Source: Radio New Zealand
The erosion on the side of the cliff on the Hutt River. WELLINGTON WATER / SUPPLIED
Continued erosion at a closely-watched cliff means it is now almost touching a main sewer pipe on the Hutt River, forcing authorities into action.
After 15 years monitoring the cliff as it got worse, a $2m project has now begun to protect the pipe that carries all of Upper Hutt’s sewage south.
“We’ve reached a threshold where we’ve said we don’t want it to come any closer to the pipe now,” Wellington Water chief operating officer Charles Barker said.
The cliff had eroded to within about two metres of the pipe and just a few metres from the edge of State Highway Two at the popular Taita Rock swimming spot.
The erosion at the cliff. WELLINGTON WATER / SUPPLIED
The pipe, originally buried over two metres below ground, under the cycleway at the top of the 6-7m-high cliff, was close to being exposed.
A manhole cover for the pipe was just a metre from the edge.
“The risk to the pipe is increasing, but there’s not an imminent risk that over the next year the river is going to be able to wash out that part,” Barker said.
The public “wouldn’t expect us to get to a point where there’s actually an imminent risk that the pipe is hanging by a thread before we took some action”.
A cycleway that runs above the pipe had to be moved three times, taking it closer and closer to the edge of SH2 now just 4-5m away.
An aerial image of Taitā Rock, the river and SH2. WELLINGTON WATER / SUPPLIED
Monitoring since 2010 showed slow erosion, and not big floods, was the threat to the pipe in the first place, but also the cycleway and highway.
Since 2022, the two local city councils, regional council and NZTA had been discussing what to do.
“All of these assets are affected, but while we’ve been trying to figure out how we come to some agreement about what we should do, Wellington Water and the Hutt City and Upper councils have decided that our tolerance for this risk is reduced and we would just like to make sure that our asset, which would be the asset that impacts the quality of the water in the Hutt River, doesn’t fail,” Barker said.
‘No one’s going to thank us if our pipe breaks’
“At the end of the day, we have to take responsibility for our pipe,” Barker said.
“No one’s going to thank us if our pipe breaks and we say that wasn’t our fault. We’re never going to let ourselves be in that position.”
The two local city councils were among those that own Wellington Water, and they were paying the $2m.
Swimming – people like to jump off the rock – would be able to carry on, Barker said.
Engineers were looking at how to protect the pipe short term, such as with mesh or a small retaining wall at the top of the cliff, while a long-term fix was sought.
“We want to buy ourselves enough time to make sure that what we do in that area, which is a really sensitive area and it’s really important to iwi, is appropriate,” Barker said.
“This is one of a number of risks that we have across all our networks and we need to take a prudent risk-based approach of where we place our money to mitigate what risks.
“And what I think is really heartening is that before this risk gets to an imminent point, our councils have funded the remediation.”
The pipe at Taita Rock also carried sewage from Manor Park and about half of Stokes Valley.
Hutt City Council said about $300,000 had been spent so far looking at short and medium-term options, with another $2m for the actual work earmarked for 2026-27.
“Further funding for the long-term solution will become the responsibility of Tiaki Wai, the new council-controlled water service provider” that begins operating in July, it said.
Upper Hutt City Council did not answer a question about exactly how much it would put in now or in future but said its agreement with Lower Hutt was to cover about 30 percent of the costs of maintaining trunk sewer mains.
“Collectively both councils work together to understand in advance what costs an annual basis will be but pragmatically have to reprioritise when the unexpected happens,” chief executive Geoff Swainson said in a statement.
Last year Wellington Water had to fix the sewer main beside SH2 a few kilometres further south at Melling in a $5m project to combat corrosion.
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– Published by EveningReport.nz and AsiaPacificReport.nz, see: MIL OSI in partnership with Radio New Zealand
