Extra week of delays after second slip discovered on south side of Brynderwyn Hills

The first slip caused by this month's severe weather. Photo / Waka Kotahi Transport Agency

A second slip has been unearthed on Brynderwyn Hills amid repairs to damage caused by this month's severe weather.

Waka Kotahi Transport Agency had warned motorists about potential hour-long delays to journeys over the Brynderwyns this week as they fixed a slip on the south side of Brynderwyn Hills at the gateway to Northland.

However, they announced on Thursday that crews had discovered a second slip next to the damaged area.

The agency said the subsidence was revealed to be deeper seated than originally assessed.

"Repairs must be undertaken immediately to avoid further movement and will require an additional week of work."

Traffic management will remain in place from October 3 to October 7 between 6am and 5pm so workers have full visibility to ensure their safety, Waka Kotahi said.

The disruption is predicted to add up to 10 minutes of added travel time and won't apply to the weekend as no work will be carried out on Saturday and Sunday.

The national roading body said completion of the slip repairs was critical to avoid further movement that would impact the lane and require more invasive and lengthy repair work.

During the work, traffic management and a temporary speed limit of 30km/h will be in place between Atlas Quarries at the south side of Brynderwyn Hill and the summit.

Motorists were encouraged to use the suggested alternate route via Kaiwaka Mangawhai Rd to the south of the site and The Braigh in Waipū in the north.