THE LATEST HAZARD REPORTS FOR THE ORC: IMPORTANT UPDATE

May 12, 2023

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On Wednesday this week, the ORC councillors were presented with 2 reports about Glenorchy. John G spoke in a personal capacity at the public forum.

The first report is called the Damwatch Report, which is all about flooding hazards, didn’t contain much new stuff - it highlighted risks to the Rees bridge abutments - and it turns out it was just a report that reviewed all the previous reports! It is a good read into the history of everything though. It pretty much dismissed anything practical for the Kinloch Road, which JG naturally disagreed with, and Councillors agreed to note the Geosolve report from 2016 which recommended what has happened to date as a short to medium term option - ie reactive raising of road and rocks in areas that are attacked by the Dart.

The second was the Tonkin at Taylor report on earthquake risk - liquifaction & lateral spreading. JGs reading is that it effectively writes off half of the town because of the cost of what they say is needed.

The ORC staff were supposed to have undertaken a Social & Economic Impact assessment to inform options going forward but they haven’t, and JG made the point that because they haven't the engineers are deciding for us what is worthwhile or beneficial or not.

Both reports are here - https://www.orc.govt.nz/managing-our-environment/natural-hazards/head-of-lake-wakatipu/investigations-reports-and-presentations

There was a very good discussion at the council meeting - almost 2 hours - and lots of questions and supportive thoughts from the Councillors. Apart from the social & economic impact report, ORC staff are going to produce (because we’ve asked them to do so) a risk assessment. Ie we know what the hazards are, but we need to quantify the risk to life and property so we can work out where to make the most impact.

The ORC aim is that by June next year, they will have worked with us to go through all of this and there will be a set of agreed ways forward for the town. It is then up to everyone else - government, property owners, insurers etc to start implementing these.

There have been 2 ODT news reports about this. However, they are only available to subscribers so the text is below. The first was ahead of the meeting and the second was after the meeting.  

Glenorchy liquefaction risk may threaten insurance.

Residents of an Otago town under threat from the Alpine Fault might struggle to get insurance if not enough is done to address a severe risk of liquefaction.

A report by Tonkin + Taylor, set to be discussed at an Otago Regional Council meeting today, highlights the extent of the risk to Glenorchy from a significant earthquake.

It warns engineering solutions aimed at addressing the liquefaction risk could cost "into the hundreds of millions of dollars" and still not prevent severe damage to parts of the town.

The council previously said liquefaction in the town when the Alpine Fault ruptured could be "comparable or worse than the most affected areas of Christchurch" in the 2010 and 2011 earthquakes and the chance of such an event happening in the next 50 years was "very high".

The town is also under severe threat from flooding and the council is investigating ways to mitigate both risks.

In the report to today’s meeting, Tonkin + Taylor looks at potential engineering options for reducing the risk posed by liquefaction, which range from geotechnical improvements for large land areas to strengthening or retrofitting existing building foundations.

It warned the most expensive option — which involved ground improvement across the wider township — could cost "into the hundreds of millions of dollars" and still not protect some parts of the town from severe liquefaction damage.

This would involve temporarily lifting and possibly relocating existing buildings and constructing new foundations underneath them.

The option of just constructing a strip of deep ground improvement on public land running along the edge of the lake would likely come to "many tens of millions of dollars".

On the other hand, doing little could make it difficult for residents to get insurance.

"At the more robust end of the range, there could be many cases where undertaking the work would be impractical or unaffordable.

"At the less robust end of the range, there could be many cases where new buildings might not meet minimum Building Code requirements for building consent, or where it may become more difficult to obtain insurance because of the high residual risk," the report says.

The report adds to a body of evidence outlining the risk Glenorchy faces from both liquefaction and severe flooding as both the regional council and Queenstown Lakes District Council seek to understand the threats and possible solutions.

A report prepared by Damwatch Engineering into flood mitigation options for the Rees-Dart floodplain areas, which was made public last year, is also being tabled at today’s meeting.

It identified stopbank improvements, planting next to the Rees River, raising floor levels of existing buildings and retreat from highest-risk areas as potential mitigation options.

The regional council is set to carry out further risk assessment work in the coming year and complete an adaptation strategy in the 2021-31 long-term plan period.

Glenorchy report needs ‘balance’.

Alarming reports of "red zones, collapsed houses and cars sinking into the ground" at the head of Lake Wakatipu have prompted concerns the Otago Regional Council could lack regard for community wellbeing.

Councillors yesterday discussed two engineering consultancy assessments of natural hazards in the Glenorchy area, about 50km from the Alpine Fault, as work moved into a new phase of "what can we do about it?"

Glenorchy liquefaction risk may threaten insurance

Glenorchy Community Association chairman John Glover, speaking in a personal capacity at yesterday’s ORC safety and resilience committee, was concerned councillors were being presented a report that assessed the viability, or futility, of maintaining Kinloch Rd without any work done on its value to the community.

Mr Glover noted during the public forum the council was "charging ahead" looking into what it could do in the area when it had not fully considered "what matters most", by completing a social and economic impact assessment.

"It really worries me that the quantification of social impact and the economic impact seems to be less important than the need to state that rocks are expensive, whatever that means.

"It also worries me — quite frankly depresses me — that the ORC chooses to send out a media release about Glenorchy with images of red zones, collapsed houses and cars sinking into the ground whilst pointing out that the best options are impractical and unaffordable and the cheapest may not meet consent requirements.

"I’m not sure that’s how you take a community on a collaborative journey with you."

After the meeting, Mr Glover said there had been a lot of community engagement by the council but things like a risk assessment seemed to be a low priority.

"It’s a piece of the jigsaw that is still missing and we keep on reminding the scientists and the engineers — who clearly love to work in that space of ground engineering and concrete — that there’s more to it than that.

"And we need some information to balance those [engineering solutions] against."

Council operations general manger Dr Gavin Palmer said the council was tasked with identifying natural hazards.

"There is still much to be discussed with communities with regards to risk mitigation," Dr Palmer said.

"ORC does not take its responsibilities lightly, and its goal was to communicate the reports to the community and keep the dialogue going.

"Community meetings are planned where people can voice their views on these reports.

Along with flooding risks faced by the town, a Tonkin + Taylor report said engineering solutions aimed at addressing the liquefaction risk for Glenorchy could cost "into the hundreds of millions of dollars" and still not prevent severe damage to parts of the town.

A council media release before the meeting referred to "sand volcanoes" during an earthquake causing cracks in the land into which cars could fall.

Cr Michael Laws said he felt "very sorry" for people who lived in Glenorchy.

"I don’t think in all my time at the Otago Regional Council I’ve ever been so depressed by a report in my life," Cr Laws said.

Cr Alexa Forbes said the forthcoming social and economic impact assessment was crucial.

"This is really, really big news and really hard for a community to take, and this is a really important piece of work.

"We just can’t say things are affordable or unaffordable until we know the impact of them.

"I understand that it’s really hard to do all these things at once ... but I think that community is feeling pretty singled out."

Dr Palmer said the council was doing the work it could do now.

"Actions for how the big issues are dealt with will actually come out of the [planned] adaptation strategy," he said.

"And that’s going to require engagement with those other organisations to come up with a mutually agreeable action plan for whatever those things look like."

 

 

 

 

 

 

 

 

 

 

 

 

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