Microtunnelling contractor Rob Carr is the tunneller of choice in the Fulton Hogan Delplant Beca joint venture’s (FHDB) sewer works beneath the streets of South Melbourne on behalf of South East Water.
The Hanna Street Stage 1 capacity upgrade project is part of the larger South Melbourne Sewerage Capacity Upgrade being undertaken by Melbourne’s water utility, South East Water.
Proactive and necessary
Population density in South Melbourne is increasing as time goes on. The existing sewer system is expected to experience significant strain as this happens. In addition, the system needs to be proofed against future extreme weather events in order to protect the South Melbourne catchment.
Josh Sneath, Rob Carr’s Project Engineer for Hanna Street Stage 1, confirms these concerns with a practical view from the ground level.
“With the number of high-rises going up in the surrounding area, we are getting ahead of the strain predicted for the current sewer system,” Sneath says.
Not without challenges
Work commenced in late September 2022, with Rob Carr beginning 270 m of microtunnelling and installing glass fibre reinforced plastic (GRP) pipe for the new network.
The project also requires two segmental shafts, one with an internal diameter (ID) of 6 m, and the other a 4.5-m ID.
“There’s also an eight by five metre pile shaft,” says Sneath. “We’re constructing it over the South Yarra main, where we’ll eventually install a GRP manhole.”
The pile shaft will connect up the branch sewers that Rob Carr is constructing and tie them in with the South Yarra Main, bolstering the whole network.
The work is not without its challenges, of course. But Rob Carr is no stranger to delivering on technically difficult jobs.
With the number of buildings going up in the area, as well as other complications surrounding the location, the company is still delivering well on the project.
“We’re working in a tight community space, so we have to keep our footprint as small as possible,” says Sneath.
Teams have managed to keep most of the roads in the area open with at least one lane of traffic continuing to minimise the impact on the surrounding community.
The tie-in to the South Yarra main will occur via a 2-m ID brick drain which, according to Sneath, is likely to be the most difficult part of the overall project.
This sentiment is echoed by Colm Dickey, Rob Carr’s Construction Manager for the project.
“The sewer flow has to be kept live during the tie-in work and while we’re building the manhole, which obviously presents some technical challenges,” says Dickey.
In order to complete the work, the teams have to install a flume pipe while the sewer is live.
“There’s some tricky brick removal sequencing involved in that, we have to be very careful about which brick we remove as we go,” says Dickey.
Once the bricks are removed the flume can be installed and Rob Carr’s teams can get to work constructing the manhole.
Constant teamwork is the key to success
Completing a major project in such a heavily populated area is a difficult ask, but one that has succeeded largely because of Rob Carr’s long proven track record of teamwork and its focus on collaboration and communication with project partners.
Dickey has not worked directly with FHDB before but has witnessed Rob Carr’s strong relationship with the JV first-hand during his work on the Hanna Street Stage 1 project.
“The collaboration really has been phenomenal,” he says. “We’ve worked through any and all issues that have arisen, from executing the tunnelling to the technical side of things – like monitoring ground and water conditions.”
“It’s an interesting project, with a lot of collaboration needed to keep it moving,” says Sneath. “Tie-in works are on track to start in January, and we should be finished with stage 1 by April or March next year.”
The Hanna Street Stage 1 project once again demonstrates what can be achieved when operators are able to work closely together with a unified goal, a virtue that Rob Carr explicitly shows time and again as the company assists in future-proofing Australia’s infrastructure one successful project at a time.
For more information visit Rob Carr.
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This article appeared in the December edition of Trenchless Australasia. Access the digital copy of the magazine here.