By Tim Wood, General Manager, Asset Management, Melbourne Water
Melbourne’s population is growing. By 2030, more than six million people are expected to call the city home. A booming city means greater demand on services and infrastructure and this includes the sewerage system. Here are two projects that demonstrate how we are embracing technology to help us meet demand and achieve our goals in a safe and efficient way.
Population growth is not the only challenge for Melbourne Water – the organisation which manages Melbourne’s extensive network of underground pipes and tunnels. Some sections of this sewerage system were built more than a century ago and are coming to the end of their working life.
With these challenges in mind, Melbourne Water is taking big steps forward to improve and innovate the sewerage system to continue to successfully transfer sewage to our treatment plants. We recognise the actions we take now will define our future. Our mission is to ensure Melburnians have a secure and reliable sewerage service today, tomorrow and for generations to come.
Epsom road sewer relining
Melbourne Water has recently completed upgrade works to 1.6km of the Epsom Road Main Sewer. The 100-year-old sewer transfers sewage flows from Melbourne’s inner western suburbs to the North Yarra Main to the Western Treatment Plant in Werribee.
Melbourne Water and the service provider’s project team worked on this project night and day, every day, for more than four months. Given it was in a highly trafficked area, we aimed to minimise disruption to the local community and key stakeholders including the Melbourne Showgrounds.
Approximately 3.5km of bypass HDPE pipe were installed during the works to manage up to 550L/s flows. The unique bypass methodology was a combination of surface mounted and immersed electric pumps. Confined space personnel had to traverse up to 150m of sewer pipe, downstream of 5m head surcharged sewer pipe. A mechanical plug (plug valve) was fabricated specifically for the ovoid shaped pipe, providing a safer environment for the workforce and to control the flows to prevent sewer spills.
Sewer access manholes were located in major roads and had to remain trafficable for trams throughout the works. Prior to the relining works, 150 tonnes of built-up rubble was removed from the sewer. To renew the sewer, we used a trenchless technology technique called Cured in Place Pipe (CIPP) relining.
Installed up to 23m deep in the ovoid brick sewer pipe was 1.2km of UV (Ultraviolet) CIPP liner. A unique methodology was developed to install the CIPP liner within an offset chamber 276m away from the nearest access point, making it the longest liner in Australia.
The relining technology allowed us to reline the inside of the existing sewer with a new, structurally sound liner which became the new wall of the sewer. The benefits of the trenchless approach were:
• Disruptions and inconveniences at street level were kept to a minimum, and residents and businesses weren’t impacted by the method of open trenching
• Upgrade works were completed more efficiently Melbourne Water’s project was successfully delivered by service provider John Holland KBR, Interflow and Welltech.
Hobsons bay main sewer
Deep beneath the Yarra River, Melbourne Water’s biggest sewer project is underway. The Hobsons Bay Main, which was built in the 1960s, is being upgraded. This involves building a duplicate sewer, which will allow sewage flows to be diverted. The duplicated sewer will be used in the future to build capacity for our growing population, particularly in the Fishermans Bend precinct.
The project began in September 2021 and is expected to take three years to complete. The completed Hobsons Bay Main Sewer will be 720m long and cross beneath the Yarra River from Spotswood to Westgate Park at depths of 30-35m. It’s a critical part of Melbourne’s sewer network, transferring around 30 per cent of the city’s wastewater to the Western Treatment Plant.
One of the challenges with planning construction works on this historic site is the outdated drawings and inability to accurately assess the condition of the surrounding sewer and structures. To safely gather further asset information, the Flyability Elios 3 drone was trialled because it can safely operate in dark, GPS-denied environments and can travel several hundred metres negotiating bends, obstacles and terrain that typical crawlers cannot overcome.
The team chose to investigate using this drone as it features a protective cage, which not only enables the collection of data from previously inaccessible and dangerous environments but also captures CCTV footage of a very high quality – 4K Video at 30 frames.
Footage can be viewed directly at the surface by the operator. The device features LEDs providing 10,000 Lumens of light, as well as a rotating LiDAR sensor capturing up to 300,000 points per second. Although it is not as accurate or precise as a terrestrial scanning system, it can still generate very high-quality data and a clean 3D point cloud to support design workflows.
It flew from the surface down through the opened ‘gatic’ lid whilst the pilot remained on the surface. No personnel were required to intervene during the flight. The scanned data is dimensionally relatively accurate and the point cloud can be used to generate further 2D/3D deliverables such as a CAD drawing, BIM model and 2D plan.
The drone demonstrated its ability to negotiate within a sewer conduit as well as a complex drop structure. This method offered a very low risk and efficient way for capturing accurate as-built data in sewer structures. The information gained through this process will be used to assist with detailed design. It can also assist Melbourne Water assess existing conditions of assets.
The Hobsons Bay Main upgrade will be carried out in several phases including shaft construction and tunnelling beneath the Yarra. The project is being delivered by John Holland. Work is happening at the back of Scienceworks, so visitors can look at the construction area through in-built viewing windows in a hoarding, which also has colourful information presented on it about the sewer lifecycle and water literacy, providing a great educational opportunity.