The cost of the Waimea dam has seen a sharp increase, thanks to “unforeseen geological conditions” to the tune of an extra $25 million, bringing the total cost of the project up to $129.4 million.
Waimea Water CEO Mike Scott says that rock designated for use as drainage material in the embankment has become a concern.


“Some rock was found to be more fractured and breaking up more readily than expected,” Mike says.


The rock in question was originally meant to be used for the drainage zones of the embankment of the dam, but rock testing in January this year has shown this rock is not of a high enough quality to be used.


Mike says that one of the possible solutions will be to import rock from nearby quarries, which will contribute to adding $25 million to the project.


“We’ve always been clear that geology was the big risk in this project,” Mike says.
Ratepayers across the Tasman District may bear the brunt of this additional cost. Under the agreed funding model, the council is committed to funding any cost increases over $3 million.


“This does not automatically mean it’s funded entirely through rates,” says Mayor Tim King.


Tim says the council is hoping that other funding partners will look at contributing to the cost increase, referring to partners like Waimea Irrigators Limited, Nelson City Council, and the Government.


“This remains an essential community project. As we look around the country, the impact of underinvestment in long term infrastructure is hitting home. We remain committed to this as the best solution to our water shortage needs.”


“It’s extremely disappointing to be facing these increased costs. It was always a possibility.”


Tim says the funding need is not immediate, and that the funding that has already been allocated to the dam will last through 2020 and into 2021.


Tim says that the cost increase will be part of a conversation about whether debt caps and rate caps need to increase, and whether other projects are pushed out or altered.


The mayor admitted that if funding could not be found, if the council had to fund the entire cost increase of the dam, it would work out to be a 1.9 per cent increase on total rates revenue.


“If there is no other external funding available, ratepayers will be up for another $23.5 million,” says Tim.


“We’ve relied on a lot of external advisors, there have been questions asked about every aspect of this project. The advice provided lead the last council to proceed with the project. With hindsight, a greater budget would have been useful,” Tim says.


Max Clark, who ran for Mayor in 2019 against Tim, and was against the dam, says that the the whole process has been ‘neglectful.’


“My understanding is that they didn’t do the geology properly in the first place.


“If you were putting in a subdivision you would have to test your rock – I think it’s neglectful to go ahead without properly testing the geology.”


“The particular rock that they’re having issues with doesn’t hold water – it’s unsuitable. It can’t hold pressure, so it just crumbles, and water leaks through.”


“It will mean that other projects will get cancelled.”


A 2014 Dam design report undertaken by Tonkin and Taylor identifies that “the grading for the class 3 material … shows little or no breakdown into fines following compaction”


The report also makes clear that the rockfill “easily satisfies the requirements for a CFRD embankment.” Waimea Water CEO Mike Scott said that while testing was undertaken, the rock varies from place to place across the site.


“Some rock was found to be more fractured and breaking up more readily than expected.”

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