O Mahurangi – Penlink to fully open in 2028

While O Mahurangi – Penlink is still scheduled for completion in 2028, NZ Transport Agency Waka Kotahi (NZTA) had planned to open some sections of the road earlier near Stillwater and Ara Wēiti. However, a major slip at the project’s largest fill site has now delayed construction of these sections. While NZTA is still working to understand the full scheduling impacts, the project will now open as a single completed corridor.

Cracking in the ground which was first identified in December last year required all activity in the area to pause while it could be assessed. Extensive testing and monitoring showed a deep layer under the surface (deep shear plane layer) was significantly weaker than experienced on other similar sites on the project where earthworks had been undertaken. 

Due to the slips continued movement, emergency works were declared in March to allow remediation works to be undertaken sooner. This minimises the risk of the slip damaging existing assets and private property.   

Regional Manager Transport Services Stephen Collett acknowledges that this delay will be frustrating to residents of Stillwater and Ara Wēiti, as well as all road users that wanted to use the road to access State Highway 1 earlier.  

“As the project uses a cut fill balance approach for earthworks, the material at this location is unable to be stored elsewhere until we can implement a solution. Until the solution can be implemented, earthworks are unable to continue at the previous pace along the alignment.  

“Despite the delay, O Mahurangi remains on track to open in line with the Wēiti River bridge, giving people the complete benefit of the project from day one. This will ensure a seamless and more connected journey to and from State Highway 1” says Mr Collett. 

While remediation works are completed, construction has continued at pace in other areas of the site, including: 

• the placement of beams and deck for the future overbridge at State Highway 1 are in place
• the ramps from State Highway 1 are starting to be formed
• future alignment along Duck Creek Road has had beams placed, decks poured and barriers installed. Next the team will dig out the earth from under the bridge to build the future State Highway 19
• the western side abutment of the Wēiti River bridge is completed and the two land-based piers are at their final height. An additional two in river piers are currently being constructed.
• landscaping along the alignment has begun
• approximately 600,000 cubic meters of earth has been moved (about 250 Olympic sized swimming pools). 

Once complete, O Mahurangi – Penlink will unlock long term benefits for the Auckland region, providing a more resilient network to get people where they need to be faster, supporting economic growth and connecting people to new housing developments.