The Rockhampton to Yeppoon pipeline is capable of transporting up to 15,000 mega litres per annum to supply urban users on the Capricorn Coast and provides significant environmental benefits as it removes the need to extract water supplies from the Sandy Creek coastal dune system. UEA was contracted by Rockhampton Regional Council to install steel casing where the pipeline crossed under the State highway and Yeppoon Road.
The highway and road crossing designs specified the installation of a 1025mm diameter steel case to accommodate the 750mm DICL at the two State highway crossings and a 900mm diameter steel casing to accommodate the 600mm DICL for seven Yeppoon Road crossings. A 450mm diameter steel case was also required to accommodate a 355mm polyethylene pipe. The allowable tolerances for the crossings where to +/– 300mm in the horizontal, +/– 100mm in the vertical and +/-0.5mm grade
To undertake this project UEA used its 80 tonne and 160 tonne auger boring machines – capable of drilling 300mm to 1025mm diameter holes. UEA engaged local surveyors and construction companies bringing with them invaluable local knowledge. The bore lengths ranged from 24 metres to 60 metres in length.
The client required the drilling phase of the project to start in January 2008 so that all crossings were installed for the civil construction contractor installing the open cut sections. 18 metres in to the first bore Rockhampton encountered its first heavy monsoonal rain of the year which resulted in the project being shut down for 8 weeks. Once back on site the launch hole was re-excavated and extra bracing was installed on the head wall to stabilise the highway batter and drilling recommenced. As the bore progressed large cobble (from 100mm to 500mm) was encountered that formed part of an old river bed. Due to the large diameter casing the cobbles were able to be removed safely by hand. With the case successfully installed under the Highway the 750mm DICL was strapped with the required spacer blocks and installed using the boring machine.
The process was repeated for the remainder of the contract with similar issues overcome by the experienced team of operatives. The ground conditions varied from site to site (clay to hard rock intrusions) and as there was limited geotechnical information UEA had to adapt to the changing conditions by modifying the cutter heads on site or at the UEA workshop.
The contract required each installation to be independently pressure tested to 1600kpa prior to connection to the open cut sections. This requirement was incredibly unique for this type of work but in conjunction with the DICL supplier an end cap was designed and constructed. A reduced pressure test requirement of 800 Kpa was agreed upon with the final test to be completed as part of the overall pipeline test.
For more information about this project or UEA Trenchless, please send enquiries to Steven Hopkins.