The Rangitāiki Floodway upgrade was conceived as a result of the Edgecumbe Stopbank Breach of 2004. The breach caused an estimated $35 million in damages and lost production.
In 2017 the Edgecumbe Stopbank breach caused upwards of $90 million damage.
The Rangitāiki Floodway project is a multi-stage project designed to take pressure off the flood-prone Rangitāiki River. This is done by increasing the capacity of the floodway thereby reducing flood levels in the Rangitāiki River from upstream of Edgecumbe to the river mouth.
Rangitāiki Floodway Stage 6
Previously a ponding option downstream of Fonterra was being looked at to reduce the overall project costs. This option has now been abandoned.
This is because detailed design showed that this option was in fact going to be a more expensive option and the benefits are not as great as originally assessed.
Consequently the stopbank raising option is now the preferred option. The detailed design also showed that for all options the scale of work required had been under represented in previous modelling results.
Due to the above, Stage 7 of the Rangitāiki Floodway was brought forward to be completed before Stage 6.
The reason for this is that Stage 6 is a far more complex stage and more time was needed to complete the detailed design and geotechnical testing to inform the final design.
The final estimate for Stage 6 has now been produced and is shown in table 1 below:
||LTP Cost Estimate (000)
||Updated Estimate (000)
It is acknowledged that this is a substantial increase and it is important to get your feedback on the cost increase for Stage 6.
Rangitāiki Floodway Spillway
During 2018 consultation was undertaken within the local community on options for the spillway design. The proposed option was for a lower fixed crest weir with contingency radial gates and was generally supported at the culmination of the consultation on 24th November 2018.
The option that had been prepared prior to this consultation taking place in the Long Term Plan (LTP) was for a lower fixed crest weir with no contingency allowance.
Table 2 below shows the increase in cost for the Spillway.
||LTP Cost Estimate – Lower Fixed Crest Weir (000)
||Lower Fixed Crest Weir with contingency gates (000)
Given the increased cost in Stage 6 we felt it was important to re-confirm with the local community that the lower fixed crest weir with contingency gates was still the preferred option, see question 6 on the survey form.
Impact on rates
In the information document below are examples of different property types and the impact the above proposals will have on rates. Please review these before filling out the survey which is linked below.
Crown Infrastructure Partners (CIP) funding
Central Government has announced that it wants to help with economic recovery once we are out of the Covid 19 restrictions. We have put the Rangitāiki Floodway project up as a “spade ready” project that Central Government could help fund. If successful, the increased costs outlined in this letter could be offset by the CIP funding.
The Rangitāiki Floodway project is a multi-stage project to take pressure off the flood-prone Rangitāiki River by diverting some of its flow.
Increasing the capacity of the Floodway reduces flood levels in the Rangitāiki River from upstream of Edgecumbe to the river mouth. This will in turn reduce pressure on Rangitāiki River stopbanks during large flood events.
The project works in stages
- Stage 1: Channel widening. Physical works were completed in the 2011/12 construction season ($3.2 million).
- Stage 2a: Channel widening. Physical works were completed in the 2013/14 construction season ($2.4 million).
- Stage 2b: Channel widening. Physical works completed in the 2014/15 construction season ($2.4 million).
- Stage 3: Stopbank raising. Physical works completed in the 2015/16 construction season ($2.05 million).
- Stage 3a: Channel widening and wick drains. Physical works completed in the 2016/17 construction season ($2.4 million).
- Stage 4: Channel widening. Works were completed over 2017-2019 construction seasons ($4.3 million).
- Stage 5: Bifurcation, bridge and road works completed 2019/20 construction season ($2.5 million).
- Stage 6: Stopbank raising in 2020/21 ($10.9 million).
- Stage 7: Stopbank raising and spillway land purchase 2019/20 ($5.7 million). Spillway upgrade in 2021/22 ($2.8 million).
- Spillway upgrade in 2021/22 ($2.8 million).
Project updates and monitoring
Follow this project and receive regular project updates via email.