Sea Cliff Bridge: Connecting the coast

Sea Cliff Bridge is an eye-catching addition to the New South Wales coast. Construction of the iconic structure was complex and overcame some major challenges.In 2003, a large embankment slip on Lawrence Hargrave Drive on the New South Wales coast between Sydney and Wollongong resulted in a complete road closure.

The road had been susceptible to rock falls, slips, mud and rock slide in the past, due to high rainfall, erosion and other consequences of the coastal environment.

An analysis undertaken by the road owner, the Roads & Traffic Authority (now Roads and Maritime Services), found that the risk of the existing slope profile was too great and opted to find an innovative solution to reopen the road for residents affected by its closure.

The RTA employed an alliance delivery model for the project – the first road construction alliance for the organisation. In this instance, the LHD Link Alliance was formed and comprised Laing O’Rourke (Barclay Mowlem at the time), Maunsell, Coffey Geosciences and the RTA.

Approximately 26 different solutions were put under the microscope, including tunnels, avalanche shelters and other structures before the final methodology was selected.

The alliance identified the best option for the coastal road was to deliver a near-shore bridge that used both in-situ cast balanced cantilever and incremental launch techniques.

The 665-metre-long structure is a curved, balanced cantilever bridge joined to a 150-metre curved incrementally launched bridge.

The scope of the project included other key technical challenges, such as a mudslide chute and catchment basin, new roadway at both ends of the structure and a 120-metre-long cantilevered structural widening of the road at the northern end.

The final structure also included a three-metre-wide pedestrian throughout the full length of project and a cycleway.

Precise accuracy was required for the curved design of the bridge, given the various angles, falls, slope and complex characteristics involved in each separate segment of the structure.

Surveying and placement measurements had to be exact so that when the concrete was poured into the traveller formwork, it was in the right position for the structure to be successfully tensioned.

Given the complexity of the environment, the project required considerable rock face reshaping and stabilisation works, especially as the project aimed to mitigate embankment slips and rock falls that had befallen the road previously.

The construction of safe access roads on the unstable slopes of the area was also one of the major challenges for the project team.

The design and construction process on the overall project took nearly two years, with the opening ceremony officially held on 1 December 2005, nearly three months ahead of schedule.

The success of the alliance model and the project team’s approach on the bridge’s construction has helped lead the way for similar project deliver models in the state, including some of those employed on the wider Pacific Highway upgrades.

A competition was held to name the new bridge, and the appropriate Sea Cliff Bridge was selected.

The completion of the Sea Cliff Bridge allowed Lawrence Hargrave Drive to be reopened after two years of closure, reconnecting the local area and forming part of the Grand Pacific Drive.

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