When Tweed Shire Council’s civil design team began planning the widening of Tweed Coast Road, they knew the project would be about far more than just adding lanes.
A $79 million upgrade, stretching 6.1 kilometres from the Pacific Motorway interchange at Chinderah to Grand Parade at Casuarina, is no easy task.
The widening of Tweed Coast Road is intended to address traffic growth, support major new developments, and deal with a challenging mix of environmental, flooding, and utility constraints.
Stage one, now in detailed design, covers about three kilometres from the motorway southwards. It is a $30 million package that includes not just roadworks, but environmental studies, noise attenuation planning, as well as integration with major sewer and water upgrades.
“The project aim is to widen the coastal road from two lanes to four lanes,” said Chris Hawkins, Civil Engineering Designer at Tweed Shire Council.
“That’s earmarked to probably roll out over the next 10 to 15 years.”
Council’s role is to produce the concept design for the full corridor and take the stage one design to 80–85 per cent completion, before handing it to a design-and-construct contractor for finalisation and delivery.
That is where the team’s choice of Civil Site Design software, developed in Melbourne by Civil Survey Applications, has proven critical. Being Australian-made, Civil Site Design offers the advantage of local support and training, along with outputs such as long sections and cross section plans that match Australian requirements.
Designing for a complex environment
On paper, the widening may look straightforward – a “cookie cutter” expansion of the existing road. In reality, the site throws up a host of constraints.
The corridor runs through state-mapped wetlands, meaning the project footprint must be minimised. With residential developments along the route, noise impacts need careful modelling. Additionally, recent history has underlined the scale of the flood challenge, with major events in 2017 and 2022 inundating parts of the area.
Flood mitigation has been one of the most intricate elements of the design.
“We had to work with flood consultants and send them design TINs [triangulated irregular networks] so they could build 3D models,” Hawkins said.
“We’re only talking in some instances of lifting or lowering the road 20 or 30 millimetres, so it was quite critical.”
The site’s extremely flat topography – plus or minus a metre across most of the corridor – makes traditional drainage almost impossible.
Instead, the design incorporates low-flow crossroad culverts and targeted drainage upgrades to address localised flooding, including areas affected by an unusual ebb-and-flow effect when the nearby Tweed River bursts its banks.
Layered over these environmental and flooding issues is a major utilities task.
Three large sewer rising mains will be installed to service growth along Tweed Coast Road, alongside two significant upgrades to Council’s sewer outfall. Council’s water unit is also planning parallel asset upgrades, requiring close integration between road, stormwater, water, and sewer designs.
Civil Site Design in practice
For Hawkins and colleagues behind the water and sewer design, Civil Site Design’s core road, drainage, and pipe design tools have been central to managing these intersecting challenges.
The software sits within the team’s existing Autodesk Civil 3D environment, providing a familiar platform with powerful, purpose-built civil functions.
One early win was in managing and interrogating underground services.
After survey pickup, the team could quickly convert services into 3D strings, compare them to final design levels, and identify potential clashes with proposed stormwater or other infrastructure.
“From an investigation point of view and looking at potential clashes, it’s been very good,” Hawkins said.
Maintaining design consistency across such a long corridor has been another benefit.
Starting from concept long sections and cross sections, the team built the detailed model in parallel with utility planning.
“At the end of the day I had to come up with the final road levels before my colleague could start designing water and sewer assets,” Hawkins said.
Civil Site Design’s dynamic updating features have streamlined that process, particularly on complex intersections and roundabouts.
Stage one includes two major roundabouts with tight driveway access and heavy vehicle turning requirements. Hawkins used Civil Site Design alongside third-party vehicle tracking software to ensure designs met sight distance and clearance standards for everything from B-doubles to triple road trains.
The team also leveraged Civil Site Design’s design automation and customisation capabilities. Local drafting standards – including template blocks for kerbs and channels – are built into the system, reducing rework and making it easier to produce outputs that are construction-ready.
“It makes tackling that a lot easier,” Hawkins said.
Integrating flood and drainage design
The project’s drainage design may be modest in scope, but it has been shaped by detailed flood modelling made possible by Civil Site Design’s ability to output accurate design surfaces for external analysis.
Those models confirmed the influence of tidal flooding on this inland stretch of road – a factor that has driven design decisions such as bidirectional culverts to manage post-event backflow.
Where possible, Civil Site Design’s pipe and pit design tools have been used to improve local cross-drainage, especially in pockets where topography and development patterns create ponding.
The sand-based soils help with infiltration, but the software has allowed the team to fine-tune invert levels and layouts to improve resilience without unintended impacts on surrounding properties.
Faster, smarter outputs
For Hawkins, some of the most tangible gains have come in producing design documentation.
Even with roundabouts – a relative rarity for the team – Civil Site Design’s templates and editing tools made it quicker to generate and adjust kerb returns, super elevations, and intersection geometry.
“Just tweaking a few templates here and there and re-running it, and then cross-checking against the intermittent kerb profile files… we were only up to 15–20 millimetres difference in kerb heights,” he said.
The result is more confidence in the accuracy of the design, and less time spent on manual drafting or correction. For a team working to tight deadlines before handover to a design and construct (D&C) contractor, that reliability matters.
Built on experience, ready for the next generation
Tweed Shire Council has been using Civil Site Design for close to two decades, pairing it with Autodesk Civil 3D since the early days of both platforms.
That long experience has built a comfort level that makes it easier to explore new functions and adopt updated versions. The design crew makes regular use of Civil Survey Applications’ tutorials and online resources, which Hawkins says have been invaluable for learning new features on the fly.
For councils considering the software, his advice is simple: it’s easy to pick up and run with, even for less experienced designers.
“The way the programs are written now and the graphical interface, it’s a lot more friendly,” he said.
“It does what it says it does. You can safely say it’s giving you very good information and the overall use of it has been very easy. I’m very happy with it.”
Shaping the delivery program
While stage one’s construction staging is “pretty clear cut”, Civil Site Design has helped in planning temporary transitions where future works will tie in.
In some cases, that means designing a temporary resheet to connect proposed levels back to the existing road, ready for later upgrades. Those efficiencies will help keep traffic moving and reduce rework when the next stage is funded.
As the project progresses, Council’s integrated approach – road, drainage, and utilities designed in one environment – are set to pay dividends. By the time the D&C contractor takes over, the design will be well-resolved, compliant with local standards, and supported by detailed, accurate documentation.
Civil Site Design continues to provide a flexible, precise toolset to make that possible.
To learn more, visit civilsitedesign.com.au
