Microtunnelling contractor, Rob Carr, has commenced construction of a new 1 km long wastewater pipe running under the heart of Brisbane, Queensland. The Urban Utilities project is part of a major infrastructure upgrade to cater for population growth in the city’s north, which is expected to increase by 37,000 over the next 30 years.
An Australian Bureau of Statistics report based on data from 2019-2020, found greater Brisbane’s population was growing faster than anywhere else in the country, at a rate of 1.9 per cent per year, and its popular northern suburbs are booming. Urban Utilities is responsible for providing reliable water and wastewater services for the growing city, with the utility servicing more than 1.6 million customers across Brisbane, Ipswich, Scenic Rim, Somerset and Lockyer Valley local council areas in South East Queensland.
To cater for the expected 37,000 additional people in the north Brisbane region who will be relying on the utility’s services over the next 30 years, Urban Utilities is investing $45 million to upgrade the area’s essential wastewater network, by building the Breakfast Creek Trunk Sewer Main Upgrade. Stretching from Bowen Hills to Windsor, the 1 km long and 1.8 m internal diameter pipeline will be one of the largest in the utility’s 9000 km wastewater network, transporting up to 400 L of wastewater per second once complete.
Urban Utilities spokesperson Michelle Cull says the project is a key aspect of the organisation’s plans to support population growth in the region.
“We plan well ahead for the future and the population in this catchment area on Brisbane’s northside is expected to grow by around 40 per cent over the next three decades,” she says.
“That means a lot more toilets flushing, washing machines running and showers being used, so it’s important we continue to invest in essential infrastructure for our growing community. The new sewer will run beneath some of Brisbane’s busiest roads, including the Inner City Bypass, and will transport the wastewater from thousands of homes and businesses to our Luggage Point Resource Recovery Centre, where it’s treated.”
Construction of the sewer will utilise microtunnelling, with Rob Carr contracted by Urban Utilities’ delivery partner Fulton Hogan Utilities to complete the trenchless design and construction, taking place at depths of up to 14 m, around four storeys, below ground.
“By using this state-of-the-art technology, we’re able to carry out this significant upgrade while minimising impacts on traffic, customers and the community,” says Cull.
“The project is a feat of engineering and it’s a far cry from the traditional tunnelling methods used by miners to build the city’s largest and oldest sewer pipe – the S1 Main Sewer – in 1915.”
Rob Carr general manager Angelo Soumboulidis says the company was contracted for the project after working closely with Fulton Hogan Utilities on a design which leveraged innovation.
“We have a strong reputation as a leader and innovator in the industry with a proven track record of delivering high-quality work,” he says.
“Working closely with our client, Fulton Hogan Utilities, our innovative final design solution minimised disruption to the surrounding community and limited environmental impact.
“Our commitment to providing innovative solutions to our clients’ needs and our dedication to delivering exceptional customer service were also key factors in our selection for this project.”
Rob Carr is using a 29 t Herrenknecht microtunnel boring machine (MTBM) named Leila Perry after the granddaughter of George Edmonstone, a politician who made significant contributions to Brisbane in the late 1800s. The family has also gifted the land where construction of the project is taking place.
The 29 t MTBM is also one-of-a-kind, having been transformed into a colourful work of art created by a local high school student. The design is inspired by Brisbane, representing the city’s iconic jacaranda trees, the Brisbane River and Story Bridge.
On 13 March, the MTBM was lowered into the launch shaft in Perry Park, on the corner of Folkstone St and Edmonstone Rd in Bowen Hills, beginning its journey west towards Windsor. The machine will pass underneath the Inner City Bypass before reaching a retrieval shaft adjacent to the Airport Link northbound entry ramp and Lutwyche Road intersection where it will be recovered.
The MTBM will tunnel through Brisbane tuff rock up to 150 MPa traversing an innovative alignment, and will use pipejacking to install 334 lengths of reinforced concrete pipe which will form the new sewer main as it progresses.
Rob Carr project manager Thierry Candito says the contractor is excited to be contributing to such an important project, ensuring the growing city of Brisbane can continue to enjoy essential services now and into the future.
“This project is very interesting and challenging,” he says.
“The pipejacking operation is only one part of the project. We have many activities happening in parallel that we need to plan and coordinate carefully.”
To be ready for the MTBM launch, Rob Carr first had to excavate and complete an underpinned segmental shaft up to 15 m deep. In parallel, the company started construction of the first stage of connecting the tunnel with Urban Utilities’ existing S1 sewer.
While this work was ongoing, the contractor also installed a 10 t portal crane on the surface, which will provide logistical support for deliveries to site and lower jacking pipe to the foot of the shaft. The company is also concurrently constructing the receival shaft using the caisson sinking technique.
Once the MBTM completes its journey to Windsor, Rob Carr will undertake high density polyethylene welding of the pipe joints, while also carrying out the second stage of the S1 tunnel connection. Once this has been completed, Rob Carr will move onto constructing maintenance holes at either end of the pipeline alignment.
Candito says the experience and knowledge of Rob Carr in delivering complex projects will help them to meet three of the key challenging aspects of the installation, including the MTBM passing under a live rail crossing.
“We are working closely with our client Fulton Hogan Utilities and Queensland Rail for this operation, and are implementing a 24/7 rail monitoring system,” he says.
“We have selected the optimum location to set up a theodolite that will continuously check target prisms installed along the rail. Through a cloud-based website, we will be able to monitor the rails in real time while the MTBM operates underneath.
“With this live input, we will be able to better manage the operation of the machine.”
The MTBM will also travel underneath a creek in the area and Rob Carr is working with Fulton Hogan Utilities to finalise the parameters and a process for executing this important section of the alignment.
“We have completed additional boreholes and a geotechnical investigation to have the most accurate data along the tunnel alignment,” says Candito.
“We have completed an MTBM face pressure analysis with the data received and are now reviewing it with third parties to ensure it is satisfactory. We also plan to stop the machine prior the creek, complete cutter head maintenance and check machine’s system, allowing us to mitigate risks of a breakdown or maintenance while traveling below the waterway.
“Finally, the last challenge is our people, who are the ones making this project a reality. We need to ensure they are working in the best environment possible and give them the opportunity to continue to grow throughout the project and keep them safe.”
Soumboulidis says the project is an opportunity for the company to once again illustrate its expertise in microtunnelling and trenchless pipeline construction.
“The project is incredibly important to Rob Carr as it represents our commitment to providing innovative and cost-effective solutions that meet our clients’ needs,” he says.
“We are able to showcase our expertise in microtunnelling and complex civil works, delivering efficient solutions, whilst simultaneously minimising our environmental impact.”
Construction of the project is expected to take 18 months and be completed in 2024.
For more information visit Rob Carr’s website.
This article appeared in the April edition of Trenchless Australasia. Access the digital copy of the magazine here.
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