Southern Corridor Improvements, Auckland, New Zealand

Delivering critical motorway expansion design at accelerated speed

In June 2013, the New Zealand Government announced a plan to accelerate Auckland transport projects to a value of NZD 815 million to support the city’s rapid growth and to help ease its congestion issues. The Southern Corridor Improvements is one of the first of these projects.

The project comprises widening a 7.8 kilometre stretch of the existing Southern Motorway (SH1) between Manukau and Papakura. This will help to address congestion resulting from existing lane imbalances and will assist with the redistribution of traffic when the alternative Auckland motorway, the Western Ring Route, opens in 2017.

Accelerated design challenge

Aurecon was appointed as the Waka Kotahi NZ Transport Agency's Principal Advisor for the Southern Corridor Improvements in March 2014. The project team has since risen to the acceleration challenge of delivering scheme development, gaining planning approvals and awarding a physical works contract for construction by August 2015; an unprecedented  timescale of less than 18 months.

To mitigate the time-critical activities of planning approvals and property acquisition, Aurecon identified potentially affected parties early and formed effective working relationships with these key stakeholders. This helped support the accelerated nature of the project delivery.

The safety and capacity improvements were kept within the existing motorway designation where possible to minimise effects on adjacent land owners and on the environment. Permanent land acquisition was limited to three areas.

The project includes provision of a new 4.5 kilometre walking and cycling facility between the Papakura and Takanini Interchanges to support active transport modes, and will enable a coastal edge of the Manukau Harbour to be opened up to the local community. It comprises redevelopment of an existing maintenance yard to create a public space that overlooks the Manukau Harbour.

Delivering a sustainable motorway expansion design

Construction of the NZD 268 million project began in October 2015 and major works are expected to start in January 2016.

The work includes:

  • 11.6 kilometres of  new traffic lanes within a constrained urban environment
  • Safety and capacity improvements by reconfiguring the existing Takanini Interchange
  • 4.5 kilometres of shared use path including an architecturally designed pedestrian bridge at the southern end of the project
  • Upgrade and widening of 16 existing bridges and construction of six new bridges, the most challenging of which passing over the North Island Main Trunk railway
  • Replacement of the existing substandard median barriers with a high containment concrete barrier which integrates new light-emitting diode (LED) lighting
  • Environmental improvements, such as:
    • Treatment of storm-water runoff within low impact environmentally sustainable treatment solutions (wetlands and planted swales)
    • Urban design treatment that incorporates Matauranga Māori design principles
    • 4.5 kilometres of new noise walls
    • Significant areas of planting which include eco-sourced indigenous species
    • Salt marsh restoration within Pahurehure Inlet

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