The seven shore approaches were completed for submarine cable as part of EnergyAustralia’s Botany Bay Cable Project, which will ensure a reliable power supply for the inner metropolitan area.

The area is well known for its environmental, cultural and historical significance and this determined many of the strict environmental considerations in a sensitive coastal setting, such as noise reduction for nearby residents and restrictive site conditions.

Ancon set up its 600,000 pound Gallagher rig at the end of Anzac Parade in

La Perouse, and drilled seven 500 m long bores under the La Perouse National Park into the bay area known as Astrolabe Cove between Bare Island and La Perouse Point.

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Six 500 m long bores were drilled to a diameter of 450 mm and lined with a 315 mm diameter high density polyethylene (HDPE) pipe. The seventh bore involved the installation of two 110 mm HDPE pipe for fibre optics.

This was particularly challenging work, requiring a separation of a minimum of 2.5 m between each bore. The HDPE pipe was joined with butt fusion welding in a nearby cove and towed into position for insertion. Each weld was required to be internally and externally de-beaded and gauged.

Minimising the impact

A key element of the work was to maintain the pristine marine environment. Ancon developed special procedures for drilling the holes with equipment and drilling fluids that were acceptable to environmental authorities and local residents. Measures were also taken to contain any possible spills of drilling fluids at the site.

There were considerable site restrictions in the busy neighbourhood of La Perouse.

Limited space meant that the drill pad was only 40 m by 30 m, and was located 30 m from residential apartments and the shopping precinct.

An important condition of the contract was to minimise the effects of the drilling works on residents, businesses and tourists. Site fencing was erected to reduce the visual impact of the equipment and activities. Acoustic barriers were built to minimise noise from the equipment, with noise level and vibration monitoring undertaken for the duration the project.

Residents and businesses in the area were kept informed of activities likely to affect them and Ancon restricted work to daylight hours, five-and-a-half days per week.

The drilling work took approximately five months to complete, averaging about 22 days per 500 m bore. Now that the shore approaches have been completed, EnergyAustralia will install 2.5 km long power and fibre optic cables under a busy shipping channel from the south side of Botany Bay to La Perouse on the northern shore.

The project was successfully undertaken five weeks ahead of the scheduled completion date. Ancon has now moved the HDD drill rig to Agnes Water, Queensland, where it is being used to install shore crossings associated with the construction of a desalination plant.