A permanent fix for the western section of the Darlington Upgrade Project’s lowered motorway will be put in place to ensure the Government is satisfied the contractor is fully compliant with its obligations for the project.

From Monday, 16 January 2023, work will begin on a permanent soil nail solution on the western side of the lowered motorway walls.

This will be similar to the remediation work undertaken on the eastern lowered motorway walls following a collapse in May 2019.

At that time, revetment walls on the eastern side of the lowered motorway collapsed while the Darlington Upgrade Project was still in its construction phase under the former Liberal government. The collapse arose out of a defective design that was the responsibility of the main contractor for the Darlington Upgrade Project, Gateway South (GWS - a consortium of Fulton Hogan and Laing O’Rourke).

GWS redesigned the eastern walls and completed installation of piling and/or soil nails for all of the eastern walls on the lowered motorway. In July 2020, GWS provided design and proof engineer certification in relation to these works, however the former government did not ensure equivalent remediation works were undertaken at the same time on the western side.

While design and proof engineer certification has also now been provided for most of the lowered motorway’s western walls, the area encompassing Sturt Road bridge from Mimosa Terrace to Flinders Drive has remained Uncertified due to the continued presence of moisture.

As a result, GWS has not been able to achieve project completion.

A pre-condition to achieve completion under the contract is an obligation to provide certificates of compliance for the eastern and western walls of the lowered motorway.

GWS has continued to provide regular commitments that the certificates for the Uncertified Area are imminent, however it has been unable to fulfil its obligations to provide the certificates or bring the works to completion.

As has been previously stated, the Malinauskas Labor Government has remained steadfast in its representations to GWS that it will not entertain issuing completion until the certificates are provided.

Since 2019, GWS has continued to undertake extensive monitoring and site investigations to non-conforming works in the Uncertified Area, and recently detected increased movement on a section of the western walls of the lowered motorway between Sturt Road and Flinders Drive.

It is likely the movement of the walls has been caused by an inundation of water following an overly wet winter and spring in 2022.

As a result, it has been determined that immediate remediation is now required.

Speed and lane restrictions are in place on the western side of the Darlington Upgrade Project’s lowered motorway ahead of these remediation works.

As a precautionary measure, two lanes of the western side of the lowered motorway have been temporarily closed, with speed restrictions in place between Sturt Road bridge and Flinders Drive.

Additionally, the right turn lanes of Main South Road surface road into Sturt Road eastbound will be temporarily restricted.
It’s anticipated these restrictions will remain in place for two to three months.

Motorists are advised to take extra care when travelling in the area, allow extra time and observe signage and instructions of traffic management staff.

Quotes

Attributable to Infrastructure and Transport Minister Tom Kousantonis

We have already seen what can happen if the design flaw that led to the 2019 collapse of the concrete retaining walls on the eastern side is not properly dealt with.

GWS has spent nearly three years monitoring and undertaking site investigations and remediation works to the western walls. Those remediation works included the installation of trench stops to prevent potential moisture ingress towards the walls, grouting of obsolete electrical conduits, reconfiguration of planter drainage systems and lining of stormwater pipes and pits.

But it hasn’t been enough.

As I told parliament on May 2 last year, despite these extensive works undertaken by GWS, the consortium has not been able to achieve certification of the Uncertified Area. The Government has previously written to GWS requesting a definitive action plan detailing how it will bring the works to completion. 

However, the recent testing and monitoring shows why a permanent solution needs to be undertaken immediately.

This has gone on too long – we will not tolerate a repeat of what occurred three years ago.

It was gross negligence and mismanagement by the former Liberal government not to insist both embankments were remediated simultaneously back in 2019 – when the original fault was identified and while the project was still in its construction phase, so the works would not have impacted on commuters.

Unfortunately, this will now entail unwanted disruption for road users while the western part of the lowered motorway is closed for several weeks.

We apologise to road users for the inconvenience – but it is beyond time this project is brought to completion.
Importantly, this remediation will be at the expense of GWS – not taxpayers.

I am advised this expense is likely to be in the order of around $7 million.