First a bridge, then two pipes and now four pipes are being suggested as the best way to transport water across the Mataura River in Gore.
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, Gore district councillors voted to start exploring options to lay pipes under the river and Beca was commissioned to complete a geotechnical investigation into proposed drilling sites.
Councillors were updated on the progress made by the project at the council’s assets and infrastructure committee meeting last Tuesday.
In a report tabled at the meeting, Three Waters assets manager Matt Bayliss said expressions of interest for the drilling component of the project were called for in June and there was only one joint submission from Fulton Hogan and drilling specialists Hadlee and Brunton.
Given the technical complications associated with the job, the companies advised they would only consider undertaking the work under a design-build contract model.
"In brief, the way this is proposed to work is that the council would engage the contractor to undertake the required drilling design work so that the risks and costs can be accurately understood."
When these were known and if the price and level of risk were acceptable to the council, the contractor would then be engaged to undertake the drilling work.
However, if the council decided the cost and/or risk was too high it would have the option of terminating the contract and considering alternative options.
Hadlee and Brunton had reviewed the geotechnical results and had not raised any significant concerns.
The next step in the project was to negotiate a design-build contract with Hadlee and Brunton.
During the discussion, Gore District Mayor Ben Bell said he was glad councillors had decided to drill under the river given the December 31, 2025 deadline Taumata Arowai gave councils to bring drinking water up to the new standard.
"I know it’s highly technical and there’s a long road to go but I’m glad at least we’ve got a shot to meet those regulations."
Cr John Gardyne asked whether there would be one tunnel or two for the pipes and what size the pipes would be.
Three Waters project engineer Terry Trotter said originally two 225mm pipes were proposed but now four pipes of a smaller diameter had been suggested by Hadlee and Brunton.
"[This] would give extra capacity over and above the two pipes ... initially asked for plus it’s reducing their risk."
Cr Neville Phillips said he was concerned if four pipes were laid under the river that would make the project even more risky.
Three Waters manager Aaron Green said four pipes across the river was less risky, which was why it was being considered.
Chief executive Stephen Parry said the project and alternative ways of getting water across the river were "laced with risk".
"There is no kind of cottonwool safe route to get to where we want to."
Mr Bell asked if drilling four channels increased the costs.
Mr Trotter said Hadlee and Brunton had not indicated the cost would be higher.
