O Mahurangi project update

19 June 2025

Crack showing ground movement at the largest fill site on the project, Fill 9 where the future Ara Wēiti connection/Link Road 2 will be located.

Programme delay

A slip at the largest fill site on the project on has delayed construction to the Stillwater and Ara Wēiti section of the road. While we are still working to understand the full impacts, the project will now open as a single completed corridor instead of the staged opening previously planned.

The overall project timeline is still on track for completion in 2028.

What has happened?
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 found to be 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. 

Why has this caused a delay?
The project uses a cut fill balance approach for earthworks. The slip has occurred in Fill 9 where approximately 3500,000³ metres of cut earthworks will be placed. The cut material, due to be placed at Fill 9, is unable to be stored elsewhere. Until the solution can be implemented, earthworks are unable to continue at the previous pace along the alignment.

How will this impact me?
The project will now be opened as one in 2028, as opposed to the staged opening previously planned.

What have you done since the slip was observed?
Since December, we have undetaken extensive monitoring and investigations, including over 20 bore holes. The information from these investigations has allowed us to assess the best solution. Since Emergency Works was declared we have been able to start remediating the slip by installing groundwater pressure relief drains which help to stabilise the ground. This will allow us to prepare works for a buttress while we complete the design and enabling construction of the final solution.

Have a look at our FAQs here for more information on how we are addressing this. https://www.nzta.govt.nz/projects/penlink/frequently-asked-questions/

Event flyer

Stillwater information event

We know this change to the staged opening will be frustrating for the community, especially residents in Stillwater and Ara Weiti. 

We will be holding our next inforation drop-in evening at the Stillwater Boating Club on Wednesday 23 July from 4-7pm. Please come and ask the team any questions on our upcoming works and changes to the programme. 

SH1 bridge

What's happening in July

State Highway 1 and Ara Weiti Road
In July, we will be undertaking a variety of activities on the SH1 northern motorway at night. Full closures will be in place between Oteha Valley Road and Silverdale to allow this work to happen. Full details will be notified closer to the time.

The earthworks team is continuing the cut to fill operation on the on- and off-ramps for SH1. Along Ara Weiti Road work progresses on the road widening, installation of the precast concrete panels on the bridge at Link Road 1 and construction of the retaining wall by Link Road 2.

Stillwater
The final concrete pour for the eastern pier (Pier 4) pile cap has been completed, enabling the start of pylon construction. A tower crane has arrived and will be erected to lift materials for the Wēiti River bridge, and work continues on the retaining wall for the future SH19/Duck Creek Road interchange.

Early July there will be a temporary river closure, please see below for more details.

Whangaparāoa 
Construction is underway on the future Beverley Road / Whangaparāoa Road intersection. Other works include the installation of stormwater drainage lines.

Weiti River Bridge

Wēiti River bridge progress

The western side abutment of the Wēiti River bridge is completed and the two land-based piers are at their final height. An additional 2 in river piers are currently being constructed.

Upcoming river closure

July will see the last of our three months of temporary Wēiti River closures, to ensure safe and continuous supply of concrete for the Pier 4 pile cap.

The final closure is from From 5pm Monday 7 July to 9am Wednesday 9 July.

The channel closure does not affect vessels navigating the river downstream of the worksite.When the work is complete, we will reopen to the 18-metre-wide navigable gap for vessels to pass through.

We apologise for any inconvenience caused and thank all river users and neighbours for their patience during the ongoing construction of the new Wēiti River Bridge. Should you have any questions regarding this closure, please don’t hesitate to contact us.

More information

For more information on the O Mahurangi project, contact us at omahurangi@nzta.govt.nz or by calling 0800 7365 465.

Visit our website www.nzta.govt.nz/penlink.