He said these cost and time factors meant the design and construction phases at Airport Rd gained an almost unstoppable momentum of their own after critical decision-making mistakes were made by the working group in October 2003 "and by a council that was misinformed in February and November 2004".
From 2003-05 he said the council's management and governance structure was "entrenched and overly trusting". And too much responsibility was delegated to a small number of staff and consultants to develop the concept design.
Nor did council have sufficient in-house engineering expertise to adequately contract manage its consultants on the project. And because staff and consultants enjoyed close and long-standing working relationships, it "mitigated against objectivity being applied to the preferred design".
Mr Domm said the plant was untried and untested anywhere in the world; a hybrid option created entirely by council staff and their consultants.
At a meeting in Wellington in October 2003, council staff and their consultants unilaterally decided to develop the hybrid option instead of evaluating the four shortlisted options as council had previously been advised.
"Council was misinformed of critical decision-making meetings in February and November 2004," he said.
He said council was told in February 2004 that the lagoon design was relatively low risk and based on proven technologies but council was not advised the proposed design was untried and untested "and by definition ... entailed significant risk at that point".
Mr Domm said the incoming council (November 2004) was "seriously misinformed" that an independent peer review had affirmed the lagoon design.
"This advice was incorrect. Council was not adequately advised by staff of the outstanding issues and risks raised by the peer review panel."
He said the peer review panel was shut down prematurely by council technical staff the month before "and before even viewing any detailed design".
"Cost cutting was clearly the key driver in selecting the preferred design and risks were consequently downplayed."
Major shortcomings included construction completed over time and over budget, the original aerators were faulty, trade waste loads were miscalculated and sludge accumulation underestimated.
Mr Domm said after 2008 inadequate advice was given to council about operational problems with the plant, and the replacement aerators were not able to function properly because of the plant's basic design fault.
"The evidence is very strong that significant flaws at critical early stages of council's decision-making process in 2003-04 allowed an untried and untested plant to be constructed, contrary to the historically more risk-averse and sensible approach of the wastewater treatment industry. Significant risks were downplayed."
He said councillors were incorrectly advised at critical decision-making stages and a "crude, low-cost plant ... ultimately failed at a cost to the Whanganui community of $27 million," he said.
"There are those who argue that the failed plant could still be made to work with the expenditure of say another $15 million and that this would be a low-cost solution compared to building a more sophisticated and proven design.
"This is the same false economy that prevailed in 2003-04 resulting in great cost to ratepayers," Mr Domm said.
