St Marys Bay separation project

A water quality improvement programme to reduce overflows and clean up local waterways.
Start–finish: 2020-2024
Location: St Marys Bay
Status: Design
St Marys Bay latest newsletter

Project update

We have been working our way through the area undertaking investigations and now have a preliminary design for the public network. Read more about the public network design and the factors that go into the design of our new network.
We will soon be applying for the necessary consents.  While much of the work will be done in the road, which is designated for this purpose, some of the public network will also require resource consents. This is where the effects of pipeline construction on the environment, such as vibration, ground settlement and works near trees requires careful management and monitoring.
Our contractors are still working through properties to undertake further investigations of private property drainage. There are approximately 455 properties that may require separation so don’t be concerned if we have not made it to your property yet, we are still working our way through to investigate each property’s unique drainage one by one and talk to property owners about our findings. Our engineers will then design and present to the owners the most practicable option to create a separate network for each property. See the ‘design’ section to understand the factors that contribute to placement of the pipelines.
We will continue to work with affected residents directly as we work through planning toward construction and update you as the project progresses. We are aiming to start construction later in the year or early next, once planning is complete.

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Why is the project needed?

In the older parts of central Auckland, wastewater and stormwater were designed 100+years ago to flow through the same pipes called a ‘combined network'. While early last century this was considered great engineering as a response to ‘great stink’, over 100 years later and with population growth and infill housing means they are no longer suitable. During heavy rainfall, stormwater can overwhelm the combined network causing diluted wastewater overflows into our waterways and beaches such as St Marys Bay and the Harbour. These overflows are getting more frequent with population growth and extreme weather events. See: Why do we need to replace combined wastewater systems.

Modern networks and private drainage are now built to ensure wastewater and stormwater flow through separate pipes. Wastewater contains organic contaminants including bacteria and viruses that can make people sick so this needs to be contained and transferred to a treatment plant where it can be made safe before being discharged to the environment. Stormwater (rainwater) that flow off roofs and over land does not need to be treated to the same standard and can be discharged to the environment with little or no treatment. See: Stormwater and wastewater.
We've been working with Auckland Council on a major initiative called the Western Isthmus Water Quality Improvement Programme. This includes a range of infrastructure projects including the Central Interceptor and other local separation projects, prioritising areas where beach and water quality is at its poorest.
In St Marys Bay, we plan to separate and upgrade the old combined network to today’s standard to reduce pollution from wastewater into the environment, particularly when it rains. To do this, we will build a new network of pipes, using the combined network and creating one each for wastewater and stormwater while also separating private drainage on properties that are still combined. The project is jointly funded by Watercare and Auckland Council via the water quality targeted rate, and separation of private drainage will be at no cost for property owners.
Refer to the map below which shows the general catchment area for St Marys Bay.

St marys bay separation project catchment map

What's involved?

The project involves construction of a new wastewater network and (generally) using the current combined network as a stormwater network. At the same time, we will also refurbish the existing pipes where required and complete the necessary connections from private drainage pipelines to the corresponding public pipelines.
We will also separate private property drainage, and complete connections into the relevant wastewater or stormwater network.

The scale and extent of both public and private property drainage means there will be a lot of construction work required across the St Marys Bay area. We will need your help to ensure that the project flows smoothly so that the new network caters for the future needs of the area. We are here to answer any questions and work with you.

Timing of the works

St Marys Bay timeline of the works

If you would like to understand the different stages and what’s involved in more detail, please refer to sections outlining each stage of the process below:

St Marys Bay investigation work

Investigations in the area

Our contractors will be out and about in St Marys Bay undertaking investigations to inform the work that will be required.

st marys bay design elements

Design information

Design elements of the new public network and private drainage.
consents associated with the st marys bay project

Consent applications

Find information on what consents will be required and related documents.

st marys bay construction work

Undertaking construction

Find out what you can expect from construction works in the area.