Laying the foundations for the Mitchell Freeway Extension

Construction is well underway on the Mitchell Freeway Extension, which will provide a vital connection for Perth’s expanding northern suburbs.As Perth’s population and economy continue to grow, the city’s north has become a hotspot for commercial and residential expansion.

The burgeoning industrial hub at Neerabup is one such site at the forefront of the city’s northern growth.

“Neerabup has taken off over the last few years and getting bigger and bigger – it will become quite an important commercial industrial area,” explains Chris Raykos from Main Roads Western Australia.

Mr. Raykos is the Project Director on the Mitchell Freeway Extension project, which involves extending the freeway by six kilometres and improving the key transport route to the city’s northern suburbs.

The scope of the project includes the six-kilometre extension of dual carriageway with two lanes in each direction and other integral upgrades and reconfigurations.

New interchanges are being built at Burns Beach Road, Neerabup Road and Hester Avenue as well as shared paths for pedestrians and cyclists, including underpasses and a footbridge.

Neerabup Road is being extended from Connolly Drive to Wanneroo Road, while Hester Avenue and Wanneroo Road will both undergo upgrading in sections to provide better east-west connectivity.

The Flynn Drive/Wanneroo Road/Neerabup Road intersection will also be reconfigured as part of the development.

“The project will help drive employment to the local area, which will eventually employ thousands of people, by providing better connectivity. The idea is to get more people coming from the region to the north rather than up through the city,” says Mr. Raykos.

The project came to life in December 2012 following Main Roads’ development of a Strategic Business Case and funding approval from the Western Australian Government. Subsequently, the Federal Government also provided significant funding for the project.

The Strategic Business Case identified the current traffic issues in the area, and what needed to be done to ease congestion, facilitate growth and make Perth’s north more accessible.

“The Strategic Business Case also identified the benefits for traffic coming from the north to the south, particularly for light freight around the metropolitan network,” he adds.

Main Roads undertook preliminary land approvals and geotechnical investigations after the funding was approved. The tender to design and construct the vital extension was then released to market and awarded to CPB Contractors (formerly Leighton Contractors) in April 2015.

Design began immediately and the project team started preliminary construction in June 2015, with a view to finish the extension by December 2017.

Challenges from the outset

“Before the design and construct contract was awarded, we had a lot of stringent environmental approvals to meet, including approvals to clear some vegetation,” explains Mr. Raykos.

“The land for the freeway extension was set aside in the Metropolitan Regional Scheme but we still had to secure the site for Neerabup Road, and that was going into Neerabup National Park and required minimum disruption to the land.”

“We had to make sure we had heritage clearance as there were a number of indigenous and European items. Some of the items of European heritage dated back to the early 1900s, which we had to protect.”

The stringent requirements for environmental approval were even more challenging in partnership with the tough geotechnical qualities of the site. “The land contained quite a lot of karsts and hard limestone,” adds Mr. Raykos.

The land needed to be prepped for the project, which included bridge foundations. The rough terrain and underground karsts – a special type of landscape formed by the dissolution of soluble rocks, including lime and dolomite – made it tricky for the dozers required to navigate and clear the site.

“We did expect to encounter hard limestone and karsts, which are quite common in this part of Perth,” says Mr. Raykos. “We conducted risk assessments through the preliminary planning and a big focus was to do with the karsts and hard limestone. We also wanted to make sure that dozers could break up the hard rock.”

CPB had its own treatment for karsts that enabled the contractor to prep the site for construction effectively and safely.

Construction begins

After the preliminary works were finished, the first major construction stage of the project began – the bulk earthworks.

Mr. Raykos says it has been quite a standard operation of removing material from the site to make way for pavement construction, but the volume of work was immense.

“The earthworks have been quite significant. We’ve moved a couple of millions of cubic metres of material,” states Mr. Raykos.

A large portion of that material was moved off site and repurposed by CPB on other projects.

The next phase in the project is the actual pavement construction for the six-kilometre extension, which is now underway.

This stage in the freeway’s extension has thrown some unique challenges into the mix as it involves the project team working in close quarters with residential properties, live traffic, public in general and the Northern Suburbs passenger rail line.

“We’re working next to residential areas so we have to make sure there aren’t any vibration, dust or noise issues around peoples’ homes,” asserts Mr. Raykos.

Sustainability and innovation

Mr. Raykos says many innovations and sustainable concepts have been incorporated into some of the project’s major elements. Like many road projects these days, post-consumer waste is being repurposed in road construction.

“We were approached by the industry to look at using ground glass in embankment construction, and we’re now also trialling a section of pavement with ground glass,” he says.

CPB has a design specification with Main Roads for the use of ground glass in the pavement subbase that will be used in the project.

The contractor will lay a 150-metre section of pavement with 15 per cent ground glass in the subbase as well as a 150-metre control section at Wanneroo Road.

The plan is to monitor this section of pavement over the next few years to see how the ground glass pavement behaves over time.

“I think this is a growing innovation that will develop further and use other materials that are environmentally friendly. If you don’t have to use as much limestone it will help reduce virgin quarry resources,” says Mr. Raykos.

Main Roads will also trial new, more energy efficient LED lighting on a the freeway.

“The whole idea is to introduce new economical and environmentally friendly lighting that will fit in with the current network,” says Mr. Raykos.

New LED lighting systems that don’t require any complex installation and that can be retrofitted to suit the lighting systems already existing on the network will be trialled as part of the project.

“If this trial is successful Main Roads will then consider the option of upgrading the Main Roads network to LED lighting,” he adds.

CPB will also construct a number of fauna underpasses as part of the environmental requirements of the project.

These innovations and environmental considerations all go a long way to helping the project team reach some internal and external sustainability goals under the Infrastructure Sustainability Council of Australia’s Infrastructure Sustainability rating system. “We are aiming for an IS rating as well, and CPB has a certain standard it is aiming for,” says Mr. Raykos.

Major milestones

The construction of the interchange overpasses is another major phase for the project team.

“Lifting the beams for the Neerabup Road and Hester Avenue bridges have been big undertakings, as is any bridge lift,” says Mr. Raykos.

The Hester Avenue beam lift was undertaken in June, and was the first bridge to be put in place. Neerabup followed in mid-July and the Burns Beach Road bridge lift was completed at the end of August.

CPB will also construct a footbridge over Burns Beach Road as part of the project.

Not only have these significant sections of the project been successfully completed, but they have been done well ahead of time. “We’re looking at finishing by mid-2017 – six months earlier than originally planned,” says Mr, Raykos.

Part of the success so far has been the relationship with the community and stakeholders, particularly through the project’s community reference group.

“The reference group includes the local community and local businesses. They’ve been involved all the way through the project and have been consulted during detailed design and their comments were taken on board where appropriate,” he says.

Mr. Raykos also pins much of the project’s success down to the relationship between Main Roads and CPB as well as the contractor’s legacy with the Gateway WA Project, which was completed in March this year.

The success of Gateway WA has rippled through the state and some of the practices employed by CPB on the billion-dollar project have been carried over to the Mitchell Freeway Extension.

“CPB brought good management systems over from the Gateway Project, which has been an extremely successful project,” he says.

The same customer relations team that worked on Gateway WA is working on the Mitchell Freeway Project, which Mr. Raykos explains has been integral to the successful communication between the project team and the community.

“CPB has some very good systems and an very high-quality work and safety environment. We take safety very seriously on site and I think CPB is one of the top performers in that area.”

“Their safety is spot on and their environmental management is fantastic. Their overall performance is A-plus.”

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