Historic landfill sites a risk to rivers and sea

There are fears historic landfill sites like this one in McCormacks Bay could cause an ecological disaster like what occurred at the Fox Glacier landfill last year. Photo: Geoff Sloan

Nine closed landfills across Christchurch filled with "unknown materials" could be vulnerable to releasing waste into rivers and the sea.

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.

The Fox River clean-up in progress. Photo Kristine Logan

City council manager of resource recovery Ross Trotter said the city council will be attempting to identify the "unknown materials" within the sites.

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."

Ross Trotter. Photo: Supplied

Trotter said materials, such as metals, general municipal waste, building waste and industrial wastes, were all commonly disposed of in these landfills up until the establishment of modern regulations.

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.

The city council is planning to spend nearly $1.5 million shoring up the old Bexley landfill to prevent further erosion. Photo: Newsline

Hilton said this was a nationwide issue.

"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.

CITY LANDFILLS POTENTIALLY AT RISK: