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Raising the stopbanks

The stopbanks on the Waipaoa River will have to be raised by twice the height first planned, which could double the cost of the Waipaoa Flood Control Scheme upgrade, the District Council’s Future Tairawhiti committee was told.

The original consent application involved raising the stopbanks by 0.5 to 1 metre in height, at a cost of $16 million.

Upgraded hydraulic modelling by Hawke’s Bay Regional Council staff has seen a need to increase that to 1 to 2 metres in extra height — with a total project cost now estimated at $20 to $35 million, not including cycle trails proposed for the top of the stopbanks.

The cycle trails were estimated to cost $2 to $3 million.

Mayor Meng Foon said the estimate variance from $16 million to $20 to $35 million was a huge difference.

“How are we going to facilitate that process?” he asked.

Chief financial officer Pauline Foreman said the $16 million referred to the last long-term plan, 2015 to 2025.

The next report was talking about the 2018 to 2028 long-term plan, for which costs had been upgraded and incorporated the full costs of the project over 30 years of the infrastructure strategy.

Two peer reviews were done so GDC could be confident about HBRC’s modelling work.

An update on the project included in the chief executive’s activity report to the committee said the updated hydraulic model had resulted in the stopbank design heights doubling those in the resource consent application the council submitted last year.

The consent hearing, originally scheduled for last December, was adjourned for additonal river modelling work and is now expected to occur in the spring of this year.

Because the consent approval has been delayed, construction work for stage one will not start before the 2018/19 construction season.

The $2.9 million budget allocated for construction this financial year will not be spent.

Because of the critical nature and importance of the project, the underspent budget of approximately $400,000 to $500,000, was approved to be carried forward to the 2019/20 financial year.

'Wake-up call' underlines stopbank urgencyThe activity report said 13 properties wanted for land acquisition had been purchased since June 2017. Three more were still to be bought, which was envisaged to be completed by December.

Total land purchases were forecast to be $1.85 million.

Lifelines director David Wilson said it had been planned to hold the consent hearing in September but that was likely to be pushed out further, depending on how discussions went with affected parties.

Mr Foon said construction was due to start in the summer of 2018/19.

“This is a critical piece of infrastructure that we need to do for flood protection,” he said.

“The Makauri Aquifer recharge is equally important.”

It was good that the Hawke’s Bay Regional Council’s modelling work had been confirmed after peer reviews.

Mr Wilson said there would be some construction starting in 2018/19 construction season.

It was a smaller portion of work that was not contestable and could be done while they looked at the wider consent parts of the scheme.

Malcolm MacLean said Ormond residents were very grateful there had not been one more day of rain in the latest storms, because the stopbanks were so close to being overtopped.

“This brings you back to reality, doesn’t it — this should not just drift on, we should seriously push on with it.

“We have had that wake-up call and we should push this project as fast as we possibly can."

The Waipaoa River (pictured). File picture