One of the major slips impacting the road on the northern end of SH1 Mangamuka Gorge

SH1 Mangamuka Gorge - update

Kia ora,

Almost two weeks after the closure of SH1 through Mangamuka Gorge, conditions are still highly unstable, and the ground is still moving. Before any repair work can begin, we need to wait for Maungataniwha to settle to ensure the safety of our workers and avoid further movement hindering any repair work.

Two of the major slips under the road are at either end of the Gorge, meaning we’re unable to safely get the heavy machinery or equipment required for any repair work through at this stage.

It’s not just the land on either side of the state highway that has been impacted. The surrounding Maungataniwha Ranges have also sustained a multitude of landslips which is adding to the instability of the road and surrounding area.

The soil in the area is generally crumbly and unstable to begin with, which makes the stability of the land in the gorge particularly susceptible to the effects of severe weather, including heavier rainstorm events.

Our crews have cut a track through one of the largest landslips to allow access for construction vehicles to pass through

What are we doing now?

The three slips over the road have now mostly been cleared and the debris is being temporarily stockpiled within shoulders and roadsides in the Gorge until it has dried out and the dumpsites have been once again setup.

There has been some concern about moving earth impacted by Kauri dieback disease. The landslips being cleared are on the southern end of the Gorge and only the northern side is impacted by Kauri dieback in some areas. The team will take great care to ensure the protection of biodiversity in the area.

We are working hard to restore access for light vehicles as soon as we can but there are significant issues to resolve.  If we are able to do this, journeys would still be disrupted as we expect there would be multiple one-lane sections requiring traffic management. This would be a shorter-term solution for those who need to cross the Gorge for essential purposes.

Our geotechnical assessments are ongoing, and we anticipate we’ll have more information to share about the next steps forward in the coming weeks.

SH10 Bridges

To ensure the continued movement of vital goods through the region, temporary access for overweight vehicles has been reinstated to use the SH10 Waitangi River Bridge (just north of the Puketona roundabout) while SH1 remains closed through the Mangamuka Gorge. The 50km/h temporary speed limit remains.

The Parapara bridge (6km north of Taipa) is also restricted to a 50km/h.

Restrictions on use of these bridges were put in place earlier this year, following the detection of deterioration during routine inspections. The condition of the bridges is being very closely monitored, with a structural engineer regularly checking them.

We’re working to assess how/if the bridge will be repaired without impacting traffic.

Detour route

SH10 is the official detour route while SH1 Mangamuka Gorge is closed. You can see on the map below the area between Kitchen Road and Makene Road is closed.

The Twin Coast Discovery Route is also open and provides a scenic alternative for light vehicles and campervans.

More information

For more information on the SH1 Mangamuka Gorge slip repairs, contact us at northlandproject@nzta.govt.nz

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