Horizontal Directional Drilling

Horizontal Directional Drilling (HDD) is a trenchless drilling technique which can be used where underground pipe needs to be installed horizontally beneath existing infrastructure and environmentally sensitive areas.

In total, we are installing more than 27 km of underground pipeline for the Aura and Harmony Program:

12 km between the Ewen Maddock Water Treatment Plant and Aura
2.6 km between the new Tanawha reservoir and Harmony, and
12.5 km between Aura and the Kawana Wastewater Treatment Plant

Twenty per cent of this pipeline will be delivered by HDD to protect culturally and environmentally sensitive sections of the pipeline alignment such as adjacent to the Mooloolah National Park and through a section of the Kawana Forest Bushland Reserve.

We avoided major traffic disruption by drilling under Caloundra Road, near the intersection with Racecourse Road.

The HDD process involves the following steps:

Above ground, the pipe is strung out and drilling rigs are in place.
Entry and exit pits are dug and a small diameter pilot hole is drilled through the bore path.
Drilling fluid is pumped through the drill pipe to the drill bit where high pressure jets and the bit cut through the soil. The fluid carries the cutting material back to the entrance pit.
The pilot hole is enlarged to the required size, which may take several passes of increasingly larger reamers.
The pullback of the pipe within the pre-reamed hole.

Unitywater is committed to utilising technologies like HDD that deliver better outcomes for our community and help to protect our environment.

Pictured: HDD drilling rig in Kawana Forest.