The West Gate Tunnel, a much-needed alternative to the congested West Gate Bridge, was proposed by Transurban in 2014 and is now well underway with a fleet of contractors offering their expertise on the project.
With much of the existing pipe infrastructure in and around the works zone not meeting the new service life requirements, Rangedale Rehabilitation and Renewals (RRR) was a key part of the rehabilitation scope of works which included a massive DN 1130 gravity stormwater pipe.
The reinforced concrete pipe, that discharged into the Maribyrnong River, was in a tidal area so spent much of the time completely underwater.
“It was littered with barnacles, typical in shallow and tidal waters, that had built up over many years”
CCTV inspection also revealed the pipe had been compromised from silt build up in the water and would therefore require extensive high-pressure water cleaning and spot rehabilitation works before being completely relined to meet standards.
RRR experience and UV set up for underground infrastructure and rehabilitation put them in good stead to meet the requirements of the project, however they had many safety, financial and environmental considerations to meet.
“Access was going to be our biggest hurdle”, explained Kermeen. “The upstream end of the pipe was very difficult to access as it was underneath a very low bridge, so all our rehabilitation and cleaning works had to be conducted from the river end of the pipe.”
“This was a very unusual approach as there wasn’t the option for excavation works.”
“From our initial assessments we knew it would be necessary to build a koffer dam to stop the flow of water to the pipe inlet before we could commence cleaning the pipe.
This dam would also be vital when it came time to reline the pipe to eliminate water coming into the pipe.”
As one of RRR biggest DN’s to date and many stringent safety regulations to consider, the crew of 7 got to work conceptualising a plan for the client’s safety team to review.
“Our plans underwent an extensive and robust review process”
says Josh Challis, Operations Manager.
The upstream pit that was to be used to reline the pipe had been classified a ‘confined space’ work environment, meaning it had not been designed to be occupied by a person for a long period of time.
“Once deemed a ‘confined space’ there were a lot of red flags to overcome and our approach was appropriately scrutinised”, explains Kermeen.
The dam itself took just over 2 weeks to set up and involved constant maintenance as the rock bags sank further into the riverbed as the tide changed.
The upgrade commenced in end of April after extensive covid related delays, and once all parties were comfortable with the measures in place to manage the hazards and risk, cleaning commenced.
“The team used high-pressure water to remove the silt and barnacle build up from the river and conducted regular CCTV inspections to check progress,” explains Challis.
As the Maribyrnong River faces various environmental threats from pollution and contamination, RRR installed an environmental barrier for the purpose of intercepting the flow of water carrying contaminants.
They were also unable to discharge anything in the waterways, so had to dispose of all cleaning residue externally with their industrial vacuum truck.
SAERTEX-LINER® MULTI Type S+, a UV-cured fibreglass-reinforced lining tube, was selected for the relining part of the project, as it promised a short inflation rate and cure time which was vital on a project where works were dictated by the tides.
This liner also has a technical service life of 100 years. Kermeen confirmed.
“The design life and ease of use of this UV product was definitely a benefit on this project.”
“What we like about this product and UV technology in general, is that you’re not committed until the lights goes on. It is a forgiving process when you need extra time, particularly if you are met with bad weather.”
By the time it came to execute the reline, a large crane related to the greater West Gate Tunnel Project, had been moved into the area, posing another logistical challenge as RRR couldn’t get their UV truck as close to the installation site as usual.
It was also a very labour-intensive job with the heavy liner, as the RRR conveyor couldn’t get close enough to perform its duties.
“Aided by a crane, the crew had to move the liner into place over the bridge to the opening at the river end of the host pipe, where the liner was then manually pulled into place.
Once everything was in place, the liner was inflated, the UV light train was inserted, and the liner was cured in 1 hour at 0.35 meters per minute.
“The reline itself was the easy part,” explains Neil.
“Although this project took some high-level planning to ascertain all the risks associated, we see the long-term efficiency gains to be had with UV technology and SAERTEX-LINER’s.”
Challis also agrees, “UV technology is here to stay. RRR has invested in their equipment and can offer many efficient and effective ways to rehabilitate pipelines with trenchless techniques.”
Pipe Core are proud to be the distributor for SAERTEX multiCom® in Australia and New Zealand and more information is available at: https://pipecore.com.au/saertex
Call 1800 747 326 for stock enquiries.