Herne Bay collector tunnel

Project overview

In combination with Watercare’s new Central Interceptor tunnel, 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 our swimmable beaches.

Italian tunnelling company, Ghella, is continuing early works as we progress towards signing the final contract, when a Construction Programme will be finalised.

We will construct a 2.1m-diameter tunnel for approximately 1.5km using a micro Tunnel Boring Machine (mTBM). The pipeline will pass beneath the streets 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), which are manholes in the roadway or on private property.

• 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 using open trenching to lay pipes.

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

The map below shows the location of the proposed works.

Main tunnelling and shaft site works

Early works contractor, Ghella, has completed service investigations across the project area. Over the next few months, we will carry out service relocations in preparation for the main Herne Bay Collector construction.

There will be three construction sites in the Sarsfield/Wallace/Argyle Street area, all located in the roadway at intersections. Service relocations are currently scheduled to from early January until April. All sites are fenced to keep everyone safe while we establish the area and put in a raised working platform. The sites will then be set up for a longer period of main construction works (shaft excavation and tunnelling) with altered traffic management plans put in place.

Site safety and traffic management

All our work sites are fenced off with hoardings for the safety of the passing public and our workforce. Traffic management may include stop/go controls or single lanes and areas of no parking, as and when temporary road closures are needed.

We will aim to reduce the impact to road users as much as possible and alternative routes around our sites will be available. You will always have access to your property. Please work with and obey all traffic signs and directions for everyone’s safety.

Areas affected by traffic management plans

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.

Now that service investigations have been completed, we will relocate services in preparation for site establishment. Power cables and some streetlights will be relocated on Curran and Sarsfield Streets. In the southwest corner of the park itself, we will relocate fibre and communication lines as well as wastewater and water pipes.

The image below shows the location of the shaft and the control chamber.