Perfect Contracting completed excavating a pair of tunnels under a residential property at Sydney’s north shore. Built to give easy access to the waterline, the 51m long passage would link to an 18m deep vertical shaft that would soon house a lift.

The scope of work for this project involved:

Concrete cutting;

Demolition in the existing house to accommodate drilling the vertical shaft;

Works on a horizontal shaft;

Building a false floor at the tunnel entrance consisting of multiple layers of geofab due to the proximity of the tunnel to the harbour and the need for constant mist for dust suppression;

Tunnelling toward the vertical shaft using Brokk;

Loading spoil into bulker bags with the excavator and storing until the weekly load out onto the barge.

All bulky items, including machinery and waste, had to be transported by barge due to the limited property access.

We used a Brokk 200, a Perfect Kubota 2.5t excavator, and numerous bulker bags to complete the task.

There were several additional factors to consider during the project: the residential location required low levels of vibration and noise, the tunnel’s confined space design limited machinery mobility, necessitating tracking of the Brokk and the Kubota to the entrance for re-entry; and exhaust fans were utilized to extract dust and waste air, with air monitoring continually in place.

After several months of work, both teams broke through and connected the shafts, with detailed excavation taking place, followed by the handover.