Mangamukas still on track to open before Christmas

Anchors being installed on the $160 million State Highway One, Mangamuka, repair job, which should be finished by Christmas

The road over the Mangamukas is still on track to open before Christmas, with some of the heavy machinery used starting to pack up.

NZTA said despite recent storms, work at the gorge continues at pace, with many of the more than 35 slip sites in the final stages of repair.

State Highway 1 over the Mangamuka Gorge in the Far North has been closed twice in recent years.

The 13km stretch of highway was wiped out by a series of 15 slips in a major storm in August 2022, just over a year after the highway reopened after a 12-month closure.

Repair work had been under way for less than six months when a storm in April 2023 resulted in another 20 slips - some of them massive - that covered 1.3km and required repairs.

Then heavy rain on June 19 and 20 threatened to further delay the opening with a massive slip falling down the hill.

Works are going on around the clock to get the job finished as soon as possible.

Piling work is going on around the clock to get SH1 over the Mangamukas opened by Christmas

The two-year job to fully fix SH1 over the gorge has been so extensive and complex that an extra $60 million to finish it was allocated in May’s Budget. That takes the total cost to $160m.

“Over the past month, our teams have been busy with key tasks including installing permanent piles, anchors and capping beams. Running three teams a day where possible means we’re making good progress and overcoming the unique challenges of each site,” Kylie Harris, comms and engagement manager for main contractor CLL said.

“We’re continuing to closely monitor the more recent slip, now referred to as Slip A47. Since the heavy rain on June 19, there has been no significant movement, and our experts are finalising the repair plan. We expect to carry repairs out over the next couple of months. This new slip will not impact us reopening by Christmas this year.”

Contractors are working on all the critical slips and have finished piling on nine of the slips, three of which are complete, and they’ve drilled the final 1050-millimetre diameter piles for slips A1 / A2. Work on the newest slip, slip A47, will start shortly.

Kylie Harris, comms and engagement manager for the project for main contractor CLL, grew up in Kaitāia and is among about 75% of the total workforce on the site who are locals

“The Mangamuka Gorge Slips Repairs Project is making significant headway. Out of the 557 permanent piles required for the project, 329 are substantial 1050mm diameter piles, with drilled depths ranging from 14 to 33 metres. As of now, only five of these large piles remain to be drilled.”

Harris, who grew up in Kaitāia, said July 19 marked a milestone as one of the drilling rigs completed its final pile and was demobilised for transport back to Tāmaki Makaurau.

She said the demobilisation process was complex, involving a nine-axle truck which had to manoeuvre carefully. The truck safely turned around at the Peria Valley Rd intersection before reversing a few kilometres up the gorge, navigating through two active sites where all operations were temporarily halted. The rig was then loaded and commenced its journey south.

One of the drilling rigs that completed its final pile on the Mangamuka repair project recently called into Pamapuria School on the way back to Auckland, much to the delight of the children

“In a heartwarming send-off, the tamariki from Pamapuria School came out to support and farewell the 70-tonne machine, showing their appreciation for the hard work of the entire project team,” Harris said.

She said the massive rig needed to be transported from the northern side due to its size and stopped at the school to show the excited children the rig.

“We parked out the front of the school in their bus bay so the kids could see it.”