Ara Tūhono Puhoi to Warkworth - Delivering world-class Connections

Presenters: Hannah Giess

The Ara Tūhono – Pūhoi to Warkworth project is a new 18.5 km long motorway, north of Auckland, New Zealand. It has been designed to offer a safer and reliable route and help further develop infrastructure and roading networks within the Northland Region. The Project is unique in its geological and geographical features, comprising of steep hill country to flat farmland and flood plains. The difficult topography has created ongoing challenges with how ESC is managed across the Project, with unstable ground conditions requiring innovative ways to manage run-off when traditional ESC devices cannot be built. One of the biggest challenges that has been faced by the Project Team is the number of slips that have occurred, the largest being a 60,000 m3 slip in the steepest gully of the Project – an immense effort was required to stabilise this material when 200 mm of rainfall was predicted in the coming week.

The Project takes pride in its environmental compliance and with an Adaptive Monitoring Programme has been able to achieve sediment yields that are far below what was predicted in theoretical modelling. This has helped the Project gain approval for open area extensions up to 26 ha over the original set limits. A strong relationship with the regulator, no significant environmental incidents or infringements, has shown the Construction Team that with a high standard of compliance comes increase in productivity. A collaborative relationship with the project stakeholders and a strong communications focus has allowed the project to share good news stories, innovations and updates to the community via a range of different media outlets. The Project also hosts a range of visits for the Construction Industry as well as sharing lessons and providing opportunities to suppliers to test products on one of New Zealand’s largest earthworks projects.

Learning Objectives: 
  • Appreciate the key challenges for a large scale earthworks in a highly variable climate and with a highly erosive geology
  • Understand the best practice erosion sediment controls utilised on large scale earthworks projects in New Zealand
  • Understand how an Adaptive Monitoring Framework can be used to achieve good environmental outcomes & increase productivity

Presented by: Hannah Giess – Senior Environmental Advisor, Fletcher Construction