Work is progressing at Mangahauini Gorge on State Highway 35 as crews continue strengthening the river control structures that protect SH35 during periods of high river flow.

As work reaches the next phase, the road will be operating under single lane traffic light management from mid-April.

With structural reinforcement now in place, the next phase of the programme involves completing further stabilisation works along the gorge and managing river alignment to reduce future scour (erosion caused by the fast-moving water in this awa).  

From next week through to August, when the project is expected to be completed, the road will operate under single‑lane traffic, controlled by 24/7 traffic lights.

A 30km/h speed restriction will be in place, and delays of up to 5 minutes are likely.

As works progress along the gorge, traffic will switch between the southbound and northbound lanes, but single‑lane access will remain in place for the full duration. 

When traffic shifts to the northbound lane, road users will be on the new road alignment, which is a big milestone for this project.  

These staged changes allow crews to safely access different parts of the embankment and river structures while keeping SH35 open for the community. 

Notes:

Work to build a roughened channel in the riverbed is progressing well.  Around half a kilometre of the riverbed will be shaped and lined with carefully arranged hanbars (large concrete blocks) to help contain the riverbed at its steepest and most destructive section. Around 1,150 hanbars have now been installed with only 50 still to be delivered to site.

This project is expected to be completed in August.

Mangahauini culvert work

Also from next week, 500 metres south of the main Mangahauini site, culvert and drainage work will begin.

A new culvert will be installed across the full width of the road which requires excavation, so traffic will need to share a single lane while construction is underway.

The road will be reduced to one lane under stop/go traffic management Monday-Friday between 7am and 6pm.The works are expected to take 9 weeks to complete, although this may change depending on weather and ground conditions.

A 30km/h speed restriction will be in place, and delays of up to 5 minutes are likely.