits to the homeowner. Ideally, water efficient appliances and gardens would be mandated for the Armstrong Creek development. Installation of water efficient gardens in preference to traditional gardens will require support from the City of Greater Geelong, Barwon Water and the land developer. A choice 48
must be made at the landscaping phase of development of estates or housing to install water efficient gardens. This action may need to be mandated.
7.3.3
Wastewater reuse
Options 7a and 7b that include wastewater reuse provided positive net present values. Each option also includes rainwater tanks, water efficient appliances and gardens, and water sensitive urban design measures. The business models for the delivery of these elements have been discussed above. Note that the viability of the integrated water cycle management strategies is dependent, in part, on transfer of some of the benefits accruing from stormwater management to the provision of wastewater reuse strategies. Both Options will involve the provision of a third pipe infrastructure by land developers at a cost of about $1,500 per dwelling. Provided that the construction of housing is planned to accept treated wastewater the cost of additional plumbing is expected to be $250 per dwelling. All land developers were willing to provide this infrastructure. It is assumed that the land developers will pass this cost onto the homeowner. Option 7a involves the provision of treated wastewater from Black Rock. This Option will reduce the cost of providing trunk water infrastructure by about 65%. The avoided costs of trunk water infrastructure, headworks charges and connection fees will provide funds that will contribute to delivering this option. The avoided costs of trunk water infrastructure accrue to Barwon Water. These benefits are only realised if Barwon Water accept the reductions in trunk infrastructure and will need to be counted to accurately account for this Option. Note that this study has only counted reductions in indicative trunk water infrastructure within the development. The indicative net costs to construct this Option are about $10.7 million or $485 per dwelling. In a business model where Barwon Water deliver the wastewater solution, these additional funds may need to be sourced from an Infrastructure Contribution Plan managed by Council that transfers some of the stormwater benefits to the provision of the wastewater solution. Note that the Essential Services Commission limits headworks charges for provision of treated wastewater to $550 per allotment. The annualised and operating costs of this option can be offset by the sale of treated wastewater. Note that this study has not counted the sale of treated wastewater and the wastewater service charge has not been considered because all wastewater is discharged to the existing Black Rock treatment plant. The price of wastewater supply from Black Rock will need to be greater than operating costs to deliver the treated wastewater to Armstrong Creek of about $1350/ML (this includes management costs [20%] and profit [6%]). In a business model involving a private infrastructure provider, Barwon Water could sell treated wastewater from a treatment plant at Black Rock to the private infrastructure provider. The private infrastructure provider will have access to the headworks charges of $550/allotment, connection fees of $420/allotment and can charge for the supply of the treated wastewater. These funds would pay the costs of providing the infrastructure to deliver treated wastewater from Black Rock to households at Armstrong Creek. The operating costs for the private infrastructure provider to deliver treated wastewater to households at Armstrong Creek are about $920/ML. The operating costs of Barwon Water providing the treated wastewater to the private infrastructure provider are about $430/ML but Barwon Water will also need to access funds to construct the wastewater treatment plant. Some of these funds can be sourced from the reduced requirement for trunk water infrastructure at Armstrong Creek. However, construction of the wastewater treatment plant may require additional funds from another source. This solution could be delivered by joint venture with the land developers. 49
The annualised cost of the wastewater treatment plant will need to be included in the price of the treated wastewater supply to account for the requirement for additional funds to deliver the plant. It is unlikely that a private infrastructure provider can make a viable business case from this situation. In any event, provision of a wastewater treatment plant at Black Rock is unlikely to provide the required flexibility of development timing at Armstrong Creek. Option 7b involves the provision of treated wastewater from treatment plants located within the Armstrong Creek development. This option reduces the requirement for trunk water infrastructure by 65% and for trunk sewerage infrastructure by 17%. The avoided costs of trunk water and sewerage infrastructure, headworks charges and connection fees will provide an indicative net benefit of $26 million from the delivery of this Option. This will allow a return of $1,180/allotment to land developers for provision of the third pipe distribution system. Barwon Water will need to allow reductions in trunk sewerage and water infrastructure. These benefits will need to be transferred to the provider of treated wastewater for assist with the costs of delivering the trunk wastewater reuse system. The operating costs of the treatment plants and wastewater reuse system are about $1077/ML (including management costs and profit). A 65% reduction in wastewater flows to Black Rock indicates that 65% of the $371/hh/year sewerage service fee can be assigned to the operation of the treatment plants at Armstrong Creek. An annual service fee of $5.3 million can be charged for provision of wastewater treatment at Armstrong Creek. The net operational benefit of wastewater reuse equates to $451/ML with additional excess revenue derived from the sale of treated wastewater. Considerable additional revenue is available from this Option. A wide range of business models are possible in this situation. Importantly, this option can allow timely development and flexibility of infrastructure provision and financing. Barwon Water could install and operate wastewater reuse system including the wastewater treatment plants at Armstrong Creek. This process will allow the use of existing processes within Barwon Water for managing and providing water services. However, Barwon Water admit that they do not have experience with provision of third pipe wastewater reuse schemes and may not be able to fund the early provision of the necessary infrastructure. All of the land development groups interviewed during this study expressed interest in the provision of wastewater reuse via a third pipe distribution scheme. They were prepared to form joint venture partnerships to fund the early delivery of necessary infrastructure and a wastewater reuse scheme. There is an opportunity for a consortium of land developers to partner with Barwon Water to provide the Armstrong Creek wastewater reuse strategy, or for the land developer consortium to provide the necessary infrastructure and for Barwon Water to manage that infrastructure, or for the consortium to partner with a private infrastructure provider to provide this wastewater strategy for Armstrong Creek. Current Victorian legislation allows for all of these business models. A private infrastructure provider would provide all sewerage infrastructure, wastewater treatment plants and distribution systems at Armstrong Creek. This entity would use funds from the land developers and levy headworks, connection and sewer service fees from the dwellings at Armstrong Creek and charge for the use of treated wastewater. The private infrastructure provider will need a works approval from the EPA, to achieve registration as a “sewerage authority” for Armstrong Creek, and to negotiate a bulk water agreement with Barwon Water for transfer of a proportion of sewerage to and from the Black Rock trunk sewer. The City of Greater Geelong could facilitate the EPA approval processes for a private water authority.
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7.4
Establishing competition for wastewater reuse markets at Armstrong Creek
Water and wastewater services are currently delivered to the community by state owned water monopolies. These monopolies are required to return dividends to state treasuries from the sale of water and the provision of sewerage services. As such, a competitive market for wastewater reuse services is only available if the state government allows other entities to provide this service. State legislation currently exists that allow alternative service delivery from private infrastructure providers and water authorities. A private water authority can be created with approval from the EPA and the Minister for Water. This status has been achieved by Sirex at the Forest Lakes project. Nevertheless, there is a significant dormant market for wastewater reuse that exists with the desire of the community, land developers and Councils to water gardens and provide green suburbs. The value of the amenity of household gardens and community open space is far greater than the current unit cost of water used to dismiss wastewater reuse strategies. A strong market for wastewater reuse for non-drinking water uses exists in the community that is currently not serviced. This is a market for wastewater reuse at Armstrong Creek. It is noteworthy that State government legislation allows for the mandating of third pipe wastewater reuse systems and, therefore, a guaranteed market potentially exists for the supply of treated wastewater to Armstrong Creek. The provision of wastewater treatment plants within the Armstrong Creek development to service the demand for treated wastewater also provides the additional opportunity for multiple development fronts and to reduce “out of sequence” infrastructure provision costs. Concerns about the timing, costs and viability of water supply water from the proposed Melbourne to Geelong pipeline are also a significant driver for alternative local water solutions at Armstrong creek. Similarly, concerns about the actual impacts of the supply of desalinated seawater from Wonthaggi and from the “Food bowl modernisation project” on water supply in Geelong are are driver for local water solutions. There are some potential barriers to wastewater reuse at Armstrong Creek. Barwon Water’s perceived resistance to wastewater reuse and third pipe systems was seen a significant barrier to a wastewater reuse strategy at Armstrong Creek. Land developers have had bad experiences, in the past, with poorly planned and designed third pipe wastewater reuse systems delivered by water utilities. Land developers were concerned about resistance to new ideas (such as more detailed design of wastewater reuse systems) could lead to lengthy delays in designs and approvals. The process of obtaining approvals from the EPA and the Minister for Water for establishment of a private sewerage authority was also seen to be a potential barrier to provision of a wastewater reuse system at Armstrong Creek. Nevertheless some significant opportunities were also apparent. Competition between Barwon Water and private infrastructure providers may drive improved designs and provide a wider range of opportunities. It may be possible for City of Greater Geelong to utilise its land use planning powers to mandate the provision of wastewater treatment plants within the Armstrong Creek development. Importantly the land developers and City of Greater Geelong support the provision of wastewater treatment plants within the Armstrong Creek development.
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7.5
Avoiding or deferring the need for regional infrastructure
It is proposed to construct the Melbourne to Geelong pipeline by 2012 at a cost of $142. The Options (7a and 7b) that utilise an integrated water cycle management strategy reduce the ultimate water demands from Armstrong Creek by 73% or about 16 ML/day. Importantly, Option 7b that includes the use of wastewater treatment plants within the Armstrong Creek development also reduces sewerage discharges from the area by 65% or 8 ML/day. Option 7b reduces the cost of indicative trunk infrastructure within Armstrong Creek by about 21%. Given that the Armstrong Creek development will produce the majority of Greater Geelong’s growth in water demand to 2030, reductions in water demand generated by the integrated water cycle management strategy will impact in the requirement for regional water infrastructure. In addition the Northern Water Plant with produce water savings of 5.5 ML/day by 2012. Adoption of an integrated water cycle management strategy at Armstrong Creek will defer the requirement for the Melbourne to Geelong pipeline from 2014 to 2033 (19 years). Using an interest rate of 5%, the net present value of deferring the pipeline is about $80 million. If the Barwon Water and City of Greater Geelong also meet the objectives of reducing residential water use by 25% using permanent water saving measures and water conservation measures, the need to the Melbourne to Geelong pipeline can be deferred until 2043 at a net present value of $102 million. Selection of an innovative water management strategy for the Armstrong Creek land release area will have profound impacts on the requirement for regional water infrastructure. This decision will also defer the requirement to upgrade the Pettavel basin and Bellarine transfer main. 7.6
Assumptions
This study has undertaken an integrated systems analysis at a strategic planning level to explore opportunities for water cycle management at the Armstrong Creek development. This process and time constraints have necessitated the use of some key assumptions that may impact on the impact on the results. Also, some additional analysis may be required to further explore some of the issues raised in this study.
7.6.1
Selection of BAU water supply scenario
All Options in this study have been compared to a Business As Usual (BAU) strategy that is dependent on desalinated water. The full energy costs of desalination have been counted in contrast to the common water industry practice of justifying high energy water strategies by claiming that use of green energy will neutralise the energy impacts. The full energy impacts of each Option have been counted for two important reasons; firstly the delivery of “green power” to water solutions is not usually guaranteed or included in the economic assessment of a project, and secondly; green energy options should be utilised to reduce our society’s greenhouse emissions in preference to justifying otherwise non-optimum water strategies. It is also an industry practice to assume green energy for a preferred Option and count the energy impacts of all of the alternatives. The energy impacts of all Options must be equally considered in any analysis. If must be assumed that all Options employ green energy or all Options do not employ green energy. In either case, the energy impacts must be counted because they will be a proxy for either the relative need to provide green energy or the relative magnitude of greenhouse gas emissions. In addition, the construction of the Wonthaggi desalination plant will add capacity to Melbourne’s 52
water supply system but the transfer of a proportion of this capacity to the Geelong region will be dependent on rainfall runoff into various dams around Victoria. As such, the provision of water to the Geelong region will remain tied to the uncertainty of rainfall runoff into dams created by climate change. In contrast, local reuse wastewater and rainwater harvesting will provide a buffer against the impacts of drought and climate change on runoff into dams. Finally, this study has not counted the additional costs of transferring water from Melbourne to Geelong which will include additional energy costs and bulk water charges that must include full recovery on costs. The use of current costs and energy profiles for the supply of water in Geelong may impact on the results of this study but will not accurately account for the actual water costs and energy impacts in Geelong’s water future. A subsequent study could analyse a full range of possible water futures for Geelong and account for the potential range of outcomes for the Armstrong Creek development.
7.6.2
Expected water demands at Armstrong Creek
This study has assumed that the Armstrong Creek development will attract residents from both Melbourne and Geelong. As such the new demographic and related water use profile at Armstrong Creek was expected to be different to the current average household water use in the Greater Geelong region (about 216 kL/annum prior to level 4 water restrictions). This study also assumed that prudent water planning should be based on household water demands that are not based on a recent history of severe water restrictions. Household water use profiles used in this study have been derived from the Greater Geelong Pt. C location which represents a growing area with a mixed demographic. This study has also analysed a range of housing sizes and dwelling types in preference to the use of an average household water demand. It is the author’s view that the use of averages in this type of water resource planning can produce misleading outcomes. In any event, the weighted average household water use in this study of about 262 kL/hh/annum is higher than the average household water use from the Greater Geelong region. In addition, this study has assumed that the industrial, commercial, open space and school areas within the Armstrong Creek development will ultimately generate a non-residential water demand that is about 34% of total water demand. The ultimate water demand for the Armstrong Creek development is unknown. It would not be prudent to under-estimate the likely water demands in this new area. Note that accurate water resource planning is reliant on a robust estimation of the BAU water demands that are then modified by a range of water management Options. Nevertheless, additional analysis of the Armstrong Creek development should examine the impacts of assuming that average household water demands in the BAU Option equate to 216 kL/hh/annum and that non-residential water demands are 27% of total water demand (assuming that only commercial developments emerge in the employment precincts. Importantly, the reducing the expected water demands in the BAU Option will have the effect of creating considerable improvements in the benefits and opportunities outlined in this study.
7.6.3
Economic analysis of different business models
This study has completed a single economic analysis from a whole of community perspective that has revealed significant opportunities for the Armstrong Creek development. These opportunities have not been further explored using an economic analysis from the perspective of Barwon Water, land developers, homeowners and the City of Greater Geelong. The opportunities for Armstrong 53
Creek revealed in this study should be explored from the perspective of each of these entities to determine the need for shared policies and financial resources to deliver an optimum water cycle management strategy for Armstrong Creek.
7.6.4
Stormwater volumes
This study has revealed that an excess of stormwater runoff volumes will be generated by the Armstrong Creek development with “best practice’ stormwater management. These excess stormwater volumes will provide an additional opportunity for stormwater harvesting and may need to be managed to protect the RAMSAR wetlands downstream of the development. This type of stormwater harvesting is often reported to be a simple and inexpensive option. However, implementation of a stormwater harvesting strategy poses considerable logistic and financial challenges that are revealed by the detail of any project. An additional study by Bonacci Water is exploring the opportunities for stormwater harvesting.
7.6.5
Council approvals
This study has revealed that use of decentralised Water Sensitive Urban Design (WSUD) allows considerable flexibility and opportunities in the Armstrong Creek development area whilst producing a high level of stormwater management. However, the benefits of strategies are dependent on City of Greater Geelong’s capacity to understand and approve innovative stormwater management approaches in a reasonable time frame.
7.6.6
Systems analysis
This study has carried out detailed systems analysis of a range of integrated strategies from a high level planning perspective. It has used indicative trunk infrastructure networks to assess that likely infrastructure trade offs within the Armstrong Creek development using a network linear analysis of each system. A hydraulic analysis has not been conducted to further analyse each of the infrastructure strategies and detailed designs have not been carried out. It is expected that detailed design and subsequent analysis of the development will reveal even greater benefits that discussed in this study. This was the outcome for the Pimpama Coomera project. 40 This study has utilised the considerable detail and integrated analysis required to understand the actual performance of integrated water cycle management strategies. It is important that further studies and subsequent designs of integrated water cycle management strategies for Armstrong Creek continue to use the necessary details and systems analysis demonstrated in this study. Use of average assumptions and discrete analysis methods will not lead to improved understanding of the opportunities provided in this study.
7.6.7
Regional infrastructure
This study has not counted the benefits of avoiding or deferring the need to augment the regional water supply for Greater Geelong by use of local water management strategies at Armstrong Creek. The Options with integrated water cycle management that produce considerable water savings at Armstrong Creek will have a positive impact on regional water security and will impact on the requirement to augment the regional water supply.
40
WBM (2003). Pimpama Coomera Water Futures Masterplan – strategic stormwater planning study. Gold Coast Water.
54
8
CONCLUSIONS AND RECOMMENDATIONS
The Armstrong Creek urban growth area provides Council with a unique opportunity to create a sustainable ‘extension’ of Geelong’s urban area to accommodate the population expansion proposed for the area. By adopting a progressive and innovative approach to planning and design, Armstrong Creek can be a smart, green community with enhanced lifestyle and amenity, meeting a range of community sustainability goals. Armstrong Creek will be the main driver of increased demand on water, sewer and stormwater infrastructure in the Geelong area over the next 10 years. An integrated systems approach to infrastructure planning and design will reduce the water, sewer and stormwater infrastructure needed or alternatively, allow the new infrastructure to service other expansion of Greater Geelong. By planning and designing for the best mix of water management options that include wastewater reuse, rainwater harvesting, demand management and water sensitive urban design of stormwater, larger regional strategies are not required to provide certainty about future urban water supplies. Armstrong Creek can be developed as a green and inviting “drought proof” suburb with a minimised carbon footprint by adopting infrastructure planning and design principles that make use of all available water sources from within the development area before relying on large external infrastructure upgrades. A localised infrastructure solution also provides increased flexibility in the timing and rate of development. Both Council and Barwon Water will need to adopt an open minded approach to the results arrived at from the use of the progressive and innovative analysis techniques contained in this report for the above benefits to be realised. Option 7b provided a range of performance outcomes that were consistent with the objectives of this study. The Option combines rainwater tanks, water sensitive urban design and water efficient appliances with treated effluent from wastewater treatment plants within the Armstrong Creek development used for toilet flushing, garden watering and open space irrigation. Class A+ treated effluent will be distributed to households and commercial users via a third pipe distribution network. Option 7b was found to provide combined water savings of 73%, a decrease in sewerage discharges from the Armstrong Creek area by 65%, and considerable reductions in the requirement for water and sewerage infrastructure that overwhelm the costs of providing and operating the infrastructure. This option also provided the greatest reduction in greenhouse gas emissions The provision of an integrated water cycle management strategy that includes wastewater reuse within the Armstrong Creek development (Option 7b) may be a more reliable water source than BAU. In addition, an innovative strategy that incorporates wastewater treatment plants located within the Armstrong Creek development will allow timely allocation of financial resources and infrastructure to the project. This strategy will also have improved the security of water supplies in the greater Geelong region allowing the avoidance or deferral of some regional augmentation strategies. The requirement from the Melbourne to Geelong pipeline can be deferred by 19 to 29 years at net present values of $80 to $102 million. This decision will also defer the requirement to upgrade the Pettavel basin and Bellarine transfer main.
55
9
APPENDICES
9.1
Appendix A: WATHNET networks
18 J 13 J 3 J
2 R
23 D
5 J
19 J
24 D 25 D
38 S
26 D 4 J 8 D
7 D
6 D
12 D
11 D
10 D
14 J
17 D
34 S 35 S
20 J
27 D 28 D
39 S
9 J
16 D
40 S
15 D
21 J
29 D
36 S
31 D
30 D 43 D 44 D
37 S
32 D
22 J
33 J 45 D
41 S
1 W
42 R
Network file: ../AC/BAU.net Title:
Printed on 28/02/2008 at 15:34
Figure A.1: Schematic of the BAU network used in WATHNET. Note that the dashed blue lines indicate the trunk sewerage system and the solid green lines indicate the water supply network.
18 J 13 J 5 J
3 J
2 R
38 S
50 J
23 D 24 D
19 J
25 D 26 D
4 J 8 D
7 D
6 D
46 J
12 D
9 J 11 D 47 J
34 S
39 S 10 D
17 D 53 J
16 D
36 S
20 J
28 D
14 J 15 D
21 J
29 D
40 S 52 J
48 J
35 S
27 D
51 J
30 D 43 D
54 R
44 D 49 J
37 S
22 J
33 J
32 D
45 D
41 S
56 R
Network file: ../AC/BAU_WW_in.net
55 J
57 S
58 S
1 W
31 D
42 R
Printed on 28/02/2008 at 15:36
FigureTitle: A.2: Schematic of the network used in WATHNET showing the additional wastewater reuse distribution system for wastewater treatment plants located within Armstrong Creek.
56
9.2
Appendix B: Stormwater simulation using design storms
18
19
8
7
9 10
2 11
20
12
13 3 14
15
4
5
16 6 1 17
Figure B.1: Stormwater network used in WUFS to simulate existing conditions at Armstrong Creek. File: C:\WUFS1.3\Armstrongcreek.wufs Description: Armstrong Creek
Printed on 28/02/2008 at 16:10
146 198 197
26
140
125
20
7
131 132
136
143
127
145
19 47 184 51
2
23
40
48
41
30 38 37
35
54
53
171
170
109
80
81
89 66
87
88 4
62
16
61 77
72
73 74
17 78
60 55
58 59 79
161
103
82
83 107 84
85 117
102 101 114
193 5
90
194
91 104
100 99 98 111
112
15
14 110
86
57 186
12
178 108
56
50
156151 160
202
65
11671
152
162
163 169
64
33 34
46
49
52 63
181
180
70
187
45
69
67
185
36
182 172
68
43
179 190
13
31 32
3
10
134
168
183 173
75
28 29
39 22
44
76
42
27
135
150 148 149 155 175 176 159 158 147 157 177 174 154 165 166 192 11 191 167 153 164
196 21
133
9 203
18
129
137 189
126
141
128
130 123 188
24
142
138 124
25
8
144
139
92 199 97
93
96
94
95
115 120 200 121
106
201
6
195 118
119
122
1
105
113
File: C:\WUFS1.3\ArmstrongDev.wufs
Figure B.2: Stormwater network used in WUFS to simulate the developed catchments. Blue Printed on The 28/02/2008 at 16:12 nodes indicate detention basins and the red nodes indicate developed clusters. The red arcs denote flow directions used in the analysis.
Description: Armstrong Creek
57
9.3
Appendix C
Figure C.1: Climate data used in the MUSIC analysis.
Figure C.2: Schematic of the existing conditions network used in the MUSIC simulations. 58
Figure C.3: Schematic of the network used to simulate BAU conditions in the MUSIC Simulations that include constructed wetlands and GPTs.
Figure C.4: Schematic of the network used for the WSUD Options in the MUSIC simulations. 59
9.4
Appendix D
See attached
60
9.5
Appendix E
See attached
61
