The Wanaka Community Board was yesterday surprised to hear the town's estimated $19.5 million Project Pure wastewater disposal system is producing twice the predicted amount of sludge, but was relieved to learn the council does not have to pay extra landfill costs.
Consternation was also expressed over staff enthusiasm for a proposal to spread treated wastewater over 130ha of farm land at the nearby town of Lake Hawea because it would be cheaper than building an in-ground disposal system.
Three separate Queenstown Lakes District Council staff confirmed during the Wanaka Community Board meeting yesterday the newly-commissioned Project Pure plant was producing unexpectedly large quantities of sludge, which the plant contractor is transporting to the Queenstown landfill.
"Seventy-eight tonnes, when it was predicted 30 tonnes. I am not sure if that is a glitch or an ongoing thing," solid waste services manager Stefan Borow told the board yesterday.
Utilities general manager Mark Kunath later clarified, in response to questions from the Otago Daily Times, that a skip containing 6-7 cubic metres of sludge was being trucked from Wanaka Airport's treatment plant to Queenstown every three days.
It had earlier been envisaged the town would produce 6-7 cubic metres of sludge a week.
Responding to board members questions, water services manager Garry McGraw said he did not know whether the extra sludge would significantly increase landfill operating costs, although he agreed there was a substantial cost for the contractor. Nor did he know why there was a discrepancy with the estimates.
Mr Kunath said he believed the council was not paying to dispose of any more than 30 tonnes but would check that.
Cr John S. Wilson said it would also be helpful to go back to the initial information provided to the public about Project Pure and compare the present impact on rates to the amounts initially raised in consultation.
"There will be a lot of new members of the community who might not have that information and others who will have forgotten," Cr Wilson said.
The board's agenda items yesterday caused much mirth during the tea break, with Cr Wilson suggesting Queenstowners had long suspected Wanaka people were "full of it".
But while able to make light of the Upper Clutha district's fertile growth spurt, Cr Wilson is concerned that ratepayers understand the reasons behind high capital and operating costs for infrastructure.
The Otago Regional Council was instrumental in prompting the QLDC to build Project Pure, the QLDC's most expensive infrastructure investment to date, with the goal of stopping the discharge of treated effluent into the Clutha River.
The ORC has now given the council a similar ultimatum about discharges to the Hawea River.
That prompted a staff investigation and scoping report into three disposal methods for Lake Hawea, which Mr McGraw also outlined to the board yesterday.
The scoping report was to be discussed with Lake Hawea Community Association members last night, although costings have not been completed.
The staff have suggested dropping option three (considered the most expensive), pumping Lake Hawea's waste to the Wanaka Project Pure site, in favour of option one (the least expensive) of a pond and irrigation system whereby effluent is sprayed on to farmland.
Option two was a mechanical treatment system with direct infiltration of treated effluent into the ground.
"Option three requires a lot of upgrade work at Project Pure to take the extra capacity. That really makes the extra cost prohibitive for a small community," Mr McGraw said, adding option one was not only the cheapest but the most sustainable and suitable for staged development.
Lake Hawea has about 1500 permanent residents, compared to Wanaka's 5000, and is predicted to grow to 5200 by 2030.
However, several board members were concerned that applying effluent to frozen land during the winter could result in ponding on top of the soil.
There were also concerns about potential odour and what might happen if the land owner no longer agreed to irrigate with the effluent.
In response to board members' questions, Mr McGraw said a centre pivot irrigation system would be used and the effluent would be about 10degC in winter, so it would melt any snow.
He doubted there would be problems with tenure, as all around the world landowners were keen to irrigate with effluent because it made grass grow well.
Mr McGraw agreed there would be no escaping the production of sludge with a pond and irrigation system and a ground dispersal system was probably more prudent.
