Westland District Council assets and engineering manager Vivek Goel is being investigated by the Serious Fraud Office.

A Westland council executive under investigation by the Serious Fraud Office (SFO) had plans to build a sewage plant for at least six months before trying to get council to vote on it.

His department spent at least $100,000 of ratepayers' money on the project.

A Stuff investigation earlier this month found Westland District Council (WDC) assets manager Vivek Goel had plans to give a South Auckland cake decorator with no experience in waste management a $7 million contract to build a sewage plant.

Further inquiries show Goel's department spent at least $100,000 of public money on costs such as consultation.

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Floods in March 2016 wiped out Franz Josef's oxidisation ponds, so WDC started looking for solutions to the small town's growing sewage problems.

Goel told both council and residents that the tiny community of 440 people needed the multimillion dollar plant.

He was specific – it had to be a intensive wastewater plant, built on Douglas Dr just out of town, by a contractor he had sourced himself but would not identify.

That contractor was Techno Economic Services, owned solely by South Auckland cake decorator Neha Bubna. Bubna, a recent immigrant from India, specialises in birthday and special occasion cakes.

All councillors from the previous council denied knowing about the existence of Techno Economic Services until details appeared in the media this month.

Goel said the option of oxidisation ponds for Franz Josef, considered much cheaper by the current council with estimates of below $1m, would not get West Coast Regional Council (WCRC) approval.

WCRC told Stuff it did not give advice on the likelihood of consents until the proper paperwork had been submitted.

Goel asked Opus International Consultants to prepare two reports on his plant plan in April or May. Councillors were not informed.

When asked by Stuff if that consultant spending was approved, chief executive Tanya Winter did not respond.

Winter's five-year council contract, which is due to expire in September, has not been renewed. The decision was made by council about the same time the SFO announced it was investigating Goel.

Opus sent Goel a report on May 22, 2016, stating: "Westland District Council intends to site the new Franz Josef wastewater treatment plant on a plot of land on Douglas Drive."

Goel was the only recipient of the report.

The May 2016 WDC meeting, held four days after Goel received the report, did not include a copy. Nor did the meeting in June.

The report was included in the minutes from the July meeting. At that point councillors were debating how to fund the sewage system already selected by Goel in Franz, rather than the kind of sewage system that ought to be put in place.

The May meeting notes indicated a $99,474 loan had been earmarked on behalf of the council, with a side note saying "being used for Franz prelim designs and scopes."

It is unclear who approved the loan.

The notes said $66,788 of the loan had already been used, with a forecast to use the rest by year's end.

They also said his department had spent $36,685 on the "design and build for new WWTP (wastewater treatment plant)".

In November, Goel asked Opus to prepare another report weighing up nine different Franz sewage-disposal plans.

That report concluded the option Goel had originally selected was the best. The document, which Goel used to justify his plan, included comments for each option like "WCRC cannot guarantee a pond system would be consentable at next renewal".

Only Goel's recommended option lacked a "consent status" category.

There were other inconsistencies. For example, Opus did not find out the owners of the land highlighted as proposed pond sites, yet it did for all the other options. Land ownership was considered by Opus to be one of the key determinants of whether an option was appropriate or not.

Opus declined to comment, saying the firm needed permission from Winter to publicly release any information.

Goel's plan was rejected by a newly elected WDC on November 24.

Goel declined to comment.