Remedial work complete on landfill site uncovered by Rangitīkei River

The landfill closed in 1997.

Around 8000 cubic metres of waste material and soil have been pulled from the ground after erosion exposed an old landfill to the Rangitīkei River.

The exposed face of a long-disused landfill near Hunterville was discovered in 2018 and residents raised the alarm with Rangitīkei District Council.

Central Demolition was recruited to remediate the site.

Managing director Ian Butcher said the first job was to stop any further erosion immediately.

“There were discussions around changing the course of the river but the cheapest and easiest option was to sheet pile in front of the landfill itself,” he said.

“After that was completed, we had time to excavate the whole landfill. A massive amount of stuff came out of there.”

In all, his team excavated around 8000 cubic metres of material using 30-tonne excavators and off-road dump trucks.

River protection measures such as a decanting bund and silt fences had to be put in place before that work could take place, Butcher said.

“We also used a chemical which binds any particulates in the water so they sink to the bottom and we could excavate it out at a later date.

“If it did go into the river it was completely clean.”

Butcher said the soil coming out of the site was stockpiled and tested by Whanganui company WSP.

“That testing highlighted levels of hydrocarbons or any asbestos and we were able to separate that.

“Some had to go directly to Bonny Glen (landfill site near Turakina) but the rest was put through a big screening process to get out all the old car bodies, containers, you name it.”

The remaining fill made its way to a Manawatū District Council sewerage treatment plant in Feilding.

That saved a huge amount of money, Butcher said.

Around 8000 cubic metres of soil and material was removed and tested from the former landfill site.

“Dumping it at Bonny Glen would have probably been around $3 million in tip fees.”

The final part of the project involved planting willow trees at the site to prevent any further erosion.

According to the Rangitīkei District Council, the landfill closed in 1997.

It was once 300m from the river’s edge but over time the river eroded the river bank to the point it impacted the edge of the site.

The land itself is owned by the Crown but the management of the site is the responsibility of the council.

Rangitīkei mayor Andy Watson said it had been an expensive project and an “incredibly environmentally sensitive” one.

“It’s something we had to tick off and do.”

The Chronicle asked for the total cost of the project but a Rangitīkei District Council spokesperson said it was still being worked through and would be “made available soon”.

Other groups involved in the project were Horizons Regional Council, RST Environmental Solutions and Central Environmental, which Butcher is also the director of.

“This was a collaborative approach and we needed to call on the advice and support of all these people,” he said.

“It worked out really well in the end.”

Nothing of any real monetary value was found during the excavation.

“I would have loved to have (found something) but there was nothing - unless you consider tyres valuable,” Butcher said.

“Obviously all the steel and truck motors and bodies were sent to the scrappies (scrap metal dealers).”

He said landfills were usually uncovered when a new construction project was getting under way.

“Quite often, they are just buried and forgotten.

“Previous to this, we did one on the new highway at Ōtaki. That had a huge amount of asbestos in it but fortunately, the Pūtōrino Rd one didn’t have any.

“In terms of contamination level, it was pretty low. There was still a huge amount of plastic though.”