Case studyFigtree Place: a case study in water sensitive urban development (WSUD)
Introduction
The maxim “Think globally, act locally” is usually understood to refer to worldwide environmental values being achieved through positive, affordable action taken by local communities. This fusion of ecologically sound practice with economic viability is central to the concept of sustainable development (WCED, 1990). A microcosmic interpretation of the maxim can be that “global” refers to city infrastructure and “local” may be identified with individual dwellings or commercial/public buildings or groups of such buildings that, collectively, comprise the city.
While this interpretation of “global” may be used to develop practices which are ecologically sustainable in the full range of utilities found in a metropolis (transport, power, sewerage and gas) the focus of this article is on the services which provide water and the disposal of stormwater. Water sensitive urban development (WSUD) is a local solution to the global problems created by reliance on conveyance and centralised storage/discharge of water in cities.
Developments which are “water-sensitive” involve water conservation and stormwater retention strategies employed at the urban allotment or “cluster” level to reduce infrastructure costs and environmental degradation of aquatic environments. The principles of the WSUD approach have been incorporated into a demonstration project in Newcastle, New South Wales, Australia. Newcastle is a major Australian coastal city 160 km north of Sydney. With a population of 140,000 plus 350,000 people living in the surrounding region, Newcastle is the largest urban concentration in Australia after the five mainland capital cities.
In August 1995, Newcastle City Council adopted its “Environment management plan: a vision for a clean and healthy city”. This plan built on some important initiatives already underway in Newcastle, funded by the Australian Government’s “Building Better Cities” programme. The demonstration project described in this paper resulted from collaboration between the two Agencies and NSW Department of Housing and relates to redevelopment of a 0.6 ha portion of the Hamilton Bus Station site (3.0 ha area) called “Figtree Place” in central Newcastle. The redevelopment involved the construction of 27 housing units. This study reports early and significant findings that have emerged from the two-years monitoring programme.
Section snippets
The site and its capabilities
Previous occupation of the Figtree Place site as Newcastle’s main public transport hub went back to the early 1900s with initial use by trams and more recently buses. Over the years serious spillage of hydrocarbons had occurred leaving the deep-sand site (sand depth: 10 m) in a highly contaminated state with “hot spots” of PAH, TPH, heavy metals, pesticides and oil and grease. Concrete “capping” was used as a remedial action and the area subsequently used for bus parking.
Geotechnical testing at
Approval agencies: reactions and requirements
There were five main areas of concern for approval agencies represented on the project Steering Committee:
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the potential for undetected contaminants being released into the groundwater;
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the possibility that water retention practices might produce a groundwater “mound” that would compromise the structural integrity of buildings;
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the potential for health problems as a result of unsanitary water, collected from roofs and used in hot water systems, being ingested;
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the potential for a repeat of drought
Layout and main features
The plan of Figtree Place is shown in Fig. 1. Its main features are:
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27 home sites:
Single bedroom residences 3 Two bedroom residences 18 Three bedroom residences 6 The effective housing density is 45 units per ha;
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underground rainwater tanks fitted with “first flush” diversion devices; between four and eight houses per rainwater tank;
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gravel-filled trenches at front or rear of 19 home sites: trenches receive rainwater tank overflow and provide recharge to groundwater;
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all runoff from paved area
Monitoring details
A comprehensive monitoring programme (manual and automated) is being conducted to assess water quality, water use, social acceptance of water-sensitive design elements, maintenance issues and economic performance (Coombes et al., 1999b). The manual sampling programme accesses water quality of roof runoff, first-flush pits, raintanks and hot water systems on a monthly basis. Table 1 lists the currently monitored bacterial and chemical parameters: guideline values taken from the Australian
Roofwater
One of the early monitoring priorities was to determine the quality of water in the roof to hot water system pathway. This priority arose from concerns expressed by approval agencies (see Section 3). Roofwater was collected in the form of bulk and first-flush (first 2 mm of rain) samples for five different roof aspects (west-north, west-south, south, east and north) over 40 rain events in July and August 1998. The samples were analysed for compliance with the chemical Guidelines listed in Table
Water use, social acceptance and stormwater results
Measurement of internal water use at Figtree Place (partly occupied) during the period June to December 1998 showed a 65% reduction in expected mains consumption. During the period, December 1998–November 1999, the development was fully occupied but the tank water system was inoperative for long periods due to redesign/reconstruction activities. Nevertheless a 30% reduction in internal mains water consumption was experienced during this period. Based on these performances, it is anticipated
Project cost-effectiveness
Much has been learnt about the design, management and maintenance of the Figtree Place demonstration project during the initial period of operation. A greater understanding of the design requirements and discovery of many construction/design shortcomings has enabled redesign and reconstruction of elements of the development. This has resulted in improved knowledge of the construction costs and design issues applicable to other sites (Coombes et al., 1999a).
In the approximate economic analysis
Conclusions
This paper summarises early results from the Figtree Place demonstration project. Although experience has revealed significant flaws in the construction/design of the project much has been learnt from “worst case scenario” monitoring and analysis. Some important conclusions that support implementation of WSUD are provided:
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Hot water (storage) systems supplied with rainwater contaminated with bacteria, can deliver water meeting Australian Drinking Water Guidelines provided that they are operated
Acknowledgements
The efforts of Frank Cosgrove, Mike Mouritz, Lincoln Hawkins and Neil Roser from Newcastle City Council and Jerome Argue of Northrop Engineers Pty Ltd ensured that the Figtree Place concept became a reality. Hugh Dunstan of the Department of Medical Sciences at the University of Newcastle has provided invaluable assistance in the quest for greater understanding of microbiology and water quality issues. The authors also gratefully acknowledge the funding provided by Newcastle City Council and
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