Critical Brynderwyn Hills work to futureproof the route from extreme weather events is on track despite recent rain. 

New Zealand Transport Agency/ Waka Kotahi (NZTA) is three weeks into its planned two-month closure of the Brynderwyns’ Hills. 

Roading crews have been working around the clock and earlier this week were estimated to have cut about 66,500 m3 of soil, weighing more than 93,000 tonnes. 

The progress on a southern stretch of the State Highway 1 route was recorded in time lapse footage. 

More than 520 staff have been inducted onto the project, including a dedicated kiwi sniffer dog named Pearl, an online NZTA update says. 

Kiwi sniffer dog Pearl with her handler Steve is keeping kiwi safe from roading work being done in the Brynderwyns. Photo / Supplied 

Workers had been clearing vegetation, transporting machinery to various earthworks sites, doing earthworks, and installing permanent piling on two retaining walls. 

A core sampling machine was being used to drill down five metres so engineers could check the strength of the pavement layers and its ability to hold horizontal nails to support the road and walls. 

Soil nails up to 15m long would be used to stabilise slopes. 

A five-tonne skid steer - nicknamed “Racing Snail” - with a broom is being used 12 hours a day to keep the site clear of debris and stop the road becoming slippery in wet weather. 

Detour routes, which cost more than $5.5 million to upgrade ahead of the project, had been effective as vital links between Northland and Auckland. There have been two crashes on the detour routes - one involving a logging truck that toppled and blocked the road, and a collision between two cars. 

The road reopens on March 27 for Easter then closes again on April 3 for further work.