O Mahurangi project update

31 March 2025

First beams placed on SH1 overbridge

First beams are placed

The team took advantage of the SH1 closure last week to place the first beams on the future SH1 overbridge. 

The new bridge is 1 of 6 connecting Whangaparāoa to SH1 creating a more resilient network, getting people where they need to be faster, while supporting economic growth in the region and connecting people to new housing developments in the region. It has been future-proofed to allow for SH1 to be widened in the future.

In total 6 beams (Super T Girders) will be placed across the highway, the last 2 will be installed this week. Each beam is 34.5 metres long and weighs around 68 tonnes,  requiring a 600 tonne crane to lift them into place!

Weiti River bridge piers are growing

What's happening in April

State Highway 1 and Ara Weiti Road

Earthworks will continue on both sides of SH1 and along Ara Weiti Road, as well as drainage pipe installation along the new alignment.

Now the beams have been lifted onto the SH1 overbridge, we will be pouring concrete to construct the bridge deck later this month. We are also starting to construct a retaining wall at Link Road 2 where Bridge 4 will tie into Ara Weiti Road,  and a MSE wall for the bridge abutments at Link Road 1. 

The team are conducting a pavement trial which will inform how we construct the pavement layers on the entire project. 

Stillwater

The Weiti River bridge is taking shape with the land based piers having been completed and the river piers extending in height. The temporary props (support structures) used to build the bridge deck, are being constructed. 

In late April a section of Duck Creek Road will revert back to 2 lanes with traffic lights controlling site access points during work hours only. These changes will make the journey to and from Stillwater quicker for drivers. 

Whangaparāoa 

Now the barriers along Whangaparāoa are in place and the Cedar Terrace intersection is temporarily closed, the team will continue construction of the future re-aligned Whangaparaoa Road. 

In the former Cedar Reserve, you will notice us starting to relocate our site office as we remove the exisiting one opposite Wiriana Place.

Earthworks continue along the alignment from Whangaparaoa Road to Weiti River, with a strong focus on stabilising the earth. We will also be installing drains - bored and gully, as well as culvert outlet and watermain tie-in works. 

High Reach Drill installing rock bolts (photo credit: Geovert)

Machinery spotlight - High-Reach Drill

A High-Reach Drill (HRD) is used to install rock bolts and crest pins at Cut 20, where the Wēiti River Bridge lands on the Whangaparāoa side of the river.  

The HRD has a 20 metre maximum drill height, which is very high!

Rock bolts and crest pins are used to stabilise and reinforce rock faces. The reinforced steel bars are installed into pre-drilled holes and grouted into place. The bolts work by transfering loads from the exterior of the wall to the load bearing solid rock behind. This 'knits' unstable sections of rock together, preventing movement.

View of soil site facing north

Managing excess earth

Along the project alignment we have 23 fills and 24 cuttings. That's 1.3 million cubic metres of earthworks! We've excavated around 800,000 cubic metres to date, with the majority being placed in the fill sites along the route. 

If you have driven south along East Coast Road or State Highway 1, you may have noticed some works south of the future overbridge. We are placing excess earth here. This more efficient use of resources is better for the environment as we are not having to truck it to landfill.

Northern maintenance notifications are going digital

Do you regularly travel north of Johnstone Hill Tunnels? Notifications for maintenance activities on our northern state highway network are moving to digital.

You can sign up for email updates by clicking here, or check out the flyer below.

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.