Report raises new landfill safety fears

Fears have been raised that Canterbury's $35 million Kate Valley landfill may be unsafe.

Claims are being made that new information still to be publicly released could threaten the future of the North Canterbury site.

Privately-owned gas and oil exploration company Green Gate reports that a test well sunk 500m from the landfill shows the land is unstable and fractured. It also may have active faultlines and is not impermeable contrary to landfill operator Transwaste Canterbury's findings.

If a fault below the landfill moves and ruptures the surface, the multi-layer 3m-thick liner encompassing the waste could be damaged allowing toxic contaminants to leak.

Transwaste, which is jointly owned by Canterbury Waste Services (CWS) and six local Canterbury authorities, is aware of the new concerns.

Transwaste chairman Gill Cox said the concerns were "highly unlikely to have merit".

"Canterbury people can rest assured that Kate Valley landfill has been designed to ensure that it will still be operable even after an earthquake event of a magnitude likely to cripple most other components of the public infrastructure."

Transwaste expected the new data would reinforce seismic evidence showing the landfill was properly designed.

The March 2004 Environment Court decision that approved the landfill accepted evidence from engineering geologist Mark Yetton that rock layers under the site were intact.

Green Gate director Stacey Radford said testing had found traces of hydrocarbons (oil and natural gas) near the surface, believed to have seeped from depth. A test well was sunk in May but the Kate-1 well failed to find oil.

Radford said he then offered the new geological information to Transwaste and Environment Canterbury (ECan) in August, concerned the rock layer under the site was not impermeable.

He said Transwaste was not interested in the information.

"We offered it to them. We were trying to be responsible citizens, but they basically told us to `get stuffed'. They didn't want to know."

He said it appeared the hydrocarbons had been transported, and the only way that could have happened was through broken terrain.

CWS general manager Gareth James said the company retained "100 per cent confidence" in the site's suitability.

"The data from well-drilling in the well location could not possibly show what is under the landfill, as the well was located several hundred metres to the south," he said. "The issue of fractured rock layers under the anticline is irrelevant. The depth of any such layers is well below the confining layers close to the surface that make Kate Valley landfill one of the safest in the world.

"Transwaste will always review any data potentially relevant to the landfill. No-one has a greater interest in making sure it is safe and reliable."

An agreement had been made for Green Gate to release its drilling information to Transwaste a year after if was reported, James said. Green Gate had "verbally offered" a financial interest in the exploration area and the geological data. That was declined because of the existing agreement.

Yetton said Green Gate had drilled down deeper than 1km, beyond the level of concern to Transwaste. Continuing excavation had not found any active faults below the landfill.

- © Fairfax NZ News