Herne Bay collector tunnel

Project overview

In parallel with the Central Interceptor extension to Point Erin, the Herne Bay collector tunnel will collect combined wastewater and stormwater overflows for safe treatment at Māngere Wastewater Treatment Plant. This new infrastructure will significantly reduce overflows into the environment and improve the quality of inland waterways and swimmable beaches by the end of 2028.

We will install a 2.1m-diameter tunnel for approximately 1.5km using a micro Tunnel Boring Machine (mTBM). Construction will occur sequentially over different road sections, with the pipeline passing beneath the road at depths ranging from 9-22 metres.

We will also:

• Install eight tunnel shafts, along with intercepting shafts connections to existing engineered overflow points (EOPs)

• Install small diameter pipelines along Marine Parade (600mm in diameter) and local connections to the existing engineering overflow points (between 200mm to 450mm in diameter). These will be constructed via open trenching.

• Establish two temporary Construction Support Areas (CSAs) one at Salisbury Reserve and the other in the area beside the Curran Street motorway on-ramp.

We have selected Italian company, Ghella, as the contractor for the project. The company is currently part of the Ghella Abergeldie Joint Venture, contractor for the Central Interceptor project. Ghella brings 150 years of international tunnelling experience to the new works. We aim to establish our first site in July 2025 and take around 36-40 months to complete.

Construction will occur sequentially over different road sections. We are working towards a start date of Q3 2025 for a 36-month construction programme. At present we are in design mode and will shortly begin the contractor selection process. We will provide updates as we approach each major project milestone.

The map below shows the location of the proposed works along with existing infrastructure and the Central Interceptor tunnel.

Point Erin Park: South-west corner works

We are making good progress planning for the Point Erin Park south-west corner works (control chamber and plant room), which will integrate with the main Herne Bay tunnel (HBT) project. The image below shows amended design of the control chamber as well as the location of the first HBC shaft which has been moved into the park. We have our refined thinking around the connections to the EOP (engineered overflow point).

We will commence required early works, service relocations in the main, from mid-2025, followed by shaft excavation over the summer.