Yarra Valley Water is currently installing 91 kms of a reticulated pressure sewer network in the Dandenong Ranges, a feat made possible only with the advent of trenchless technology.
For many years, development of the Dandenong Ranges has been held back by lack of access to a sewerage network. These areas are reliant on septic systems that require property owners to manage their own wastewater onsite.
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, and preserve and improve the environment.
But installing a sewerage system in the Dandenong Ranges is a challenging task. Delivery partners Interflow, Melbourne Pipelines and Pressure Sewer Services Australia (PSSA) are currently successfully installing DN50 to DN90 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, talked about some of the challenges their drillers have encountered in “the Hills”, as they’re known locally.
“Our drillers are experiencing all sorts of ground conditions in the Dandenong Ranges. 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, and offer 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,” said MacDonald.
MacDonald explains it wouldn’t be called “the Hills” if there wasn’t steep terrain.
“We excavate flat areas for better drill rig set up and longer drill lead-ins facilitate better drill rig set-up to suit site conditions. Longer hoses for drilling enhance the ease of navigation through steep properties.”
And the wet weather this year? A philosophical shrug, “it is what it is”, said Shem.
For more information about Yarra Valley Water’s project, visit the website.
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