West Gate Tunnel 220kV Relocation Works

Quick Facts
ClientCPB Contractors and John Holland (CPBJH JV)
LocationWest Melbourne, VIC
TimingMarch 2019 - November 2019
SectorRegulated

The Victorian Government has partnered with Transurban to deliver the West Gate Tunnel Project, which will give Melbourne a second freeway link between the west and the city.

Quick Facts
ClientCPB Contractors and John Holland (CPBJH JV)
LocationWest Melbourne, VIC
TimingMarch 2019 - November 2019
SectorRegulated

Introduction:

The Victorian Government has partnered with Transurban to deliver the West Gate Tunnel Project, which will give Melbourne a second freeway link between the west and the city. Awarded to construction contractors CPB Contractors and John Holland (CPBJH JV), works include an upgrade of the West Gate Freeway and the construction of a new road and tunnel connecting the West Gate Freeway with the Port of Melbourne, CityLink and the CBD. The project will be built over five years, opening in 2022 to provide a vital alternative to the West Gate Bridge, quicker and safer journeys and remove thousands of trucks from residential streets.

As part of the construction works to widen the current freeway from 8 to 12 lanes, Zinfra were engaged by CPBJH JV to undertake major power utility relocation works on the AusNet 220kV transmission line assets. The contract includes lattice tower decommissioning, to be replaced with a combination of 6 monopoles and 2 new lattice towers, and reconductoring of the lines. A critical component of delivery includes the substantial freeway crossing of the West Gate Freeway with a line span reaching approximately 325 metres over existing traffic lanes, with the freeway kept operational during peak periods. The 220kV line will then feed into AusNet’s Brooklyn Terminal Station (BLTS).

Project overview:

These works form a part of Australia’s critical national power infrastructure; the Western Metro Ring Transmission Grid. All works undertaken on these high voltage transmission lines are undertaken with the permission of AusNet Services who own and operate this network. To ensure these works are undertaken by the appropriate expertise, and works are consistent across the nation, the scope of work and timing is determined via significant consultation with AusNet Services. Permits are then issued for work to take place during specific periods of lower demand during the year.

Works to install the two monopoles along the north side of the West Gate Freeway are now complete. The much slimmer structures carry the 220 kV power lines and take up a much smaller footprint than the traditional lattice towers, that are being decommissioned. These new poles reach a height of 58 metres when fully assembled and are considered some of the largest constructed poles in AusNet Services’ network. Further works to complete the remaining monopoles and lattice structures is still underway.

Peter Iancov, Zinfra’s MD, highlights “This contract award reaffirms Zinfra’s market leading transmission capability and experience including highly complex brownfield environments. It also demonstrates our ability to engage in collaborative client relationships to meet current market demands, while mobilising a large team of highly skilled transmission linesmen to meet project needs.”

I have being driving past these for the last few weeks and must say I’m absolutely amazed at how quick they went up but even more impressive is how the new towers have improved the visual amenity of the corridor. This should be the new standard! Well done
Member of the public

Project Challenges:  

Working in confined areas

Working adjacent to the West Gate Freeway and within the project boundary, also meant working within a confined workspace. As a result, this meant that drop zones were smaller and potential interaction with vehicles were high. This required mitigation measures to be reviewed continuously and required improvements implemented.

Public Safety

Safety was also a concern due to the works involving the transfer of high voltage power cables from existing lattice towers to the new monopoles and stringing high voltage power cables between the two monopoles directly above the overpass for example. To ensure the safety of pedestrians and cyclists, the overpass was required to be temporarily closed while working on the power cables overhead.

Constraints with outages

Working on the AusNet network meant that outages had to be negotiated for their length, recall time and times of outage. Due to peak loads, public events and various other factors, dates and duration of outages were subject to change. This required the project team to maintain a degree of flexibility and to meticulously manage the required interface coordination in order to minimise delays.

Interfacing with wider project teams

As expected with the extent of works required to complete the West Gate Tunnel Project, the number of contractors and subcontractors working within the project boundary is substantial. Consequently, ongoing negotiations have been required to allow safe access to unrestricted work areas in order to allow crews to carry out the required works.

Project Outcomes:

Despite the various challenges faced, the project team was able to complete the overall outage in the required timeframe. With an original outage duration of 18 days, the project team were able to successfully complete works within 16 days, despite weather delays during various periods of construction.

With over 18,000 hours worked, there have been no recorded safety or environmental incidents as of 30 June 2019.

The construction program continues to be delivered in line with the overall project program.

Zinfra was further engaged by the JV to complete relocation enabling works on the Jemena Electricity Network for 66kV and 22kV distribution assets as part of the delivery of the 220kV line.

“I have being driving past these for the last few weeks and must say I’m absolutely amazed at how quick they went up but even more impressive is how the new towers have improved the visual amenity of the corridor. This should be the new standard! Well done.”

Member of the Public.