Merriwa-Willow Tree Road major landslide

Filed in Just In by July 21, 2021

THE Merriwa-Willow Tree Road failure that started as a series of dangerous tension cracks, has now turned into a major landslide.

The original $9.6 million Merriwa-Willow Tree Road upgrades were meant to bring it up to B-Double standard, however the road washed away in January 2020, after upgrades were not built to specification and failed to include adequate stormwater and rain catchment infrastructure.

The Upper Hunter Shire Council first confirmed the road failure in June 2020, saying it would require at least three years of rectification works.

The road was then officially closed on January 21 and geotechnical engineers have since been scrambling to find ways to rectify the failure, which is expected to cost up to $15 million.

Major rectification works will be required in four separate areas stretching across 1,800 metres of road, with Council to approve Phase 1 of the works next Monday at the July ordinary meeting.

Upper Hunter Member of Parliament, David Layzell visited the failure site yesterday, accompanied by Upper Hunter Shire Mayor Maurice Collison and general manager Greg McDonald.

Mr Layzell reported the Merriwa-Willow Tree Road has now failed to the point where it is “completely impassable.”

Upper Hunter Shire general manager Greg McDonald, Upper Hunter MP David Layzell and Upper Hunter Shire Mayor Maurice Collison standing on the failed Merriwa-Willow Tree Road. Photo supplied.

“A single lane road being left open has been raised with my office numerous times, so I was committed to visiting the site to get an update. Nonetheless it is obvious that with this degree of landslide, it is certainly not safe or feasible to have any traffic on it safely,” Mr Layzell said.

“The recent rains have exacerbated the issue and the original design did not sufficiently allow for high rainfall and stormwater management along the route,” he said.

“It is obvious from the current state of the road that the Upper Hunter Shire Council took the correct decision to completely close the road for safety reasons,” he said.

“The meeting today was a pre-start inspection before the Phase 1 works commence to remove the failed material from the road, which will allow further geotechnical work to take place which will further inform the design process,” said Mr Layzell.

The current state of the Merriwa-Willow Tree Road failure. Photo supplied.

Phase 1 works include cutting a drainage line along the road and removing the failed material to allow further geotechnical design to be undertaken.

These works are expected to take approximately three months and cost $1.5 million.

Tendering for the rehabilitation works (Phase 2) will commence in October and will be awarded to a civil contractor by the end of the year.

Four civil contractors have already been engaged on a “pre-tender” basis to provide early advice on the best option in terms of build ability and each will be given the opportunity to tender after the final geotechnical design is complete.

Phase 2 rehabilitation works are expected to begin in January 2022 and take 18 months to complete, depending on weather conditions and additional geotechnical advice. 

The total cost of rehabilitation works will remain unknown until geotechnical designs are completed, however Upper Hunter Shire Council will be using a pre-approved $5 million loan and the State and Federal Government has committed to look into ways to assist with the project once the full extent of the rebuild cost is known.

In April, Upper Hunter Shire general manager Greg McDonald revealed the rehabilitation works may cost up to $15 million, $5.4 million more than the original project budget.

Merriwa-Willow Tree Road snapshot

Reconstruction overview

  • The works are required in four separate areas along a 1800m section of road;
  • These areas of road failure occur between 1100 and 2900 along the road located approximately 40 kilometres from Merriwa and 33 kilometres from Willow Tree. 

Programme of works

  • Phase 1 works will involve cutting a drainage line along the road and removing the failed material;
  • It is critical that these works commence ASAP to allow further geotechnical design to be undertaken;
  • It is expected to take approximately three months and is expected to cost $1.5 million.

Phase 2 design work

Phase 2 works will commence once the design has been completed and the works have been tendered and contracted.

  • Three engineering designs that have been recruited to solve the problem;
  • The suitable design will be selected based on build ability, cost and geotechnical considerations;
  • Four civil contractors have been engaged on a “pre-tender” basis to provide early advice on the best option in terms of build ability;
  • Early involvement gives contractors the chance to find innovative means to build the project in the fastest time possible;
  • Each contractor will be given the opportunity to tender on the full documentation when it is issued;
  • Cost planning work is underway to determine how much works are expected to cost;
  • Both State and Federal Governments are waiting for this cost report to be issued;
  • Final design work will be complete in September.

Phase 2 Construction Works

  • Tendering for the project will commence in October;
  • The project will be awarded to a civil contractor by the end of the year;
  • It is expected that Phase 2 construction works will commence in January 2022;
  • The works are expected to take 18 months, which subject to geotechnical advice and weather, gives a completion date in late 2023.

Project Management

  • The project design is being undertaken by GHD Engineering, a global engineering consultancy;
  • The project is being managed by a Project Control Group made up of representatives from Transport NSW and Upper Hunter Shire Council.

Funding

  • The project will be initially funded by the Upper Hunter Shire Council loan facility that has been undertaken for this project;
  • Council will use funds available from the $5 million loan facility that they already had pre-approved;
  • The motion to start Phase 1 works will be taken to a Council meeting next Monday, July 26;
  • Both State and Federal Government have committed to look into ways to assist with the project once the full extent of the project rebuild cost is known.

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