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Water Campaign™ case study

CITY OF MARION, SOUTH AUSTRALIA

Glade Crescent Reserve Wetland

: Corporate action

: Water quality

A print version of this case study is available to download. [PDF document, 700KB]

The City of Marion, South Australia, covers an area of 55 square kilometres to the south west of Adelaide and has a population of 82,229. Council is an ICLEI member and has been a participant in the ICLEI Water Campaign™ since 2005.

Synopsis

Glade Crescent Reserve is a large (13 hectare) area of undeveloped open space in Hallett Cove. The City of Marion has identified the site as a high priority due to water management issues and the need to improve the Reserve to provide a natural community asset.

: Project Plan highlighting proposed stages of construction

Waterfall Creek is part of the stormwater drainge system, taking the runoff discharged from adjacent suburbs to the coast. Currently this water has a high sediment and nutrient load and flows directly into Gulf St Vincent. Waterfall Creek also carries an environmental flow from a nearby spring most of the year.

Council undertook a feasibility study and proposed that a wetland be constructed to improve stormwater quality as well as creating recreational, environmental and educational opportunities at the site.

The development will require re-contouring and filling the land. It was identified that this could be achieved at a minimal cost to Council by recycling and reusing excavation material as fill. This will reduce the amount of material being sent to landfill and the associated high disposal costs.

The development will provide a high quality recreational reserve for the community, provide opportunities for community participation and education and improve the amenity and appearance of the area, while improving the quality of the water being discharged into the Gulf.

Motivation

Glade Crescent Reserve is centrally located in the southern precinct and is close to the Hallett Cove Shopping Centre, skate park, Capella Oval and the Coast to Vines Rail Trail.

Due to the Reserve’s proximity to these facilities, its redevelopment has been identified in Council’s Open Space and Recreation Strategy 2006–16 as a high priority.

Council recognised the Reserve as having significant potential for a range of passive and active recreation opportunities for the community as well as environmental education opportunities.

: Excavated material being crushed and sorted for use as fill

Due to its topography, lack of access and steep embankments, the Reserve is currently difficult to maintain and as a result is degraded and overgrown with weeds.

Rubbish and debris is often dumped or transported by stormwater into the area and it is difficult to remove.

The redevelopment will require substantial re-contouring of the embankments and filling of the gullies.

This will create improved access and will enable gross pollutant traps to be installed, while removal of weeds, planting of native species and increased use of the area will promote safety and reduce vandalism.

The stormwater currently leaving the area via Waterfall Creek has high sediment and nutrient loads and high levels of pollutants. The quality of this water will greatly improve with the creation of the wetland that will naturally filter the stormwater.

Process

: Project Concept Plan highlighting wetlands and recreational opportunities including a picnic area and play ground

A consultant was engaged to undertake a feasibility study of the site.

The outcome of the feasibility study was a proposal to construct a wetland to improve stormwater quality and provide a potential source of water for reuse, as well as the associated recreational, environmental and educational opportunities.

A concept plan for the wetland and associated facilities was subsequently prepared for consideration by the Council and consultation with the community.

The proposed wetland water body will consist of three connected ponds with a combined surface area of 1 hectare, when full. It will be designed so that water flow can occur between ponds in two ways depending on flow rate, ensuring high flows can move through the system without damaging the wetland or surrounding properties.

To construct the wetland Council will need to use fill to re-contour the site. Council currently produces 11, 000m3 (18, 000 tonnes) of excavated material each year. The estimated volume of soil required to redevelop the Glade Crescent Reserve by re-contouring the shapes and slopes is 58 000m3, with the option of levelling the eastern part of the Reserve involving an additional 92 000m3 of fill.

: Cross section of the wetland pond system

Council will recycle the excavated materials from its construction and maintenance works. This will be stockpiled at the Council’s nearby depot, crushed and sorted to meet the Environment Protection Authority standards required for use as fill. This will prevent the material being taken to the Reserve on a daily basis for a long period of time with the associated noise, dust and visual blight.

Potential risks including public safety, mosquitoes and algal blooms were identified and the following solutions adopted:

The pond embankments will have a gentle slope to ensure people can walk out if they happen to fall in.
Fencing and railings will be constructed in locations adjacent to deep water.
Signage and other methods of restricting access when ponds are overflowing will be installed.
The choice of path surfaces, finishes and cleaning arrangements was designed to address potential problems after a flooding event, such as deposits of mud and debris.
Proactive maintenance, involving desilting of ponds and monitoring and removal of plants and debris along pond edges, will minimise the risk of mosquitoes breeding.
Algal blooms will be controlled by appropriate design and regular maintenance of the wetland.

The redevelopment of the Reserve will be staged over a six-year period, with an option to continue filling for a further seven years.

Some of the maintenance requirements considered in the design stage include:

Pond 1 will have a concrete floor to ensure machinery can be used to remove built up sediment.
Improved access to the site will enable gross pollutant traps to be installed on the stormwater outfalls leading to the wetland.

Council also conducted community consultation, which consisted of invitations to talk to Council staff, attend a public meeting or provide written submissions on the concept design.

The community were generally supportive of the project and there was even some interest in the development of a friends group for the site. Further community consultation will occur during the detailed design stages of project implementation.

Costs

Council estimates the cost of developing the wetland will be approximately $1.2 million. The proposed staging of the development will enable funding to be distributed over a number of years to suit the availability and the reuse of excavated materials.

It is expected that the major cost of the construction works at the reserve will be offset by the avoided waste dumping charges,however additional funding will be required and external grant funding support will be sought.

Savings and benefits

Financial benefits

Waste dumping charges of $319,000 were provided in the 2007/08 Council budget to dispose of the excavated material to landfill. The savings in avoided dumping charges will be used to fund the project.

Water quality benefits

Water quality in Waterfall Creek and water entering Gulf St Vincent will be improved with the introduction of the wetland. The wetland will attract wildlife to the area and indigenous plants will be maintained in the reserve, which will result in increased biodiversity in the area.

The cleaning and retention of water in the wetland may also provide opportunity for reuse, which will be investigated at a later stage in the project.

Community benefits

The development will provide a recreational space for the community and significant opportunities for education and scientific studies. Interpretative signage will be installed to highlight linkages with the Hallett Cove Conservation park, local flora and fauna, wetland processes and the maintenance and opportunities for caring for a wetland.

Further information

Rudy Tieman
Manager Infrastructure Projects
Marion City Council
Ph: +61 (0) 8375 6715

Marion City Council website

Contact details

For further information about the ICLEI Water Campaign™ in Australia please contact:

ICLEI Oceania
4/267 Collins St
Melbourne Vic 3000
Ph:   +61 3 9639 8688
Fax:   +61 3 9639 8677
Email:   oceania@iclei.org
Website:   www.iclei.org/oceania/water

Acknowledgements

Thanks to Rebecca Neumann, Environment Project Officer, and Rudy Tieman, Manager Infrastructure Projects, for assistance in producing this case study.

Photographs supplied by Council.

Quoted population figures are taken from the Australian Bureau of Statistics Report 3218.0, Regional Population Growth, Australia 2006-07, March 2008.

Call for future case studies

Does your council have an initiative that could be promoted by the Water Campaign™ as a future case study?

We’d like to hear if your council has implemented an innovative water saving initiative or project to improve water quality. Contact your Water Campaign State Manager with details.

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