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We received a $29.3 million contribution from the Crown Fund to help fund water and transport infrastructure to improve resilience and support new homes in Ōtaki. You can read more about this on our A blueprint for Ōtaki page.
This includes building two new reservoirs for Ōtaki. The reservoirs will improve the resilience and firefighting capability of the Ōtaki water supply.
Artist impression of the Ōtaki Reservoir number 1 with trees near fully grown.
Ōtaki has limited water storage and relies on bores and pumps to supply the community. This system does not meet good practice standards. If a problem occurred with the pumps or the treatment station, then most of Ōtaki would lose their water supply. The new reservoirs will provide 24 hours of water storage.
The new reservoirs will:
- improve the resilience of the Ōtaki water supply
- improve firefighting capability for Ōtaki
- provide water storage for emergencies and times of high demand
- support the significant housing growth planned for Ōtaki
- be more energy efficient.
The reservoirs will be designed to withstand a one-in-2,500-year earthquake, making them some of the strongest structures in the area. During a major earthquake, the tanks are designed to move a small amount. Movement of around 25mm to 100mm can be expected to occur in a 2,500-year earthquake. Designing for some movement results in better seismic performance compared to a reservoir that is totally locked in place. Pipework will include flexible joints to allow for any movement of the tank.
Reservoir number 1 is being built at Te Manuao Road. We chose this site because of its height above sea level, and closeness to the water reticulation network.
16 February 2024 – A five-month project to install the main pipes to and from the new Ōtaki Reservoir is now underway.
Three pipelines will be laid. Two pipes go between the reservoir - from the top of Te Manuoa Road, to the County Road pump station - and an overflow pipe from the reservoir to the stormwater network in Pohatu Lane.
On Te Manuao Road, the pipes will be laid in a trench dug in middle of the northern road lane. Traffic management will be in place and detours might be necessary at times. Our crew will work as quickly as they can and minimise disruption as much as possible.
Last year, we worked with the community to develop a planting plan to screen the reservoir from homes. 2500 native trees and flaxes will be planted on the site around the reservoir.
We also strengthened the ground so it can support the reservoir's weight. To do this, our crew installed 44 steel columns, and around 600 6-to-8-metre deep stone columns ready for construction of the tank in 2024.
Ōtaki Reservoir planting plan.
Steel columns being pushed into a pre-drilled hole
Building a stone column
Reservoir number 1 by the numbers:
5.5 million litres (5,500m3)
volume of the reservoir
diameter of the reservoir
depth of water in the reservoir
height of the reservoir
maximum height of the reservoir above sea level
the number of native trees that will be planted around the reservoir
reservoir design life (length of time the reservoir can be used with maintenance but without major repair being needed)
reservoir designed to withstand an earthquake of this frequency (making it the strongest structure in the area)
length of pipes to be installed, made up of 1.8km to convey water from the County Road pump station to the reservoir, 1.8km to carry water from the reservoir back to join the reticulation network at the County Road pump station, and 0.5km of pipes for overflow or flushing from the reservoir to join the stormwater network
estimated total cost of reservoir project including associated pipework
Expected construction timings for the reservoir
|Earthworks – clearing the area and building earth bunds to help screen reservoir
|Trenching from tank site to Te Manuao Road for pipework
November 2023–February 2024
|Ground improvements to provide a strong foundation for the tank
|Build concrete pad for reservoir
|Install pipes from reservoir site to County Road pump station
|Construct tank and control equipment
|Plant native trees to screen the reservoir and create a natural environment
|Fill and calibrate tank
|Reservoir fully operational
The second new reservoir for Ōtaki will hold between 0.5 to 1.0 million litres of water. It will serve the area around the Waitohu Plateau (properties above the 25 m contour). The new reservoir will supplement the existing Waitohu Reservoir which is nearing the end of its design life and does not meet modern seismic standards.
As at November 2023, we have contracted a property consultant to identify possible site options for the new reservoir and to assess two sites for a potential new water supply bore. When possible reservoir sites are identified, we will engage with neighbours who could be impacted. We expect to identify a preferred site before the end of the year.