Managing sediment for healthier waterways
Published on 04 March 2025
Our Water Plan 2019-2023 has removed 130 tonnes of sediment annually from ponds and wetlands to protect water quality in local rivers, including the Birrarung (Yarra) and its tributaries. However, accurately estimating sediment in ponds can be challenging without detailed plans of the assets.
Audits and desilting results have shown that many of the older sediment ponds found in Banyule are full, and we regularly remove more sediment per year than the water plan target (which will be revised in the upcoming Integrated Water Management Plan).
Sediment, washed into wetlands during rainfall, contains pollutants like oil, fertilizers, heavy metals and potentially PFAS chemicals. This can harm aquatic life by clouding water, lowering oxygen levels and coating plants. PFAS chemicals are particularly concerning as they do not break down and can be toxic to animals. However, constructed wetlands are specifically designed to capture and treat this pollution to protect downstream waterways.
Sediment ponds in these wetlands help capture coarse sediment and pollutants, while plants in wetlands use nutrients from finer sediment for growth. Desilting the sediment ponds every 7 years allows them to keep functioning properly, but under the Environment Protection Act 2017, sediment must be tested and classified for transport and disposal.
After desilting Southern Road Wetland on Darebin Creek in Heidelberg West, 450 tonnes of sediment was removed, with 210 tonnes remaining after drying onsite. This sediment was classified as Category C material under the Act, with trace PFAS detected.
Council had the option to send the dried sediment to landfill or recycle it at a soil processing facility. Recycling, which aligns with our Towards Zero Waste Plan and Sustainable Procurement Guidelines cost slightly more but offered environmental benefits by reducing landfill waste, supporting the circular economy and producing sustainable soil products.
Council chose the environmental win, and the project was completed under budget, supporting Council’s sustainable goals and contributing to a healthier Darebin Creek.