Northern Interceptor Pipeline Project

Type of project: Wastewater Infrastructure

Client: Fletcher (Watercare)
Location: Auckland, North Island, New Zealand
Completed in: 2020

The Northern Interceptor Pipeline Project was a new wastewater pipe designed to redirect flows from the North-western areas of Auckland (New Zealand) to the Rosedale Wastewater Treatment Plant in Albany.

The final pipeline design incorporated dual DN500 HDPE PN16 sewage rising mains and a DN200 HDPE conduit for future fibre optic cable installations under the Upper Waitematā Harbour and Te Wharau Creek.

The total drilling length was more than 5,000 m, each of the triple-harbour crossings exceeding 1,100m in length through parallel curves, and each of the triple-Te Wharau Creek crossings exceeding 560m in length.

The crossings were completed in challenging rock and clay conditions, requiring detailed planning and preparation to ensure the crossings were constructible and risk was as low as possible. The bottom hole assemblies were manufactured utilising variable jet configurations to overcome the East Coast Bays Waitematā rock and sticky clay. The project also needed to complete detailed planning and negotiation to secure suitable stringing areas, as the urban location of the pipeline meant that options large enough to be safe and suitable were severely limited.