Block and rock before you dig

— filed under: News, Print Edition

The Port of Melbourne Corporation ensured a main trunk sewer under the Yarra River, would not be punctured by ship’s anchors or dredging, by placing heavy steel plates over it and rock berms either side, during an integral part of the Channel Deepening Project.

A support frame about 23m high was purpose built to accurately place 44 specially-designed plates over Melbourne Waters Hobsons Bay main sewer, which runs across the Yarra River, just south of the West Gate Bridge.
Called the Yarra Tree (see photo), it is a stable, non-propelled structure, that was securely installed on the riverbed during operations. It was lifted and placed in position by the projects existing grab dredge and crane barge Goomai (see other photo).
Most of the frame was underwater with only an upper section visible during operations. The plates, each measuring 6 by 3.5m and weighing about 25t, were teamed with rock berms placed either side of the sewer.
In line with international best practice, PoMC is using state-of-the-art technology to carry out high precision dredging works around essential services that exist underneath the Yarra River and across Port Phillip Bay.
Protection measures were extensively researched and assessed in consultation with service owners.

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