We successfully diverted a 600 metre section of the North Yarra Main Sewer. Diverting the sewer was a massive job that involved excavation, piling, tunnel boring and changes to traffic – and we built it without interruption to sewerage services.

About the North Yarra Main Sewer

The original North Yarra Main Sewer was 2.6m in diameter, over 100 years old and made mostly of bricks. It’s a vital piece of infrastructure sits 13-15 metres below the ground and carries 20 percent of Melbourne’s sewage.

Map showing the location of the sewer diversion.

As part of the project, a 600 metre section of sewer that ran below the centre of Whitehall Street in Footscray and Yarraville was diverted. This was done to protect the sewer from tunnelling and prevent disruptions to sewer services across Melbourne’s north and west.

Program of works for North Yarra Main Sewer diversion. Click image to enlarge.

About Mollie - our mini tunnel boring machine

To keep the old sewer operating all the times, a mini tunnel boring machine (TBM) called Mollie created a route for the new sewer. As the mini TBM moved through the earth at the rate of about 12 metres a day, glass reinforced plastic lining was installed around the tunnels to seal it and strengthen the structure.

Once the new sewer was ready to operate, a gap was opened in the wall of the old sewer so sewage can start flowing via the new tunnel.

Over 9,000 cubic metres (3.6 Olympic size swimming pools) was excavated during the diversion works.

See the moment Mollie broke through

We caught the West Gate Tunnel Project's first TBM breakthrough on film - watch the video to find out more about Mollie and diverting the North Yarra Main Sewer.

More information

For more details, see the North Yarra Main Sewer diversion factsheet (PDF, 3 MB).

If you have any questions, our team is available 24 hours a day on 1800 105 105.