The first stage of the project involves the construction of a new sewer tunnel approximately 14 kilometres in length and will be completed by 2025. This new sewer will collect wastewater flows from parts of central Auckland and Waitakere City and transfer them to the existing Mangere Wastewater Treatment Plant (WWTP).
Stages two and three of the project will be completed by 2040.
As part of the principal engineer adviser team led by AECOM, Jacobs Associates will lead the tunnel and shaft conceptual design efforts for the initial phase of the work. Jacobs Associates has identified challenges to the design, including
- Challenging tunnelling conditions within a region of basalt-filled valleys and volcanic vents;
- The siting of facilities within heavily urbanised areas with tight space constraints; and
- Defining appropriate excavation methods for an underwater crossing of the Manukau Harbour.
The new system will address future dry weather capacity needs as well as mitigation of wet weather overflows. The project will also be designed in accordance with provisions for projected population growth in the Auckland region.
AECOM Regional Director Dean Kimpton said “Watercare’s Central Interceptor project will help address the risks associated with ageing wastewater infrastructure and provide a significant opportunity to consider cost-effective solutions for addressing overflows in other parts of the network.”
