The second instalment of a four-stage strategy to install a secondary 900 m long DN 1400 glassfibre reinforced plastic (GRP) sewer line under Lonsdale Street in the heart of Melbourne’s CBD, the Lonsdale Street Sewer Upgrade is progressing on schedule through the work of expert trenchless contractor Rob Carr and major Melbourne water utility City West Water (CWW).
Melbourne’s sewer network is more than a century old and a range of sewer works have been tabled by the Victorian State Government in order to prevent the prospect of an outdated and inefficient system.
Rob Carr was appointed by CWW in June 2019 and, with its design partner SMEC and client CWW, liaised with all relevant stakeholders to ensure the project commenced on schedule and in an orderly fashion.
Launch time
After weeks of excavation activities, Rob Carr completed the 23 m deep, 6 m inside diameter (ID) launch shaft on time in late February 2020, with all jacks set and the microtunnel boring machine (MTBM) lowered in at the site on Lonsdale Street between King and William streets.
Rob Carr Construction Manager Andrew Scarr says, at the time of launch, the team was continuing to work on the retrieval shaft near the corner of Lonsdale and Elizabeth streets.
“The piling has been completed and we’re excavating at the moment. We’re about 4 m down and we have to divert a sewer, then we’ll be dig down to approximately a 9 m depth for the retrieval of the MTBM,” says Mr Scarr.
The 900 m tunnel will be completed in two shots of 550 m and 350 m respectively, with 1,500 mm outside diameter GRP pipe to be used. Mr Scarr says Rob Carr anticipated the initial 550 m drive would be completed in approximately seven weeks.
“We currently have around 15 staff working on site, which will ramp up to just over 20 once we move to working double shifts,” he says.
“During the drilling of the mainline we also have to complete a short 20 m drive from the Elizabeth Street retrieval shaft into an existing manhole before we retrieve the MTBM. We then we have to turn the machine around and drill the remaining 350 m down to Spencer Street.”
With works going ahead as planned and on schedule, Rob Carr anticipates works are on track to be completed by late 2020.
For more information visit the Rob Carr website.
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