Source: Radio New Zealand
A slip on State Highway 2 through the Waioweka Gorge in January. Supplied/NZTA
The Transport Agency (NZTA) has picked a cheaper but less effective option to fix the highway through Waioweka Gorge north of Gisborne that leaves a greater likelihood of closures than a costlier “full” fix.
A newly released business case shows the recommended option would cut closures by 53 percent while a full fix would cut them by 70 percent.
But it would still deliver 83 percent fewer days closed, a 7.5 percent cut in deaths and serious injuries, and halve the cost of freight detours.
State Highway 2 through the 48km-long gorge was still being repaired and only partially open weeks after 40 slips shut it during January’s storms.
It was regularly out of action, costing the economy at least $8 million a day.
In the May 2024 business case – the latest there was – the NZTA board actually “endorsed” the full fix of 83 sites because that would make funding it a bit more certain.
But it instead recommended fixing 58 out of the 83 sites of rockfalls, slips and erosion on what it called a “lifeline route” – those 58 most likely to cut the road.
The other 25 less risky sites to fix would be “separately funded” and not start till 2029.
It suggested this was the quickest path.
“There is urgency to address as many sites as possible quickly and it is recommended that TREC [the project] deliver funding tranches 1 and 2 now,” the report said, “with funding of lower consequence … sites delivered through future operations and maintenance programmes or future capital works programmes.”
The difference in cost was put at $36-43m in 2023 dollars. A much cheaper third option was discarded.
State Highway 2 through the 48km-long gorge is only partially open weeks after 40 slips shut it during January’s storms. Supplied/NZTA
The agency told RNZ it was now reviewing all the sites to see if the report or the costs needed updating.
However, it also said last month that the 2024 business case was “complete and does not need any further work. So it can be utilitised without delay, subject to funding availability”.
The gorge was the country’s only stretch of highway to be rated in the worst at-risk category by a 2020 assessment.
The draft business case was begun in 2022 but storms delivering more damage kept on catching up on it.
“This 2022 business case was substantially complete, including engagement activities and inclusion of iwi in the business case process, but it was not yet submitted for approval at the time Cyclone Gabrielle hit.”
Some locals, saying Tairāwhiti had been suffering too long and too often, had called for the government to look at alternative routes north to Ōpōtiki but it said the clean-up had to come first.
The highway was closed for over three weeks after January’s storms and was on stop-go signals at times during the day and still shut at night as roadworks carry on.
The report said the board endorsed a full fix to ensure that if extra funding came available in future, it could be released for it.
The full fix was to “ensure a resilient level of service for this lifeline route”.
The estimated total costs were put at between $130m and $153m for the recommended option; and between $166m and $196m for the full fix.
The business case cautioned about leaving any risky sites ultimately unfixed.
“If lower risk sites remain unfunded there is potential these sites will deteriorate further and reduce the long-term resilience outcomes of the … investment.
“Without proactive interventions the demand for emergency funding and repairs on SH2 through Waioweka Gorge will continue.”
Of the 25 “maybe” fixes, 13 were of level three risks and 12 of level one and two. Four and five are the worst.
“Confirming full tranche 1 funding and obtaining additional tranche 2&3 funding will remain a high priority for the TREC team.”
The Transport Rebuild East Coast Alliance, or TREC, was set up to rebuild roads after Gabrielle in February 2023.
The business case had envisaged starting in 2024 on 32 projects in tranche one, then tranche two through to 2029, but was overtaken by events.
The full fix had a higher cost-benefit ratio of 1.3 versus 1.2 for what was recommended ($1.20 value back to the wider economy for each dollar spent).
Eight key risks were led off by three “high” ones: That costs would rise, the quake hazard from the Koranga Fault and how sensitive the area was to local iwi and hapu.
“Please note that future investment in the corridor is subject to funding approval,” NZTA told RNZ.
TIMELINE
- 2020 – Waioweka Gorge is officially rated NZ’s riskiest highway
- 2021 – Waka Kotahi preparing a business case for gorge highway
- 2022 – Business case mostly complete
- 2022-24 – Eight extreme weather events
- 2023 – In February, Cyclone Gabrielle damages road
- Later that year Transport Rebuild East Coast (TREC) is set up to rebuild
- 2024 – Business case completed in May
- 2025 – June and September rain closes road
- Five repair projects begin after September
- 2026 – 40 slips shut the highway in January
- By March 2026 it is stop-go past roadworks during the day, closed at night
- Business case is done but unfunded
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– Published by EveningReport.nz and AsiaPacificReport.nz, see: MIL OSI in partnership with Radio New Zealand
