14 Mar Civil Defence Work by Fraser Thomas in Nelson
In August 2022 a significant rain event occurred, causing severe flooding across the Nelson, Tasman and Marlborough regions. In response to this significant natural disaster event, our Nelson and Marlborough regional branch manager and senior engineering geologist, Raquel Miller, was engaged by the local Nelson/Tasman Civil Defence team to be part of the first responders’ team, for the response during the state of emergency. As part of the first responders team Fraser Thomas was tasked to carry out assessments across the Nelson and Tasman region, where either red, yellow or white placards were placed on structures or properties, as a result of the impact they had suffered during the rain event.
A major part of Fraser Thomas’s involvement in the Nelson and Tasman regional recovery program, was addressing slope instability issues such as flood damage to structures, minor to major landslides, that either impacted dwellings or local infrastructure, or posed an ongoing risk. Another part of this work was the planning of carrying out urgent remediation of areas impacted or at risk of being impacted in the near future, to assist in reopen the roading network and to allow people to get back into their homes.
In particular, a large landslide occurred on a slope within a residential area, located on the slopes above the Maitai area, where three large trees, including their roots, slid down the slope onto the road below, toppling over, with the upper end of the tree’s resting on the roof of a dwelling downslope of the landside, and the landslide debris also collected a car from a private driveway pushing it across the road where it posed a risk to rolling down onto the dwelling below. A significant amount of mud came down and was blocking the road access. Another hazard identified during the site assessment as that there were five standing trees, which were deemed to be a risk of toppling over during high winds, due to ground instability issues surrounding the slope they were growing on. This landslide closed all access to the multiple properties.
To reopen the road and access to private properties, Raquel Miller from Fraser Thomas was tasked with being the lead geotechnical engineer on behalf of the Civil Defence team, for executing the planning and site remediation of the hazards, to reopen the road access to residents, and to allow people to get back into their homes safely, that were impacted directly by the debris. Part of Raquel’s role was to plan the recovery operation, where she had to work closely with private land owners, Nelson City Council and the Civil Defence team, and manage subcontractors who were both local (Nelson Tree Specialists) and out of town arborists (Tree Tech), a highly skilled earthworks company (Berkett Contracting) and one of New Zealand’s largest commercial helicopters, a Black Hawk from Kahu NZ, to carefully remove the trees, car and debris from the slip area. This was a very complex and high risk operation, which required geotechnical oversight throughout the entire operation, to ensure all personal were safe and the hazards were not going to create further risk to private home owners downslope of the slop area.
Fraser Thomas continues to aid in the region’s recovery effort, through being a part of the Nelson City Councils recovery program. We have worked closely with Nelson City Council and other consultants, to come up with remediation options, where council land has impacted infrastructure or private properties. This has included assessing some very complex landslides, which caused significant damage to houses and infrastructure, during the August event.
