Australian Bridge Repairs Near Completion

FRIDAY, SEPTEMBER 30, 2022


Officials in Port Macquarie-Hastings, Australia, have announced that work on the Rawdon Island Bridge has reached its final stages, after underwater inspections found damaged piles last year.

While the bridge was closed temporarily in 2021, the structure provides the sole access on and off the island for residents. The final stages of rehabilitation, which are set to begin the coming days, will include work on the deck of the bridge, improving the structure and providing a smoother surface.

Project Background

The Rawdon Island Bridge, built in 1961, spans 164 meters (538 feet) across the Hastings River in the local government area of Port Macquarie-Hastings in Australia. It is the sole road access to and from Rawdon Island and Little Rawdon Island.

The structure features a reinforced concrete bridge, with a blade pier and dual piles. Prior to its latest inspection, the bridge had last been inspected in 2019.

Back in March 2021, following flooding in the area, the Port Macquarie-Hastings Council ordered inspections of all bridges, including underwater inspections of bridges over major waterways. In June, inspectors of the Rawdon Island Bridge found major structural issues on the pylons that support structure, putting it at high risk of collapse.

Because of this finding, the bridge and waterway beneath were closed the beginning of July to reduce the risk of further damage and maximize the safety of residents. It is reportedly believed that the structural issues were not caused by the flood, but were a result of a fault during its construction.

The Council reported at the time that the damage during the underwater inspection was “unexpected,” and appeared to be related to poor original construction techniques and quality control procedures. This resulted in ongoing degradation and loss of the pile materials at these isolated locations immediately above riverbed level.

Several piles with damage were identified, with the most extensive amount of erosion (88%) located at Pier 4, Pile 2. Other significant damage included:

  • Pier 3 Pile 1 (upstream) = 43.7% loss;
  • Pier 3 Pile 2 (downstream) = 51.7% loss; and
  • Pier 4 Pile 1 (upstream) = 33.9% loss.

Temporary measures were put in place for residents to help manage the immediate impacts caused by the closure, with the bridge shutdown affecting about 50 households. Only emergency vehicles and foot traffic were permitted access on the structure at the time.

The structure was reopened to light vehicles with strict traffic conditions on Aug. 30, 2021, with additional bridge sensors and monitors in place. It was reopened under the following safety conditions with a load limit of five TGVM:

  • Monitor the bridge using surveys and/or sensors on a daily basis and monitor during any weather event;
  • Enforce the reduced traffic loading;
  • Manage vessels on the river to avoid impact, particularly at piers three and four;
  • Close the bridge during a weather event involving heavy rainfall and increases in river velocity; and
  • Once the council is satisfied its compliance obligations are met.

Then, earlier this year in February, it was announced that the specialist underwater repairs were completed. The project was managed by the Council’s contractor Duratec.

The contractor was reportedly involved in highly specialized underwater work to repair the critically damaged concrete piles. Crews accessed the bridge foundations via a platform stationed on the water enabling them to transport and install customized fabricated steel jackets to act as ‘sleeves’ to wrap around the damaged piles.

Specially formulated grout was then injected into the compromised points. Concrete was poured into the sleeves to encase and strengthen the existing piles.

The Council reported that specialist divers worked up to eight hours each day in challenging conditions, including muddy water, strong river currents and the threat of bull sharks. As a result of these repairs, some of the temporary traffic restrictions were lifted to increase the load limit and provide two-lane access across the bridge.

“We understand this has placed a strain on the local community, and we’ve made concerted efforts to fast-track the project where possible. This also involved working in close collaboration with various third parties and government agencies to ensure we had their support to remove or reduce the red tape,” said Group Manager Community Infrastructure Planning and Design Blayne West, at the time.

“This repair project is technically challenging, and it’s been a huge effort by the team within Council and our contractors to achieve this major milestone. We’re lucky to have such impressive and experienced talent on staff at Council, and within our local area, to deliver this unique bridge project.”

Typically, similar projects would take up to two years to be completed, with extensive research and design, environmental assessments and approvals, contract tenders, sourcing materials and scheduling operation works. However, these repairs were completed in just six months due to the unique situation of the bridge providing sole access on and off the island for residents.

The next steps were expected to include repairing the concrete on the bridge piers above the water line, repairing and strengthening the blade walls, installing corrosion protection and completing the project with improvements to the bridge deck. 

Latest Milestone

Yesterday (Sept. 29), the Port Macquarie-Hastings Council announced that it is preparing to enact the last stage of works in the rehabilitation project, marking the end of critical repairs. With the recently completed bridge pier repairs, alongside the pile repairs, the Council noted that it has strengthened the bridge and extended the life of the existing structure.

Rehabilitation work reportedly experienced “significant” delays due to the impacts from a number of floods in February, March and July of this year. Because construction access to the bridge is primarily from a scaffolding system, safe access was impacted by flood debris and assessment.

According to the release, West said that her team are feeling confident in the progress to date.

“The scale of this project has been significant, and it has been a technically difficult and absolutely critical project to get right,” West said. “The safety of the local community has been front of mind throughout, and it’s great to be at this stage in the repair process.

“These pier repairs have strengthened and extended the life of the existing bridge structure for another twenty-five years, and have been built to withstand ongoing deterioration. There will be some further interruptions to traffic conditions while we complete this final stage, but we thank the community for their understanding while we work to finalize the project.”

The final stages of the project will include addressing the deck of the bridge, improving the structure and providing a smoother surface. Bridge deck work is anticipated to begin early October.

Two full bridge closures are planned at night on Oct. 5 and Oct. 6, between 8 p.m. and 5 a.m. Final timing is reportedly subject to the weather.

The Council also added it will be working with island residents to communicate the changes. The repair project website notes that, due to the experienced delays, bridge repairs are now forecasted to be complete by December 2022, pending any future flooding within the Hastings River catchment.

   

Tagged categories: Australia; Bridge Piles; Bridges; Bridges; Health and safety; OC; Ongoing projects; Program/Project Management; Rehabilitation/Repair; Safety

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