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We're committed to solutions
We're taking critical action to reduce the likelihood of debris balls washing up on NSW coastal beaches and Botany Bay beaches.
Where debris balls come from
Investigations indicate that debris balls that washed up on beaches since October 2024 most likely came from our network. For coastal beaches, we've identified the Malabar Deep Ocean Outfall. For beaches in Botany Bay, we've identified the Mill Stream Emergency Relief Structure.
Debris balls are made up of soap scum, cosmetics, traces of bacteria commonly associated with wastewater, petroleum hydrocarbons, human hair and fatty acids. They probably formed due to an increased load of fats, oils and greases accumulating in the wastewater system over time. Oceanographic factors and weather conditions played a role in why they appeared on our beaches.
Our commitment to you
Our ongoing commitment to waterway protection, pollution prevention and water recycling initiatives is crucial for safeguarding the health of our coastal and bay environments, and securing a clean, sustainable water supply for Greater Sydney communities.
We remain fully committed to working transparently with the NSW Environment Protection Authority (EPA), councils, government agencies and the community, keeping everyone informed as new findings emerge during the ongoing investigation. Protecting the environment is our priority. We take the findings of these investigations seriously, and are committed to addressing the issue openly and proactively.
If you still have concerns, we're happy to discuss them with you. Please call us on 13 20 92 8am–5:30pm Monday to Friday (except public holidays).
How we aim to prevent future events
Targeted actions at Malabar
We're taking targeted, site‑specific actions within the Malabar system to address the conditions identified through the debris ball investigations.
In the immediate term, we're conducting ongoing inspections and, where safely accessible, cleaning material where sources of accumulated fats, oil and grease have been detected within Malabar.
Across the next 5 years, we're planning repairs and renewals to key parts of the Malabar facility to improve how solids are captured and removed. This includes upgrading scum removal systems and restoring and desilting parts of the ocean outfall system.
New programs
We're introducing new programs to help reduce the amount of fats, oils and grease entering the wastewater system. Through education, engagement and practical support, we can help households and businesses adopt better disposal practices.
Improved infrastructure and facilities
We're investing in improvements, including:
- Upgrades to inland wastewater treatment assets through the Malabar System Investment Program (MSIP). The MSIP will increase capacity across the network to meet population growth, improve treatment performance and reduce discharge from the Malabar Deep Ocean Outfall.
- Upgrades to Cronulla and Quakers Hill water resource recovery facilities, including secondary treatment enhancements. This will ease pressure on existing infrastructure, reduce reliance on existing deep ocean outfalls and deliver better environmental outcomes.
- Recycled water schemes to ease pressure on our coastal facilities and reduce pollution. This will lower the volume of wastewater that needs to be treated and released into the ocean.
How we'll support councils
We recognise the financial burden clean-up efforts have placed on local councils. We're committed to support them with these costs.
Based on analysis of tides and winds, we'll review claims for clean-up costs from these local government areas:
- Central Coast
- Northern Beaches
- Bayside
- Waverley
- Randwick City
- Sutherland Shire
- Wollongong
- Kiama.
If more debris balls wash up on beaches in the future, we'll take the lead in coordinating clean-up efforts with councils and the EPA. Please contact us if you wish to claim for damages.
Debris ball reports
In October 2024, the EPA began investigating the cause of debris balls found along NSW beaches.
As part of the investigation, we:
- engaged an independent oceanographic modelling expert to determine the dispersion of the debris balls
- completed a sampling and analysis program at our wastewater treatment plants and parts of the pipe network
- assessed our deep ocean outfall systems and wastewater pipe network to identify where the debris balls could have originated from.
Together, these 4 reports reflect the progressive development of our understanding of the debris ball landings, with each investigation building on earlier findings as more evidence became available.
Oceanographic modelling helped narrow down possible timeframes and locations. While it was not conclusive, it guided further investigation.
Independent sampling and laboratory testing found no evidence the debris came from ships offshore. Instead, the debris shared characteristics with fat, oil and grease (FOG) found in land‑based wastewater systems. Testing showed the debris balls float and may have entered the ocean at different locations and times, helping explain why they appeared on multiple beaches. Overall, the results pointed to a small number of possible land‑based wastewater‑related sources rather than a single cause.
A review of Sydney Water's wastewater network then confirmed that FOG mainly enters the system through everyday activities and can build up over time. Evidence of FOG‑related debris entering waterways was found to be limited and location specific.
Bringing all findings together in the final report, the analysis indicates:
- Botany Bay beaches were most likely affected by material linked to the Millstream Emergency Relief Structure.
- Open coastal beaches were most likely affected by material linked to the Malabar Deep Ocean Outfall.
The current working explanation is that FOG built up within part of the Malabar outfall system and on separate occasions, small amounts may have broken away and entered the ocean. No similar build‑up was found at the North Head or Bondi systems.
While not every detail can be confirmed with certainty, the investigations provide a clearer picture of the most likely sources and are guiding actions to help prevent similar incidents in the future.
Contact our media team at media@sydneywater.com.au to request copies of reports.