Queenstown Lakes District councillor Niki Gladding, who first revealed the council was considering the move, said she was aware national water security lobby group Aotearoa Water Action, of which she was a member, was considering taking such action.
Any prosecution of the council could cost the district’s ratepayers a "fortune", Ms Gladding said.
"There’s been no legal advice, no evidence of an emergency and no evidence of the options assessed," she said.
The heightened risk of bird strike at nearby Queenstown Airport from ponding in the Shotover wastewater treatment plant’s failing disposal field was being used as a "convenient solution" for other problems, she said.
An assessment of alternative actions, such as placing bird netting over the disposal field, had not been presented to councillors, she said.
She suspected council staff had been talking to government officials about the issue.
"I think they're hoping the rules change, and by the time this gets consented, it’ll be easy to get a direct discharge to water.
"That's a really dangerous game to play."
Speaking to media yesterday, council property and infrastructure general manager Tony Avery confirmed it would invoke "emergency provisions" in the Resource Management Act to begin directly discharging about 12,000cum of treated effluent into the river each day.
The council was facing "ongoing non-compliance" with its resource consent for the disposal field, and the Queenstown Airport Corporation had asked it to take "urgent action" to address the aviation safety issue.
The council was taking "responsible steps" to deal with the situation, Mr Avery said.
The organiser of a protest near the treatment plant yesterday said she was "thrilled" by the turnout of about 100 people and response from passing motorists, but expected the council to go ahead with its plans anyway.
However, Queenstown resident Nikki Macfarlane, who said it was the first protest she had been involved with, let alone organise, said it had succeeded in raising the issue’s profile.
It had also given those taking part more confidence to speak out on the issue and other council decisions they were concerned about.
"There seems to be total delusion among senior management at the QLDC where they think they're communicating well and think they're being transparent.
"That’s certainly not the perspective of the general community."
Infrastructure operations manager Simon Mason told media yesterday issues with the "rate of soakage" of treated effluent in the disposal field were first noticed in 2021, about two years after it was commissioned.
It had become increasingly "clogged" with suspended solids from the effluent, causing ponding and increasingly frequent spillovers.
The council had concluded expanding or remediating the field were not viable solutions, and since last spring had been "facing the reality the disposal field is not fit for purpose".
A shortlist of options for an alternative disposal system was now being prepared, but whichever was chosen would take an estimated five years to design and build.
One option was building a gravity-fed disposal field on the Frankton Flats, possibly using deep bores, after pumping the treated wastewater up to it.
Mr Mason said the discharge of 12,000cu m daily amounted to 2% of the flow of the Shotover River and 0.2% of the Kawarau River, both at low flow.
Asked if he would let his children swim in the Kawarau River once direct discharge began, he said he was a resident who felt "passion for these rivers".
"I would happily let my children swim there."
Mr Avery said the highly treated wastewater would have no impact on downstream users, and be "undetectable" in the Kawarau River.
Council staff had discussed direct discharge with iwi representatives in the past few days and would continue to talk to them. They were "cautious" about the move.
The Otago Regional Council (ORC) has taken the council to the Environment Court for an enforcement order because of the spillovers of effluent from the disposal field.
Mediation between the councils is continuing, but evidence filed with the court has revealed the regional council became concerned in late 2023 about the "under-treatment" of discharges from the treatment plant itself, and the subsequent failure of an earth wall around the disposal field.
In a statement, ORC chief executive Richard Saunders said any use of emergency provisions under the RMA was a decision for the QLDC.
However, it would have to formally notify the regional council within seven days of beginning the direct discharge, and lodge a resource consent application for the activity within 20 working days.
The regional council continued to monitor the discharge from the treatment plant to ensure it remained of "high quality", Mr Saunders said.
Its weekly testing at eight locations showed the plant had been compliant with its resource consent to date.
The QLDC had to sample the discharge to the disposal field monthly, and supply those results to the regional council.
"They have generally been sampling and supplying results more regularly than this."
The QLDC has allocated $77.5 million through its long-term plan to develop and build a new disposal system.
Once direct discharge begins, it will effectively mean a resumption of the situation before the disposal field was commissioned in 2019, when treated wastewater flowed directly into the Shotover River.
