Kererū Gorge Culvert

The anticipated timeframe as at early March 2024 is:

Enabling works (Feb-March)

Construction (March-December), which will include:

• Ground improvements
• Pile and pile cap installation
• Foundation installation
• Arch construction
• Fill over the arch and headwall construction
• Pavement construction and barrier installation
• Signage, road marking
• Final touches

This timeframe will be further refined once the contractor is engaged and will be dependent on the impact of weather events or other unforeseen circumstances.

Regular updates will be provided to the community via newsletter and Facebook.

Prior to the cyclone the culvert carrying the Whanaukini Stream under Kereru Road was a 1.5m diameter pipe culvert. Cyclone Gabrielle caused catastrophic damage. 50m of road embankment were lost and water eroded the level of the stream in the gully by 8m, so there is now a gully approximately 18m deep.

The time and expense of constructing any interim solution at this site would be similar to that required for a permanent solution, and so a temporary solution was ruled out. Work has been carrying on with urgency to investigate solutions, secure funding and work to get construction underway as soon as possible. While we understand some use of private land has happened as a bypass route, Council is not able to formalise this as a road suitable for public use.

In total, the full programme of recovery work will be phased over 7-10 years at a cost of $800 million. Kereru Gorge is one of the first projects programmed and construction is intended to begin in March 2024.

Investigation into an interim solution found that the time and expense would be similar to a permanent solution, and so a temporary solution was ruled out.  An alignment across private land was considered as one of five options.

Work has been carrying on with urgency to investigate solutions, secure funding and work to get construction underway as soon as possible.  We understand the impact on community, and so construction of a permanent solution here is in the first tranche of construction for cyclone recovery.  In total, the full programme of recovery work will be phased over 7-10 years at a cost of $800 million.  Kereru Gorge is one of the first projects programmed and construction is intended to begin in March 2024. 

Any alternative alignment route would need to go through a full feasibility study with Waka Kotahi which could result in the new alignment being deemed uneconomic. There is no  guarantee that Waka Kotahi would fund this. It is possible that reopening Kereru Road at all could be deemed uneconomic. Additionally, even if approved and subsidised, such a project would have a longer timeline than the proposed solution.

While we understand some use of private land has happened as a bypass route, Council is not able to formalise this as a road suitable for public use.

The centreline radius of the bend will be approximately the same as the existing, but the overall road width will increase from ~6.0m width to 11.0m (2 x 4m lanes + 2 x 1.5m shoulders). The horizontal and vertical curvature and superelevation has been designed to meet current best practice for a road of this type.  

The use of helicopters was considered early-on in the design process, but during Stantec’s research into this, the lifting capacity of the largest helicopter readily available in New Zealand (the Sikorsky UH60 Black Hawk helicopter, with a total external load lifting capacity of 3.6 tonnes and owned by Kahu NZ) was deemed insufficient. To the best of Stantec’s knowledge a sky crane suitable for this project is not readily available in NZ.

Council has engaged Fulton Hogan as our contractor for the enabling works. On 28 March, Fulton Hogan were also engaged for the first portion of the Kererū Gorge rebuild. 

The destroyed culvert had a 1.5m diameter and a cross-sectional area of 1.8m2. The proposed culvert has a single span of 15.5m, a rise of 9m and a cross-sectional waterway area of 113m2. This sizing far exceeds the ‘100-year + climate change’ flows required by the New Zealand Bridge Manual. In fact, the sizing of the culvert is such that it even exceeds the ‘1000-year + climate change’ flood flows by a factor of two. Due to the considerable oversizing of the culvert the probability of the culvert blocking due to flood debris accumulation is considered very low.

From a maintenance perspective, the new structure, due to its increased waterway area, will be re-categorised as a bridge or major culvert and will require structural inspections every two years by Council.

The design team has estimated 10 days risk component within the construction section of programme.  Once a contractor is on board the construction programme will be better detailed. 

The culvert is expected to be received the end of June/early July. Payment has already been made and manufacturing will follow. The culvert itself cannot be manufactured in New Zealand and has to come from overseas (Australia).

Two bridge options were discussed at the meeting on 26 February:

A. Option 3: Approx. 50m long 3-span bridge at the current site, estimated cost $7.9m and mitigating factors included:

• Large crane not viable at this site
• Tight horizontal radius and sag curve problematic for bridge design
• Extensive slope stabilisation required
• 6% superelevation

B. Other permanent option considered - A longer multi-span bridge (Estimated $30m total w 50% contingency) downstream. Connects the two straight sections of Kererū Road bypassing the ‘u-bend’ altogether.   This option was discounted because:

• Cost prohibitive due to the size of span being 4x that of option 3 (above) and possibility of NZTA not funding it
• Time prohibitive due to private land aquisition negotiations and being extremely hard to construct
• The piers required for the bridge may collect debris, putting the bridge at risk during future flood events

Kereru Gorge is being funded by Crown Infrastructure Partners (CIP) under the cyclone recovery programme at a 100% subsidy rate. This 100% funding comes from a cyclone recovery projects funding pool across HDC.  Additional spend here increases the total rates requirement and/or the time to complete the whole recovery programme. HDC are seeking to make the most efficient use of this Crown support.

Not significantly. It is currently expected that access to the construction site will bepredominantlyfrom the Maraekakaho side of the gorge. 

Road safety improvements have been programmed and installation is expected to be completed by mid-March. This will include installation of edge marker posts and curve warning signs where needed along the full length of Salisbury Road. 

Maintenance of Salisbury Road 

The road will be graded each fortnight and rolled after each grading. The road will continue to be monitored to ensure it is kept in the best  condition possible.

We ask the community, if they notice any maintenance issues to report it online or call (06) 871 5000 so that a contractor can be allocated to this work straight away. 

The chip seal has broken down at one location and we are looking at possible solutions to address this. This will likely be asphalting, which will be done as soon as possible 

An advisory notice will be issued to trucking companies and signage installed advising vehicles about maximum recommended lengths.

In the year prior to the cyclone $17,277 (53% subsidised) was spent on the  maintenance of Salisbury Road. The cost of the cyclone emergency response work was $1,200,982 (93% subsidised) and since then a further $413,205 (53% subsidised) has been spent on maintenance and resealing. 

In order for maintenance of a specific site to be clearly identified and contractors assigned, we ask the community to call (06) 871 5000 or report via the Fix-It form on the HDC website. This will enable jobs to be logged and tracked.

Works at Kereru Gorge and at the Olrig Bridge 411 are not interconnected. Olrig bridge 411 is suitable for overweight vehicles up to 53 tonnes when travelling under an overweight permit. It is a legal requirement for all hauliers to follow any restrictions imposed by a permit. With the current weight limit we do not anticipate Olrig Bridge impacting the works at Kereru Gorge.

On the roading recovery section of the Hastings District Council website, there is a dedicated project page for the Kererū Road 3rd Gorge Culvert rebuild. Progress and milestones will be kept up to date here.

The presentation from the community meeting held on Monday 26 February and FAQs are also available on this webpage.

Hastings District Council do support Central Hawke's Bay District Council (CHBDC) with the grading of Guavas Road when requested.

All road closures appear on the Hastings District Council website. In the immediate aftermath of Cyclone Gabrielle emergency services and transportation companies were advised via newsletter that there were multiple road closures across the district and to refer to this webpage. Kererū Road Gorge has appeared as being closed for 12 months now and it is signposted on Kererū Road itself. Additional and larger signs have also been added.