Perched high on top of the Caloundra Headland in Queensland a new 160-metre long boardwalk meanders along the coastline taking in commanding views of the Coral Sea.
Tod Consulting were Lead Structural and Civil Engineering consultants on the project and Director Hamish Gray said the success of the recently completed project did not happen by chance.
“The Caloundra Headland Boardwalk upgrade has been a resounding success for Sunshine Coast Council and you only have to see the local community and tourists out there in droves walking, running, cycling, sitting on the boardwalk and taking in the views to appreciate how well the project has been accepted,” Hamish Gray said.
“But that level of acceptance doesn’t come by chance; it is the result of consideration of the community’s desires and needs, an understanding of the environment in which the structure sits and careful selection of materials by the design team in conjunction with council,” Mr Gray said.
Pictured – Caloundra Headland Boardwalk takes in some commanding views of the Coral Sea.
The new boardwalk replaced an old concrete path that had been there for decades positioned immediately adjacent to the local road, with the path not meeting Disability Discrimination Act (DDA) or shared pathway compliance.
“Embedded into the concrete pathway were also hundreds of memorial plaques featuring the names and details of local people who had served and died in conflicts around the world,” Hamish Gray said.
“These memorial plaques were hugely valuable to the community, and it was the desire of the community to see the plaques incorporated into the new design of the boardwalk. So, when the old concrete path was demolished, each plaque had to be carefully removed before being sent away for refurbishment as organised by the local RSL branch and council,” Mr Gray said.
“From a design perspective, we had to adapt the balustrading and kerb rail to accommodate the plaques and make sure they were readily displayed and looked effective,” he said.
“That fed into the post design as well as the substructure underneath, so everything was moved and amended to make room for the plaques and ensure they became a significant aesthetic element of the finished piece.”
“But they also needed to be low maintenance for Council in terms of their connection to the new boardwalk balustrading, kerb rail and approach footpaths; and two methods were employed to fix the plaques to the balustrading and kick rail including screws or doweled then epoxied.”
On Remembrance Day in 1955 the Caloundra headland Memorial Walkway was dedicated as a War Memorial and a monument and plaque were installed. Caloundra Headland marks the start of the “Brisbane Line” during World War II and to mark its historical and strategic significance, the Caloundra City Council granted the request to install plaques bearing the names of deceased defence personnel, both military and civilian along the walkway. By the end of 2021 about 2,400 plaques had been installed commemorating the life and service of Australian and Allied Defence personnel. For more information click here
Pictured – Around 2,400 memorial plaques line the walkway from Kings Beach to Shelly Beach in Caloundra.
On top of the community sensitivities relating to war memorials there were also environmental aspects that impacted the design of the boardwalk.
“This entire stretch of coastline is important marine habitat especially for green and loggerhead turtles so ensuring that lighting along the boardwalk did not disrupt the turtles’ natural navigation while at the same time meeting lighting requirements under Crime Prevention Through Environmental Design (CPTED) was paramount,” Hamish Gray said.
The Moreton Bay Marine Park was declared in 1993 and stretches from Caloundra to the Gold Coast taking in some 3,400km2 including many river estuaries and seaward to the limit of Queensland waters. The park protects a range of marine and coastal environments and is home to migratory wading birds, humpback whales, dolphins, dugong, grey nurse sharks and marine turtles. For more information click here
“Initially we discussed pole lighting with shades towards the beach but we were worried about residents having lights shining back at the apartment building on the other side of the road,” Mr Gray said.
“So we looked to another nearby structure for inspiration; that’s the Mooloolaba boardwalk that has lighting embedded within the balustrading and casting light down illuminating just the boardwalk as opposed to everything around it,” he said.
“Taking the Mooloolaba concept, we incorporated the lighting into the hollow steel posts of Caloundra Headland boardwalk instead of in the handrails themselves with a grill directing the light downwards onto the boardwalk surface.”
“The lighting achieves a very attractive glow, is hardwired LED with a long-life expectancy and is maintenance friendly with easy to access control boxes mounted directly under the deck.”
Pictured – Lighting was cleverly incorporated into hollow steel posts of the boardwalk to protect marine life. Photo by Michael Keenan and supplied by 02LA landscape architects.
Having good input from council and other subject matter experts working on the project also led to improved outcomes for valuable trees and important plant species found along the headland.
“Several sensitive trees and important vegetation were identified during the design phase of the project and so it was determined that if we pushed our joist out to 250mm to increase spans of some bays, then impact to the root zones would be significantly reduced,” Hamish Gray said.
“Interestingly when the contractor went back and collaborated with Wagners CFT, the 250mm joist spans for the Fibre Reinforced Polymer (FRP) substructure rationalised the balustrading connections and these deeper joists were utilised to the outer joist bays, throughout the length of the boardwalk.”
Pictured – Increasing joist spans reduced the impact to root zones of important native vegetation. Photo by Michael Keenan and supplied by 02LA landscape architects.
The steepness of the site and accessibility to large equipment was also a major contributor to the overall design of the boardwalk.
“This is a steep coastal site that was completely unsuitable for large pieces of equipment that you would need for the installation of traditional foundations, and the impact that would have on the environment was unacceptable; so we had to think outside of the box and come up with a concept that would work for this project; and given the geotechnical parameters of the site, micropiles certainly fit the bill,” Hamish Gray said.
Micropiles are high performance, high capacity, small diameter (50mm to 300mm) – drilled and grouted in place – designed with a centrally placed steel reinforcing member consisting of single (or multiple bars), used to take compression and tension loading. They can be installed with relatively small drilling equipment, as single piles or in pile groups, in those areas of limited access or restricted headroom and with minimal impact to existing surrounding structures. For more information on micropiling click here
“Micropiles have a hollow steel bar with a rod through the middle surrounded by grout which has a sacrificial drill head and bar so you can drill right through rock; and what you are left with is a threaded rod sticking up out of a concrete column,” Mr Gray said.
“So basically we had to design a stirrup that the 125 FRP post could attach to, that would also attach to the micropile; and we’d done something similar on the Park Road boardwalk near Noosa National Park in 2019 so the connection idea we had, had proven to be successful in previous projects,” he said.
“The benefit here is that you don’t have to pour a little concrete pile cap to tie the pile to the posts and while the little caps themselves aren’t that big, it’s the sheer number of them on a project like this so your cost savings on materials are significant.”
“Plus you also negate safety issues and the necessity for heavy equipment in forming up the concrete piles on a steep slope like the one we had at Caloundra Headlands so there is also safety in design.”
“However, connecting directly to the piles can pose greater risk at the construction phase through reduced construction tolerances. If you have a pile out of position with a traditional concrete pile cap you have some opportunity to adapt the pile cap to accommodate the offset position of the stirrup and also ensure verticality of the stirrups and therefore post. So, whilst we set a verticality and +/-100mm pile position in any direction limit, we also ensured we had some adaptability with our superstructure to accommodate potential tolerance issues.”
“Durability with the stirrup connection was also a major consideration; we wanted to use a stainless steel stirrup but because of galvanic corrosion potential with the micropile rod, the stirrup needed to be galvanized for compatibility with the micropile rod.”
“This was resolved with a hot metal zinc spray on the steel stirrup followed by several coats of two pack marine paint.”
Pictured – The boardwalk incorporates an FRP substructure and decking with stainless steel handrails and timber accents.
Fibre Reinforced Polymer (FRP) is the ideal material for this project owing to its durability and inert nature.
“Understanding the vision of your client is so very important on a project like this, as while an entire structure constructed from FRP would likely have been the most durable and cost effective long term solution for the project, it wasn’t the vision Sunshine Coast Council had,” Hamish Gray said.
“So they’ve utilised all those strengths of FRP in the substructure and complimented that with more traditional, natural looking materials like timber which Sunshine Coast Council structures are renowned for; and that’s in response to the needs and desires of what the community wants,” Mr Gray said.
“This design strategy and material selection meets the needs of Council from the perspective of achieving highly durable structures with reduced maintenance and replacement cycles coupled with the expectations of the community on how it should look and feel to touch,” he said.
“We are thrilled with the outcome of this project and pleased that all the thought and consultation that went into its design has paid off. We look forward to seeing this structure being well used by the local community and visitors to the area in the future and applaud our partner businesses on this project for their excellence in design and construction.”
For more information on the Caloundra Headland Boardwalk as part of the 73km Caloundra Headland Coastal Pathway visit Caloundra coastal pathway | Sunshine Coast Council
For more information on Tod Consulting Tod Consulting Engineers and Landscape Architects 02LA Caloundra Headland Coastal Pathway
Photo by Michael Keenan and supplied by 02LA landscape architects.