Lower Waitaki Plains residents could wait more than a month before any action is taken to remedy their contaminated water.
Otago Regional Council scientists found E coli spikes 150 (colony forming units - or viable cells - per millilitre) times above the Ministry of Health drinking water standard maximum acceptable level during routine three-monthly checks earlier this year.
On 15 June, the council warned 119 bore owners they should assume their water was contaminated with the bacteria.
The ministry's drinking water standards state that E coli levels should be less than 150 colony forming units per 100 millilitres.
The councillors met last week to discuss changes to an aquifer in an attempt to lower E coli and rising nitrogen levels.
However, council chief executive Sarah Gardner confirmed the decision was put on hold until its next meeting in August so a scientific presentation and further conversations with stakeholders could be held first.
"The first real challenge is that we need to identify the source of the contamination," Ms Gardner said.
An investigation is underway to determine the cause.
"Really until we get that source [of] information, we have to wait," Ms Gardner said.
The number of residents who could not drink their groundwater was unknown, she said.
Several people in the area chose to have individual bore treatment plants so they could drink their water, she said.
Federated Farmers North Otago provincial president Simon Williamson said farmers were taking matters into their own hands.
"It's important for the farmers to know first and foremost what's going in your backyard," Mr Williamson said.
Several farmers were testing their own water for E coli, he said.
Clare Easton and her husband tested three bores on their Lower Waitaki Plains dairy farms within days of receiving their letter.
All three came back clear, Mrs Easton said.
Infection from the bacteria could cause severe stomach cramps, diarrhoea, vomiting, and serious kidney problems in some cases.