Granite Island Causeway, Nostalgic Infrastructure

For many South Australians, the Granite Island Causeway ignites memories of summer holidays, road trips to Victor Harbor and beautiful Clydesdales.

Together with DIT & McConnell Dowell our team were the lead designer on the design and construct of the new $43m Granite Island Causeway project. Our team were responsible for all modelling, civil design, structural design, lighting design, maritime design, and geotechnical investigations. The new concrete and steel structure has a 100-year design life, built to withstand the surrounding environmental conditions. The horse-drawn tram will remain part of the new Causeway, which also includes a pedestrian walkway, rest areas and improved safety features.

Digital brings benefits

Digital Engineering played an essential part in the design development of the Causeway. This project required various in-situ and precast or manufactured elements constructed offsite. There was also a requirement for an increased tolerance level due to the maritime nature of the construction. WGA identified the need for each aspect of the design to be modelled to a high level of accuracy. This helped identify and eliminate risks that might arise later down the line – offering greater predictability of building performance, price and programme.

“A 3d model allowed stakeholders to visualise and interpret the design leading to more informed decisions.”

It was essential to have a coordinated approach for this multi-disciplined project that required multiple authoring software programs. A federated model was created and issued to stakeholders regularly to allow the client, contractor and design team to visualise and interrogate all aspects of the project. It ensured everyone could visually see the project in 3d rather than visualise and interpret it. That immediately removed any uncertainty and allowed the project team to make more informed precise decisions.

Although most of the Causeway is linear, the geometry did pose some challenges. It required complex modelling techniques and option engineering to consider all aspects to provide a set out of the new Causeway that achieved the desired outcomes. The significant considerations were the curvature of the new rail design, a strong desire to have as much repetition as possible for precast elements, respect for the temporary works construction method and existing structural and civil elements.

“A point cloud and laser scan of the horse-drawn tram identified gaps in the original design”

This new 630m Causeway has been designed to accommodate various vehicles, most importantly, the existing rare horse-drawn tram cars. There were no drawings of the fully restored tram cars and using a tape measure to document all the intricate parts was difficult. WGA’s laser scanner and drone were used to resolve design issues quickly.  

After completing a laser scan of the horse-drawn tram cars, the team used the point cloud data to analyse it against the design model. This provided reassurance that all clearances could be achieved, especially during the curvature of the new Causeway.

Environmental sensitivities

During the 7-month construction period, Southern Right Whales were to make their annual migration around SA’s Southern Fleurieu Peninsula. Conscious of the noise and vibration of construction works whale spotters were positioned around Granite Island and in boats as a precaution. Construction was immediately paused if a whale came within an unsafe distance.

The Granite Island Penguin colony was also protected and over the project life cycle, the colony increased from 16 to 22!

“Protecting the marine ecosystem was fundamental.”

Open to the public as of Dec 2021, we are incredibly proud to have been part of the team to deliver this iconic project successfully. The new Granite Island Causeway is an environmentally responsible design that will continue to deliver social and economic benefits to the Victor Harbor region and benefit South Australian tourism for years to come. 

WGA News: Granite Island Causeway, Nostalgic Infrastructure Article Image
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