“The only cost-effective way to disinfect that risk is with UV [ultraviolet] light.”
He said Whanganui’s potable water came from bores at Kai Iwi.
Potable water is water that is safe for human consumption.
From there, it is pumped 15km into town to the main reservoir at Westmere, Venter said.
At a strategy and policy committee extraordinary meeting on March 19, Venter told councillors initial costings “came back lighter than what we need”, with a shortfall of about $1.8m.
The UV upgrade at Westmere is estimated to cost $3.7m.
Venter’s report to the committee said draft changes to the Drinking Water Quality Assurance Rules, released by Taumata Arowai last November, showed a potential way for the council to achieve the correct classification without an active protozoa barrier.
But that required 36 consecutive daily samples plus weekly sampling for the remainder of the year, with zero detections.
“This is an expensive and resource-intensive process requiring significant budget to cover additional staffing and testing requirements.”
Venter told the committee that if UV treatment was not installed, “we risk boil-water notices and not being compliant with our potable water supply”.
“I strongly recommend we do not take that risk.”
He said he presumed the costs of the UV treatment would eventually be transferred to the new council-controlled organisation (CCO) for water services, a partnership with Ruapehu District Council.
The CCO will begin operating from July 1 next year, with Whanganui District Council financing the $6.7m set-up cost.
That debt will also be transferred to the new entity.
Speaking to the Chronicle in 2023, Whanganui’s senior water engineer Dave Rudolph said UV treatment was completed using a pressurised capsule.
“The capsule contains multiple lamps and water flows through the light,” Rudolph said.
“It doesn’t need much contact time. The light gives the water an instant barrier for viruses.”
All elected members, except councillor Kate Joblin, who was absent, voted to add $1.8m to the council’s 2026-27 budget.
Councillor Glenda Brown said Whanganui’s water was “very well looked after”.
“The reason we are doing this is because of new regulations, not that we’ve got anything wrong.
“We are very well-placed with the specialists we have.”
Public consultation on the council’s draft annual plan, which proposes an average 5.8% rates rise, runs from March 31 to May 3.
The final plan must be adopted before July 1.
Mike Tweed is a multimedia journalist at the Whanganui Chronicle. Since starting in March 2020, he has dabbled in everything from sport to music. At present his focus is local government, primarily Whanganui District Council.
