When DBCA called upon Paul Terpkos to engineer a lookout with an architect college Craig Poletti at the Kalbarri National Park, one question beckoned: “Why don’t we go bigger?”
A skywalk that celebrated the majestic 80-kilometre Murchison River Gorge seemed fitting, where guests could appreciate its form.
DBCA concurred, but the design had to meet key criteria.
First, it had to fit within the landscape, provide optimal views, welcome guests of all mobilities, respect traditional owners, and allow for unsupervised access to avoid additional fees.
Seven years later, visitors to the Kalbarri Skywalk can now navigate 100m above the gorge on two separate platforms, extending 25m and 18m each.
What’s more, they’re accessible via newly-sealed roads with parking available for those travelling with a caravan.
National park guests can wander the Kalbarri Skywalk at their own leisure for no extra charge.
A SENSITIVE APPROACH IN CONSTRUCTION
Paul and Craig settled on a cantilevered design, with the platforms working like two diving boards.
“We had to load the cantilevers to minimise bounce,” Paul explains.
The preliminary technical investigation identified that the rock required crumbling, so construction could clamp in the platforms and anchor them down 10 metres.
“We had to cut the landscape in a careful way so we could use it for seats and as elements for the walkway.”
Craig consulted with the Nanda People to minimise environmental impact at the sites in this culturally significant region. With the custodians providing artwork and fascinating local insights incorporated into the interpretive signage.
By carefully removing the rock during excavation, builders could reuse it at the on-site cafe.
DESIGNING THE PLATFORMS
The right materials keep the site free of charge, says Paul.
“Some platforms like the Grand Canyon are glass but the problem is you have to put on socks so it doesn’t scratch.
“Someone has to be there [to oversee it].”
But at the Kalbarri Skywalk, guest can see downwards into the gorge through the gridded surface, made from fibre-reinforced plastic.
A pathway through the walk has a finer grid for guests accessing the site in wheelchairs or with walking aids. The strategy proved very successful.
“A guest sent me a Youtube clip filmed at the lookout, in an email thanking me.”
Guests have two surfaces on which to navigate the skywalks, a coarser grid providing views 100m below.
ENGINEERING IN THE AESTHETICS
The Department wanted “nothing shiny” and something with a 100-year lifespan. So Paul opted for COR-TEN steel.
“COR-TEN Steel has special weathering properties. It rusts slowly and creates a skin so it protects itself.
Paul paid significant attention at the joins to avoid concentrated rusting.
“Over time, you lose a little thickness but we’ve factored that in.”
To manage the bounce, the design underwent substantial wind tunnel modelling tests.
It was also tested to ensure it could safely support more than it could contain within the area.
“The platforms had to be at least 400kg per square metre to safely hold guests [but following the wind test results and accommodating the lifecycle] it was made stronger again.”
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COR-TEN steel creates a skin to protect itself.