Kaikohe drought resilience project

Project details

The council draws drinking water for its Kaikohe water supply from two sources. Wairoro Stream meets about 70% of the town’s needs and water from the stream is treated at a plant at Taraire Hills. The remaining 30% is drawn from a bore at Tokareireia (Monument Hill) and treated at a plant on the hill summit.

Water shortages in the town were acute during the 2019/20 summer following record low rainfall in 2019. At the height of this 2019/20 drought Wairoro Stream flows dropped to less than one litre per second at the council water intake and Kaikohe taps were in danger of running dry.

To ensure the town is more resilient to future droughts a second much deeper bore has been drilled at Tokareireia to access greater supplies. This will provide a more reliable secondary water supply to Kaikohe’s main source, the Wairoro Stream.

Drilling of the new (second) bore into a deeper aquifer below the existing Monument Hill water supply bores, began in December 2020 and, after some construction complications, was completed on 24 February 2021.

The new 120-metre bore accesses more sustainable groundwater and can supply about 350 cubic metres of water a day, but will only be used if the Wairoro Stream is running low. 350 cubic metres a day is similar to the current bore’s sustainable (long term safe) yield.

The new bore’s impact on nearby springs and other surface water resources and its response during dry periods was tested by looking at two scenarios:

using the deep bore exclusively over summer, then using the existing bore in winter to allow the deep aquifer to recover
or using a combination of the existing bore and the deep bore and allow them to recover in winter.

The new production bore is made of 200mm carbon steel casing to 99m, it also has a telescopic stainless steel screen assembly to 121m.

Iwi approval has been gained for the project delivery.

Project costs

This project has an approved budget of $1.18 million.

Project milestones

Stage 1 - Bore design and quality testing

Drilling of the new (second) bore, began in December 2020 and was completed on 24 February 2021. This bore accesses more sustainable groundwater and can supply about 350 cubic metres of water a day.

Stage 2 - Sustainable yield assessment and consenting

To provide a sustainable supply of highly secure potable water for the Kaikohe community, testing of the bore confirmed flows and investigated impacts on surrounding groundwater sources. Testing started on 4 March 2021, continued for 5 days, and was then analysed.

Testing included: 1) a step test 2) a constant discharge test 3) recovery monitoring after the pumping.

Stage 2 was completed in October 2021.

Stage 3 – Reticulation and electrical design

Northland Regional Council granted consent for the project in March 2022 and construction began in May. This included extra monitoring conditions agreed to with the Waikotihe Trust.

Physical works have included installing a pump, laying a trenched pipe to connect the bore to the Monument Hill Water Treatment Plant, connecting electricity and fibre, as well as creating an access road. Most of the construction work was completed by 30 June.

Air valve installation, bore headworks and pipework were completed in July. Water pressure testing on the main water line for the new bore was completed in September. Upgrades to the water treatment plant (on the hill summit) have also been part of the project. A new purpose-built facility meets the compliance requirements of Taumata Arowai (water services regulator for Aotearoa) of enabling continuous online monitoring of the water supply.

It was hoped the project would be running by summer 2022/23, but supply chain delays and a series of storms have impacted the project, with resources being temporarily allocated to emergency works.

It is now anticipated that the new bore will be providing the town with water by June 2023.