Stormwater Treatment Facility at Parklakes Estate
The Stormwater Treatment Facility at Parklakes Estate is designed to provide treatment to stormwater runoff from the 82 ha estate, as well as adjacent upstream catchments. The stormwater treatment facility consists of an inlet basin which collects runoff from the estate and discharges the design flow into a wetland. The wetland will then discharge into the receiving environment, an urban lake. The inlet basin and wetland also serve as part of a lake re-circulation system. The stormwater treatment facility and lake also act as a means to achieve pre-development flow, detaining the increased runoff associated with urban development and lessening flooding stress on downstream environments. This system has been designed using best practice principles and aims to ensure long-term lake health and to provide a valuable asset to the Parklakes community and the greater Sunshine Coast.
- Chris Walker 07 5443 7777 (Office) 0416726860 (Mobile) 07 5443 7577 (Fax) P.O. Box16 124 Duporth Avenue Maroochydore, Qld 4558
- 20 Weeks
- Parklakes Estate Yandina-Bli Bli Road Bli Bli, Qld 4560
- Approximately $2.8 million
- Sunshine Coast Regional Council
- Reef Bill Pty. Ltd.
- Covey Associates (Civil and Environmental Design) • Key designers include Chris Camp, Chris Walker & Damion MacDonald LandGraphics (Landscape Architecture and Design) • Key designers include Rob Burrell and Anthony Powers
- Hall Civil Contracting Pty Ltd (Civil Construction) Corporate Landscape Services Pty Ltd (Landscape Management)
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The objectives of the projects are threefold;
• Firstly, to ensure that runoff from the estate is treated to the desired level before discharging into the lake. This will be achieved through the gross pollutant controls installed throughout the development and the stormwater treatment facility. The initial component of the treatment facility is a 3,000 m2 (4,700 m3) inlet basin. This inlet basin will remove secondary pollutants such as coarse sediment and some fine particulates from stormwater runoff. The inlet basin will discharge design flows into a 10,500 m2 wetland. The wetland will act to remove secondary (fine particulates) and tertiary pollutants (very fine particulates and soluble nutrients and heavy metals).
• Secondly, to maintain long-term lake health and discourage algal blooms and eutrophication. This will be achieved through the re-circulation system. When activated, a pump will circulate water from the lake back into the inlet basin and into the wetland. This will provide further treatment to the water and achieve the desired retention time in the lake, limiting eutrophication and algal blooms. Solar panels will be installed on the adjacent sports reserve buildings to continuously feed into the power grid to offset the use of the re-circulation pump.
• The final objective of the project is to provide a highly amenable and interactive environment for the local community. The landscaping for the stormwater treatment facility has been designed for a dual purpose; to mimic and enhance the existing natural open forest environment of Bli Bli and promote biodiversity within the wetland, which will provide a habitat for a range of aquatic species. The stormwater treatment facility can also be utilised as a ‘living laboratory’, fulfilling an educational objective. It is envisioned that the stormwater treatment facility will be utilised by local primary and secondary schools, as well as by research facilities, such the University of the Sunshine Coast. -
The key challenges to this development are as follows;
• Firstly, the challenge of constrained space and the need for a large-scale treatment area. Adjacent to the stormwater treatment facility will be a local area sports reserve, which requires a significant amount of space. Combined with the existing property boundaries and an approved development master-plan, it limited the areas in which the treatment facilities could be constructed. The initial plans called for a smaller wetland and a larger lake, but after consultations with Council and other stakeholders, the design was shifted to create a more prominent, linear wetland which achieved the required treatment area without encroaching on the sports facilities and property boundaries.
• Another key challenge was erosion and sediment control. With large scale earthworks, it was critical that this issue was managed, particularly as it was adjacent to the output point of the development. Furthermore, there were active construction sites within the Parklakes Estate, which discharge onto the stormwater treatment facility. Continuous active and adaptive on-site management of both upstream and on-site works has been required to ensure that erosion and sediment mobilisation is mitigated. Phasing the project to stabilise certain areas prior to further works occurring has helped to mitigate many erosion and sediment control issues and promoted progressive establishment of the site.
• Cost was a significant issue to deal with. Construction began mid-way through the Global Financial Crisis and budgets could not be exceeded. To meet the existing budget, the timeframe needed to be kept to a minimum. Unfortunately, approximately 3 months of wet weather occurred midway through construction, but due to phasing of the project, adaptable management and design flexibility, additional costs were kept to a minimum. -
Key lessons learned from this project were;
• The need for flexible design. As cost was a significant issue, budgets and pricing estimates needed to be closely monitored to save capital where possible. When certain aspects of the stormwater treatment facility were considered overly expensive (e.g. wetland outlet structure), time was spent investigating alternate structures that achieved the required end. In case of the wetland outlet structure, approximately $40,000 was saved.
• The need to manage sediment and erosion on a large scale construction site. Midway through the project, we experienced approximately 3 months of wet weather and some very severe storm events. The project was phased to construct many of the detention areas at the onset of construction and as such many of the flooding issues that many have been experienced downstream were mitigated. Initially, there were some sediment and control issues identified on-site, but consultation with the Council, the contractor and Covey Associates led to quick resolution of these issues.
• Managing sediment and erosion issues on upstream construction sites. Parklakes Estate is an on-going development, with 8 of 13 stages completed and the remaining 5 stages to be constructed concurrently with the stormwater treatment facility and during its establishment phase. The remaining stages discharge into a conveyance channel which terminates in the inlet basin. As such, it is critical to manage erosion and sediment within active stages to prevent impacts to the stormwater treatment facility. As Covey Associates are the project managers for the entire estate, we were able to work with and direct the contractors constructing the remaining stages to effectively manage erosion and sediment issues. While there were some initial issues that occurred at the start of the wet weather, by working with the contractor and the Council, these issues were quickly mitigated. -
This project is innovative in that it actively incorporates a large scale treatment facility into a developing residential community. The treatment facility will act to treat runoff from the entire estate, but also will serve as an area of research and education for the local schools and the University of the Sunshine Coast. Furthermore, the stormwater treatment facility does not consider the urban lake as part of the treatment process, but rather as the receiving environment. The stormwater treatment facility is designed to ensure long-term lake health by treating stormwater runoff before it is discharged into the lake. A recirculation system also will be installed, which will act to achieve the optimum retention time in the lake, thereby limiting the likelihood of algal blooms and eutrophication as well as providing further treatment.
An intensive landscaping schedule has been established for this project. A dense riparian planting schedule (6 plants/ m2) has been nominated with the aim to establish the stormwater treatment facility and urban lake riparian zones. Such areas are critical to establish early on, as the wetland and lake riparian zones play a key role in algal competition, nutrient uptake and limit the growth of floating macrophytes.
