Tararua District Council met on Tuesday 31 October to progress solutions for Dannevirke’s impounded water supply.

For the recording of the meeting, Frequently Asked Questions (FAQs), full details of the report and more information about the project please go to: Dannevirke Impounded Water Supply | Tararua District Council (tararuadc.govt.nz).  Please also refer to this update: Decisions made on the Dannevirke impounded water supply | Tararua District Council (tararuadc.govt.nz)

In this Extraordinary Meeting, Councillors and the public were updated on the detailed design for repairs to the dam and the outcome of recent peer review workshops.

Funding of $3.2 million was sought for raw water or water from source  pre-treatment and $400,000 to purchase a raw water storage Kliptank and a further $2.5 million for a 6 Mega litre treated water storage tank.

Another key focus of the meeting was for councillors to consider the recommendation to delay a decision on the physical works that were previously earmarked for starting January 2024, due to outstanding geotechnical investigations, supply challenges with sourcing a pre-treatment facility, and issues relating to the liner system.

The paper prepared for the meeting by the Project Team working on the Impounded Supply proposed these improvements be considered under urgency to reduce risk to Dannevirke’s water supply in the short to medium term, while also adding long-term resilience to the impounded supply.

All these recommendations were passed by Council. However, the decisions weighed heavily on the Councillors as they had to strike a delicate balance between community safety and the financial impact on ratepayers. There were divided opinions among the Councillors, with Councillor Johns, Long, and Wallace, opposing the purchase of the treatment plant and Kliptank. Councillor Long also voted against allocating $2.5 million for the treated water storage tank.

Council expects to go out to the public to consult on options for the physical works to the Impounded Supply next year.

A public meeting has been planned to provide an opportunity for the public to discuss the decisions. The meeting will be held on Wednesday, 15 November 2023, 6.30-8.30pm at the Hub.

Tararua District Council Mayor Tracey Collis says that while a delay to the physical works is frustrating for the team and community: “We have to take seriously the latest recommendations from our technical advisors, because we have to get this right.”

At the same time, work continues on options for permanent repairs to the dam. “Because of the significant amount of investment needed for permanent repairs we will need to consult with the community on those options. By the time we consult, we will know whether supplementary sources are viable.”

Two test bores are being drilled at sites on Laws Road this week to explore the potential for drawing water adjacent to the  Tamaki River underground, which could potentially provide a supplementary source, further increasing resilience. Council expects to have an indication of the viability of the bores by the end of the year.

“The pre-treatment facility we are looking to purchase could be installed in May 2024 and the extra water storage operational in six months. A silver lining to the delay to physical works on the dam is that we won’t have to dewater the dam this year as previously thought. This means we should  have the impounded supply as part of our water supply system throughout the El Nino summer, which is forecast to see dry conditions across the district.”

The pre-treatment facility won’t just be for Dannevirke - it is intended to be transportable so if it is needed in other parts of the district in the future, it can be relocated.  “We are also actively looking into making available 200L rainwater tanks at cost to the whole Tararua community, and expect to be able to update you soon on this initiative.”

“We know the long-term problems with the impounded supply are still there and the project team is working incredibly hard to get all the information we need to enable a decision to be made on a permanent fix, while concurrently fast tracking the water treatment and storage measures that will increase resilience in both the short and long term.”   

The report says the latest advice Council has been given after the temporary repairs in June 2023 is that the impounded supply has continued to deteriorate  but the risk of immenent failure is less likely.

“While this is reassuring we are doing everything we can to mitigate against the risk of dam failure in the coming months. This includes dam safety monitoring to provide early warning of any further deterioration – providing the best chance to act to maintain the dam and keep it operational and operating the dam at a maximum depth of 8m.”

“The biggest threat to water supply at the moment is the coming weather. If there is little rain we will still be able to draw water from the Tamaki River but at a low take – however, this would mean water restrictions and boil water notices at times if there is high turbidity. It is important that we are realistic about this as a community and take collective and individual action now.”

“We all need to be thinking about fixing leaks, getting the water blasting done and filling up home emergency water supplies in November and being ready to start conserving from December or as soon as the weather turns.”

If you have any specific questions you would like answered about the plans for the Impounded Supply, please email them to: communications@tararuadc.govt.nz