700 new homes within Clyde North’s new Kilora Estate (VIC) will now be connected to a 13m deep branch sewer line. Despite unpredictable ground conditions and wet weather, the sewer was constructed on time via 1.3km of trenchless technology, and will go on to provide a much-needed service for the expanding population of Melbourne.
Califam Constructions was chosen as lead contractor, with Pezzimenti Trenchless brought in to complete trenchless construction. SMEC Urban as project manager oversaw the installation, which is now connected into the South East Water service.
Because of the project’s impressive depth due to existing sewer levels and contour of the land, traditional open-cut construction was off the cards, with microtunnelling providing a much faster, safer and more cost-effective solution.
“Depths for these types of installations are typically around 7-8m,” said Joe Pezzimenti, Director at Pezzimenti Trenchless.
“This depth of 13m meant open-cut would have been too slow, let alone unsafe for workers and very expensive.”
Management of groundwater on site was also a major consideration for the team at Pezzimenti Trenchless. To keep groundwater at bay, 24 hour pumps were installed and continued to run until works were complete.
The type of ground was also a great challenge for drilling, as it ranged from hard siltstone to non-supportive clays.
“The ground conditions continued to change across the drill site,” said Mr Pezzimenti.
“As each type of ground required a different cutting tool, cutters needed to be modified to handle the changing ground conditions. As well as this, the head needed to be retracted on a couple of occasions to change over cutters on our microtunnelling heads.”
“Wet weather compromised our access to the site on many occasions, and certainly kept us on our toes,” said Mr Pezzimenti.
A large amount of time was also spent setting up each launch shaft along the project line, says Mr Pezzimenti. Because they were so deep, safe entry and exit was of highest priority. Califam provided specially-built shoring shields which made the job as safe as possible for each of the workers.
HOBAS Jacking pipe was used throughout construction with outer diameters ranging between 324mm, 376mm to 550mm. The longest single drive was 131m in length and 80 per cent of the job was completed with pipe of 550mm in OD.
The construction was straight on grade, in line and from manhole to manhole, with grades of the pipeline up to 1 in 400. This grade is very flat with no room for error.
According to Mr Pezzimenti, working with Califam Constructions was a great success.
“CCTV inspections were carried out shortly after construction revealing that the pipeline was successfully installed on line, on grade and within tolerance. We can definitely thank the excellent support and teamwork offered by the guys at Califam for that.”
The pipeline was completed in July 2015.
About Kilora Estate
Kilora Estate is located approximately 44km south-east of Melbourne and is comprised of 366 housing lots. The area is subdivided into 14 residential areas and includes a community facility, state primary school, regional open space and drainage corridors.
The construction of the Kilora branch sewer is part of stage 1 of development, with South East Water in charge of the area’s sewer outfall strategy. SMEC provides engineering, surveying, planning, and urban design services across the site.