In its most recent transport plan – Transport @ 3.5 Million – the Western Australian Government has mapped out its vision for the future of the state’s transport infrastructure as Perth’s population grows to a projected 3.5 million by 2050.
The plan looks at where people will live and work when the population reaches that mark, and outlines the transport system so that public and freight can keep moving as the city grows.
Part of that long-term vision requires significant infrastructure investment to ensure the city’s road network capacity, efficiency and productivity are at a level that can accommodate this growth.
NorthLink WA is part of that plan, with the Federal and Western Australian governments investing a total $1.12 billion in the initiative.
NorthLink WA creates a non-stop transport route between Morley and Muchea in the north, increasing road capacity and relieving congestion. NorthLink WA will also take the pressure off the traffic volumes on the Great Northern Highway, the state’s existing major northern road, by shifting an estimated 80 per cent of heavy vehicles over to this new route.
It will be constructed in three sections – the Southern Section: Guildford Road to Reid Highway, Central Section: Reid Highway to Ellenbrook and Northern Section: Ellenbrook to Muchea.
The tender for the Southern Section was awarded to John Holland in January 2016. The contract for the second Central Section was won by the Great Northern Connect Team (a joint venture between BGC Contracting and Laing O’Rourke) this January and the Northern Section contractor is yet to be announced.
The first stage of the momentous project – the Southern Section: Guildford Road to Reid Highway – is well underway.
“After receiving the award in January, we started on the design phase of the project, which was then finalised in November. We started on site with early works in May/June last year, clearing the site, conducting geotechnical investigations and commencing earthworks,” explains Ben Johnston, John Holland Project Manager on the Southern Section of NorthLink WA.
The Southern Section involves some key construction works to provide a freeway-standard, free-flowing link from Collier Road through to Reid Highway, via the Tonkin Highway.
The project requires upgrading the Tonkin Highway to a six-lane freeway between Guildford Road and Reid Highway, as well as the construction of new interchanges at Collier Road, Morley Drive and a flyover of Benara Road. The Morley Interchange includes a roundabout at ground level that will connect with a raised Tonkin Highway – the first interchange of its kind in the state.
“The Morley interchange will be quite unique from a Western Australia perspective. With the highway running over the top, the roundabout will be 140 metres long and 70 metres wide, which will significantly reduce congestion in Morley,” says Mr. Johnston.
Likewise, the construction of the Collier Road bridge will prove a unique component of the build.
“The single point, urban interchange bridge is a very complex structure and the designers have come up with a top-down construction approach to building it,” says Mr. Johnston.
The retaining walls are constructed first using intersecting concrete piles, which are layered into the ground. The bridge deck is then constructed, which includes both precast beams and in-situ concrete and connects to the piles and finally, the earth beneath the bridge is excavated. “It’ll be quite a unique looking structure when finished,” he adds.
A new four metre-wide shared cycling and pedestrian path will be built alongside Tonkin Highway and extended all the way to Muchea as part of the central and northern section contracts.
Once complete, the southern section of NorthLink WA will also eliminate two of Western Australia’s most dangerous intersections.
“The grade separation work we’re doing there will provide significant benefits in reducing congestion and take away the safety concerns around that particular part of the road,” says Mr. Johnston. “Overall, it’s a $176 million task to design and upgrade the existing Tonkin Highway to provide a free flowing link for all road users.”
The challenge ahead
“The most challenging aspect of the project is managing all the existing volumes of traffic on one of the main arterial roads in Perth at all times,” says Mr. Johnston. He explains extensive planning and modelling have gone into the design phase to ensure traffic flow isn’t affected by the construction, and the changes will optimise traffic volumes along the busy highway.
“One major challenge we’ve encountered so far has been to do with the existing services in the area. There’s a significant number of services that need to be relocated, including major high pressure gas, optic fibre cables and overhead and underground power lines,” explains Mr. Johnston. “A lot of work has been done in identifying them and then supervising their safe removal and relocation.”
Traffic barriers, temporary traffic lanes and reduced speeds have all been implemented over the course of the work so far, which has been systematically and effectively rolled out without issue.
Residential and community areas surround the site, as do school zones, which impose strict noise control and safety measures. Mr. Johnston says community consultation has been undertaken since day one to ensure all the road users are well aware of the changes from a safety point of view.
“A key thing for us has been our communication with the public. We’ve used letter box drops, social media, consultation groups and more to let them know about the changes to their local roads and how it affects them.”
Eight kilometres of noise and screen walls are also being installed along the alignment to help reduce any impacts on residentialxareas.
Keeping the public informed
“Stakeholder and community engagement has been really important to ensure people are well informed and concerns addressed,” says Mr. Johnston. “There are some heritage areas on site where we’ve engaged with local traditional owners to monitor the initial ground works, which is important to ensure the project isn’t affecting any cultural sites.”
Stakeholder engagement has also been crucial in the development of the environmental space.
“We’re working around the local community and have included a number of different dust and noise monitoring stations to proactively measure any issues.”
Dust is being managed by staging clearing works, hydro-mulch and replacing top soil and mulch as soon as possible, with water trucks providing additional support to suppress dust when needed.
The team has gone to a considerable amount of effort when it comes to local foliage and the natural environment. Mr. Johnston says vegetation regeneration and protection of native plants has been paramount, and the efforts gone into preserving such foliage will be evident in the final aesthetic of the area once the project is finished.
“We’ve also had to do a lot of geotechnical work to understand the level of acidic sulphate in the soil on site,” he says. The project team had to excavate some of this material but ensured there are processes in place to minimise any risk of contamination before it is reused elsewhere.
Sustainability at the forefront
As a condition of winning the tender, John Holland is using the Infrastructure Sustainability Council of Australia’s (ISCA) Infrastructure Sustainability (IS) Rating Tool scorecard to report on the level of sustainable practice employed on the project. The project must achieve at least an IS Design Rating and IS As-Built Rating of ‘Excellent’.
“Sustainability is a key requirement on the project and has been integrated into the design from day one,” explains Mr. Johnston. “We’ve used the e-tool life cycle assessment tool to understand exactly what our footprint is throughout and inform the design models across the job and we’ve used that to conceptualise where we can get better value when we make changes in the design.
“It’s certainly given us a good understanding of where we use the most energy on the project and can make the greatest savings,” he adds.
The contractor is also targeting between 12 and 25 per cent reclaimed asphalt pavement (RAP) in the road construction, which Mr. Johnston says is high for a Western Australian project.
“We’re also using recycled existing pavement for reuse on temporary works as well as the shared pedestrian and cyclist path,” he adds.
The project is using enrobés à module élevé (EME2) on sections of the project, which will help to reduce the thickness of the final pavement by approximately 20 per cent, helping save the amount of material required for construction.
Mr. Johnston says that construction is well underway, with nearly 25 per cent of the southern section finished, and is on track for its anticipated completion date of January 2018.
He asserts that a recurring message the project team is driving is about sustainability and innovation, and what can be done better to improve outcomes for the project and community as a whole.
“We’ve done a lot of work with our suppliers and contractors to educate them around sustainability and how they can get more out of a situation through innovation. We’ve found that when we look at doing things differently it benefits everyone not just in sustainability, but in other areas too.”