Severe weather events this year have caused significant damage to the Tairāwhiti local road network. Almost all of our rural network was closed post cyclones Hale and Gabrielle and 8 bridges were completely destroyed and 54 have significant damage.
The rural network was further impacted by heavy rain in June (the third state of emergency this year for the district) causing more significant land movement.
Our focus is always to reopen roads to residents who are cut off and to get access for heavy freight to support our rural communities. Priority is given to school bus routes, safe access to connect communities and forestry and farm access routes for animal welfare.
We have funding of $68M of which $50M was spent by the end of June. This is 100% funded by the government.
Our estimate of the initial clean-up costs are around $120M. We're still investigating the total cost of repairs to the network - it could range from $465 - $725 million.
How the initial $68 million funding
The $68M will be spent opening or providing temporary access for disconnected communities. This could include alternative access like temporary bridge repairs, ford crossings, using private land for road access and state highway detours.
It also includes clearing slips, removing slash from under bridges, silt clearing, roadside drainage works and tree removal.
We have 5 project work streams
S1: Repair or replacement of 61 bridges
Costs estimated at $140-160M to repair back to normal. Or $255-$320M if we add resilience (revised cost)
All this bridge work could take up to 4 years.
Post Gabrielle, we assessed all 424 bridges in our region and found 61 were either destroyed or had major issues. In the 4 months after the cyclone, staff and contractors have repaired 140 bridge faults including removing wood debris and structural fixes.
8 bridges destroyed - categorised as 'Black' serious damage
We're working with Waka Kotahi on major roading infrastructure replacement. We need to submit a benefits and economic evaluation on each destroyed bridge. This involves looking at alternative options, traffic volumes, detailing benefits of the project and economic costings.
If the evaluations are favourable and we can secure government funding, then the next challenge will be obtaining the remaining costs from ratepayers.
Design, investigation and procurement processes will take at least 12-16 months, then we would have a rolling programme of 2-3 bridges a year, depending on funding. Geotechnical investigations underway at all sites.
Residents have asked about bailey bridges, these are prioritised on a nationwide basis including state highways.
To construct a new bridge could take up to 3-4 years.
| Bridge and road | Comment | Status |
|---|---|---|
| Burgess Bridge, Burgess Rd | Ford crossing being installed for access over summer. A new bridge is subject to funding, but not likely until summer 2028. | Alternative route |
| Hangaroa Bridge, Hangaroa Rd | Temporary engineered crossing solution to be installed in summer 2024. A new bridge is subject to funding, but not likely until summer 2028. | No access |
| Hollywood Bridge, Bushy Knoll Rd | Bailey Bridge installed. A new bridge is subject to funding, but not likely until summer 2026. | Restrictions |
| Grays Bridge, Bruce Rd | Ford crossing installed. A new bridge is subject to funding, but not likely until summer 2026. | Restrictions |
| Mangatai Bridge, Te Kowhai Rd | Ford crossing installed. A new bridge is subject to funding, but not likely until summer 2028. | Restrictions |
| Mata Bridge (Huiarua), Upper Mata Rd | Geotech investigations underway. A new bridge is subject to funding, but not likely until summer 2027 | Alternative route via Tuakau & Ihungia roads |
| Pauariki Bridge, Hikuwai Rd | Ford crossing installed. A new bridge is subject to funding, but not likely until summer 2028 | Restrictions |
| St Ledgers Bridge, Ruakaka Rd | Alternative access via Ruakaka Rd. A new bridge is subject to funding, but not likely until summer 2026 | Restrictions to 3.5T on wet days |
| Table updated 3 October 2023 |
10 bridges with major structural issues - categorised as 'Red' significant damage
These bridges require immediate repairs, due to the risk we could lose them completely in a further flood event.
By September repairs have been completed on Arakihi Bridge, Carlson Bridge on Waikura Rd, Littleworth Bridge on Pehiri Rd, Mangareia Bridge on Walker Rd, Whakoau Bridge on Mata Rd.
| Bridge and road | Comment | Status now |
|---|---|---|
| Awatere Bridge, East Cape Rd | Bailey bridge installed. The permanent fix is programmed for summer 2024. | Open to up to Class 1 traffic. Heavy trucks still need to use the ford crossing. |
| Makarika #2 Bridge | Temp repair done. Abutment fix programmed for summer 2024. | Closed to heavy traffic |
| Mangaheia #4 Bridge Tauwhareparae Rd | Debris removed. Steel plate installed. More work in summer 2024 | Closed to heavy traffic |
| Waikereu Bridge, Riverside Rd | Temp repair done. Design for permanent fix to be completed summer 2024 | Open to all traffic |
| Waitangi Bridge | Designs underway | Restrictions in place |
| Table updated 19 September |
43 bridges with major scouring - categorised as 'Orange' moderate damage
With major scouring around the abutments, work is needed before they become bigger structural issues. There are 20 bridges in the Waipaoa area, 17 in Uawa and 6 in the Hikurangi area.
S2: Tiniroto Road at the Hangaroa Bluffs
Costs estimated at $35 - $50M to repair back to normal. Or $65-$130M if we add resilience (revised cost)
We're looking at all options to fix this but a long term fix could be up to 3 years away,
The road suffered significant damage at the bluffs - 1400m of road was undermined with river protection works partly or fully destroyed. The 2 lane road was scoured away and reduced to less than one lane in parts. It required repairs to the retaining wall structures and rock protection works. The road had reopened to single lane access.
Following the June rain event
A helicopter fly over of the site, engineers discovered tension cracks that could come down on the road without warning.
Geotechnical engineers inspected the bluffs between the 35 - 37km mark. All 3 bluffs were found to present imminent and extreme risk to road users. Extreme injury or death is a probable consequence should road users be impacted by falling material.
Given the unpredictable nature of the hazards identified, concrete barriers have been installed at either end to close it to all traffic.
The road closure will remain in place until adequate remedial or protective measures can be implemented.
For access Hangaora and Tiniroto residents are using the Parikanapa Road bypass.
Parikanapa Road is 4WD vehicles only. Heavy trucks need to contact Council's Journeys team for access.
Light or 2WD vehicles need to drive to Wairoa and then on to the state highway back to Gisborne.
Tiniroto Bluffs reports
June 2023 Tiniroto Road Site Inspection Report by LDE
July 2023 Addendum to the Inspection Report - Risk Mitigation Options and Costs
S3: Drop outs and retaining wall repairs
Costs estimated at $80M-$105M. Or if we add resilience $120 - $255M
Work could take up to 2-3 years to fully complete.
We estimate there's over 250 major drop outs or sections of roads impacted by river erosion across the entire network.
These sites will have signs and road cones to make them safe until we can get engineers and geotechnical assessments completed. Initial site assessments could be completed by August 2023. The more complex issues may not be completed until the end of October 2023.
Waihau Road
In the June, a major landslide washed out part of Waihau Road at the 4km mark. Geotechnical engineers inspected the site where 5m of the road has been lost. They advised this is part of a much larger 110m fault. This section of road will remain closed for some time.
Work starts on a temporary road for residents only. The work will take several weeks and starts at the end of September weather dependent.
Background and advice from engineers for short term remedial options
Engineers consider the site to be a high risk of ongoing movement and cannot rule out a large rapid evacuation failure occurring. Any of the following works may not be able to be completed safely, until there is evidence of the slope movement arresting and soil moisture levels returning to a normal level. They've considered the following options to enable emergency access: new culvert and backfill washout. Attach sock/flume or similar to culvert to protect outlet; road retreat into colluvial slope above the road; combination of retreat and culvert.
They consider the risk of traversing the slip to be significant, and if movement continues any remedial works are unlikely to withstand significant movement, which may prevent vehicle access, especially emergency services.
Long term remedial options
If a wedge type failure mechanism is confirmed, then the risk of evacuation would be considered too high to reestablish
access over the current alignment even during dry conditions.
We're looking at the alternative option to maintain access to Waihau Beach settlement. Advice is that a significant road realignment is required to avoid the landslide. This will take some time to work through.
Waihau Road slip report
27 July updated report - LDE Report on Waihau Road Slip
S4: Silt removal
Cost estimated at $15-20M
It's estimated that there's over 650,000 cubic metres of silt to be removed from drains, slips and roads. This needs to be carted to a disposal sites once the sites are ready to take the material. In places the silt still needs to dry out before it can be removed.
S5: Slash removal
Costs estimated at $130M
We've removed slash from 77 bridges at a cost of $1.7M.
Staff have scoped the cost to remove all the slash in the catchments where bridges have been destroyed or majorly impacted. The risk if this debris is not removed is it may compromise any future bridge repair wok.
Assessments are completed and procurement to remove and dispose of it is being developed.
Landslide dam on Tauwhareparae Road
Update 28 August - the landslide dam on Tauwhareparae Road has been assessed as low to minimal risk of failure.
The dam of water is being actively monitored and inspected, especially after rain. The landslide dam is quite small at 1.2ha and water is freely flowing through it which reduces risk. The gradient on the dam is low, which also reduces the risk of rapid failure. The dam has been assessed as having 26,000m3 of water in it and measures 5m deep and 20m wide.
