As regional utilities make moves to fortify and expand their networks around the state, trenchless operators are overcoming challenging geology and preserving environments with expertise.
Sewer Network in Dandenong Ranges
Yarra Valley Water is installing 91 kms of a reticulated pressure sewer network in the Dandenong Ranges. The geological make-up of the ranges, as well as a number of hard-to-access areas, has necessitated the use of trenchless technologies
For many years, development of the Dandenong Ranges has been held back by lack of access to a sewerage network. Homes in the area rely on septic systems that require property owners to manage their own wastewater. Some of these older systems discharge grey water directly into storm water drains, impacting delicate ecosystems and waterways. The new sewerage network will allow the local community to modernise while still preserving the delicate environment.
The project faces several challenges. Delivery partners Interflow, Melbourne Pipelines and Pressure Sewer Services Australia (PSSA) are installing DN 50 to DN 90 polyethylene pipe around existing services, dense and protected vegetation, narrow roads, steep hills, and a community going about their daily lives.
Shem Macdonald, construction manager for Melbourne Pipelines, talks about some of the challenges their drillers have encountered.
“We’ve gone from friable red soils in Monbulk to hard ground, boulders and cobbles higher up in the hills. The drillers’ experience and expertise are needed to determine how we deal with each ground type: do we knock floaters out the way, grind through them or cut our losses and stop to excavate and remove them?” said MacDonald.
“We’re also relying on proving pot-holes and excavations to provide a better idea of ground conditions so we can make more informed decisions on our own drill rig selection, positioning and set-up, and using B&M Infrastructure’s pneumatic drill rig for exceptionally hard ground.”
The narrow lanes, dense vegetation and limited space mean contractors are using small water trucks, vac trucks and excavators to reduce their footprint. Site dumpers transport materials, equipment and longer hoses to the drill truck, offering more flexibility with drill truck set-up.
“We have a variety of trenchless options for property connections such as horizontal directional drilling, a piercing tool, hydro borer and bed borer,” says MacDonald.
HDD protecting native wildlife in Gippsland
Water and wastewater in Warragul and Drouin are getting an upgrade as part of the western ring main project.
The towns include two of the most rapidly growing populations in the Gippsland region, prompting the company to keep ahead of this growth by constructing a new 4.3 km water main.
Warragul has only a single main running through the centre of town, says Gippsland Water’s project engineer for the new pipeline, David Suter. The new water main will provide much needed redundancy to the Warragul system.
Horizontal directional drilling (HDD) has been chosen to complete the project, as the area is home to some important native species including the Giant Gippsland Earthworm, Warragul Burrowing Crayfish and Strzelecki Gums.
Running the pipeline along already disturbed areas such as the roadside, combined with the use of HDD, will enable operators to keep the impact on these species to a minimum, as well as reduce the cultural heritage and potential artefacts of the area’s Traditional Owners.
The pipeline will assist development in the south-west growth corridor of Warragul, while serving double duty by increasing the volume and security of water supplies for the town of Drouin.
Works on the pipeline are expected to be completed in late 2023, with further work possible in the future to extend it to the south basin, in line with potential urban development.
Heavy hitters for SRL shortlist
Progress towards Melbourne’s suburban rail loop (SRL) is rolling ahead with the announcement of the shortlisted firms vying to build the massive project.
Three joint ventures, all global industry leaders, have been shortlisted for the tunnelling contracts for what is being called a ‘city-shaping’ project in Melbourne’s eastern suburbs:
- CPB Contractors, Ghella and Acciona Construction Australia: These companies bring with them a wealth of experience in tunnelling and transport infrastructure. Past projects include Brisbane’s Cross River Rail, Sydney Metro and the Caulfield to Dandenong level crossing removal
- John Holland and Gamuda (Australia) Branch: With extensive experience, these have been responsible for a number of projects in Melbourne – Melbourne’s metro tunnel and city loo – as well as abroad
- Webuild and GS Engineering and Construction Australia: Well known globally, these have worked on the North East Link tunnels, as well as projects in Asia and the Middle East.
SRL CEO Frankie Carroll was encouraged by the interest in the project.
“This competitive process has been a massive vote of confidence in Suburban Rail Loop – with construction giants from around the world vying to partner with us to deliver this city-shaping project,” said Carroll.
The project is well on track with the first contract to be awarded next year for twin tunnels between Cheltenham and Glen Waverley.
Initial works on SRL have already begun in Clayton and major works have been given the green light due to an extensive Environmental Effects Statement.
Jacinta Allan, the Minister for Suburban Rail Loop spoke indicated the project could generate up to 8000 local jobs, creating opportunities for professional growth.
“SRL East is a project Victoria needs… this is an exciting day as we move closer to the start of tunnelling,” said Allan.
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This article appeared in the December edition of Trenchless Australasia. Access the digital copy of the magazine here.