Belimbla Park is situated approximately 75 km south west of Sydney and has a population of approximately 520 people. PSP Belimbla Park contacted Infrastructure Constructions to install a 125 mm diameter PE pipe over a distance of 340 m between the existing pump station and the low pressure sewerage line recently completed for the Belimbla Park area.

Trenching and horizontal directional drilling (HDD) were required to complete this project, with the pipeline installed in solid rock and crossing a creek which flowed into Sydney’s main water catchment. The pipe route also had to be within 500 to 1,000 mm from the outside lane markers of the major arterial road which snaked its way through the valley.

It was decided that if the entire project was trenched, a major traffic hazard would occur due to excavators moving constantly up and down the length of the job, not to mention the back filling. If HDD was used on the entire project then there was an almost certain chance that a frac-out would occur when drilling between the drain pipe and the road itself, which was made up crushed sandstone and road base when originally constructed.

Due to the area surrounding this project, PSP Belimbla Park placed a high emphasis on environmental considerations. It was therefore decided to use HDD down to the creek (230 m) and trench from there back to the manhole (110 m). Using both methods, environmental impact and traffic hazards were minimised and safety to all on site, including the local population, was ensured.

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Before starting, all environmental and traffic controls were set up in accordance to PSP Belimbla Park specifications. Once in place the JT4020, fitted with a mud motor in conjunction with a recycling system, was set up on the high side of the valley. At the same time an excavator was put to work to trench the 110 m to the HDD exit pit on a 1 per cent grade. This was then connected to the existing manhole and backfilled.

Working the mud motor using pitch and roll, the bore path was brought to within the 500 – 1000 mm window off the roadside and was then carefully steered around several bends until it reached the exit pit. The mud motor was then removed and an 180 mm diameter reamer attached and pulled back up the hole to increase it to its final size. The 125 mm diameter PE pipe was then connect to the reamer via a swivel and slowly pulled back up the bore. Once in place both bore pipes were then fused together and successfully pressure tested.