What’s next for the Coromandel’s roads and infrastructure?

A catastrophic landslide resulting from excessive rain has effectively cut off Coromandel visitor and community access via State Highway 25A.

The highway traverses the region from Kopu to Hikuai, and images of the damage inflicted have shocked the public and left many speculating the highway may be impassable for a significant period.

A source close to Thames-Coromandel District Council said many of their peers, who are understood to include roading engineers, have suggested the highway could be out of action for as long as two years. Waka Kotahi NZ Transport Agency spokeswoman Cara Lauder was also at the site last Thursday and told Checkpoint she was “stunned” at the size of the slip. Lauder wasn’t able to say how long it would take to fix, or whether it might be done by Christmas.

Thames-Coromandel District Mayor Len Salt said he was “confident the [central] Government will step in to help” with the recovery project.

Salt visited the site on February 2 with Emergency Management Minister Kieran McAnulty. The minister was briefed on the emergency response by local Civil Defence controller Brian Carter and visited the Emergency Operations Centre in Thames.

An aerial view of the State Highway 25A Kopu to Hikuai road that was washed out near the summit during heavy rain on the Coromandel Peninsula at the end of January.

McAnulty also spoke to iwi and community health leaders, including representatives of iwi-based health provider Te Korowai Hauora o Hauraki, and John McEnteer of the Hauraki Māori Trust Board. They discussed the welfare and community response efforts, particularly those affected in semi-isolated communities of the peninsula.

Speaking with RNZ, Salt said: “By the time we got up there, the crews on site told us that in the previous 24 hours, another 60 or 70m had dropped away. It was quite a revelation to see the extent of that, and it gave us an idea of the scale of what it’s going to take to fix that. While we were there, there was more debris falling off the sides down into the drop at the bottom.”

He was confident the minister and the Government would be stepping in to provide a solution “as soon as possible”, and stressed the area “cannot do without access” to SH25A.

Waka Kotahi experts have been looking at what interim measures can be put in place, said Salt, but with the size of the landslide, there is little room for a bypass cut.

“So we’re looking at, is there a way to get through round the side — do another cut — or do we have to have to go all the way around the bottom and around the coast road, which is a very long diversion?”

Slips at the summit of the State Highway 25A Kopu to Hikuai Road, which was washed away in recent heavy rain.

He was unsure if there could be permanent repairs on the same site or whether a new route around the slip would be needed.

“What I see is something that a bridge would go over — but it would be a big bridge. Whether it can be rebuilt in the same place or whether they have to work with DoC to find alternative routes through there, I don’t know.”

“That was what we were certainly thinking before it did this. If we have to build a massive bridge across it, though — if it does get to that kind of scale, those things do take a bit longer,” she said.

SH25A was not the only area to be adversely affected by the heavy-rain events.

A massive slip smashed into the back of a Coromandel home along State Highway 25 near Thames on February 1, prompting the evacuation of houses. A police spokesperson said the landslip was reported about 8.20 am. Police assisted Civil Defence to evacuate two houses in Thames Coast Rd and one house in Adams Rd in Thornton Bay.

DoC’s Coromandel campsites and huts closed amid a weather emergency, and the Coromandel Refuse Transfer Station flooded and was forced to close.

Excess water in the Koputauaki debris dam catchment meant a controlled release of water was undertaken on Monday, February 6.

Investigations revealed the debris dam contains about 10,000 cubes of water — about as much as a rugby field filled with water 2m deep — posing a risk to the community due to the possibility of a catastrophic failure. Seven homes, the Koputauaki bridge and the community marae are at risk of damage in the event of a dam failure, according to the district council.

A solution intended to relieve the dam by a semi-controlled release of this built-up water was conducted using a helicopter and monsoon bucket to slowly erode a specific area of the debris dam so that trapped water can begin to flow steadily into the Waiwhango River.

As a precautionary measure, 11 homes had to be evacuated beneath the debris dam. Traffic flow was restricted by police. Speaking with RNZ, Salt said there “had been a slip and some of the farmland behind the small settlement of Koputauaki had slumped. It’s dragged some debris and some soil down into a gully, you’ve got some trees and bits of vegetation which have built up and blocked that and you’ve got a buildup of water behind it. As the water built up and there was more rain, there was concern it could let go causing a real danger to the people living below it”, he said.

Despite the evacuations, a district council release said effective multi-agency co-operation had led to the safe completion of the operation.

“Between 2pm and 3pm, Fire and Emergency New Zealand USAR [Urban Search And Rescue] staff oversaw an air operation that involved monsoon buckets full of water from the debris dam being dropped on the debris dam, slowly eroding the earth until water could begin to flow steadily into the Waiwhango River.

An aerial view of the State Highway 25A Kopu to Hikuai road that was washed out near the summit during heavy rain on the Coromandel Peninsula at the end of January.

“Staff from NZ Police, along with council contractors working with Koputauaki community members, kept the area downstream of the dam clear of people and vehicles. Initial assessments indicate the operation has had some success in increasing the flow of water from the debris dam.

“This could only be achieved by working together with other agencies and community groups,” Civil Defence controller Julian Snowball said. “This operation is proof of the power of collaboration.”

Council media spokesman Michael Dobie said the mapping of the extent of water displacement from the operation was ongoing and being monitored. Affected locals were to be kept safe, with a close eye being kept on the effect of any further downpours.

A series of public information meetings is to be hosted by Coromandel MP Scott Simpson to help brief and inform residents, businesses, and road users on the status of the peninsula’s battered roading network.

Simpson said: “Over the last couple of weeks, we have experienced an enormous level of rainfall, which has devastated our region’s transport network and caused a portion of State Highway 25A to collapse. Naturally, we need this main arterial highway reopened as soon as possible, but it is a massive task, and people should be prepared for a lengthy closure.

“Once conditions have stabilised, NZTA will be in a better position to advise their plan and timetable. I’ll be pushing them hard to provide as much information to the public and all road users as soon as they can. To this end, I’ve organised public meetings in Thames, Whangamatā and Whitianga which will include briefings from NZTA and TCDC representatives.”

These will be held on Friday, February 17, from 10am to 11.30am at the Whitianga Town Hall; 1.30pm to 3pm at the Whangamatā Memorial Hall; and from 6pm-7.30pm at the Thames Civic Centre.