Last update: 5 December 2023
How long will it take to fix SH25A Kōpū to Hikuai?
SH25A will reopen by 20 December 2023 – three months earlier than anticipated.
A bridge was chosen to reconnect SH25A, based on the ability to build back better and in the shortest possible time.
Waka Kotahi is acutely aware of the sacrifice locals, businesses and communities are having to make. The inaccessibility, extra travel time and costs, access to healthcare, impacts to freight, businesses, tourism and day-to-day life are front of mind for everyone working on this project.
While a bridge of the type proposed would usually be expected to take 12 to 14 months to construct, Waka Kotahi worked with the contractor to accelerate delivery. The initial intention was to have the route open by the end of March 2024.
Why have we chosen a bridge?
A bridge was selected as it will reconnect the Coromandel Peninsula communities in the shortest time possible, it’s the safest and most resilient option, and work can continue throughout winter.
How much will it cost?
The cost of the bridge construction is expected to be approximately $43 million, under the initial $50 million estimate.
What kind of bridge will be built?
The bridge has been constructed on the same alignment as the existing highway, it will have three spans and be 124 metres long. It will have 2.1m deep steel beams and these were fabricated in Napier.
Will there be a cycleway on the new bridge?
The design includes 1.5m shoulders for use by cyclists.
Do we have the expertise in New Zealand to get this done?
We have the expertise in New Zealand to construct bridges. There are plenty of examples within the region such as the Kōpū bridge, the structures being constructed as part of the Takitimu North Link project, and Waikato Expressway.
When will we start?
Work on site started in June 2023.
Why aren’t we creating a temporary bypass?
An investigation into a temporary bypass was undertaken and determined to not be viable. Temporary access or quick fixes are not possible – the steep topography requires extensive earthworks and retaining work to form slopes for regular vehicles, or temporary staging across the slip. Ground conditions are so poor even drilling equipment requires a digger to assist when shifting location.
Why did it take three and a half months to decide which option was suitable? Couldn’t we have started sooner?
Immediately following the weather event, the situation was taken very seriously. The site is complicated due to the geography and amount of road surface and earth lost in the slip. Before a decision on a solution wasmade, geotechnical investigations needed to take place, access to site was limited until it was deemed safe, ie the site had stopped moving. The site could not be accessed until 1 February. A dedicated team of professionals were focused on investigating a solution that could be built as quickly as possible.
Did we consider a tunnel?
A tunnel option was discounted early on, due to programme constraints. A tunnel boring machine must be selected and typically bespoke to suit the geological conditions, ie open face or closed face, selection of diameter, method of transporting the spoil etc. A tunnel boring machine typically takes 12 months to be built once the type of machine required is selected. The tunnel option would also require launching shafts and realignment to tie in to the existing state highway.
How big is the slip?
The slip was approximately 110 metres wide.
Why did a slip happen at this location – did you know it was at risk?
The slip happened due to several factors. When the road was constructed, we believe it’s likely they used the material cut from the hillside as the fill for the gully. By today’s standards this material may well be considered unsuitable, although, this is yet to be confirmed.
Weather has a major impact on roads – both the surface and the underlying pavement layers, as well as the ground material further below. Given the significant volume of rain the Coromandel has experienced over the past few months the area has become saturated, which has affected the integrity of the underlying layers.
The site was not a known risk prior to mid-January 2023. We first noticed cracks in the road on 15 January, and the site has progressed from there to what we see today, exacerbated by the weather event on 27 January.
How do we prevent this type of slip from happening again? Better road construction or maintenance?
Slips can happen anywhere, as shown by Geonet data, which suggests there were over 450 landslides in the Coromandel following the weather event on 27 January. While we do have better techniques for managing slope faces now, we don’t have the funding or resource to proactively resolve all potential issues ahead of time.
What about the rest of SH25A, either side of the slip?
A We have taken advantage of the road closure to carry out a programme of work to ensure the whole corridor is up to scratch, safe and more resilient. Work undertaken has included slip clearance and slope stabilisation, more than 20 undersized culverts replaced, side drains repaired and improved, new seal, road markings and signage.
Are there any other areas along SH25 or around the Coromandel being monitored or at risk?
Many locations on the Coromandel Peninsula road network were compromised and are vulnerable following the storm events this year. We have a programme in place to progressively repair these. Works are being prioritised and sequenced to minimise disruption to traffic, particularly over the summer holiday period.
Work is underway at Ruamahunga – traffic will go down to a single lane there until just before Christmas as there will be workers on the slip face above the road.
Ongoing recovery work at several other sites across the peninsula will be worked on this side of Christmas and then work thatwill cause traffic disruption, such as lane closures will be minimised until after Waitangi weekend.
With works at the Coroglen underslip near completion, the next sites to start will be Wharekaho, Pumpkin Hill and Thornton Bay, followed by Kereta Hill and Te Kouma Hill.
How many vehicles on average use SH25A Kōpū to Hikuai road?
At the SH25A Hikuai telemetry site, it suggests approximately 3700 vehicles per day use this road, of those 311 are heavy (8.4%).
What is the alternative route for SH25A Kōpū to Hikuai and what are the travel times?
While SH25A is closed, access to the east coast of the Coromandel is via SH2 Paeroa/Waihi and then SH25 to Whangamatā etc.
SH25A detour map [PDF, 913 KB]
Driving times around the Coromandel(external link)
Why don’t you build a Bailey bridge on SH25A?
A typical Bailey bridge span is approximately 30 metres, and the slip is currently around 110 metres long. If this solution was used, we’d need a number of sections and at least two piers - which would have to go very deep due to the height from the previous road level to the bottom of the valley. While this is a possible solution, it would not be a straightforward installation, and there are trade-offs – such as the time it takes to investigate and design a short-term fix vs impact on the construction programme for the long-term solution.
Can you build a new section of road or tunnel from the helicopter pad through the hills to near the summit?
While there are many possible solutions, there are trade-offs – such as the time it takes to investigate and design a short-term fix vs impact on the construction programme for the long-term solution.
Who is funding the rebuild of SH25A and other flood damaged roads?
Funding for the recovery works has come from the National Land Transport Fund and the Government’s North Island Weather Events Response and Recovery Fund.
Where else on the Coromandel are there slips or roading issues?
Check state highway travel information on our Journey Planner website(external link)
What are you doing for the rest of the Coromandel roads affected by the recent weather events and now part of the SH25A detour?
For people who call the Coromandel home, a functional state highway network in and around the district is vital for daily life and we’d like to reassure you, we’re prioritising our maintenance and repairs. To keep the SH25 network open, the following work is completed or underway:
- Regular monitoring of significant slip sites and geotechnical inspections every two months.
- Prioritising the clearing of drains and culverts.
- Continuing to clear vegetation to maintain a clear space for heavy vehicles.
- Monitoring traffic and truck volumes around the Peninsula.
- Monitoring travel times around the Peninsula so any causes of significant delay are identified and quickly acted on.
- Updated destination signage so visitors find the best way to their destination.
- Continuing to assess the safety and capacity of one-lane bridges and critical intersections.
- Carefully planning of the timing and type of maintenance work to minimise impacts on road users, landowners and communities.
- Implemented safer speed limits in locations along SH25 so they are safe and appropriate while SH25A is closed.
Our priority is safety, the safety of our people, and getting highways open as quickly as possible.
How many one-way bridges are there in the Coromandel?
There are 12 one-way bridges in the Coromandel.
What else is being done to fix the bridge issues in the Coromandel?
There are 12 one-lane bridges in Thames-Coromandel that have condition, capacity or performance defects and issues that may lead to replacement or significant modification over the next 10 years.
The oldest of these is Manaia River Bridge, built in 1912.
Some of these already have business cases underway to restore or replace them; all of them are regularly inspected and monitored to ensure they remain safe.
Waka Kotahi has an active state highway bridge maintenance, strengthening and replacement programme, with safety the number-one priority.
Here’s what’s been done in recent years:
- Hikuai River bridge – Bridge deck replacement was completed late November 2022.
- Waiwawa River bridge – Strengthening work completed 2022.
- Waiomu Stream bridge – Foundation protection construction completed 2021.
- Maukoro bridge – Footpath repairs completed 2021.
- Kereta Hill retaining wall – Repairs completed 2021.
- Ohinemuri River (Mataura) bridge – Repairs completed 2021.
- Cloudburst culvert – Retaining wall repairs completed 2021.
- Grahams Stream footbridge – Cycling and walking footbridge opened November 2021.
Here is what we’re working on right now:
- Pepe Stream bridge – Business case for replacement is completed and approved, and detailed design, consenting and property investigations are underway. The funding is yet to be confirmed, but we are well placed to seek funding for construction in the 2024-27 National Land Transport Programme.
- Onetai River bridge – Replacement project is at detailed design stage, with funding approved under the 2021-24 National Land Transport Programme.
- Kirikiri Stream bridge – Replacement project is currently out for tender, and it’s anticipated work will begin over the summer of 2023-24.
What happens if all roads to Coromandel Town and East Coast beaches are shut down? How will emergency and essential services be accessed?
For short-term closures we will work quickly to restore access to essential services. For longer-term issues we will look at how we can create alternative access – a recent example of this is the temporary road created on State Highway 23 on the road to Raglan, around another slip site.
In these instances, we also work closely with emergency services and essential service providers to ensure supplies and services can be accessed by communities.
What about business owners on the Coromandel Peninsula and transport operators whose businesses have been affected by the road closures?
Waka Kotahi has plans underway to mitigate the impact the closure of SH25A has on the rest of the Coromandel state highway network. We appreciate just how vital it is that access to/from and around the Coromandel is maintained, and that the roads are as resilient as possible.
We will be working closely with Thames Coromandel District Council and Hauraki District Council on this.
What about the annual maintenance programme – will this still be completed?
A weather event of this scale will potentially have an impact on the state highway summer maintenance programme. There’s a significant amount of response work underway, and it will be followed by recovery work. While this is being done, not all planned maintenance activities can be completed in the affected regions. Following the weather events, and the damage assessment is completed, Waka Kotahi will better understand how the maintenance program is affected.
Before Christmas contractors nationally had completed 35% of the renewal programme. This was a greater percentage compared to last season, and Waka Kotahi considered the programme to be on track.
When was SH25A built?
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 Kōpū end in 1960.
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.
SH25A or the Kōpū-Hikuai Road was officially opened on March 23, 1967. In 1973 the road was sealed.
For more information about the history of this vital connection, take a look at the SH25A history.
