The Queenstown Lakes District Council's investigation into Wanaka's unpleasant odour continues next week with a re-examination of the decommissioned oxidation ponds on Ballantyne Rd.
The ponds developed an unappealing pong during heavy rainfalls in December and January, sparking complaints from several neighbours.
Now the council's utilities committee has been asked to consider the matter at its meeting in Queenstown on Tuesday.
Neighbour Jo Dippie said the smell had been appalling for all people living in the area.
"We've smelled them out to the end of Ballantyne Rd at the airport.
"That was a few days before Christmas and after new year, when it was just foul . . . One day I just had to leave the house because it was just horrific," Ms Dippie said.
The ponds were made redundant last year after Wanaka's new $19.5 million wastewater treatment plant at Wanaka Airport was commissioned.
Neighbours living there have also been complaining about odours, forcing the council to last week start an engineering review, to be completed in about six weeks time.
QLDC infrastructure services general manager Mark Kunath said yesterday complaints about the Ballantyne Rd ponds had been logged on October 30, December 17, January 6 and January 20.
Other complaints may also have been received, but were not showing up yesterday in a search of the requests for service register.
When the decision was made to decommission the ponds, it was recognised that drying was best done over the summer months, Mr Kunath said.
The ponds had dried out significantly but the unforeseen rainfall reactivated bacteria, which gave rise to the odour, he said.
The council has tried to mitigate the odour by applying lime, which has been partially successful, but affected residents still had concerns.
Options include continuing to stockpile and cover the material (prior to disposal), or removing the material to dry at the Victoria Flats Landfill near Queenstown.
The latter option would cost about $2.8 million.
Mr Kunath said the recommendation was to continue with drying and stockpiling material on site, as well as mitigating odour by applying lime as needed.
It was a low-cost approach in the best interests of the community, and Mr Kunath understood there were now 20 tonnes of lime on site ready to be applied.
"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 Rd area," Mr Kunath said.
He accepted it was not an instant fix for the immediate neighbours, but stockpiling should be completed by March.
It was frustrating for the residents, and the council wanted the best solution for everyone, Mr Kunath said.
"I am confident that there will be a significant improvement in the odour issue through implementing the existing plan," he said.
Once the sludge has dried and the area has been neutralised, the land can 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.
