In January 2016, Zinfra was awarded a significant project by Transport for NSW (TfNSW) as part of TfNSW’s Power Supply Upgrade Program.
TfNSW is the lead agency of the NSW transport cluster, which includes Roads and Maritime Services, Sydney Trains, NSW TrainLink and State Transit.
The Power Supply Upgrade Program involves construction of new electrical infrastructure and upgrades to substations, sectioning huts, overhead wiring and feeders across the Sydney Trains network – all required to meet expected power requirements of the future rail network.
Under the Power Supply Upgrade Program, Zinfra is delivering the design, construction and commissioning of a new substation at Gosford South and a sectioning hut at Wyoming.
The 2 x 5MW rectifier 66kV substation will support the 1,500 volt traction power supply needed to run the new fleet on the Central Coast and Newcastle rail line.
The new substation at Gosford South and the Sectioning Hut at Wyoming will replace the existing Gosford substation. Zinfra General Manager, John Gardner, emphasised the significance of this project for Zinfra.
“This project is strategically important as it represents an important step in our strategy of entering new markets, in particular the rail sector, leveraging off our core utilities capability.”
Zinfra’s success in winning this work stemmed from an innovative approach to the tender, which included an internally generated engineering solution.
This alternative approach provided TfNSW with cost savings, a reduced building footprint and improved operational capability and performance for the required electrical upgrades and assets.
This project at Gosford is by no means straightforward – the location, the site conditions, the surrounding environment, the local community, and proximity to the rail corridor and road infrastructure all mean the project has many challenges.
Challenging conditions
The site of the new substation is challenging. The small site is sandwiched between the railway corridor with its live overhead power lines and trains, Fagans Bay, part of Brisbane Water National Park, and ecologically significant mangroves. The Brian McGowan Bridge flies over another side of the site, ferrying a constant stream of traffic on the Central Coast Highway.
The ground, which is located only metres from the water’s edge, is sandy and unstable. A careful process involving extensive testing and sampling was needed to determine a suitable depth for the footings for the substation. Ultimately, forty piles drilled to a depth of up to eight metres were required.
The confined space means the demarcation and management of the respective parking, lay down area, construction zone and designated pedestrian walkways is critical for site safety.
Once construction of the substation building begins, the tight space will present new challenges when using cranes to lift and manoeuvre the precast concrete walls, GIS (gas insulated switchgear) and other high voltage electrical equipment into place.
In-service railway lines
Working alongside the active Central Coast and Newcastle rail line, with both up and down running mains and three active sidings, brings its own set of challenges.
The construction team works with a wide exclusion zone alongside the rail corridor. When works are required within that exclusion zone, a whole new layer of safety controls and precautions come into play.
A large part of the project, to date, has involved an underline crossing (ULX), the installation of conduits under the railway lines and the adjacent sidings.
The works can only be conducted under stringent permit conditions when the high voltage power is turned off and only over weekends, known colloquially as ‘possession weekends’.
The possession weekends run from 4am on Saturday morning through to 10pm on Sunday night. Coordinating the works, resourcing and rolling shifts is a complex logistical exercise.
Throughout the possession weekends, project update meetings are held every six hours to ensure works are tracking to plan and to adapt or change plans accordingly. Handover between shift supervisors must also be comprehensive.
The ULX possession weekend in June involved removing the rail lines and sleepers and installing concrete encased conduits to a depth of 3.2m.
The rail assets then had to be reinstated and the earth compacted sufficiently to avoid the trains bouncing (known as ‘pumping’ in the industry) on that section of the track. Extensive, ongoing testing is required to monitor the integrity of the track after these works.
The installation of the conduits was also extremely challenging, “Under the sidings, the ground is peppered with services,” explained Zinfra Construction Manager, Michael Byrne.
“We found communications, power, low voltage, water and signalling assets. It was extremely slow going and tough working at a depth of three metres. Not only were we working carefully underground, but we had to be careful of the 1500v DC overhead line, which had to be de-energised for the ULX work.
Two consecutive possession weekends were carried out during the final two weekends of October, when Zinfra carried out works to remove and replace power poles and extend an existing stanchion across the sidings.
Stakeholder complexity
The Gosford project has many stakeholders who need to be informed, consulted and coordinated. Zinfra’s Community and Stakeholder Relations Officer, Petra Campbell, has ensured residents and businesses in the local community who might be impacted by the works are kept informed with regular notifications delivered by mail and in person.
Ms Campbell’s Stakeholder Relations and Community Plan is so thorough it includes a local rough sleeper, whom she had approached personally, to ensure absolutely no one was omitted from the consultation process.
The nearby Central Coast Stadium, which has a capacity of 20,000 spectators, means heavy foot traffic past the site, particularly on weekends. Site security and public safety are paramount considerations for Zinfra when managing this community risk.
Other key stakeholders closely impacted by the upgrade works are the Central Coast Council, Roads and Maritime Services (RMS) and Sydney Trains. The latter operate the power distribution network for the trains and are responsible for the issue of permits for possession weekends.
Environment
“TfNSW are very environmentally aware,” said Mr Byrne, “And Zinfra is very proud to be meeting TfNSW’s environmental target of 95 per cent recycling of construction waste. All soil, concrete, timber, steel, plastics – everything on the site – has to be dealt with responsibly.
“After the removal of the old buildings and sheds on site, even the old rainwater tanks have been kept and will be put back into use at the end of the project.”
Potential “acid sulphate soils” required all excavated material to be stockpiled, sampled, tested and treated as required prior to removal to neutralise environmentally harmful processes.
In addition, the small site is within metres of ecologically significant mangroves and waterways. Minimising ground disturbance, lack of pondage space and run-off are significant challenges for Zinfra to manage while delivering the project.
Care is taken to contain and cover stockpiles for sediment control, and numerous levels of gravel filter bags have been put in place between disturbed ground and stormwater drains to protect waterways from sediment and pollutants from the site.
AEO status
This project for TfNSW was the catalyst for Zinfra to attain Authorised Engineering Organisation (AEO) status with the transport agency.
On 1 August 2016, Zinfra Group was officially awarded AEO status.
“We congratulate Zinfra Group for attaining AEO status and look forward to their contributions as a delivery partner for Transport for NSW,” said Jim Modrouvanos, Executive Director of the Asset Standards Authority, a part of TfNSW.
Having the assurance of being an AEO will enable Zinfra to produce and undertake engineering solutions for TfNSW with a significantly streamlined assurance process – saving time and resources to allow Zinfra to deliver more efficiently and autonomously.
The next piece of the project puzzle is the construction of the new substation building at Gosford, including installation of basement concrete slabs, ground floor columns and drainage works. Once built, the GIS and other electrical equipment will be craned into the building and a removable roof installed over the top.
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