Alphington Sewer Project

Project Location

Alphington, VIC 3078
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Project Description

After servicing Melbourne’s northern suburbs for nearly a century, the North Yarra Main Sewer and Kew North Branch Sewer were in a worrying state of disrepair. With flows across the network often exceeding capacity, contamination risks increasing, and the outdated brick construction fast approaching the end of its serviceable lifetime, a major reconfiguration and upgrade was essential. As the tunnelling and trenchless subcontractor to Principal Contractor Lendlease, Rob Carr worked in collaboration with Melbourne Water (Asset Owner) and the Designer on this upgrade. The project included 1.5km of open trenching, 1.3km of microtunnelling, construction of 24 manholes, modifications to six siphon sump well installations and decommissioning of 2.3km of existing sewer and siphons. Rob Carr overcame key challenges on this project, including maintaining service continuity, site access and constructability limitations, constrained tunnelling environment, intersection with existing infrastructure in brownfield environment, length and grade of microtunnelling required, variable ground conditions (including river crossing), and the management of soil contamination risks. In the end, several innovations developed with our Client and Designer delivered the solutions required to successfully complete this project. One key solution delivered was the use of the ‘underpinned precast segment caisson’ for construction of the launch shaft on the main microtunnelling alignment. This provided a compact, clean, safe and suitably-sized working environment and facilitated seamless tunnelling operations. Another was the delivery of the curved microtunnelling alignment required to mitigate previously mentioned construction risks. Due to the length of the tunnel (580m) and its trajectory, navigational visibility was greatly restricted. To overcome visibility constraints and reduce the need for physical surveying within the tunnel, the team utilised a new navigation system with the capacity to determine exact position and movement tendency of the machine, displaying data in real time. This new device reduced physical surveying needs from every 15–25m to 80–100m. The works undertaken by Lendlease and Rob Carr were successfully delivered approximately 18 months ahead of Melbourne Water and the community’s expectations. The project went on to win both the Civil Contractors Federation Victoria Earth Awards 2016 (Category 5 – projects valued at over $30 million) and the National Civil Contractors Federations Award 2016 for the same category.


Status
Completed

Duration
August 2014 – July 2015

Client
Melbourne Water

Value range
$10 million - $15 million