Mt Messenger contractors making strides underground and overhead

Contractors have offered a sneak-peak at two of the main features of Te Ara o Te Ata — the Mt Messenger Bypass on State Highway 3 in Taranaki.

A huge road-heading machine is excavating a 235m-long tunnel under the highest point of the maunga and construction of a 125m-long bridge toward the southern end of the project is underway.

The six-kilometre $360 million bypass aims to deliver a safer more resilient route north out of Taranaki, avoiding an existing steep and windy stretch of highway which includes a narrow tunnel.

Waka Kotahi project manager Caleb Perry said the tunnel, which was 65m below the summit, was a key component of the project.

“The tunnel is 235m-long or will be once we’ve broken through and it’s excavated in two headings. What we’re standing in now is the top heading and the final road level will be about 3m below our feet here.

“So, we break through with this top heading out the other side probably in about October/November time this year. Then we bring all the team back to the start, drop down about 3m and carry on and remove what we call the bench.”

Perry said two-lane bridge would be 13m wide by 9m high, giving an over-dimensional traffic envelope of 10m wide and 6m high when an emergency exit passage was installed one side and the lighting and fire safety equipment installed the roof.

By the numbers: Te Ara o Te Ata — the Mt Messenger Bypass

‘You run into some really good characters’

A Tūrangi local, tunnel supervisor Steve Wiley, learned his trade in Australia.

“A typical day underground is pretty much excavation, shotcrete, curing time and excavating again.”

He loved life underground.

“It’s just a challenge. You have challenging days, good days. And it’s the people, you know, you run into some really good characters working underground.”

Carlos Cooper pilots the 110-tonne road-header given the name ‘Hinetūparimaunga’ — the atua of mountains and cliffs — by project partners Ngāti Tama.

“She’s one of the nicest machines you can drive in underground tunnelling. She’s pretty good and particularly with this ground it’s pretty soft, so she’s easy cutting on this particular project.”

He also earned his stripes across the ditch.

“In Australia is where I started. I had a few mates who got into the underground game and I haven’t looked back since.”

The Whanganui man outlined his day.

“Arrive for a briefing at about 6.30am and come up here about 7am. Get into cutting mode and then it will take approximately two, two and a half hours to cut 1.2m and then we’ll much the face out and shotcrete will come in and do their bit and we’ll bolt after that and shotcrete again.”

Cooper was looking forward to emerging at the other end.

“It’s quite a relief one of those special days you can look back on and tell your grandkids yeah you were on that project and it was one to remember.”

He hoped to take a spin on the new highway once it was finished.

“Absolutely, yeah, hopefully I’ll be one of the first.”

Senior project engineer Nick Myers-Kay was in charge of constructing the project’s longest bridge — which actually involved building two bridges.

“Currently we’re standing on the 110m of temporary staging that needs to be constructed ahead of building the permanent bridge which is going to be located out to the right of us here.

“In the background here that’s the first lot of permanent earthworks that the bridge is started on. That’s pretty much where the abutment is going to start. The bridge had raking piers. That keeps the pier foundations out of the wetland.”

He said the temporary bridge — on which a 28-tonne crane was operating — helped minimise damage to the wetland below.

“The immediate challenge is the environment. I’m new to this area I’ve never worked in this region before, so I’m quite amazed at the ruggedness and steepness of the terrain around us.

“It’s obviously very beautiful country here too the bush is just spectacular, so that is obviously a major challenge for us to navigate our way around that.”

It was a point project manager Caleb Perry reinforced.

“This is a really important part of the natural environment here at the headwaters of the Mimi Stream and you can see off to the side the kahikatea swamp forest which is one of the last inland wetlands that we are working as hard as we can to protect.”

That went as far as bending trees out of the way.

“You can see around me there are few trees with tie-downs, ropes around them. We basically put a team of ecologists in a basket hang them from a crane and the try and bend some of those trees out of the way, so the temporary bridge can go through.

“After we’ve built the main structure this temporary bridge won’t be needed anymore, and the team will come back and let the trees bounce back into their natural position.”

The permanent bridge was due to be completed by September 2026.

New Zealand Transport Agency was still embroiled in a Public Works Act wrangle for land required for the project at its northern end.

If that was successful, it would take about four years to complete the bypass.

rnz.co.nz