Improving the stormwater system
We are extending the existing stormwater network to create separate networks for stormwater and wastewater. This project is part of the Western isthmus water quality improvement programme. We will deliver it in partnership with Watercare.
What the project will do
Westmere relies on ageing infrastructure built in the early 20th century. The existing pipes carry both wastewater and stormwater.
Most of the time, the network carries wastewater to the treatment plant. During heavy or long periods of rain, the system can overflow and release stormwater mixed with diluted wastewater into Waiorea / Motions Creek and the Waitematā Harbour.
The project will help reduce these overflows. This will improve public health by reducing contamination in local waterways.
What the new network will do
The new network will:
- greatly reduce combined wastewater and stormwater overflows into Waiorea / Motions Creek and the Waitematā Harbour
- improve the environment for people, birds and marine life
- increase stormwater network capacity to support future growth in the area
- reduce the risk of flooding
- replace ageing infrastructure and prepare the network for the future.
When this work will happen
We will deliver the wider Westmere stormwater separation project in four stages over several years. This will help reduce disruption to the community.
Stage 1
We have designed Stage 1 and received resource consent. Physical works are expected to begin later this year.
Stage 2
Stage 2 is now in preliminary design. We are developing a detailed design, including how individual properties may be affected. This will take around 12 months.
Once this is complete and the final business case and budget are approved, we will confirm the timeline for the physical works.
Stages 3 and 4
Design work is expected to begin in late 2026 for Stage 3 and mid‑2027 for Stage 4.
How the project will affect you
This project involves upgrading parts of the private and public stormwater systems in the area. Where possible, we will place the public stormwater system on public land, such as road reserves.
We will contact you in advance if we need to build public stormwater assets like pipes, manholes or outfalls on your property. If a contractor needs to construct private drainage on your property, they will seek your permission well in advance.
