Huia Raw Watermain upgrade

Overview

We’re upgrading and future-proofing the pipelines which carry raw water from the Lower Nihotupu Dam to the Huia Water Treatment Plant.

Benefits

As well as replacing old pipes and infrastructure, the upgrades will:

• Make our water supply more reliable, especially during emergencies or extreme weather•

• Help ensure there's enough water for our growing community in the future

• Support the opening of the new Huia Water Treatment Plant in 2033, which will help keep our water safe and clean.

What is happening now?

Thank you to everyone who took the time to provide feedback on the proposed replacement of the Huia Raw Watermain. Following environmental investigations, technical assessments, cultural input and community engagement, Watercare has identified a preferred option for the project, which will now progress to the next stage of planning.

We understand there is no option that completely avoids all impacts. However, throughout the assessment process we have carefully considered opportunities to avoid and minimise environmental, community and construction effects wherever possible.

Preferred option identified

Our preferred option is Option 6, which involves conveying water from the Lower Nihotupu Dam via a new tunnel at the Parau disposal site to connect with the Upper Nihotupu tunnel at Jacobson's Depot.

This approach improves resilience along the Huia Raw Watermain and is expected to require less disruptive works around Smiths Tunnel and the existing Huia Raw Water Aqueduct.

Option 6 also enables the existing Huia Raw Watermain to remain in service, conveying water from the Upper and Lower Huia dams.

Why was Option 6 selected?

Option 6 was selected because it:

• Improves the resilience and reliability of the overall raw water network.

• Makes greater use of existing infrastructure, reducing the need for new surface construction.

• Has the smallest construction footprint, lowest spoil volumes and lowest truck movements of the shortlisted options.

• Significantly reduces impacts on local roads, residents, businesses and recreational areas compared with open-trench construction methods.

• Supports the long-term operation of the new Huia Water Treatment Plant and Auckland's future water supply needs.

Please see below for a map of the preferred option.

The shortlisted options

In late 2025 we shortlisted four options and hosted public information and drop-in sessions to present the options and hear from the community.

Community feedback, alongside findings from geotechnical investigations and other investigations, helped shape and refine preferred options to enable us to move into concept design.

• Shortlisted options

To learn more about the shortlisted options, please watch the video below:

How your feedback helped

Community feedback played an important role in the assessment process.

Many people told us they were concerned about traffic impacts, road closures, access, construction disruption and protecting the natural environment. These themes were considered alongside technical, environmental and cultural assessments when comparing the options.

The preferred option aligns closely with what we heard from the community, avoiding many of the long-term road corridor impacts associated with open-trench construction and reducing disruption to daily life as much as practicable.

What happens next?

While a preferred option has been identified, further work is required to confirm affordability and address project risks and uncertainties.

The preferred option will continue to evolve and be refined as concept design progresses. This next phase will include:

• Affordability assessments.

• Further investigations and technical testing.

• Development of a project-specific effects management approach.

• Additional measures to avoid, minimise, remedy or offset effects where required.

We will continue to keep the community informed as the project progresses.