Completed between April and October 2010, the project involved the construction of seven road and highway tunnel crossings, 22 manholes, multiple sewer diversions and connections, and an 1,800 mm emergency relief storage for the nearby pump station, as well as the installation of 600 and 1,800 mm diameter pipelines and heavy traffic control.

Rob Carr secured the $A2.8 million contract for the project from Allconnex Water. As the head contractor for the works, they had to create an innovative plan for the design, management and construction of the project from beginning to end. Although the project contained some open-trench installation, the challenging sections involved microtunnelling in tight surroundings. The highly urbanised streets of Surfers Paradise created another obstacle that required intense planning, co-ordination and traffic control and management.

These less than favourable conditions also called for the use of some innovative pipe materials, and HOBAS CC GRP jacking pipe was selected due to its durability, low-impact installation and reduced project footprint. HOBAS jacking pipe is a GRP pipe that has thinner pipe-walls than other jacking pipe materials. The resulting outside diameter of the jacking pipe is much smaller than concrete or clay jacking pipe alternatives. Because of this, Rob Carr was able to satisfy the internal diameter requirements of the project while using a smaller tunnel boring machine.

HOBAS was also able to supply the pipe in 1 m lengths and for this reason, each pipe weighed only 54 kg. With a small shaft of only 2.2 m in diameter and no need for heavy lifting equipment, the footprint of the project was kept to an absolute minimum.

Article continues below…

The microtunnelling (via pilot auger soil displacement) section of the works (primarily 300 and 450 mm) consisted of seven lines, all between 23 and 75 m long. These lines were installed by pilot drilling due to the ground conditions being mainly sand.

“Using HOBAS jacking pipes enabled us to get the job done in very tight conditions. We have a history of success using HOBAS jacking pipe so it was an obvious choice for us on this project,” said Brett Everard, Construction Manager for Rob Carr.

Some of the major challenges of the project included:

  • Crossings over major roads and highways,
  • Restricted site access and work space,
  • High level of OHS&E management, planning and coordination,
  • Construction in wet, sandy, saturated alluvial soils
  • Multiple existing infrastructure diversions (water, sewer and power)
  • Construction of trenches and shafts in difficult ground conditions
  • Bypassing, break-ins and connections to existing infrastructure
  • Decommissioning of existing infrastructure.

Completed in October 2010, the project proved a great success for the team at Rob Carr, as was the HOBAS jacking pipe supplied for the microtunnelling portion of the works.