Feedback was unanimous from those who attended a consultation meeting about the Bay of Plenty Regional Council's Rangitāiki River spillway project on Saturday – do it once and do it right.

The spillway is designed to divert water away from the river during flood events.

The consultation session at the Edgecumbe War Memorial Hall was to discuss the reasons for increased costs of the spillway project since the council last consulted with the community about it in 2020 and also to seek feedback on two options.

Due to changes in the design of the spillway and increases in construction costs, the estimated cost of the spillway to the regional council has changed from $2.8 million in 2020 to $7.8 million, $2.1 million of which will be covered by central government funding.

The community has been asked to give feedback on this, or a second option of constructing the fixed crest weir only, which would cost $3.8 million. However, this would mean there would be no backup contingency plan if the weir did not relieve enough pressure on the stopbanks protecting Edgecumbe.

Either way, the increased costs will be passed on to ratepayers in the Rangitāiki-Tarawera Rivers Scheme area, through targeted rates.

Using the example of a 0.1 hectare residential property, the regional council projected that by 2033 the targeted rate for the scheme would increase by $86 more if the entire $7.8 million work was done, compared to $31 if only the weir was built.

The regional council's project leader Niroy Sumeran said that during the detail design phase of the project, river modelling and ground investigations identified key risks that needed to be addressed.

'We needed to create certainty that the spillway would achieve the required water flow into the floodway, while also managing seepage and erodibility (scour) of the structures when the spillway is in operation.

'These design changes include a concrete fixed-crest weir (instead of it being finished in reinforced grass), sheet pile and drainage around the structures, rock armouring and paddock contouring.

'In addition, high inflation, rising interest rates, Covid-19 and high labour costs have led to price hikes across all sectors, including construction.”

Twenty-two people attended the consultation meeting, though around 50 people had previously expressed an interest in attending.

Mr Sumeran said there had been considerable interest from the community about the project as it would play an important role in helping protect the lives and livelihoods in, around and downstream of Edgecumbe.

The project would help reduce the risk of significant flood damage to both rural and urban areas. The estimated economic damage of the 2017 event was $95 million.

He said the feedback was unanimous from those that attended that they would like to see the spillway constructed in its entirety, with the lower fixed crest weir and the contingency gates. Although an option to only build the fixed-crest weir was presented, the people in attendance understood the risk of not having contingency if the spillway was to underperform, which would result in not enough water spilling into the floodway to have the desired effect.

'The sentiment was to do it once, do it right.”

For those that were unable to attend, the opportunity to have a say online via the Bay of Plenty Regional Council's Participate page is open until April 27: https://www.participate.boprc.govt.nz/rangitaiki-spillway

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