Outspoken councillor Niki Gladding said the discharge plan was a "done deal" when presented to councillors at a confidential briefing on March 20, but it was clear council management remained unsure of the legal position.
Her comments come after contradictory statements from the council and the airport company about whether the former asked for the letter to be sent.
The letter, dated March 25, demands the council take "immediate steps" to address increased bird strike risk caused by ponding on the Shotover wastewater treatment plant’s failing disposal field.
It followed a March 19 meeting at which the issue was discussed, in a late addition to the agenda, by Queenstown Airport Corporation chairman Simon Flood, chief executive Glen Sowry, Mayor Glyn Lewers and chief executive Mike Theelen.
Mr Sowry said this week he and Mr Flood told the pair the airport company would be "putting its concerns in writing", and the letter was sent a few days later.
Asked whether the council solicited the letter, he confirmed it was "not sent in response to a request from QLDC".
However, council property and infrastructure general manager Tony Avery said the airport company was asked to "formally confirm their concerns" in writing.
The "formal decision" to proceed with direct discharge was made on March 27, when Mr Theelen signed the emergency provisions order, Mr Avery said.
All discussions up to that point, including the confidential briefing for councillors, were a "direction of travel" only.
However, Cr Gladding said the discharge plan was "crystal clear" and no other options were on the table at the briefing, "even if the legal basis for it and the communication plan had not been fully worked through".
Council management needed something in writing "or it was not going to stand up to challenge".
"Technically they’re insisting the decision wasn’t made until March 27, but effectively they knew which way it was going."
