The Bruce Highway links major regional centres to one another and to South East Queensland. Part of the daily lives of thousands of Queenslanders, it forms the transport backbone of the state. For any work to be undertaken underneath this important structure, it would be inconceivable to create road closures or disturb traffic on this highway that moves tens of thousands of people and tonnes of freight every day.
The Bruce Highway upgrade
The re-routing of a gas main underneath the highway was deemed necessary by the Queensland Government as part of a wider scheme of works to upgrade infrastructure. Re-routing the gas main would allow for a suite of 20-year planned developments to go ahead, some of which include 340 km of highway duplication, bridge replacements and intersection upgrades.
When the project proponent assigned with the task of re-routing the gas main under the highway came to choosing the technology for the job, they decided horizontal directional drilling would be the best way to keep environmental impacts to a minimum, and contracted HTD Australia for the job.
Keeping on the straight and narrow
The project required drilling two bores through rock, with each bore approximately 80 m, in order to install a 100 mm steel gas main. To perform the bores, HTD Australia chose a Vermeer 36X50 Series 2 machine and a variety of drilling tools, including the Vermeer Armour Drilling System. Because the terrain consisted of highly variable shale and hard rock, HTD needed to be sure they chose equipment that could handle the terrain.
The most complicated and time-consuming part of the project proved to be the pilot bore, which, because they were installing gas mains, required a precise grade and alignment. HTD Australia used the Digitrak Eclipse locating system to display the drill head location and locate points in a “÷real-time’ bird’s-eye view in order to meet the strict installation requirements.
Zac Chisholm of HTD Australia said “Because it was on a gas main line, we had to stick to straight height and line levels with little tolerance for moving. This is what took the most time. Additionally, the grade varied halfway through the installation, but still required us to stay reasonably flat while keeping a straight alignment.
“This was tough because of the rock conditions, which changed all the time. However, the machinery was perfect; the 36X50 handled the job perfectly and handled the rock conditions without any dramas.”
On-time completion
The project, which started in November 2011, achieved on-time completion one week later, and was well within budget. HTD Australia drilled from bush on one side, under the Bruce Highway, under the Dawson Highway, and through to bush on the opposite side of the crossing. The work required no road closures, and involved no environmental impacts to those who use the Bruce Highway as part of their daily life.
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