by Eamonn Kelly, General Manager Major Program Delivery, Melbourne Water
Melbourne Water is responsible for removing and treating most of Melbourne’s sewage. Modern and safe sewage treatment, while crucial to the health and amenity of a liveable city, is just one step in a process that begins in the pipes, sewers and drains built in the late 1800s, when Melbourne established its first integrated sewerage system.
Today, we manage a network of over 400km of sewers, nine pumping stations and two treatment plants. Each year this sewerage system removes and treats over 320,000 million litres of sewage – enough to fill 128,000 olympic-sized swimming pools.
With a system of this scale delivering a critical service to an ever-expanding population, it’s crucial that we take a proactive approach to the maintenance and rehabilitation of our assets, to ensure we can continue to rely on them into the future and service to our customers is not compromised.
Demand for innovation
A modern and efficient sewer system is something that most of us take for granted, but this wasn’t the case for the early settlers of this city. Right from the beginning our predecessors have had to innovate to meet huge growth in Melbourne’s population, and it’s a challenge we continue to face today.
We all know the tale of marvellous ‘Smellbourne’, the unfortunate nickname bestowed on our city by its detractors when, in the 1880s, Melbourne faced a huge public health problem, as waste from a city of approximately half a million was emptied into open drains.
This was the impetus for the sewerage system we have today, and many of the pipes, sewers and drains built when the first Melbourne homes were connected to the sewerage system in 1897 form part of our infrastructure base today.
As many of our sewer mains reach 100 or more years old, our approach to managing and rehabilitating Melbourne’s sewerage system has needed to become more and more proactive, as we find ourselves at a critical point for ensuring Melbourne continues to receive safe and reliable sewerage services.
Old becomes new
The Carlton Main Sewer, for example, is a single brick sewer constructed back in 1900. The sewer forms an important part of our network that services the areas of Carlton, Brunswick and Southern Coburg. Like much of this system, it was nearing the end of its operational life and needed to be upgraded.
Between October 2014 and October 2016 we upgraded this sewer using relining technology. We adopted a combination of cured-in-place-pipe (CIPP) and the Expanda methodology.
Expanda, which involves placing a machine inside the sewer that moves along and coats the inside with a PVC liner, was used for the circular sections of the sewer, and CIPP for the oval-shaped sections.
This method meant we could extend the life of this important asset by up to 50 years, whilst minimising impact on the community and environment. Using Expanda meant there was no need to open up the ground.
The majority of the works instead took place inside the existing sewer, with small sites set up around the existing manholes.
As part of this project we also constructed a new 510m sewer to take the stress off the Carlton Main Sewer during wet weather events and to cater for future population growth.
This 1.2m diameter sewer was installed under Pigdon and Scotchmer Streets in Fitzroy North, and forms a key part of our proactive planning for projected growth and demand in this area.
Operating in an urban environment
In addition to planning for aging infrastructure, we also need to meet the challenges of rehabilitating essential infrastructure in densely populated areas, and in areas that may be environmentally and culturally sensitive.
We adopt a variety of methods that help us carry out works in these locations with minimal disruption. In the last year we have managed ten major sewer rehabilitation projects within 10km of Melbourne’s CBD.
These include completed projects in Carlton, Moonee Ponds and Essendon, with another three currently in construction and a further four in the design phase.
Another advantage of using innovative technology, such as the Expanda methodology adopted for the Carlton Main Sewer upgrade, is that it allows us to rehabilitate an asset while the sewer is still flowing, minimising impact to services.
The Merri Creek Main sewer rehabilitation project is another example where we have been able to combine traditional and modern techniques to minimise community impact.
This project is currently in construction and involves relining sections of the sewer using a combination of CIPP and Expanda methodologies.
Where the sewer cannot be relined, these sections will be decommissioned and approximately 700m of new sewer pipes constructed using open-cut trenching and horizontal directional drilling.
Early this year we will begin rehabilitating the Williamstown Main Sewer. This upgrade project is a great example of the need for us to trial and embrace new and innovative techniques to ensure we are getting not only the best service life from our assets, but also minimising impact to the community.
Like many of our aging assets, recent inspections of the 100-year-old Williamstown Main Sewer revealed it is at the end of its operational life and needs to be upgraded. The sewer services over 7,600 properties in the suburbs of Williamstown, Newport and Spotswood and is a key part of Melbourne’s sewer network.
We will adopt sliplining technology – installing a new pipe inside the existing pipe – to rehabilitate this sewer to again extend the life of the sewer without having to dig it up.
This technology can also be used while there is a level of sewage flowing through the pipe. This will eliminate the need for bypass pumping, which has a significant noise and visual impact on the surrounding community, and sewerage services will also be kept operating during the works.
By using this method we will extend the life of the sewer by approximately 100 years and minimise the impact on surrounding residents and businesses during construction.
While Melbourne Water always aims to keep the customer at the centre of everything we do, our focus on proactive sewer management also holds an environmental imperative: if we can keep our assets in good working condition, we minimise the risk of sewage spills due to poor asset condition and thereby help protect the health and amenity of Melbourne’s waterways and bays.
Innovative, non-disruptive measures also mean that we can better protect indigenous and cultural values while carrying out rehabilitation works.
When we combine these with focused, carefully planned community and stakeholder engagement, our work in built up areas happens smoothly and with minimal disruption to customers.
Looking to the future
With Melbourne’s population expected to double in the next 15 years, demand for sewerage services will be at an all-time high.
We need to have confidence that our assets are performing as they should and will stand up to rapid population growth. That is why in addition to rehabilitation and upgrade projects we undertake a rigorous and proactive inspection program across our network.
Each year, we inspect over 60km of sewers and check on over 52km using closed circuit television. We also clean more than nine kilometres of sewers each year.
This ensures we know the status of our assets and can put plans in place to upgrade them as necessary, well before this reaches a critical level or service is threatened.
At Melbourne Water we’re proud to provide sewerage services to the city that’s been dubbed ‘world’s most liveable’ time and again.
As Melbourne continues to grow, we will need to continue to search for innovative ways to meet the needs of the community and protect environment and cultural values, while meeting our service obligations to our customers.
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