There was plenty of interest but few fireworks at a meeting about Whanganui's failed wastewater treatment plant on Thursday night.

About 130 people gathered at Wanganui Racecourse's Eulogy Lounge for the Wanganui Ratepayers' Association-hosted meeting, which reflected unease at the Whanganui District Council's March 9 resolution to build a new treatment plant at an estimated cost of $41 million.

Speakers at the meeting were former council civil engineer Colin Hovey and former chairman of Friends of the Shoreline Allan Wrigglesworth.

There was also a Q&A panel with Whanganui Mayor Annette Main, deputy mayor Hamish McDouall and Nic Peet from Horizons Regional Council.


The meeting was notable for its lack of fiery rhetoric. The only interjection was a brief one from council candidate Craig "Frog" Falconer, who turned up to the meeting with bottles of alcohol sticking out of his pockets.

Ratepayers Association president Graham Adams gave a brief speech at the start of the meeting, which included placing a bag of manure - which he said had been made of material from the New Plymouth wastewater treatment plant - at the front of the stage.

"This is to set the tone of the meeting," Mr Adams said.

The bulk of the two-hour meeting was given over to a talk by Mr Hovey, who explained in detail the design of the wastewater treatment plant and his understanding of why it failed.

The heart of the matter, Mr Hovey said, was that the 23 tornado aerators stopped working after six months because the United States-based company had tuned them to the wrong frequency.

"[The aerators] basically vibrated apart. And despite the best attempts of the operators to get the propellers re-tuned, they had to be replaced," Mr Hovey said.

"It was a terrible saga. It shouldn't have happened to us, but it did."

He said the original design was "extremely clever". "It should simply be put back as it was."

Mr Wrigglesworth said the plant had proven there was a strong relationship between oxygen and consent compliance.

He said the plant operator, Phil Gilmore, had noted that "clear treated effluent can be achieved when all aerators are operating".

Mr Wrigglesworth said the council commissioned a report in 2011 into the wastewater treatment plant. The report was prepared by Cardno BTO.

Cardno BTO found that only nine of the original aerators were working. Quoting directly from the report, Mr Wrigglesworth said: "Currently a large number of aerators are sitting on the side of the pond, inoperable due to mechanical issues. Within two years, 12 of the 23 aerators had failed and had not been replaced, despite the fact they were under replacement guarantee."

Mr Hovey and Mr Wrigglesworth's views are disputed by the council. Mayor Annette Main said: "Would we love to use the original plant? Of course we would. There's no reason why, if we believed this plant could be resurrected and could work, that we wouldn't do it.

"The reason we are making this decision is that every piece of evidence that we have had from international consultants is that the original plant would never have worked."

At the end of the evening, members of the public were invited to direct questions to the speakers or panel members.

Ross Fallen noted that the new plant had been consented by Horizons. He asked Mr Peet from Horizons what his organisation would think if the council decided to go ahead with a lower-cost design.

"Horizons would be very concerned. It would put the [Whanganui District] council in a tight regulatory spot," Mr Peet said.

Mr Adams told the Wanganui Chronicle he was generally happy with how the meeting went.

"I think the bad weather kept a few people away and I was a bit disappointed by the turnout," Mr Adams said. "But it went well. People were there to listen and to ask some very pertinent questions, which were well answered."

Mr Adams said there was "more to be revealed" about the wastewater treatment plant in the coming months.

He said the association's petition had attracted more than 500 signatures so far. The petition in Four Square stores in Whanganui asks the Whanganui District Council to "urgently initiate an independently chaired public inquiry in to the failure of the wastewater treatment plant. We also request that all expenditure on the proposed new plant be immediately suspended until the outcome of the inquiry is known."

It will be presented to the council on May 31.