A $630 million bypass is being built by Transport for NSW through Albion Park Rail to create a seamless link from Sydney to the south coast and return a local road to residents.
The Albion Park Rail Bypass will form the missing link to complete a high-standard road connecting Sydney to Bomaderry, NSW.
The road through Albion Park Rail is currently shared by freight, tourists and local traffic and is the last town along the Princes Motorway between Sydney and Bomaderry to be bypassed.
At 9.8 kilometres long and featuring 13 bridges, the $630 million project will look to separate local and statewide traffic streams to alleviate congestion.
The project includes connections to the existing Princes Motorway at Dapto and Oak Flats, a new interchange at the Illawarra Highway and Tongarra Road and incorporates a number of other safety and environmental initiatives.
CHOOSING THE ALIGNMENT
Over the next 30 years, 30,000 new homes are planned for the area and Transport for NSW Albion Park Rail Bypass Project Manager Scott Fayers says this residential development will only exacerbate congestion in the area.
“At the moment we have a lot of congestion in the morning and afternoon peaks, and around holiday periods that will get worse with the extra traffic from residential areas. That is the key driver for the bypass,” Mr. Fayers says.
In addition, flooding is a concern along the current Illawarra Highway.
“Past records show on average the highway has been shut around six to seven times a year. It has only been shut for short periods but obviously people are concerned about getting to emergency services if the road is closed,” Mr. Fayers says.
He says there is an alternative route, but it brings motorists up to the Princes Highway, which can also be prone to flooding.
“The project is on a floodplain, so we have consulted with local councils that have flood models and undertaken detailed flood modelling, given that we are designing in a number of complex catchments,” Mr. Fayers says.
When choosing an alignment for the bypass throughout 2013, the team was met with many challenges such as flooding, impacts on residents and traffic and working with a neighbouring regional airport and existing utilities.
“Shellharbour City Council has plans to expand its regional airport for the future, so we had to work closely with them, the Civil Aviation Safety Authority and Air Services Australia to make sure we controlled or mitigated any impact,” Mr. Fayers says.
“The interaction of the flooding risk and the airport meant one was stopping us from going up and the other from going down, so in some places there were narrow windows for us to work in.”
In the design phase between 2013 and 2018, the team worked on mitigating risks particularly during the bridge design.
As a result, some of the sign and light heights had to be reduced to avoid any impact between planes and infrastructure in the approach to the runway.
“This challenge actually changed the thickness of our bridges in a number of locations to adhere to these project requirements,” Mr. Fayers says.
On top of the airport, the surrounding land uses included agriculture, residential, commercial property, the rail line, a power station, large substation and a community sporting complex.
Prior to pre-construction, the sporting complex had to be reconfigured to enable the bypass construction.
Mr. Fayers says the sporting complex was important to the community.
“If we had taken away the complex without reinstating it, that would have had a big sustainability impact, so we did a lot of work to reconfigure it to enable bypass works,” Mr. Fayers says.
In September 2018, the concept design was finalised a
nd pre-construction activities began.
The project team chose to complete the project in stages to minimise impacts on businesses and locals in the area and disruption of the traffic flow.
The next stage to open is the East-West Link, with expected completion early 2020.
ENVIRONMENTAL IMPACTS AND DESIGN
With the majority of earthworks completed in 2019, the Albion Park Rail Bypass project has so far moved five million tonnes of earth, rock and building material, leaving a large area of exposed dirt.
To reduce dust effects on surrounding businesses and residents, dust control was an important contractual factor for the project.
“Residents at the southern end of the job were concerned because there are two quarries close by that also generate dust,” Mr. Fayers says.
“We implemented a whole suite of measures to manage dust, but the best one was progressive stabilisation as we built our earthworks and the contractor put in revegetation as they went.”
In cases where revegetation was not possible, polymer binders were applied, the surface was compacted, areas were sealed off or water carts were used to manage the dust.
Earthworks also played a large part in reducing the flooding risk for the new bypass, most of which are complete.
“We had to put a lot of material down to get above the flooding level. However, when you put a lot of material on soft soil, it wants to compress,” Mr. Fayers says.
“When you then flatten that soil, it impacts existing structures to either side of the project. We had utilities next to the road and we had to present a design to ensure we were not adversely impacting those utilities, but at the same time providing a stable foundation for the roads and bridges we are building.”
Additionally, Mr. Fayers says waste reuse and coalwash featured heavily in the earthworks stage, which is a waste material from the quarries in the area.
“We also used spoil material from other transport projects up in Sydney.
“Those projects all were struggling to find a home for this material and, in a lot of cases, it was really good material. We were in a good position to reuse that material, so it’s gone from one transport project to another,” Mr. Fayers says.
Supplementary cementitious materials were also used in the concrete for the bypass bridges.
“Instead of using standard cement, other materials are put into the concrete. These are waste products from steel manufacturing such as ash and blast furnace slag,” Mr. Fayers says.
Once the majority of earthworks are completed, the focus for the project in 2020 will be around beginning major construction on pavements and bridgeworks.
During the design phase, bridge design was the main project approach to mitigate the effects of flooding and now these plans are being implemented.
Embankments in the flood plain and two cuttings have also been constructed in the earthworks stage to reduce risk.
All 13 of the bridges will be precast concrete, seven of which will be constructed using a Super-T girder design with the remainder using plank girders.
“Part of the bridge sizing is to do with the flooding models and the other factor is cost as we are trying to get a cost-effective solution at each of the crossing locations,” Mr. Fayers says.
“Super-T girders are arranged with each of the girders next to one another and there is an air void between the girders. If a flood comes up and gets down the side of the girders, basically your bridge becomes a boat because air gets trapped between the girders.”
For the bridges in heavy flooding areas, plank girders are thinner, causing similar issues, but Mr. Fayers says the risk is nowhere near as great.
2020 AND BEYOND
All 13 of the bridges are now under construction.
Mr. Fayers says some of the key parts of the project this year will be the bridge over the rail line, starting the build on parts of the Illawarra Highway and constructing the interchange for Albion Park.
“We are creating the bridge now for the Albion Park interchange so we can temporarily switch traffic onto that, which will allow us to work on the highway that is currently under traffic,” Mr. Fayers says.
The bridge will then become part of the final alignment with a slightly different configuration as a single lane bridge.
After the bridge is constructed, which expected by 2022, facilities for an intelligent transport system will be installed in the final stages of the project. These include CCTV cameras, messaging boards and road sensors to detect traffic.
“We have set up the basic intelligent system on the project and the idea is that it will join up to a managed motorway system in the future for the entire motorway,” Mr. Fayers says.
Managed or smart motorway systems use sensors and variable signs to monitor the traffic flow and increase efficiency.
Mr. Fayers says the mix of through traffic and local traffic is creating massive queues during peak hour, a problem the new project aims to take solve.
“If we can take away the through traffic and return the original road to local traffic, that amenity improves massively, and it improves local traffic flow.”
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