Moss Vale Road, Beaumont Electrical HDD Upgrade

In June 2014, UEA commenced works on a significant horizontal directional drilling (HDD) project at Moss Vale Road at Beaumont, a town land adjacent to the tourist destination Kangaroo Valley in the Illawarra region of New South Wales. In response to the ongoing risks of service disruption and maintenance costs associated with the area’s aging overhead infrastructure, the local electrical authority replaced the existing cables. UEA was awarded the project, which was scheduled to take five weeks.

Scope of Works

The original design of the underground installation consisted of conduits approximately 680m in length, broken up into two under bores with lengths of 480m and 200m, and a short section of overhead cable connecting the two under bores. As part of the scope UEA amended the design so that the Vermeer D100 x 120 drill rig would sit at the lower end of the under bore as opposed to the higher side of the bore. The reason this design change was necessary was to reduce the build-up of pressure in the bore hole.

Construction

During the pilot for the longer bore it became apparent that due to the ground conditions the bore could not be constructed as per the original design. UEA stopped works and in consultation with their client came up with an alternate design. This alternate design consisted of increasing the length of the bore by moving the drill rig 50m further down the hill thus allowing the bore to be at a constant positive grade. The revised design allowed the bore to be completed successfully through problematic conditions.

Challenges

• UEA completed walkover tracking of the under bore through undulating ground surface and dense undergrowth which had to be removed;
• Even though challenging ground conditions encountered on the longer bore caused a delay with a new design being required, UEA completed the project within the programmed duration.