Low-level bridge at HMAS Stirling, Western Australia

RPS has supported the Department of Defence to complete a complex repair program for a low level road access bridge that connects HMAS Stirling Navy Base on Garden Island to the mainland. 

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Challenge

Since the 1960s, HMAS Stirling has served as a strategic naval base location in Australia’s West. Located on Garden Island around four kilometres off the coast of Perth, HMAS Stirling’s only road link to the mainland is via a low-level bridge constructed in the early 1970s. Providing access to essential trunk services onto the island, the bridge is a key piece of infrastructure for the Base. 

With harsh marine conditions causing the bridge to deteriorate, Defence called on RPS’ local project management team to oversee work to reinforce the structure and secure this critical road access link.  

Solution

While the bridge repairs were initially planned to progress as part of the broader HMAS Stirling Redevelopment Stage 3A project, Defence created a standalone bridge repair project due to the urgency of repair works, targeted for completion in December 2016. 

Engaged as the Project Manager / Contract Administrator (PMCA), our team worked closely with key project stakeholders to determine the best strategy for repairing the bridge within the allocated budget of $13 million with minimal operational impacts to the base.  

Completed on time and to budget, our team managed a comprehensive program of steel and concrete repairs and the installation of additional protection components that have extended the life of the asset significantly.  

Project innovations included: 

• The use of floating scaffolds to allow contractors to complete repairs both above and below water concurrently without impacting traffic access 

• Cathodic protections – where structural elements are protected from harsh corrosion via an electromagnetic system that includes a ‘sacrificial metal’ that corrodes first. 

• A bespoke pile jacket system that far better protects the bridge’s structural elements from harsh marine conditions. 

With ongoing maintenance and planned future work, the bridge is now expected to be in use until 2055, in line with Defence’s Whole of Life objectives for maritime structures at HMAS Stirling.