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The historic landfills are located in low-lying coastal areas or near rivers, leaving them at risk of being compromised by flooding, erosion, storm surge and increased river flows.
They are also unsealed and unlined, and fail to meet modern standards.
In addition to the nine across the city, there are also six landfills that pose a similar risk on Banks Peninsula.
Christchurch City Council is currently investigating and monitoring the sites.
A number of the sites are located around the Avon Heathcote Estuary.
Avon Heathcote Estuary Ihutai Trust manager Tanya Jenkins is worried they could lead to a similar disaster to what happened at Fox Glacier. In March last year, an old landfill site burst open following torrential rain and flooding, littering the Fox River and coastline with rubbish.
"All it takes is a major storm and continuing erosion and we could potentially see a situation similar to Fox Glacier,” Jenkins said.
He said it was part of the city council’s ongoing management and monitoring strategy.
It would also prioritise projects to mitigate the impacts of climate change on the old landfills.
Trotter said the excavation of the at-risk landfills and disposal of them into modern landfills is a possibility and this would be assessed on a case by case basis. He added that the costs of this approach is likely to be “significant”.
He explained how historic landfill practices have given rise to the situation.
"These sites were not lined with a barrier liner or capped with an engineered layer as would be expected today,” he said.
"This means that waste materials deposited in these landfills was not managed with modern standards and could therefore be more vulnerable to release of contaminants into the environment."
In these situations, hazardous substances like asbestos can also be an issue, he said.
The 15 potentially at risk sites include the old Bexley Landfill, which is set to have nearly $1.5 million spent on it to prevent further erosion happening to its shoreline.
University of Otago associate geography professor Mike Hilton said the landfill sites posed a threat to the environment and recreational areas.
"Some of the rubbish dumped could be toxic, like leftover farm chemicals, industrial waste, who knows?
"The Ocean Beach domain landfill in Dunedin, for example, contains asbestos and a range of things you don’t want kiddies walking over,” he said.
"This started to be recognised as a national issue after the Fox Glacier incident last year, where a lot of waste was exposed and spread along the coast,” he said.
Residents on the West Coast are still finding rubbish on beaches after last year's flood ripped open the Fox Glacier landfill.
After the old landfill split open, volunteers, Defence Force staff and DOC workers removed more than 13,000 bags of rubbish, while the Westland District Council temporarily reinforced the landfill with mesh and rocks.
- Owles Tce
- Sandy Point
- Redcliffs Park
- McCormacks Bay East
- McCormacks Bay West
- West Truscotts
- East Truscotts
- Barrys Bay
- Le Bons Bay
- Okains Bay