Two big slips hold up reopening of SH1 through Mangamuka Gorge

3 MinutesBy NZ Trucking magazineJuly 28, 2020

A decision on when to reopen State Highway 1 through the Mangamuka Gorge to local communities will be worked through this week, says NZ Transport Agency Northland system manager Jacqui Hori-Hoult.

“There are two slips on the northern side of the gorge that are causing concern and we want to take a bit more time assessing them and our next steps as to the final repairs required.”

“The weather has been good over the weekend and we‘re pleased to see these slips have stopped moving, so that‘s good progress.”

Hori-Hoult says most of the slips over the road have been cleared though there are places where the road will be reduced to one lane.

“We are looking at when we can open the road to light vehicles from local communities so they can make essential journeys without having to go via a long detour.

“Once it‘s safe to do so, we could let locals through in convoys at set times of day, but the road won‘t be open to trucks and buses for a while.”

For now, SH1 through the Mangamuka Gorge is closed between Victoria Valley Road and Makene Road. SH10 is the detour with motorists advised to allow an extra 20 to 30 minutes for their journey.

Mangamuka Gorge slip.

The biggest slip is near the bottom of the gorge on the northern side. The hillside under the road has fallen away.

The second slip hasn‘t fallen away, but it‘s caused the road to slump significantly. Trees close to the roadside appear to be holding the slip in place for now.

“Both slips are challenging repair jobs so we can‘t just rush into it. We need to have enough safe room for vehicles away from the slip face to be able to travel past the slip,” says Hori-Hoult.

Elsewhere in Northland, road maintenance crews have been tidying up after heavy rain last weekend caused slips and flooding that closed many state highways in the region. 

The estimated cost of storm response and repairs to date is $5.9 million. This does not include the final repair costs for the Mangamuka Gorge that the NZTA is working on.

Repairs are under way on SH14 at Tangiteroria where a slip under the road has reduced it to one lane. Stop/go traffic lights will likely remain in place until the weekend while road crews build up and reseal the road.

Aerial views of the slips keeping SH1 through the Mangamuka Gorge closed for further inspection and assessment.