About the replacement plant

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The purpose of this project is to replace an ageing treatment plant that is reaching the end of its operational life. In some ways, the replacement plant will be similar to the existing plant:

  • Capacity of the treatment plant: As with the ageing plant, the replacement plant will treat water from four dams in the Waitakere Ranges. As the capacity of the dams is set, the proposed plant will treat a similar volume of water, meeting up to 20 per cent of our city’s water needs. However, to improve system-wide resilience, the short-term peak production capacity will be increased.

  • Traffic: The ageing plant has around 10 truck movements per week, with additional traffic from up to 15 staff located at the site during normal working hours. Once its operational, the new plant will have similar traffic movements.

  • Noise: As with the ageing plant, most of the treatment processes utilise gravity and are non-mechanical so noise can be managed. The design of a replacement plant would minimise any ‘noisy’ components ensuring all regulatory noise limits can be met.

In other ways, the replacement plant will be significantly better than the existing plant:

  • Treatment processes: The replacement plant will offer more advanced treatment processes that are better equipped to deal with the changing water quality from the dams.

  • Maintenance: The replacement plant will be easier to maintain. Processes will be able to be taken out of service for maintenance without affecting the overall performance of the plant.

  • Safety: The replacement plant will be designed with safety top-of-mind. The layout will ensure staff and vehicles can move safely around the site.

  • Visual impact: The replacement plant will have a 10 metre buffer zone of vegetation, helping to screen most of the facility. Unlike the old plant, the new one will be architecturally designed with the environment as a consideration to ensure that the buildings blend into their surroundings by using colour and texture treatments. The two reservoirs will be screened from Woodlands Park Road by planting. The northern reservoir will be buried to further reduce any visibility from the road.

  • Robustness: Unlike the existing structures, the replacement plant will be designed and built to current earthquake standards.


The replacement plant will treat water from four dams in the Waitakere Ranges.
The replacement plant will treat water from four dams in the Waitākere Ranges.