The Herald understands Mount Maunganui’s underground water pipe network – including pipes located above where the deadly landslide occurred – will be investigated to see if they were compromised in the lead-up to the recent slip.
The underground water pipes, which are connected to Mauao’s concrete-clad water tower, provide drinking water to the Mount Maunganui area.
Tauranga City Council utilities maps show a maze of underground water pipes and water pumps – some of which are positioned directly above the campsite where the slip came down at 9.31am on January 22 killing six people.
Canterbury University senior lecturer in disaster risk and resilience, Tom Robinson, told the Herald the maunga’s water pipe network “would be of interest” to investigators.
“If you’ve got water pipes, that’s something that people are going to flag and look at,” he told the Herald.
“People would be looking at the state those pipes were in and whether they experienced any damage or were leaking. The presence of pipes itself isn’t a problem, but if those pipes were leaking and adding water into the slope, that’s a problem.”
A photo taken at 7.42am on the day of the landslide shows a small slip at the campground and an exposed blue pipe in the bank above where tents were pitched.
Local Colin McGonagle, who took the photo, told the Herald last week a “mini waterfall” was seen on the campground embankment prior to the deadly landslide.
While there is no evidence from the photo that the blue PVC pipe was leaking, neither emergency nor council staff would say whether it had concerns about the network, or if leaking pipes could have contributed to the amount of water seen by many campers flowing down the bank.
Emergency Management Duty Controller Tom McEntyre told the Herald the focus at the moment remains recovering the missing.
“Once the recovery efforts are completed, we have secured the site and have geotechnical assessments that the landslide area is stable, there will be a process undertaken to examine the events that took place before and during this tragic event,” he said.
When the Herald pressed for confirmation about whether the pipe network would be investigated, a council spokesman told the Herald “all relevant matters” would be considered as part of the council’s independent review into the disaster.
Robinson said while it would be important to consider the pipe network as a possible contributing factor, the record deluge would have been enough on its own to cause the bank to collapse.
“This area’s had so much rainfall, you wouldn’t need these pipes to be leaking to necessarily cause a problem, but that’s for the investigation to find out,” he said.
After the rainfall, multiple slips – including the deadly one at the campground and a large one behind the surf club – came down.
Herald photos also show scars in the earth to the left of Mauao’s water tower.
In December last year, contractors completed work to apply a new waterproof membrane to the water tower’s roof to protect stored water from contaminants.
A notification from Tauranga City Council in September said Downer was undertaking annual water main “scouring” at Mount Maunganui to ensure the pipes were clean and free of defects.
The Herald has asked Downer whether any issues were noted during its latest inspection but is yet to receive a response.
Robinson said Mauao is made of rhyolite rock, which is “particularly prone” to landslides when hit with heavy rain.
“It breaks down really easily when it’s wet. So that’s often a concern and that’s why we see so many landslides across the mountain any time it rains,” he said.
Given how vulnerable the maunga is to landslides, Robinson said the surface of the mountain is often made up of colluvium, which is a mix of loose soil and rock fragments left from other slips.
Michael Morrah is a senior investigative reporter/team leader at the Herald. He won News Journalist of the Year at the 2025 Voyager Media Awards and has twice been named Reporter of the Year at the New Zealand Television Awards. He has been a broadcast journalist for 20 years and joined the Herald’s video team in July 2024.