Council approves construction of proposed Rangitaiki Spillway design

Bay of Plenty Regional Council Councillors have approved increase in budget for the construction of the Rangitāiki Spillway, following overwhelming support from the community.

The Spillway needs to be upgraded as it is part of the Rangitāiki Floodway, a key piece of flood defence infrastructure to help protect the community in a flood event.

In an event, the Spillway enables water from the Rangitāiki River to pass over a fixed crest weir (lowered, concrete-covered stopbank) and into the Floodway. This will help divert water away from the Rangitāiki River and reduce the risk of significant flood damage to both rural and urban areas.

Last Thursday, Regional Council approved an increase to the total Spillway budget to $7.8M to implement the proposed design – a 114m fixed crest weir, with three contingency ‘back up’ gates. This is an increase from the original estimate of $2.8M, which Regional Council presented to the community in 2020.

There are several reasons for the increase, such as erosion protection of the fixed crest weir, which requires capping it in concrete, and placing rocks or concrete (riprap) up and down stream of the weir.

There are also further design requirements, including installation of sheet piles around the structure, sub-structure drainage and additional paddock contouring, all of which are required to manage erosion and seepage during Spillway operation.

High inflation, rising interest rates, Covid-19 and high labour costs have also led to price hikes across all sectors, including construction.

The Council decision was made following the latest period of community consultation, which was held through an in-person event and via Regional Council’s online engagement tool Participate.

Through this process, there was overwhelming support from submitters to complete the project in full. The alternative option was to construct the fixed crest weir only at an estimated cost of $3.8M, however that would mean there was no contingency ‘back up’ in a flood event.

Engineering Manager Mark Townsend, who spoke to the report, said the sentiment from the community was ‘do it once, do it right’.

“That sentiment speaks to the community’s desire for us to get the work done, and give them some assurance that their lives and livelihoods will be better protected as heavy rain events increase.”

The increased costs will be passed on to targeted ratepayers in the Rangitāiki-Tarawera Rivers Scheme. There will also be a small increase in general rates as a result.

Construction of the Spillway is expected to start in September 2023 (weather permitting), with a completion date toward the end of 2024.

Find out more about this project online: www.boprc.govt.nz/rangitaiki-floodway

ENDS