When Holroyd City Council developed its Domain Creek Dual Water Quality and Flood Mitigation Project it incorporated the innovative use of a sports playing field with a detention basin to protect downstream properties from floods (quantity), treatment of stormwater (quality) and irrigation of the field using stormwater (reuse).
The project drew worthy praise from the New South Wales Division of the Institute of Public Works Engineering Australia (IPWEA) earlier this year, taking out a high commendation in its Engineering Excellence Awards.
The concept was to increase the water quality leaving the catchment and to reduce the flooding downstream during storms in an already fully developed catchment. The $1.18 million project included construction of a sports field that acts as a detention basin during storms.
The floor of the basin is a structured soil filter which filters flood waters and directs them to an underground storage tank. A separate large tank incorporates a sand filter which treats all flows up to and within a two month storm and then directs it to an underground storage tank. The stormwater in the tank can be recycled and used by an automatic system to irrigate the playing field, catering for up to 90 percent of its annual needs.
Two Continuous Deflection Separators (CDS) were installed at the inlet to the basin, while a further three oil and sediment separators were installed within the Domain Creek catchment area to trap litter, oil and grease before they enter the Domain Creek and Parramatta River.
Assistant Director of Operations, Paul Ritchie, said that in developing the system, the major objectives included improvement of water quality in the catchment, provision of flood mitigation measures and to reduce flood levels for properties downstream from the park and the reuse of stormwater at the local park.
“The project has achieved all of these objectives,” Paul Ritchie said.
“In a recent inspection of all units, enormous amounts of visible pollutants have been trapped.
“It has achieved the removal of litter, sediment, oils and grease as stormwater passes the gross pollutant trap, CDS and sand filter units, including the soil filter encompassing the playing field.
“Over the first six months of operation, the pair of CDS at the park collected about eight tonnes of litter from a high density residential area.
“Another success is that through the reduction of our reliance on the Sydney water supply, by reusing a large portion of the stormwater, Council will recoup the capital costs for this part of the project over 20 years.”
