What is the outfall at Diamond Bay, and when will it stop?
Wastewater goes into the sea off Diamond Bay with no treatment. Sydney Water’s project page is the record of the outfall, the works that will divert it, and the dates that govern them.
What the outfall is
Sydney Water’s project page for the Refresh Vaucluse and Diamond Bay works describes the system as it stands today: the wastewater collected from Watsons Bay to Dover Heights is not treated before it reaches the sea, and at Diamond Bay it enters at three points on the cliff face. The page puts the untreated flow around Vaucluse and Diamond Bay at about four million litres.
Sydney Water frames the works around the three ocean outfalls that remain in Sydney: the Vaucluse outfall off Christensen Park, the one at Diamond Bay, and the one at Eastern Reserve. The Refresh Vaucluse and Diamond Bay project exists to divert what they release to the Bondi Water Resource Recovery Facility, and its scope covers new wastewater pipelines, a new underground pump station, and upgrades to the existing wastewater infrastructure.
The diversion is a substantial build. The new pipes run between 20cm and 37.5cm in diameter and go in with trenchless methods up to 80m below ground, and the works reach beyond the bay: they extend to Dover Heights and Rose Bay, with a new pressure pipeline along Old South Head Road and Oceanview Avenue joining the Bondi wastewater network to the new pump station. Sydney Water puts the effect at a cut of at least 93 per cent in the impact on the ocean, protecting the community’s health and the marine ecology.
From commitment to diversion, by date
Sydney Water’s project page carries the timeline for the works that will divert the outfall. Its dates, in order:
- November 2018The NSW Government commits to diverting the ocean outfalls to the treatment plant at Bondi.
- June 2020The project’s Review of Environmental Factors goes on public exhibition.
- April 2022Preliminary design consultation for Diamond Bay.
- April 2024Consultation on the draft concept design.
- April 2025Consultation on the final concept design.
- June 2026A Review of Environmental Factors addendum covers design changes.
- August 2026The contract for the Diamond Bay works is awarded.
- September 2026Site establishment at Diamond Bay Reserve, for the project’s second underground pump station.
- Mid 2028The Diamond Bay project is due to be complete.
The sequence above is Sydney Water’s, in the order its project timeline gives it.
How old this information is
The sequence is as old as its last entry. Sydney Water’s Diamond Bay dates run to September 2026, when site establishment at the reserve was due, and a completion in mid 2028, so that end of the timeline is the project’s plan rather than its record. The dates above were checked against Sydney Water’s page on 12 October 2026.
Sydney Water's project page is the record of the outfall, which is why this guide is short: it keeps to what that page sets down.