Wanaka oxidation ponds up for discussion

The future management of decommissioned oxidation ponds at Wanaka will be discussed by the Queenstown Lakes District utilities committee on Tuesday, QLDC infrastructure services general manager Mark Kunath said.

“Decommissioning of the ponds began in 2009, having been made redundant by the development of a wastewater treatment plant (Project Pure),” Mr Kunath said.

As the oxidation ponds were decommissioned a drying period had to be undertaken and eventually, once the area was neutralised, the land could be used for other purposes.

“Long term it’s a positive for the community living and working in the vicinity of the ponds but short term the process has proved problematic,” Mr Kunath said.

The ponds had dried significantly however rainfall reactivated bacteria, which in turn gave rise to odour.

“In preparing for this stage of the decommissioning process it was recognised that drying of the sludge was best done over the summer months,” he said.

It was impossible to foresee that the weather in December and early January would bring an unprecedented rainfall.

“We have attempted to mitigate that odour through lime application, which met with some success but given the concerns of affected residents it was appropriate to revisit the existing plan and consider all options,” Mr Kunath said.

The committee would be asked to consider five options which ranged from continuing with the current plan to stockpile and cover the material (prior to disposal), to an option to remove the material to dry at the Victoria Flats Landfill. The latter option carrying an estimated price tag of $2.8 million.

“The recommendation is to continue with the planned drying and stockpiling of the material on site, with a focus on odour mitigation,” Mr Kunath said.

It was accepted that the option was not an instant fix for the immediate neighbours but the stockpiling process was anticipated to be completed by March.

“The committee will want to weigh the cost of a short term fix versus the long term benefits of the pond decommissioning for the Ballantyne Road area,” Mr Kunath said.

The council accepted the process had been frustrating for affected residents.

“We are conscious of coming up with the best possible solution for all parties and I am confident that there will be a significant improvement in the odour issue through implementing the existing plan,” Mr Kunath said.