The Bondi Sewage Treatment Plant was the first sewage treatment plant attached to a major ocean outfall sewer in NSW and the first connected to a deep ocean outfall in Australia.
It was the largest sewage treatment plant in Australia at the time of its construction and was comparable in size with large overseas plants. And, it was the first treatment plant located underground in tunnels and chambers excavated from solid sandstone in the cliffs adjacent this world-renowned Bondi Beach.
WSP Golder was engaged to deliver a range of works on this project since the 1980s.
Construction timeline and milestones
- 1889 - Ocean outfall sewer at Bondi initiated
- 1910 - The original ventilation shaft is demolished and replaced
- 1936 - Construction commenced on an underground sewage treatment works at Bondi to treat sewage prior to discharge into the ocean (completed in the late 1960's)
- 1953 - Plant begins partial operation
- Late 1980's - An underground pumping station and related works built.
- 1991 - 2.2 km long submarine ocean outfall commissioned
- 1990's to 2019+ - The plant has undergone a constant stream of modifications due to continue for another fifteen years.
Delivering long-term value
WSP Golder staff has been heavily involved with the Sydney Water (local utility) asset since the 1980s when supervising the construction of the deep outfall tunnels and plant expansion. Due to the limited footprint of the plant and location within the cliff line, expansion is often by expensive specialist excavation in some form of tunnelling (drill and blast, small diameter TBM or mechanical excavation/road headers).
The high expense of upgrades often requires significant reuse of historical borehole information, construction supervision reports or review of monitoring data. Furthermore, due to different safety and design standards through the decades, there is a significant variation in the extent of excavation support installed to current design standards, requiring significant temporary works and re-support prior to advancing.
Additionally, all works must consider the impact on the plant operation and the local air/water environment as construction activities need to occur while the plant is operating as the bypass of raw untreated sewerage to the environment and community is not a considered option in the current social environment. For this reason, a significant amount of recent and future works for Golder at the plant include projects related to increasing the redundancy of the plant to operate during adverse periods, increasing capacity where possible to include remanent suburbs with untreated sewage discharge and also improving the ventilation systems to reduce the escape of fumes to the local environment.
A recent Deloitte Access Economics Report (Economic And Social Value Of Improved Water Quality At Sydney’s Coastal Beaches) indicated both the economic and social value generated from improvements in water quality as a result of the deep ocean outfalls showed that:
- The Deepwater Ocean Outfall program delivered by Sydney Water 25 years ago has provided $2 billion of social value to Sydney residents attributed to the improved coastal beach water quality.
- The total value of Sydney’s coastal beaches to its residents is around $1.3 billion per annum, of which $130 million is attributable to water quality.
- The net value add associated with beach water quality is worth around $332 million per year to the NSW economy through domestic and international tourism and the provision of ~ 3500 jobs.
- The health benefits associated with beach water quality due to the avoidance of illness of beach users is estimated at $140 million per year from avoided absenteeism, calculated from an estimated 180,000 sick days saved per year.
- In terms of biodiversity, the study suggests that changes in wastewater management, including the establishment of the Deep Ocean Outfall Program, have had a net positive impact on the biodiversity of marine communities along Sydney’s coastline, although this is difficult to quantify.
- In terms of brand value, the study found that beaches ranked in the top three when visitors think of Sydney — alongside Sydney Harbour and the Sydney Opera House.
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