Grey Lynn to Point Erin Central Interceptor extension project

A project aimed at delivering cleaner waterways and beaches by 2028.

Grey Lynn to Point Erin Central Interceptor extension project  

We are planning to build an extension of the Central Interceptor wastewater conveyance and storage tunnel from Tawariki Street in Grey Lynn to a new drop shaft in Point Erin.  

Start-finish:
August 2022 – late 2028
Location: Grey Lynn to Point Erin
Status: Planning 

Project update – St Marys Bay separation project  

We have unfortunately had to defer the St Marys and Herne Bay wastewater separation programme due to an unaffordable escalation in costs. The work has been heavily impacted by geotechnical design issues and escalating material, labour, and traffic management costs. The result has been a doubling in the original forecast.   

We remain committed to delivering a solution for the ongoing wastewater overflows in the area and have developed a more affordable alternative which will allow us to deliver cleaner beaches and waterways by 2028 with less community disruption. This solution involves an extension of the Central Interceptor wastewater conveyance and storage tunnel from Grey Lynn to a new drop shaft in Point Erin, as well as a new wastewater pipeline in Herne Bay. 

Please refer to the information below about the new proposal.  
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Want to learn more about the proposed changes?  

Join us at a drop-in session to talk with the team about the proposed changes to the separation project and the new proposal to extend the Central Interceptor to Point Erin.

Background of the original St Marys Bay and Herne Bay separation projects  

The original proposal focused on separating the old, combined stormwater and wastewater pipes directing stormwater to the environment and wastewater to the Māngere Wastewater Treatment Plant via the Orakei main. The project included a new public wastewater network, storage and a new pump station at Point Erin as well as private drainage separation and connections.   

Why has a change in programme been proposed?  

We have unfortunately had to defer the St Marys and Herne Bay wastewater separation programme due to an unaffordable escalation in costs. The work has been heavily impacted by geotechnical design issues and escalating material, labour, and traffic management costs. The result has been a doubling in the original forecast. We remain committed to delivering a solution for the ongoing wastewater overflow challenges and have been working closely with Auckland Council to find an alternative which will allow us to deliver cleaner beaches and waterways by 2028 while remaining committed to separation in the longer term. 

Note: The changes are not part of the recent National Policy Statement on Urban Density or proposed changes to the Unitary Plan and are focused primarily on delivering water quality and bathing beach outcomes by 2028. 

The new proposal  

Planning is underway for the extension of the Central Interceptor wastewater conveyance and storage tunnel from Tawariki Street in Grey Lynn to a new drop shaft in Point Erin. This will be supported by a new, smaller diameter Herne Bay wastewater pipe and a revised programme of sewer separation.  

The tunnel extension will ensure combined overflows are picked up and conveyed to Māngere Wastewater Treatment Plant for safe treatment, reducing overflows to the environment and improving the quality of waterways and swimmable beaches by 2028.  

The diagram below demonstrates the new proposal: 

Point Erin map of proposed works

To deliver this project, we will leverage the knowledge, skills, and experience of our international tunnellers and other local experts. We have also agreed with the residents’ associations to engage Ian Wallis, an independent engineer of their choice, to review the project proposal to ensure the best possible outcome for all parties.  

What is the timeline for the proposed works?  

Please see an indicative timeline for the proposed Central Interceptor works. Please note, these dates are an estimate only and are likely to change. The Herne Bay wastewater upgrade will take place in parallel and is expected to be constructed between 2026 to 2028.
Estimated timeline for St Marys Bay CI works

What's happening now?  

The team is currently in the process of designing the programme and obtaining the required approvals. Further information will be shared as it becomes available. 

Documents

Any questions?

Please email [email protected]

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