Prosecution is being considered for incidents at a faltering wastewater plant at Shotover in Queenstown, although latest testing shows disposal field samples were within allowable limits.
The wastewater plant has had two abatement notices and a total of six infringement notices recorded since 2021. The Otago Regional Council said in a statement yesterday the investigation was ongoing.
The plant, operated by the Queenstown Lakes District Council, came into the spotlight last month after it emerged heavy rain might have led to untreated effluent leaking from it.
Regional council chief executive Richard Saunders said work in and around the plant was the council’s highest priority investigation and was being taken seriously.
Regular discharge testing was taking place and tests in recent months showed the discharge was well treated and complied with the limits set in consent conditions, while the detected limits are well below the contact recreation guidelines.
"As part of ongoing investigations, ORC has sought technical specialist advice around the site since July.
"The regional council continued to investigate discharge issues on site and as this was still an active investigation, we are unable to release explicit details, as this could potentially prejudice any actions we may yet take."
He said the district council needed to go through all the treatment processes involved with the plant’s operation, to see the discharges were better contained and the site was operated as set out in their consent.
Any discharges from the plant would have ended up in the Shotover River delta and the Kawarau River, which was not a popular swimming area due to deep, dangerous currents.
Mr Saunders said the regional council was following the appropriate compliance processes.
"Compliance tools range from abatement notices, infringement notices, enforcement orders and prosecution and all are being considered in line with policy."
On November 20, regional council staff conducted wastewater sampling around the treatment plant’s disposal field.
From 10 samples collected from different locations and tested for the routine set of tests, just one was over the level of detection, and it was close to the detection limit..
The other samples were below detection limits, including all samples taken from the disposal field itself.
Preliminary results for samples taken on December 3 showed any discharge was highly treated. These test results will undergo further analysis and review by staff.
A district council spokesman confirmed the latest test results at the plant reflected the effluent was "highly treated" and did not indicate contamination of either the Kawarau or Shotover Rivers.
"It’s important to note that the disposal field itself is not relied on for treatment of the wastewater, which is conducted in the treatment plant itself. There are currently no issues with how the plant receives and treats wastewater."
The district council has allocated $77.5 million from its long-term plan for a solution.
