source : the age
A council worker has had leg surgery and residents have been warned their homes are too dangerous to return to, as investigations step up into the cause of a landslide that destroyed a Mornington Peninsula house.
The McCrae landslide on Tuesday damaged several properties – including tipping one Penny Lane house over a seaside cliff – and led to 11 homes bring declared uninhabitable.
Authorities have warned residents that they are still at least days away from being permitted to return to their homes. Many residents feel their long-time concerns regarding the area’s instability have been dismissed.
On Wednesday, the council pulled up a section of road around an earlier sinkhole that had opened on nearby Charlesworth Street to see if that was linked to the landslide. Authorities are also looking into whether an old underground water source was accidentally diverted by a landowner when building.
The Age has obtained a recording of a meeting the Mornington Peninsula Shire council held on Wednesday with affected residents, at which authorities said work to identify the source of the landslide was ongoing.
“I don’t know, but at the moment, our best case is that sinkhole that’s there, and then where the water is coming up from,” SES incident controller Mark Daw told the meeting.
“There’s so much investigation still going on, and we’re trying to do this, and trying to give you as many angles as we possibly can.“
Dale Gilliatte, Mornington Peninsula Shire’s manager of community safety, health and compliance, said a council worker who was injured when he leapt off the balcony as the Penny Lane home collapsed had leg surgery on Wednesday and remained in a stable condition.
“We are doing everything we can to support him,” Gilliatte told the meeting.
Daw said he was sorry that residents couldn’t return to their homes to collect any belongings, but it was too risky.
“At the moment, there’s no way that [anyone is] going in,” he said.
“We will organise at some point where you can come in and grab some things.”
Council and emergency services were unable to answer residents’ concerns about whether recent landslides were related to one that hit the area in November 2022 that had left two homes uninhabitable since.
During the meeting, residents expressed frustration at the council, believing not enough action had been taken by the council or South East Water since.
In a statement on Wednesday, Mornington Peninsula Shire Mayor Anthony Marsh said the council could not comment on the likely cause of the landslide until the investigation was complete.
“We are still working with the emergency services and state authorities to secure the site and investigate the circumstances surrounding the landslip,” he said.
On Tuesday, Tim Lloyd, general manager service delivery at South East Water, said: “The cause of the landslide is still undetermined. It would be inappropriate to comment further until this work has been completed.”
Speaking from the site of the landslide shortly after 9am on Wednesday, Daw said the landslip had moved about two millimetres overnight.
While there were fears that rain on Wednesday would trigger a fresh slip, the SES reported no further damage by about 5pm.
Daw said council assessors had tested the hillside after a smaller landslip a week ago, but was surprised at the size of Tuesday’s collapse.
“Unfortunately, what they didn’t think was going to happen, happened,” he said.
Tim Holt, an engineer at A.S. James Geotechnical Engineers who, on behalf of home owners, has assessed other parts of the hill that slipped on Tuesday, said he was not surprised.
“It really was waiting to happen all along there, given the prevailing conditions,” he said.
“And I’m not surprised that there’s no appropriate remediation all along there because no one seems to want to pay for it.
“This whole slope … is on the point of failure.”
Melbourne IT entrepreneur Nick Moran owned the three-storey Penny Lane home – bought for $2.1 million in 2023 – that was destroyed on Tuesday. He said his wife and daughter had narrowly escaped another 30-tonne landslip that damaged the house a week earlier.
“I know everyone goes through stuff and doesn’t necessarily get a positive outcome but on this occasion, I know how bloody lucky we are,” he said in a LinkedIn post about the previous incident.
Professor Ha Bui, the head of civil engineering at Monash University, said these signs highlighted high-risk areas, although exact prediction was tricky.
“On the Mornington Peninsula, recent weather patterns, along with reports of persistent underground water bubbling in the area, point to the possibility of internal erosion – a process that gradually weakens the soil structure due to underground seepage flow, ultimately leading to slope instability and triggering a collapse,” he said.
Professor David Kennedy, an expert in physical geography from Melbourne University, said parts of McCrae and nearby Mount Martha were vulnerable to landslides.
“It’s an old sea cliff that they’ve built on,” he said. “It would probably be 5000 to 6000 years old – that’s why it’s already very steep.”
He said the cliff was cut into granite rock that was old, weathered and broken down to a coarse, unstable sandy clay.
“That recent rain event would definitely have lubricated everything really well,” Kennedy said, referring to a large downpour on Sunday.
On other occasions, Kennedy said, he had seen soak holes – a hole under a property on a slope used to capture rainwater drainage – contribute to landslides.
With Adam Carey
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