Microtunnelling to relocate underground utilities

To enable construction of the Southern Portal, existing underground sewer and stormwater pipes need to be relocated. The project will install the new utilities using a construction methodology called microtunnelling. Use of this methodology will allow trains to continue to operate as we install new services under the tracks.


What is microtunnelling?

Traditional open-cut trenching involves digging a trench, laying pipe and backfilling the trench. Microtunnelling is a trenchless
method of pipe installation.

This methodology does not require a trench. Instead, two small micro boring machines will be used to dig an underground path, after which specialised hydraulic equipment is used to push lengths of pipe through the ground.

The machines will be selected specifically for the existing geological conditions in the area.

How will the new pipes be installed?

The first step is excavating and constructing four temporary concrete shafts, from which the machines will be launched.

The machines are then lowered into the shaft to start each stage between the temporary shafts.

The machines excavate the ground while hydraulic equipment pushes pipe through the ground behind it. These pipes will form the new sewer and stormwater main.

At completion, the shafts will be made into manholes for future access to the new services.

Where will the shafts be located?

The four temporary shafts will be located:

  1. Within the Kent Street work site
  2. Adjacent to the TRI building at Kent Street
  3. At the intersection of Railway Terrace and Dutton Street
  4. On Railway Terrace between Rawnlsey Street and the culde-sac.

There will be pedestrian and vehicle changes during this work.

How long will the work take?

The two machines will install new underground pipes in six stages between the four shaft locations.

Construction of the temporary shafts and installation of the pipes is expected to take up to 12 months.


Will I notice boring activities?

We are not boring under any residential or commercial buildings.

Residents and businesses closest to the work sites may notice noise from machinery and trucks above ground.

We do not anticipate any impacts to existing services during this time. We will work to minimise impacts from construction as much as possible.

How is the machine steered?

The machines are continually monitored during the pipe installation using a laser inside the jacking pit. As the machine progresses, it can be steered with hydraulic cylinders in the machine to maintain direction.


What will happen to excavated material?

Excavated material will be temporarily stored on-site, before it is loaded onto trucks and taken to approved spoil facilities.

What are the work hours for microtunnelling?

Most of the work will be carried out during standard construction hours: 6:30am to 6:30pm Monday to Saturday.

We will provide further notification if any work is required outside of these times.

Typical site layout


Who do I contact with an enquiry about construction?

For all enquiries or complaints, please use on of the options below: