WATER PROOFING THE WEST – STAGE ONE MOVING TOWARDS A WATER SENSITIVE CITY
Adrian Sykes
Strategic Infrastructure Executive Officer, City of Charles Sturt Woodville, Adelaide, South Australia
Abstract
This Project shows how Water Sensitive Urban Design (WSUD) approaches with multiple objectives can create ‘Water Sensitive Cities’ which offer improved amenity and more sustainable communities.
The City of Charles Sturt developed the Water Proofing the West - Stage One Project with the primary objectives of flood mitigation and stormwater reuse, within a highly urbanised area. The Project harvests up to 2,400 ML per annum, treats and stores water in rock aquifers and subsequently distributes the water through 36 kilometres of mains. The Project links water assets in two stormwater catchments and has approximately 11 Hectares of wetlands across four sites, and enhances water harvesting with the capture of excess River Torrens water, which would otherwise be discharged to sea.
The Project cost was in the order of $71.5 Million, and was funded through Local, State, and Commonwealth Governments, a private land developer, and the support of a Golf Club.
Key elements include:
Wetlands and stormwater drainage in Old Port Road;
West Lakes Golf Course wetlands;
Cooke Reserve wetlands and bio-filters;
St Clair wetlands;
River Torrens water pumped to the Port and Torrens Road stormwater catchments, then gravity flow to wetlands for treatment; and
36 kilometres of linking and distribution mains through the city.
Key Words
Water Proofing the West - Stage One, City of Charles Sturt, WSUD, Water Sensitive City
Introduction
The impact of climate change is becoming increasingly apparent in South Australia as we continue to experience unprecedented dry weather patterns. Sustainable water management practices are therefore forefront in mind for this State. The South Australian Government released the Water for Good: A plan to ensure our water future to 2050, in 2009 as an integrated water security plan which assessed six major sources of water, to develop an urban water management framework for Greater Adelaide. Adelaide’s six sources of urban water include water from the catchments in the Mount Lofty Ranges, River Murray water, groundwater, wastewater, stormwater and desalinated seawater. In Adelaide Local Government has a part to play in seeking to ensure sustainable water use primarily from stormwater and groundwater. In addition to drought there is increasing risk of minor and major storm events putting increased pressure on drainage infrastructure. It is obvious that water is fundamental to our health, our way of life, our economy and our environment.
Recently there has been a push towards WSUD approaches as a way to better manage urban water and improve liveability and the term a ‘Water Sensitive City’ has been promoted.
A Report prepared by the State’s Water and Climate Change Branch Transitioning Adelaide to a water sensitive city: Towards an Urban Water Plan for Greater Adelaide, Issues paper, October 2014 http://www.watersensitivesa.com/news/transitioning-adelaide-water-sensitive-city-issues- paper seeks input in the formation of an Urban Water Management Plan that will move Adelaide towards being a water sensitive city.
This paper provides an overview of how the City of Charles Sturt has created a vision for the Water Proofing the West – Stage One Project (Project) that utilises WSUD principles and includes flood mitigation and WSUD approaches for an integrated approach. This Project was the first major stormwater reuse and flood mitigation initiative of Local, State and Commonwealth Governments for the western suburbs of Adelaide and is centred in the City of Charles Sturt who is the owner, operator and administrator of the completed water infrastructure.
Responding to the challenges
Stormwater management and flood mitigation has been one of the most significant issues facing the City of Charles Sturt. Many parts of this City have a long history of flooding because the land is so flat and close to sea level.
In addition to flood risk the drought conditions commencing in 2003 with Level 3 water restrictions saw many Council reserves and natural vegetation areas deteriorate and many display extreme stress. There is strong community concern that dryer conditions mean significant numbers of trees are dying and many of Council’s shrubs and reserves have browned off and were dying.
From these two drivers Council developed a vision that reduced flood risk whilst also providing more sustainable water use. Council’s vision for the Water Proofing the West – Stage One Project was for a system which harvests, treats and injects water into the rock aquifers for later withdrawal and re-use (Managed Aquifer Recharge or MAR) distributing the non-potable water through sections of the city.
The City of Charles Sturt, together with the State and Commonwealth Governments, has now officially completed and opened the Water Proofing the West – Stage One Project. The Project is unique, an integrated water sensitive urban design solution to the challenges associated with stormwater management, stormwater quality improvement, flood management and water supply management in a fully developed urban area, sustaining a growing economy and enhancing the natural environment.
This Project is a major initiative by the City of Charles Sturt with combined expenditure of
$71.5 Million and was a collaborative funding project with nine funding partners from all three tiers of Government, a private land developer and the support of the West Lakes Golf Club.
Funding Contributor Contribution ($ million) City of Charles Sturt $19.46
City of Port Adelaide Enfield $ 4.43
SA State Government $20.07
Commonwealth Government $22.30 St Clair JV developer $ 5.25 Total Project Budget $71.51
Funding was gained from the State and Commonwealth Governments for both flood risk mitigation and water re-use, and it was recognition of both these aspects that enabled the capital funding opportunities to reach the Project total budget of $71.5 Million.
The Water Proofing the West - Stage One Project has five key components comprising works at Old Port Road, Cooke Reserve and West Lakes Golf Course, St Clair subdivision, River Torrens collection and transfer system, as well as the linking and distribution mains. Water assets were created across five linked sites and two stormwater catchment areas, with 11 Hectares of wetlands and biofilters, 15 bores into the rock aquifers, two pump stations, (at St Clair which also has chlorination and UV disinfection plant and West Lakes Golf Course) and 36 kilometres of distribution mains to supply recycled water to reserves, schools and as third pipe water systems in new residential developments at St Clair and Woodville West.
Water harvesting from the two stormwater catchments was enhanced with the capture of excess River Torrens water which would otherwise be discharged to sea.
The Project developed infrastructure capable of capturing and treating up to 2400 million litres of water and this will supply non-potable water annually to replace current and future potable water demands, supplying water for irrigation purposes and for domestic and industrial demands.
Additional WSUD benefits
WSUD design approaches manage water in urban environments in a way that reduces the negative impacts of urbanisation and seeks to maximise economic, social and environmental benefits. This Project has demonstrated that WSUD can be used to better manage water in new and existing urban areas and can provide multiple benefits to communities; managing flood risks and impacts, whilst delivering a more liveable city by providing more attractive and inviting green spaces, reducing urban temperatures, maintaining parks and gardens with non-potable water, delivering improved amenity, biodiversity and wildlife habitat.
Harvesting and aquifer storage of water for later re-use (Managed Aquifer Recharge or MAR) delivers the additional benefit of capturing most of the pollutant loads in the catchments.
The majority of stormwater harvested would otherwise drain untreated to West Lakes, Port River, Barker Inlet and the Metropolitan Adelaide coast, further degrading seagrass meadows and continuing to pollute Gulf St Vincent’s coastal and marine assets.
The treatment train as part of this water quality improvement infrastructure is:
As a result of the water quality measures coastal discharges show significant improvements in sediment (turbidity), gross floating materials, heavy metals, bacteria and nutrients. This best practice treatment is anticipated to provide:
80% reduction in Total suspended solids
60% reduction in Total phosphorous
45% reduction in Total nitrogen
Additionally over many years water has been extracted from the groundwater aquifer resources in this city and this is unsustainable in the long term, with existing aquifers now showing signs of increasing salinity. Following water quality improvement, water is injected into the rock aquifers and hence this Project assists in protecting and sustaining of the groundwater resources in the region. Extraction amounts are licenced and will ensure long term sustainability of the aquifers.
WSUD Project Elements Old Port Road
The 657 Ha Port Road stormwater catchment is a long thin catchment that extends from the Adelaide City Parklands through the Old Port Road to a coastal discharge at West Lakes. Areas of flood risk and nuisance stormwater inundation of the road carriageways and adjacent properties occurs with rain events in excess of a 1 in 9 month Average Recurrence Interval (ARI) frequency event. In a 1-in-100 year ARI the Queen Elizabeth Hospital will experience significant road flooding preventing access to this regional hospital.
The Project incorporates both flood mitigation works to provide 1-in-100 year ARI flood mitigation benefits in accordance with the catchment Stormwater Management Plan, and water re-use components. The topography of this catchment has meant all the works have been constructed within an active drain located within the central median. The stormwater from the surrounding catchment and excess river flows from the River Torrens are treated in 1 Ha of wetlands with a pump station to divert excess water to Cooke Reserve and West Lakes Golf Club for further treatment prior to MAR.
Water quality improvements include a net type Gross Pollutant Trap (GPT) at the head of a large 22,000 square metre sedimentation basin and stormwater detention basin for up to 10 ML of stormwater. In addition to the stormwater and water re-use infrastructure undergrounding of all the low and medium voltage powerlines was completed and landscaping created to improve the overall amenity of the area.
Image of Old Port Road wetland
Cooke Reserve and West Lakes Golf Course (WLGC)
Partially treated water from the Old Port Road wetlands is diverted to Cooke Reserve and West Lakes Golf Course with features including 17,500 square metres of constructed wetlands, 4 biofilters with an area of 4100 square metres, and 7 bores to store treated water in the T2 aquifer at a depth of approximately 240 metres. The wetlands detain water for normally three days to achieve the Environment Protection Authority (EPA) water quality criteria values required, prior to injection into the rock aquifers for later withdrawal and re-use.
Image of Cooke Reserve wetland
Image of West Lakes Golf Course wetland
In addition a pump station to store and inject treated stormwater into bores and to distribute water retrieved from MAR bores via the reticulation network is located at WLGC.
Image of West Lakes Golf Course pump station and tanks
St Clair Subdivision and wetlands
The St Clair wetlands capture stormwater from the subdivision plus a portion of the Torrens Road stormwater catchment and excess flows from the River Torrens. The following plan shows the six hectares of wetlands and the prior treatment pond devices designed to treat up to 1300 ML per annum of water.
Overview of St Clair wetlands and water quality devices
The St Clair wetlands have both flood mitigation and water re-use components. For water re-use capture the small storm events (typically up to a four-month ARI) undergo water quality improvements prior to injection into 8 bores in the T2 aquifer.
The wetlands at St Clair comprise the main wetlands that treat the bulk of stormwater and three smaller wetlands that provide pre-treatment of runoff from the St Clair development before entering the main wetlands. The main wetlands have three levels, the highest being at the NE inlet pond, from where flow goes down two weirs before reaching a Normal Water Level (NWL) of RL 3.9m.
The wetlands are designed to normally have a three day detention time at the NWL to achieve the required water quality criteria. The majority of the wetlands are at NWL, however during storm events the wetland levels may increase by 400mm to RL 4.3 m, Top Water Level (TWL).
When water levels exceed TWL the water will flow from the wetland outlet into the local drainage network in Addison Road. The outlet is designed to maintain the peak 100-year average recurrence interval (ARI) flow from the development to the pre-development 5-year ARI flow rate, thus reducing flooding pressure on the local drainage network downstream of St Clair.
Further protection for properties is provided with a spillway at RL 4.7 m and finished floor levels are to be in excess of RL 5.1 m.
Two recent photographs demonstrate the amenity value that can be achieved when incorporating WSUD design into new subdivisions:
Image of views of completed wetlands at St Clair River Torrens Transfer System
Excess River Torrens water that would otherwise discharge out to Gulf St Vincent, is taken at Bonython Park and provides additional harvested water to the Old Port Road, Cooke Reserve, West Lakes Golf Course and St Clair wetlands.
The River Torrens transfer system allows (under State Government licence conditions) the excess river water to be harvested from the River Torrens and for the water to be pumped to both the Port and Torrens Road stormwater catchments, where the pumped water then enters the normal gravity stormwater drainage systems.
A below ground pump station with associated electrical switchboards, communications boards and a new transformer has been constructed in the eastern banks of the River Torrens in Bonython Park. River water captured by the new pump station is sent through two underground pressure pipelines, constructed along Park Terrace for a distance of approximately 800 metres. At this point, the pipes separate with one pipe crossing Port Road and continuing in the Port Road median near the main Entertainment Centre, with a total length of pipe of 1,056 metres. At this location, it discharges into the Port Road stormwater system, and water travels in the existing gravity stormwater system to the Old Port Road wetlands to allow for water harvesting.
The second pressure pipeline continues north along Park Terrace and then goes into the Bowden/Brompton area, where it discharges into the existing gravity stormwater system. The length of this pipe is 2,076 metres, and water travels in the existing stormwater system to the Torrens Road stormwater system and then is harvested at the St Clair wetlands. The River Torrens pump station is actively controlled, using monitoring station infrastructure (owned and operated by the Adelaide and Mount Lofty Ranges Natural Resources Management Board) to determine the quantity of the River Torrens river flow and whether water can be harvested.
Linking and Distribution Mains
The Linking and Distribution Mains connects the St Clair subdivision and pump station, Old Port Road, West Lakes Golf Course and pump station, and Cooke Reserve and consists of approximately 36 kilometres of pipework. The pipe mains distributes non-potable water throughout the region; with a focus on demand areas including Council reserves, State and Private schools and as third (purple) pipe water at the new residential subdivisions at St Clair and Woodville West.
Dwellings at these residential subdivisions receive the non-portable water for use in toilets, for washing and for outside use through a purple third pipe system.
To ensure demands across the linking and distribution mains are reliable and robust, the system links the supply sites. If pollutants or system failures occur in one location, the system is still able to maintain supply. The system has two main distribution pump stations however it’s able to operate and continue supply with limited function with only one pump station operational.
Conclusion
The impact of climate change in South Australia has driven the need to seek more sustainable water management practices for the State. WSUD is still a relatively new approach which can be used to achieve multiple objectives relating to driving cost reductions and gaining efficiencies across design, construction and maintenance.
The Water Proofing the West - Stage One Project is a unique example of sustainable public infrastructure in a fully urbanised environment. Objectives were achieved within a WSUD context including water reuse, flood mitigation elements, and the provision of sustainable aquifer use to alleviate the challenge of increasing salinity in groundwater, whilst creating biodiversity benefits and amenity appeal. This Project showed that all this can be achieved incorporating WSUD design in new subdivisions and demonstrates how the use of these multi objectives can move Adelaide towards becoming a water sensitive city.
Some Councils are using a multitude of small bio-filters or rain gardens along roads. Although attractive these devices become a long term and expensive solution to stormwater quality improvement when maintenance operating costs are considered. The City of Charles Sturt’s approach has been to capture gross pollutants and then provide the water quality improvement devices such as sedimentation basins, bio-filters, wetlands and other WSUD structures as much larger devices which then concentrate the areas where the long term maintenance is focussed.
As this Water Proofing the West – Stage One Project demonstrates, careful WSUD design can achieve complementary results and cost savings are achievable when designs incorporate both flood risk mitigation and water re-use objectives, thus delivering multiple benefits to the final project. Combining flood mitigation and water re-use objectives within one project also offers the opportunity to seek grant funding from State and Commonwealth Governments from both the flood mitigation and water reuse grant areas.
Using WSUD approaches can create urban areas with more liveable environments and deliver a higher quality of life for communities. WSUD approaches hence create ‘Water Sensitive Cities’
which offer improved amenity and more sustainable communities.
The City of Charles Sturt Project has received awards from across industry sectors including the Local Government Managers Association, Stormwater South Australia, and the Stormwater Industry Association for the innovation demonstrated in this Project.
Acknowledgements
The success of a Project of this magnitude has only been made possible by the support and commitment of its nine funding partners. We wish to acknowledge the contribution of all parties within these funding partners, with specific mention to the strong support offered by representatives of the State Government Department of Environment, Water and Natural Resources (previously Department for Water).
References
DesignFlow (22 June 2012) ‘St Clair wetlands: Functional design’ Report for AECOM.
South Australian Government, (2009) ‘Water for Good: A plan to ensure our water future to 2050’, South Australian Government, Water and Climate Change Branch, (October 2014), ‘Transitioning Adelaide to a water sensitive city: Towards an Urban Water Plan for Greater Adelaide, Issues paper’.
Author Biography & Photograph
Adrian has more than 35 years’ experience in Local Government, State Government, and private consultancies within Australia and the USA, with qualifications including a civil engineering degree (SA Institute of Technology), a Post Graduate Diploma of Municipal Engineering (University of SA), an MBA (Technology Management) La Trobe University, and a Diploma from the Australian Institute of Company Directors.
Adrian Sykes
Strategic Infrastructure Executive Officer City of Charles Sturt
72 Woodville Road
Woodville, South Australia 5011
Tel: (08) 8408 1271, Mob: 0419 819 873 Email: [email protected]