As a recent example, Abigroup Contractors have been using Trenchless Technology to overcome many challenges on the Albury Hume Freeway Project.
The project consists of approximately 14 km of new dual carriageway freeway through the town of Albury on the border of NSW and Victoria. A major part of the freeway construction is the relocation of public utility services including sewer and watermains, communications, power and gas.
The new freeway runs alongside the Great Southern Railway Line and numerous utilities were required to be lowered or realigned under the freeway, the existing railway and various local roads.
The project is a DCM (Design, Construct and Maintain) Contract with the NSW Road Traffic Authority, which allowed the construction team to provide valuable input during the design phase. An existing utilities model was developed using 12D software based on Dial Before You Dig information, Council and RTA plans, ground survey and over 500 utility potholes which were completed during the first three months of the project. Impact assessments for each utility service were completed in consultation with the asset owner to determine protection and relocation requirements.
Wherever possible, the freeway design was adjusted to minimise the impact on assets that would be expensive to relocate or would cause disruption to the local community. This included adjusting horizontal alignments of local roads to avoid existing sewer manholes, reducing heights of fills over existing fibre optic cables, moving bridge piles to avoid existing watermains and changing alignments of retaining walls to minimise future maintenance problems for high pressure gas pipelines.
Due to the nature of the project, it was realised very early on that the relocation of the utilities would require significant use of Trenchless Technology. In addition to the utility relocations, there were also benefits of using trenchless methods for the construction of drainage and pedestrian underpasses.
Abigroup investigated the possibility of engaging a single subcontractor to complete all the bores on the project, however the timing and coordination between the bores and all the other activities (such as bulk earthworks) proved to be too difficult to juggle on such a large scale project. The final procurement method ended up being a combination of boring subcontractors engaged directly by Abigroup and boring contractors engaged through the various utility relocation subcontractors. This combination provided Abigroup with greater control over the timing of critical bores where necessary, but also minimised some of the coordination issues with having a single boring contractor wanting to complete all the bores in one mobilisation to the site.
The benefits of significant design input into the utility relocations cannot be over emphasised, with reduced problems during construction, reduced disputes regarding proposed alignments and levels, reduced clashes between proposed and existing utilities and reduced extents of relocations.
Trenchless Technology is a valuable method of construction providing a safe, efficient and cost effective solution.