The conduit was installed by directional drill and has the capacity to hold cables for existing and future electricity loads.

The conduit pipe was installed as the current location of the cables needed to be lowered 2.5 m to allow for the installation of a 1.2 m diameter council drain. As these cables supply power to the most sensitive locations in Melbourne, including Federation Square and the Melbourne Exhibition Centre, care needed to be taken not to move these cables during excavation due to both their sensitive nature and the fact that they are alive at 11,000 volts. The fact that these cables were fully exposed while the conduit jointing was completed provided a further challenge for the Multipipe team.

The location of the job proved to be a key consideration in carrying out the conduit installation. Although Multipipe had approval from Vic Roads to close the intersection of Montague Street and Normanby Road in South Melbourne, the associated traffic management costs for this closure were deemed to be too expensive.

The revised CitiPower drawings were therefore designed around using a directional drill with Vicroad’s requirements for traffic management taken into consideration. The job was scheduled to be completed within twelve days to minimise disruption. Multipipe also had to have a man on site 24 hours a day for traffic management and as a safety precaution.

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The equipment used on the job was another key factor on the job. Multipipe purchased a Case 6030 directional drill through JB Sales Melbourne, as the machine is a true 30,000 pound thrust/pullback with 4000 pound spindle/torque.

Purpose built bore pipe pulling housings were designed by Leighton Engineering for the three drill shots – 6 way, 10 way and 12 way conduit pulls. Pipe sizes ranged from 110 to 140 mm in diameter.

The ground conditions encountered varied from sand to clay. Multipipe tackled these conditions with the correct boring fluids supplied by Dmac Drilling Services Australia.

Paul Fitzgerald from Multipipe said that using a directional drill enabled reinstatement costs to be kept to a minimum, as were disruptions to what is a busy truck route.