To cater for a growing local population and support new community facilities (such as the new Fleurieu Regional Aquatic and Health and Wellbeing Centre) and residential developments, SA Water had to improve Victor Harbor’s wastewater capacity. As a regional town, Victor Harbor is also a popular tourist destination so the network had to service additional people in peak periods.
The existing wastewater network was running at capacity, and modelling showed the network was surcharging at peak periods and close to overflow. Wastewater flowed by gravity and was pumped into the town’s old wastewater treatment plant before being pumped up to the new facility operated by Trility.
The SA Water master plan for the area indicated the most efficient and cost-effective solution would be to pump wastewater from the Hayborough development area to the new facility via an alignment able to pick up flows from some of the new and future proposed development areas.
Determining Scope and Design
The first stage of this project was to develop the scope, provide constructability input, and prepare a detailed concept design for the pipeline and pump stations, enabling SA Water to create a Target Outturn Cost (TOC).
The second stage (design and construct) involved the detailed design of the proposed trunk sewage transfer system. This included the design of approximately 6.4 km of underground mains and three associated wastewater pump stations. It also included further minor connections and decommissioning of some existing infrastructure.
Maximising the Water Service
Fulton Hogan engaged WSP to undertake design services for the first stage of the project. We undertook all design works for the development of the TOC except for electrical and controls work.
There were two adjustments to the design:
- A change to the proposed trunk sewer alignment so that rather than delivering flows to the new facility, it was to be directed to the old wastewater treatment plant.
- The decision to provide a temporary pump and associated rising main infrastructure to allow pumping from the new Health and Wellbeing Centre into the existing sewage collection network until the whole system was ready.
Following approval of the project, Fulton Hogan kept WSP on as the designer in the D&C contract with SA Water. We completed the detailed design of the pipelines and pump stations. We also provided geotechnical investigation services. In more detail, our scope covered the following:
Design of Water Supply and Hydraulic Systems
- WaterGEMS and HAMMER modelling of the pumped portions of the transfer main
Design of Wastewater Collection Systems
- Planning and investigation to confirm alignment for new rising main and gravity sewer transfer mains
- Design of three submersible pump stations
- Odour assessment and mitigation options
- Surge analysis on the new system
- Consideration of emergency storage requirements
Treatment and Network Planning
- Use of GIS to support the design planning process
- Design of augmentations/modifications to the existing sewer network to allow for connection of the new works
Design of Mechanical Infrastructure
- Design of three submersible pump stations, including pump selection and valving design
- Design of connection point to the existing (old) wastewater treatment plant
- Consideration of noise and vibration limits in specification/equipment selection
Design of Structural and Civil Infrastructure
- Civil and structural design of new pump stations
- Structural design of pipeline supports
- Design of a bridge crossing
- Preliminary design of HDD sections
- Design of pump stations to avoid 100-year flood levels
- Facilitation of Safety in Design workshops throughout the design phase
- CAD drafting and design to IFC delivery
- Technical specification
- Design of ancillary works, including connections to the existing wastewater collection network and bypass/decommissioning of redundant pump station infrastructure
- Consideration of land development and easement requirements in the selection of transfer main alignment
- Use of GIS and CAD software to support the design
Addressing Current and Future Needs
WSP worked closely with contractors and SA Water to develop the initial TOC, and take this forward into design and construction. Maintaining the same team through the two project stages led to familiarity with the issues and the design, thereby resulting in time and cost savings.
There were various challenges associated with route selection, which travelled through residential and development land. The team overcame these issues with effective stakeholder engagement.
During the risk assessments and Safety in Design workshops, we identified many processes and technical issues that were resolved prior to the issuing of the final design. We also ensured there was sufficient physical space in the wet wells to contain the pumps required for future pump flow rates. This caters for population growth in the catchment area and will reduce the need to completely replace the pump stations in the future.