How safe is your land? Hazards update on the way

19:15, Nov 25 2013

Almost 2000 Nelson property owners are to be notified that their land might be contaminated as the city council takes steps to update its hazards index.

The 1818 properties, mainly in areas where there were once orchards and glasshouses, are among more than 5000 identified in a new study by the council, as being at risk from flooding, liquefaction in a serious earthquake, or possibly contaminated by chemicals once used in orchards and in glasshouses.

The research shows 927 properties in Nelson city would potentially be affected by the Maitai River flooding in a one in 100-year event, and 698 properties are at risk from the dual effects of flooding and contaminated land.

Mayor Rachel Reese said council property and infrastructure was included in the mix, meaning it would be needing to plan ahead for engineering solutions to things like sewerage infrastructure.

Large parts of Nelson now covered in homes, were once used for other activities that come under the Ministry for the Environment's Hazardous Activities and Industries List [HAIL]. The land was once planted in orchards or had glasshouses where chemical sprays were used, or was farmed and had a sheep dip tank or a fuel tank.

The focus of the changes in relation to contaminated land will be on areas still being subdivided, or which are planned to be developed. The levels and types of contaminants would vary in each location, Ms Reese said.


She said the Ministry for the Environment has set the standard for councils to apply, and stressed that the information had not altered the risk from the hazards.

"The actual risk has not increased for anyone - it's no greater now than what it was yesterday, but we are required to do this, and we must make the public aware," she said.

Nelson City Council

The main impact of the new information will be that property files will also be updated to reflect that the research has been done. Interim statements will be attached to LIM reports, which will be finalised next year once feedback is completed with affected property owners.

The council's environmental programmes manager, Chris Ward, said the only noticeable difference would be if an application was lodged for a resource consent or a building consent, at which point the property owner may be required to provide more information.

"The best thing people can do at the moment is make sure they are prepared for any [disaster] event."

The council said this latest work followed that started in July to narrow down the possible location of earthquake fault lines in Nelson city.

All councils were obliged to research and collect new information on hazards so they could help in appropriately managing the risk to people and their property.

"Council is required by law not only to investigate hazards, but to make the research we undertake available to anyone who is affected or interested," Ms Reese said.

Mr Ward said the aim of updating the information was partly to ensure councils were better prepared for any natural disaster. The issue was one for the wider community and not individual property owners alone.

"The council does a lot of research for different purposes, and part of this is about looking to see, for example, what we can do to prevent flooding in future."

Consultants had done modelling on a range of different scenarios related to the impact of the Maitai River flooding in a significant event, including the Maitai dam being breached and other variables, such as tide levels at the time. They had modelled on the present day situation and also future scenarios, taking into account climate change and possible sea level rise, Mr Ward said.

He said the extreme rain event last April, which caused sudden, severe flooding in parts of Stoke, indicated that the council did not have a good understanding of how every potential hazard might affect different parts of the city. However, research had been commissioned on modelling flows down Saxton Creek, which will be shared with landowners in the area, Mr Ward said.

He said the awareness of risks around liquefaction had been raised since the Canterbury earthquakes.

"We need to know what can happen so we can prepare for any of that eventuality."

He said soil types in Tahunanui made it more prone to possible liquefaction in a large earthquake than in other parts of the city, but he did not think that would be a surprise to many. Mr Ward said liquefaction tended to occur in areas of reclaimed land, or land near coastal areas.

Ms Reese said New Zealand was a country subject to a number of natural hazard risks, and while councils were not in a position to protect every property from every risk, it could take steps to manage risks.

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The Nelson Mail