Problems at Wānaka’s Project Pure wastewater treatment plant are not comparable to ongoing issues at the Shotover plant, Queenstown Lakes District Council (QLDC) says.

Recent performance issues at the Wānaka plant during upgrade works led to ponding in disposal fields, surface run-off and nitrogen levels exceeding consent limits.

But the upgrades at the facility are now complete and the quality of treated wastewater is starting to improve, QLDC property and infrastructure general manager Tony Avery said.

He said while the performance issue would trigger comparisons to the issues experienced at Shotover wastewater treatment plant, the two disposal solutions were different from each other, and no long-term problems were expected for Wānaka.

“Project Pure’s fields have been operating successfully for approximately 15 years now, have more modest loading rates, and discharge through free-draining soils well above groundwater,” Tony said.

“We are investigating the effects of the recent events on the disposal fields and will keep the community informed as we learn more about any remediation activities required.”

The upgrades at Project Pure which preceded the ponding involved taking one of the older reactors offline for inspection and upgrades while the remaining two reactors continued to function. 

Reactor two was successfully upgraded in July 2025 and Project Pure operated on three reactors for a period to confirm performance before proceeding with reactor one.

However, while upgrading reactor one, higher flows from winter school holidays and heavy rain events placed strain on the facility’s biological treatment process while only two reactors were available, Tony said. 

This led to treated wastewater exceeding the consent requirement for total nitrogen, periods where surface ponding occurred across the facility’s disposal fields, and surface run-off from the site during heavy rain at the end of October.

The performance issues were raised to Otago Regional Council (ORC) immediately, Tony said.

Deputy mayor Quentin Smith said he was “deeply disappointed” by the recent issues at Project Pure.

“While I am confident this doesn’t represent a ‘Project Shotover’ scale issue it does renew the need to look at redundancy and resilience issues at Wānaka,” he told the Wānaka App.

“There is no question that the rates of growth continue to put pressure on our infrastructure and this is a symptom of that.”

Quentin said he was looking at whether the council needs to bring forward the construction of a fourth reactor, expand the disposal areas, or look at temporary emergency storage options. 

Read more: Upper Clutha Ratepayers Unaffected by Queenstown Wastewater Issues

In June QLDC was ordered to pay at least $235,000 in costs after the Shotover Wastewater Treatment Plant failed, resulting in consistent ponding and treated wastewater being discharged into the river. 

“As governors, we will need to review what has happened [in Wānaka] to fully understand why and especially in the context of regulatory compliance failures at Shotover and Hāwea treatment plants,” mayor John Glover said this week.

PHOTO: Supplied