Wet Weather Overflow Abatement Program
Sydney Water
Context
All sewerage systems are designed with overflow points which prevent wastewater from backing up into people’s homes when the sewer is full. During wet weather, rainwater enters sewers through cracks or faults in pipes and through illegal sewer connections. Once the sewer pipes are full, diluted sewage spills through designed overflow points into waterways.
Prior to this project, (diluted) sewage was being discharged to Sydney Harbour via two overflows on a submain positioned between the affluent harbourside suburb of Mosman. Overflows had occurred around 185 times over ten years.
Solution
In 2010, the Sewerfix Wet Weather Alliance (SWWA) was established to deliver Sydney Water’s Wet Weather Overflow Abatement Program. Primarily targeted at swimming sites, the program was to provide benefits to the environment and human health, and was part of Sydney Water’s long-term SewerFix program of sewerage system improvements.
There were many significant challenges on this project including issues and risks relating to there being:
- No feasible gravity options necessitating a pumping station to transfer the flows
- Devising a solution to get the flow from the top of the rising main to the receiving sewer. All of the considered connections were deep or very deep tunnels for most of their lengths, presenting construction challenges and safety risk.
- Working around heritage listed assets including World War II diesel storage tanks.
- The inability to repair some of the oldest sewer pipes, should they be damaged during the works.
- Challenges associated with moving plant and equipment to site through tight, one-way residential streets
- Restricted working hours and days, owing to it being a residential community
- Odour and noise control
- Waste and water removal
- Health and safety considerations.
The success of this project is evidenced by the frequency of catchment overflows being reduced from 185 to a target of 20 spills in 10 years.
2010
Start Date
2023
Completion Date
67
Metres below Military Road
10
Year Partnership
Partners & Consultants
Sydney Water’s Wet Weather Overflow Abatement Program was delivered by the Sewerfix Wet Weather Alliance formed by
- Sydney Water
- Manidis Roberts (now RPS)
- MWH (now Stantec)
- Parsons Brinckerhoff (now WSP) and
- United Group Infrastructure.
ADVANCING RECONCILIATION
We acknowledge the Traditional Owners of the lands on which our business is based, the Gamaragal and Turrbal people. We pay our respects to their Elders past and present.
CONTACT
Level 12, 275 Alfred Street
North Sydney NSW 2060
Level 18, 324 Queen Street
Brisbane QLD 4000
+61 (0) 439 415 172
info@metaphic.com.au