Work to stabilise all high-priority slips is not expected to be completed for another three years.
Some of the largest and most high-risk landslips from Wellington’s wettest winter on record have cost more than a million dollars each to fix and have permanently altered the capital’s landscape.
More than 1000 slips tumbled down across the capital in the winter of 2022 during persistent rain. July wasparticularly wet, with the region experiencing a 200% increase in average rainfall.
A slip came down on Lennel Rd in Wadestown in 2022.
Stabilisation work on the slip above Lennel Rd in Wadestown was completed in May 2024. Photo / Mark Mitchell
Information released under the Local Government Official Information and Meetings Act shows the most expensive repair was $1.5m. This was to remediate a bank in Horokiwi and reinstate the pavement above it.
The second most expensive slip cost $1.3m. This was to stabilise a bank in Melrose to support a nearby house and restore a shared access path.
A slip came down on to Sutherland Cres in Melrose in 2022. Photo / Traffic Updates Horowhenua Kāpiti
Work to stabilise the Melrose slip was completed in May 2024. Photo / Mark Mitchell
Wellington City Council transport and infrastructure manager Brad Singh said slip repairs were prioritised based on the risk of further slippage and how that would affect property and roads.
The cost varied depending on the landslide size and the material needed to fix it.
For example, a large landslip at Wilton Park only cost $60,000 because the slope could be trimmed and planted to stabilise it.
Singh said the council predominantly funded these slip repairs, but in some instances, private property owners paid for a portion.
A large landslip at Wilton Park cost $60,000 to fix.
Singh empathised with property owners or tenants living near these slips who were worried about the cost or whether it was safe to occupy their homes.
“The most difficult conversations we have had is where we’ve had to tell a property owner that we’ll get to their slip but it’s not a high priority one - it’s not going to happen any time soon.
“For them, it is the highest priority one in Wellington because it’s their property, it’s their home.”
There was also a slip on Tio Tio Rd in Seatoun in 2022. Photo / Georgina Campbell
Repair work on the Tio Tio Rd slip in Seatoun was completed in October last year. Photo / Mark Mitchell
Singh expected it could take another three years to finish fixing the list of high-priority slips.
This timeline could be brought forward depending on what budget is confirmed in the council‘s Long Term Plan later this year.
Construction company Geovert has been contracted by the council for work on several slips.
Geovert Wellington superintendent Jason Wilderink said they were incredibly busy in the aftermath of 2022’s wet winter.
Wilderink said preparing a slip for stabilisation included creating a rope system so technicians could effectively abseil down the slope, assess its condition and remove any loose rocks and vegetation.
Large slips often require anchors to be drilled into the hill face.
Wilderink said drill depths usually ranged from between 20m to 90m.
Wilderink said his team was experts at getting to hard-to-reach places, like the work above Eastern Hutt Rd, which required a drill to be hung off a 100-tonne crane.
The slip on The Terrace in 2022. Photo / Adam Hendricks
Geovert did the work to repair a large slip at 350 The Terrace in Wellington. Photo / Geovert
The finished product on The Terrace. Photo / Mark Mitchell
The concrete that people often see sprayed across hillsides is called shotcrete, Wilderink said.
“It is a specialised concrete mix that is sprayed on to the slope under high pressure like a firefighter’s hose.”
The mix is usually a concrete base with fibres added to make it stronger, he said.
“The big advantage of shotcrete is that we can use it to make a permanent, hard-wearing surface on just about any slope we can get to.”
The slip on State Highway 59 would have crippled the capital had it happened at the start of that year, before Transmission Gully provided an alternative route for traffic, reducing the traffic movements for the road by nearly 20,000 per day.
At the time it was thought the project could cost up to $4m.
The repair and safety works above State Highway 59 took weeks.
Wilderink said it was unfortunate that weather events like the one in 2022 appeared to be becoming more frequent.
“But there are some really smart people and incredible construction techniques that are preparing and proactively working to make New Zealand more resilient.”
Georgina Campbell is a Wellington-based reporter who has a particular interest in local government, transport, and seismic issues. She joined the Herald in 2019 after working as a broadcast journalist.
