Extra geotech investigation work will add to the cost of the project and delay the decision about whether the Gore District Council will approve drilling under the Mataura River.
A route across the river is needed to pipe water from the Jacobstown wells to the East Gore water treatment station and back.
In May last year, Gore district councillors voted to start exploring options to lay pipes under the river.
Beca was commissioned to complete a geotechnical investigation into proposed drilling sites.
In June a design-build contract was signed between drilling company specialists Hadlee & Brunton and the council.
The design-build contract means the contractors provide a summary of the risk and cost of the build for councillors to consider.
If the price and level of risk are acceptable to the council, the contractor will then be engaged to undertake the drilling work.
A report written by council project engineer Terry Trotter outlining the progress being made in the project was tabled at last week’s assets and infrastructure committee meeting.
The council’s former Three Waters asset manager Matt Bayliss, who has been engaged as a contractor, updated councillors on developments which had happened after the report was written.
Mr Bayliss said Hadlee & Brunton had provided some preliminary details on the proposed drilling work.
The company has requested a further geotech investigation in the area where the drilling rig would be anchored.
The company has a September 27 deadline to provide the design details but with the additional investigation work required, that will not be completed until October.
The project is planned to be completed by August 2025 as Taumata Arowai (water regulator for New Zealand) has given councils until the end of 2025 to meet its new Drinking Water Quality Assurance Rules.
Committee chairman John Gardyne asked if the delay would affect the end finishing date of the project if it went ahead.
Mr Bayliss said it could affect the completion of the project.
Timeframes were important but so was making sure the correct design process was followed, he said.
"As long as we can demonstrate that we’re moving towards compliance and making steady progress, I think Taumata Arowai would be accepting of that."
Other councils throughout the country would also struggle to complete water quality upgrades by the end of 2025, he said.
Councillor Neville Phillips said the project had already used $123,000 of the $946,618 contingency fund for earlier additional investigation work.
He asked if Mr Bayliss knew how much the additional investigation would cost.
Mr Bayliss said he did not.
Councillor Andy Fraser said every time the project came before the committee, a new risk and more cost was identified.
If the geotech investigation found the site for anchoring the drilling rig unsuitable, what options would the council have then, he asked.
"To me there is compounded risks in this."
Mr Bayliss said he believed there was a low risk of the site being unsuitable.
However, the investigation would help the company decide the best way of anchoring the platform.
"I don’t think there’s a high risk of having to completely shift the location of the drill shot."
The investigation could save the council money, Mr Bayliss said.
"If we didn’t do the geotech investigation they would probably have to allow or assume poor conditions and potentially over design the anchoring system."
Two Australian companies had been identified who could complete a peer review of the design.
The review will cost between $10,000 and $15,000 and is expected to take about two weeks.
