Nine months to one year - that’s the estimated timeframe for reopening the vital SH25a route to the Coromandel’s east coast communities, after a catastrophic 110m wide road collapse in January.
The Kopu-Hikuai Rd, as it’s locally known, was closed indefinitely by Waka Kotahi NZTA after initial night-time closures prior to when the road dropped and sent earth cascading kilometres deep into the valley.
The nighttime closures followed routine road inspections where a “scary crack” on the highway was flagged.
Waka Kotahi’s regional manager of maintenance and operations Rob Campbell told NZME building a whole new section of road around the back of the massive hole where the road once existed was among the three options being considered.
The others were to build a structure over the 110m wide slip or building back where the road was with a retaining wall structure and filling that with material.
All investigation for these options was occurring simultaneously, as Waka Kotahi continued to test soil at the bottom of the slip.
It required workers to be anchored to stable slopes and abseil down the massive cliff face that was once a section of road.
They needed to establish how to get bigger machinery to the bottom of the slip and drill down for further investigation.
Bore holes carried out by big drill rigs prior to the slip have since disappeared.
Campbell said initial sampling had been done but determining which of the three reinstatement options was best was still a work in progress.
“It’s about which one is going to be the fastest, which will give us the resilience that we need because we don’t want to put something back that will collapse in the next big storm, but speed is critical.
“We understand how critical this is. We believe it’s a nine-month to a year timeframe,” he said.
The cost of work to reinstate SH25a was “in the tens of millions”.
“I’d be suggesting the $40 to $50 million bracket but there’s no science to that, it’s just experience,” said Campbell.
The works would be fully government funded, he said.
An old walking track in native bush above the slip could be the starting point for providing access routes to do testing required as part of the investigation.
Civil Defence Minister Kieran McAnulty did a quick tour of the Coromandel on February 2 and more recently, Transport Minister Michael Wood and Waka Kotahi engineers surveyed the latest damage caused by Cyclone Gabrielle.
The Coromandel went into a State of Emergency on the afternoon of Friday February 3 during Cyclone Gabrielle, with the risk of saturated soils moving at any time and causing slips on roads or threatening people and property.
The management of SH25a prevented any deaths or injury, Campbell said.
He said inspectors routinely checked the roading network and immediately alerted Geotech engineers to investigate.
The road was closed overnight to keep drivers safe, so inspectors could watch for warnings of danger such as vegetation that may have moved.
“Those subtle movements are warning signs and in the daylight you can see them,” he said. “We’re talking about being able to see down a big cliff. It’s a long way down and you can’t shine lights on it and expect to see, and we need to be able to make that early call.”
Multiple teams of roading contractors have worked through stormy nights and been cut off from their own families as they managed slips, cracks and vegetation that’s left Coromandel communities isolated numerous times in the last six weeks.
Geotech engineers described having hundreds of sites to investigate around the Peninsula with Gabrielle adding more than 50 new sites.
In a breakfast hosted to thank them, they shared stories of standing at the base of slip faces “that didn’t look good” and ordering in monsoon buckets by helicopter to sluice slip faces and prevent slips.
Remedial work is ongoing on many sections of SH25 and SH2 through the Karangahake Gorge which is now the fastest alternative for townships in Tairua, Pauanui and Hikuai.
Pauanui man Storm Waters, director of Storms Contracting, has a team moving tonnes of earth from the landslips. The local team had been verbally assaulted by people “who they literally drink beer with at the pub”, said Ben Buttimore, contract manager at Higgins - the lead contractor on the ground.
“At one point we had to get police there, people were losing their minds. But it’s the local knowledge that Storm’s team bring to us that enable us to be successful in these operations.”
Buttimore said the TTM crews who are often the last out in the pelting rain, and then stuck away from their families, were also getting abused by impatient motorists.
“Every time that a car comes through on a closure site like that is an absolute minimum of three minutes that the excavator isn’t working. These are really narrow roads. These are areas where you are effectively cutting an open roofed tunnel through the slips and it only takes five minutes to load a truck.
“Every time somebody wants to go through, that’s a truck that doesn’t move.
“We just need people to exercise patience, in the same way that maybe this weekend isn’t the one to bring your 20 feet game boat up the coast because the marlin are running off Mercury Bay. Essential travel really should be treated as that.”
Waka Kotahi warns that with longer-term recovery works such as slip repairs ahead, Coromandel road users should be prepared for disrupted travel for some time and should only do essential travel.
The council is treading a fine line in communicating the need for people to travel with caution and reduce unnecessary trips while also supporting Coromandel businesses, which are reliant on holidaymakers and bach owners.
In early February, mayor Len Salt promoted a Destination Coromandel campaign over the month to encourage traffic through Thames, along the Thames Coast and up to Coromandel Town and also promote the State Highway 25 southern entrance from Waihi through to Whangamatā, and up to Tairua and Pauanui.
He said the Government ministers he’d dealt with were incredibly proactive and he acknowledged Cyclone Gabrielle had delivered a harder blow to other parts of the country.
But in addition to fixing SH25a, the council needed a 100 per cent subsidy to help fix the local roads that were now under pressure, since Thames-Coromandel had a ratepayer base of just 32,000.
“As soon as SH25a shut down, our local roads get state highway traffic that they were never designed for,” he said.
“The maximum subsidy we can get for reinstatement of local roads after a certain number of weather and storm events is 71 per cent. We reached that maximum and we’ve had six extreme weather events since then. We’ve still got the rest of the financial year to go.
State Highway 25A or the Kopu-Hikuai Rd was officially opened on March 23, 1967, and changed the lives of those travelling across the Peninsula.
in 1958 work began on a route up the Kirikiri Stream Valley. It started at the Hikuai end and was followed by construction on the Kopu end in 1960.
Construction workers grappled with soil that was challenging to build on, tricky access on steep slopes and dense bush along with heavy rainfall which created slips and mudslides.
Millions of tonnes of earth were moved and by the time it was finished in 1967 the highway included seven bridges and had cost more than a million pounds to build.
Eventually in 1973, the road was sealed.
It is the university's second-highest allocation from the Marsden Fund.