A Whanganui District councillor has got into a verbal stoush with the council's chief executive officer over operational costs of the city's $41 million replacement wastewater treatment plant (WWTP).

Earlier CEO Kym Fell said council staff had refined the operating costs of the Airport Rd plant and this, coupled with low interest rates and foreign exchange movement, had produced a "more favourable" cost than that forecast in the 2015-25 10-Year Plan.

Mr Fell said based on the amended financial forecasts, pan taxes to individual properties will increase about $2.38 per week - which is significantly less than the original forecast of a $4.79 increase. And he said trade waste charges would total about $2.8 million annually rather than the $4.5 million proposed in the 10-Year Plan.

He said the amended figures would still be subject to the council striking the rates and any change would not take effect until the new treatment plant was up and running.


But Councillor Rob Vinsen disputed Mr Fell's figures.

He said Mr Fell had used a figure of $600 per annum as the forecast cost for the residential pan tax in the 2015-25 10-Year Plan.

"In fact, this was a December 2014 forecast cost that was never realistic and led to the cancellation of the contract with Hawkins Construction incurring substantial penalties," Mr Vinsen said.

He said consultants, Cardno BTO, had increased its operating cost forecast 150 per cent to get to the $600pa figure and the process was halted and reviewed by council. That led to a decision to include a $9.3 million sludge dryer in the design and a revised estimate of a residential pan tax of $407pa.

"This figure ($407) is the figure adopted in the amended 10 year Plan and not $600 as quoted by Mr Fell." he said.

"Mr Fell's announcement indicates a decrease in the trade waste levy (from $4.5 million to $2.8 million) and an increase in the pan tax from $407 to $475 a year. The correct headline in the Chronicle should have been "Wastewater costs higher than forecast - wet industries pay less, residents pay more," Mr Vinsen said.

But Mr Fell said the councillor was "challenging the semantics over my media statement".

"Cr Vinsen is now referencing the 2016-2017 Annual Plan amendments consultation document pointing to a figure of $407. Hence he believes that this is in-fact an increase. He is correct in this context, however the statement reflects the journey from the original 10-Year Plan forecasts 2015-2025 to where we are now.

"We are both right but comparing two different timelines within one scenario. I'm illustrating the journey from the original 2015-25 10-Year Plan forecasts to where we are now. Cr Rob is referring to the 2015-2016 amended 10-year Plan consultation document which indicates $407.

"The final figures will continue to be 'shifting-sands' as we refine costs further," Mr Fell said.