From the magazine, Installation, Microtunnelling, Stormwater, Tunnelling, Vacuum excavation, Wastewater, Water

Lonsdale sewer progresses below quiet CBD

The Lonsdale Street Sewer Upgrade is the second stage of a four-stage strategy to install a secondary 900 m long sewer line under Lonsdale Street. Rob Carr was appointed by Melbourne utility City West Water (CWW) in June 2019, and – in association with design partner SMEC – has been diligently working to deliver the DN 1400 glassfibre reinforced plastic (GRP) sewer line in the heart of the city.

Rob Carr successfully launched the microtunnel boring machine (MTBM) from its 23 m deep launch shaft on William Street in February 2020 after completing weeks of excavation activities. The tunnel will be completed in two shots of 550 m and 350 m respectively, with a 1,500 mm outside diameter GRP to be used.

Monitoring the location of the MTBM.

As of late April 2020, Rob Carr had tunnelled approximately 350 m through the first drive, with operations underway 24 hours a day, six days per week. Rob Carr Construction Manager Andrew Scarr says as with any tunnelling job there have been challenges, but the team was continually able to work its way through.

“We were below the water table at all points, but the permeability of the ground is quite low, so we turn on the pump twice per day at the launch shaft to keep the water down,” he says.

“At about 300 m we came into some river rock, or river pebbles – like an old riverbed. It had high inflow so that was a challenge for the operators.”

A bird’s-eye view of the sewer with 300 m installed.

Tunnelling during a pandemic

The shadow of the COVID-19 has hung over much of 2020 so far, with many operations hardly continuing in a fashion that could be described as ‘business as usual’. However, the work goes on for Rob Carr on Lonsdale Street, albeit without the hustle and bustle usually expected in a dense urban area such as Melbourne’s CBD.

Mr Scarr says after the solving some minor logistical issues with workers coming in from interstate, the surrounding noise, or lack thereof, in the project’s location was the biggest difference from when works began.

“It’s significantly quieter, like a ghost town,” he says. “Often it’s more like a quiet Saturday afternoon than a weekday with how little people and traffic is around.”

Rob Carr and CWW have been adhering to all coronavirus prevention guidelines onsite, including having ample supplies of hand sanitiser, putting up relevant signage and practicing social distancing. Through it all, Mr Scarr says the team’s performance has been first rate.

“Everyone is working well together and CWW is always on hand to help where they can, particularly with the challenges presented by COVID-19.

“We are still on track to complete the project in 2020.”

This article was featured in the June 2020 edition of Trenchless Australasia. To view the magazine on your PC, Mac, tablet or mobile device, click here.

For more information visit the Rob Carr website.

If you have news you would like featured in Trenchless Australasia contact Journalist Sophie Venz at svenz@gs-press.com.au

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