Excavating and dealing with hazardous landfill material under a seaside Dunedin sports field at risk of erosion may cost $50 million, the city’s mayor says.

However, this is the “worst-case scenario” for the historical Kettle Park landfill.

Dunedin Mayor Jules Radich told the Otago Daily Times yesterday the cost depended on the size of the landfill, which operated from about 1900 to the 1950s.

“There may be more.

“It’s quite a bit bigger than expected,” he said.

However, it was possible much of the fill, such as steel and concrete, would be able to be recycled, bringing the cost down considerably.

An aerial view of Kettle Park, a former landfill site in St Kilda that was converted into sportsfields.

“It will be some millions of dollars, but it could be way less than [$50 million].”

He reiterated his support for a groyne at St Clair Beach to provide a buffer in front of the landfill and help prevent erosion.

“It’s a very inexpensive mitigation, and it would buy time,” Radich said.

The next step would be removing the landfill and replacing toxic material with sand.

This follows a report by environmental and engineering consultants Tonkin + Taylor made public last month, providing more information on the landfill’s contents, which include asbestos, old gasworks waste and demolition waste.

Sixty boreholes were made to collect soil samples at the site.

Dunedin Mayor Jules Radich warns more problems could be found at the former landfill site.

“Contaminants including asbestos have been detected in the landfill and capping material at concentrations that present a potential risk to human health,” the report said.

Users of the sports field were unlikely to be at risk, but if the landfill material was disturbed, health and safety controls would be needed

“We note that a more significant potential risk to human health could occur if a large volume of landfill material was exposed.”

Concentrations of copper, lead and zinc were generally raised across all locations tested.

The results indicated the material was probably too hazardous to be dumped elsewhere without some form of pre-treatment to reduce leachability.

A series of storms in the past 10-15 years had eroded the dune system and continued erosion presented risks of exposing the waste itself.

The landfill site was closer to the sea than the council had thought, as well as larger — and it could extend beyond the area tested.

The council will consider its approach to the landfill issue as part of the 2024-34 10-year plan.

- Fiona Ellis, ODT