Peter Hopper Lake in Mill Park is one largest ornamental waterbodies and Water Sensitive Urban Design assets in the City of Whittlesea and is a sanctuary to over 20 different bird species, as well as the endangered Murray River Turtle. It is also the City of Whittlesea’s most visited recreational site.
The 1.5 hectare lake captures around 20 million litres of stormwater from its 25-hectare catchment area. Unfortunately, the lake faces significant challenges due to annual algal blooms and toxic blue-green algae, which adversely affect the wildlife and the lake's visual appeal. The limited size of the water catchment results in insufficient water turnover, preventing the lake from maintaining a healthy ecosystem. Additionally, untreated stormwater entering the lake carries various pollutants from surrounding roads, which propel the growth of cyanobacteria during the summer months.
Over the last two years, the City of Whittlesea has investigated issues affecting the lake and developed a comprehensive plan to restore the lake’s water quality. Council conducted a major desilting operation which removed approximately 3,000 tonnes of silt that had accumulated over the decades. Innovative chemical flocculation and centrifuge technology was trialled as part of the dredging process to help with the suspended sediment removal. Following the removal of contaminants, Council initiated additional works to enhance the asset's resilience against water quality degradation and construct additional water treatment infrastructure in and around the lake to improve the effective long term management of pollutant and nutrient loads. The upgrades include construction of a gross pollutant trap to screen litter from the stormwater inflows, removal of an existing island within the water body to reduce nutrient load from avarian wildlife, construction of a sedimentation basin to capture fine silts before they enter the main lake, and construction of a bioretention basin and installation of a pumping system that will continuously receive pump water from the lake into the bioretention basin to assist in reducing nutrient levels.
This presentation will provide an overview of the journey the City of Whittlesea has undertaken address technical challenges to investigate and determine the most effective rehabilitation solution for the lake, as well as the complexities surrounding site management prior to and during the desilting and new infrastructure construction process. Peter Hopper Lake rehabilitation is a great example of a multidisciplinary project involving civil, mechanical, electrical and environmental engineering to ensure the future sustainability of an integral urban stormwater system and much loved community asset .
The newly implemented water treatment infrastructure will effectively manage stormwater runoff from the residential catchment, exceeding best practice for the benefit of the downstream Darebin Creek. Additionally, the future re-integration of the stormwater harvesting scheme will enable treated lake water to be used to irrigate the nearby sports field, reducing potable water consumption and showcasing this project as a unique multi-objective example of contemporary water management practices.