Canberra’s population is set to nearly double in 40 years and building the necessary infrastructure to support the increase will be no easy feat.
Major infrastructure assets are typically out of sight, out of mind – often usually by design. But peel back the surface layers of our city and suburbs, and a complex network of cables and pipes is revealed. This hidden infrastructure provides us all with power, water, gas, internet connectivity, and wastewater removal. A major unsung infrastructure hero is our sewer network.
Canberra’s network transports wastewater through hundreds of kilometres of pipework with almost all of it ending up at a single treatment plant. Each hour thousands of litres of wastewater and solids pass quietly under our streets, with sections of the network making efficient use of gravity alongside pumping stations.
Enter Icon Water’s Belconnen trunk sewer project. Trunk sewers carry sewage from the main pipes and pump stations to the sewage treatment plant. These huge sewer pipes are generally more than 30 centimetres in diameter, but can be more than two metres across. These trunk sewers can be tunnelled through hills, and bridged over creeks.
The planning phase for the Belconnen trunk sewer started in 2015 and is one of Icon Water’s largest current infrastructure projects. The trunk sewer is a planned upgrade to accommodate recent and forecast population growth in Belconnen, Gungahlin and Hall. The new trunk sewer extends almost 2.5 kilometres and will augment the existing trunk sewer that services these areas. In recent months, locals may have noticed construction works near Ginninderra Drive between Copland Drive, Melba and Tillyard Drive in Charnwood.
The new Belconnen trunk sewer (as with all sewer networks) has one main job: to transport liquid waste and solids safely from sinks, drains and toilets efficiently and without incident. Reassuringly, there is little or no evidence of their existence when sewers like this are working well. Canberra residents pass above totally unaware.
Ventilation is a crucial part of any sewer network. If the wastewater network isn’t ventilated properly, hydrogen sulphide gas can build up in the wastewater pipes. This gas then turns into sulphuric acid, which can corrode even concrete, causing pipes and maintenance holes to deteriorate. This can eventually lead to serious blockages, leaks and other issues.
The Belconnen trunk sewer project uses four purpose-designed ventilation units known as odour control units (OCUs) located in Latham, Florey and Evatt to alleviate potential corrosion issues.
These OCUs are designed to extract and filter unwanted gas from the sewers below. The gas is fed through an activated carbon filter to remove any unpleasant smell. A ventilation stack then releases the filtered air. Airflow is boosted by fans. Air passes through a pre-filter and dehumidifier before entering the activated carbon filter.
To work efficiently each OCU must be located alongside the sewer network and be equipped with a smart electronic monitoring system. This allows for continual air quality checks, updates on filter conditions and overall system performance. If a fault is registered, Icon Water will be notified in real-time and be able to respond quickly.
As with all major construction projects, consultation and engagement with regulators and the community has been essential for project planning and delivery. As part of this process, Icon Water engaged independent specialists to conduct air quality and odour modelling assessments of all OCU site locations.
These specialists came back to Icon Water with findings indicating the OCUs were not expected to impact the surrounding area during continuous operation. OCU construction started in 2022 and is expected to finish by mid-2023.
The efficiency of the new OCUs to prevent corrosion and control odours in the Belconnen trunk sewer will allow Icon Water to remove several existing vent shafts in Belconnen, including some from around the foreshore of Lake Ginninderra.
Icon Water has spoken with community groups and residents seeking their input into the final look of the OCUs. There is community support to paint murals on the units, which follows expressions of appreciation of mural art on several other assets including the Hindmarsh Drive and One Tree Hill water reservoirs.
To learn more about the Belconnen trunk sewer project, visit the Icon Water website.