APUSH is being made to instigate a public inquiry into Whanganui's failed wastewater treatment plant.

The call for the inquiry is driven by district councillor Rob Vinsen, who intends to table a notice of motion at a council meeting on May 31.

He wants the inquiry to address the actions taken to try and rectify the original plant, and the need for a new replacement plant estimated to cost $41.5 million.

"If the resolutions are passed, there's three months allowed to conduct the inquiry and present the findings," Mr Vinsen told the Chronicle.


"But the inquiry must be in public and any attempt to put matters behind closed doors should be vigorously opposed."

His motion will be seconded by councillor Rangi Wills.

Mr Vinsen expects any inquiry would need three months before reporting back to a public meeting by August 31.

"It's important this matter is concluded prior to the election run-up in September," he said.

"There will be a cost to this, but the $75,000 in the draft plan for the online voting trial [which has been stopped] will cover it."

He is also launching a petition but has been beaten to the punch by the Ratepayers' Association, which is already circulating one calling on council to "urgently initiate" an independently chaired public inquiry into the failure of the plant. It also calls for all spending on the proposed new plant to be suspended until the inquiry outcome is known.

Ratepayers' Association chairman Graham Adams said the petition would be at Four Square stores in Castlecliff, Whanganui East, Aramoho and St John's Hill, Super Value in Gonville and the Durie Hill dairy. It will also be at the River Traders' market on Saturday morning and at the association's public meeting in the racecourse's Eulogy Lounge at 7pm on May 19. Mr Vinsen said he had asked the council's chief executive, Kym Fell, in March to initiate an inquiry but, as nothing had happened, he had lodged his notice of motion.

"With local body elections in October, it's important the public know the facts around why council felt it needed to abandon the old plant and build a $41.5 million replacement.

"They also need to know what the professional advice was that led council to spend $1 million in legal fees in an action against [plant designer] MWH."

The inquiry should make public all professional advice and previous confidential discussions - that was why his motion included a resolution to get consent from MWH to release all professional advice and the terms of the settlement.

Mr Vinsen said a similar resolution was put in January 2013 by then councillor Michael Laws, seconded by deputy mayor Hamish McDouall. It was lost at the time because the timing wasn't appropriate given pending legal action against MWH.

"There's no reason for further delay. The public will demand complete transparency and independence for this inquiry, so the person/s selected to conduct it must be very credible. If there is any blame to be attributed, it must be identified."