North Nowra Surcharge Main Replacement Project
- Project scheduleProject start date: 4 January 2021
- Project StatusIn progress
- Completion Date01 October 2021
The Jamieson's Road Surcharge Main (JRSM) and North Nowra Surcharge Main (NNSM), collectively referred to as the 'Surcharge Main', transport raw sewage flows from several wastewater catchments within North Nowra to the Nowra Wastewater Treatment Plant (WwTP).
Previous analyses had identified a need to upgrade the hydraulic capacity of the North Nowra wastewater collection system. The most complex component of the identified upgrades was the surcharge main crossing the Shoalhaven River Bridge. This is required to be increased in diameter from 300mm to 560mm to cater for future growth in the area.
Council’s Sewerage Asset Management Plan also identifies this critical main for replacement due to its age, criticality and risk of environmental damage should it fail.
The key objectives of the NNSM Upgrade Project are to:
- Provide infrastructure that will reduce wet weather overflows at catchment pumping stations in North Nowra by increasing the capacity of the existing system, which can now be delivered following the upgrade to the Nowra WwTP
- Replace ageing infrastructure that is at significant risk of failure or nearing the end of its service life
- Support the planned growth and development of the Nowra-Bomaderry catchments.
In order to reduce the risks associated with this pipeline system, Shoalhaven Water prepared a detailed design for the staged upgrade of the NNSM, with the proposed overall strategy outlined:
1. Stage 1 Works:
- Relining of the existing 500mm dia mild steel cement lined pipe in northern abutment (Illaroo Road)
- Construction of new 500mm dia mild steel calcium aluminate cement lined pipe (circa 350m) with Sintakote coating across the existing concrete Nowra bridge
- Construction of a new part 300mm dia ductile iron epoxy lined/part 560mm dia polyethylene (PE) pipe (circa 130m) along Lyrebird Drive
- Connections to existing North Nowra Surcharge Main at Illaroo Road and Lyrebird Drive
- Removal of existing DN300 asbestos cement (AC) pipe from the existing northbound bridge.
2. Stage 2 Works:
- Construction of new 560mm dia PE pipe (circa 1200m) between Lyrebird Drive and the Nowra Wastewater Treatment Plant (WWTP)
- Connections to proposed North Nowra Surcharge Main at Lyrebird Drive and Nowra WWTP.
Prior to the construction of the replacement surcharge main, Council completed the following key environmental investigations:
- Review of Environmental Factors September 2015
- Addendum Review of Environmental Factors June 2020.