Ulrich Glasner said Project Pure was operating well, "but the key challenge with the plant currently is it has insufficient redundant capacity to enable one of the reactor tanks to be taken offline for repairs or maintenance".
The plant was originally designed with the expectation tourist shoulder-season flows would be low enough for the plant to operate on just one of its two sequencing batch reactors for short periods, allowing major maintenance work to be carried out, Mr Glasner said.
"However, as the plant approaches its design horizon, and with the district’s shoulder seasons becoming a thing of the past, this is no longer a viable strategy without risking compliance issues," he said.
Wanaka ward councillor Quentin Smith said he "remained uncomfortable without sufficient redundancy".
"We need the upgrade and we needed it yesterday."
Mr Glasner said the design for the next stage of Project Pure, which incorporated a third reactor tank, was about to start, and it would provide the ability to take the existing reactors offline.
Cr Smith said Hawea’s wastewater was also a "high priority" for the council as consent for the existing, problematic wastewater treatment plant would expire in November 2022.
A pipeline of almost 20km has been proposed for the council’s Project Pure treatment plant at Wanaka Airport but Project Pure has to expand before Lake Hawea sewage can be added.
In January this year, council spokesman Jack Barlow told the Otago Daily Times "subject to completion of design in 2020, and construction in 2021" the upgraded plant was "tentatively scheduled" to be operating by the start of 2022.
The ODT contacted Mr Barlow for an update on the timeline for construction of the pipeline from Hawea to Project Pure but did not receive a response.
Otago Regional Council general manager regulatory Richard Saunders said the Hawea wastewater treatment plant continued to be in breach of the existing resource consent.
He said follow-up actions had already been taken by QLDC to remedy the moderate non-compliances identified and a transitional compliance plan was in place.
Part of the transition plan involved monthly water sampling of the Hawea River upstream and downstream of the plant.
"The results of this sampling have been in line with guideline levels and the ORC will continue to monitor these results and work with QLDC to ensure compliance is achieved," Mr Saunders said.
Last month Wanaka Stakeholders Group (the group opposed to the development of Wanaka Airport for commercial jets) claimed the council had agreed to spend an "extra" $2.7 million relocating the proposed expansion of Project Pure on the side furthest from the runway.
Deputy chairman Mark Sinclair said the information had been "buried" in the 2020-21 annual plan but details had come to light in an independent report by Queenstown chartered accountant Bruce Robertson, who carried out a code of conduct inquiry into the actions of Cr Niki Gladding.
Mr Sinclair said the inquiry showed the amount of $2.7 million was "over and above the actual costs of the much-needed additional wastewater processing capacity at Project Pure".
