Responding to a need: Exploring Victoria’s new sewerage systems

With modern cities ever burgeoning beyond their own boundaries and populations increasing year upon year, state of the art sewerage systems are required to respond to the need. City West Water and Yarra Valley Water are currently developing two innovative solutions as a response to the rapid residential growth that is a part of today’s urban landscape. Kate Stephenson goes behind the scenes to talk to those who are bringing the plans to life, examining two key projects that are currently in the pipeline across greater Melbourne – the Craigieburn Sewage Transfer Hub and The Spencer Street Sewer Redevelopment project.

The Craigieburn Sewage Transfer Hub

Victoria’s newest sewage transfer hub

The Northern Growth Area runs from Craigieburn all the way up the Hume to Wallan, spanning over 20 kilometres. As it continues to grow, the need to build new water, sewer and recycled water treatment plants and associated infrastructure in the area increases.
We will be spending more than 400 million dollars over the next five years to make this happen.’ Chris Brace, General Manager of Growth Futures, Yarra Valley Water.

The Craigieburn Sewage Transfer Hub is a sewage flow control facility, with on-site storage, transfer pumps and air treatment, which will fill the tanks from the Amaroo main sewer during high flow wet weather. The aim is to get waste from the Amaroo main sewer downstream to the western treatment plant, pumping and splitting sewage between downstream catchments that have limited capacity and storing flow when required. A facility of this type and size is a first for Australia and ready to set the example when it commences
operation in mid-2018.

This project is all about supporting growth and development in the Northern Growth Area (NGA). There are 128,000 new homes planned for the NGA of Melbourne, to welcome a population similar to that of Canberra. The existing sewerage network was never designed to accommodate this growth. The capacity in the local network is constrained, therefore it is only capable of receiving peak dry weather flows.

Yarra Valley Water investigated two alternative servicing strategies to get round this. The first was to build a tunnel with an estimated cost of $215m. The other alternative was a flow storage and transfer facility at a cost of $63m. The transfer hub was the smart alternative to the traditional solution. By implementing the flow storage and transfer strategy compared to the traditional tunnel strategy, Yarra Valley Water was able to reduce the sewerage servicing costs by over $100m.

‘It’s been fantastic to see it come out of the ground to know we are providing an asset to Melbourne that will support growth today and into the future.’ Sally Crook – Former Project Manager, Craigieburn Sewage Transfer Hub.

The Hub project was staged to lower community costs and to match unknown factors including recycled water demand, growth rates and
actual sewer flows.

Amaroo Terminal Manhole

Inlet Works and Drop Structure

Emergency Relief Structure to the

Merri Creek

Storage Tanks (2 X 16ML)

4 X Sewer Pump Stations

Pipelines and fittings (up to DN1600)

Air Treatment Facility

Associated siteworks including power, lighting, comms, recycled water supply, site access roads, drainage, etc.

Control integration with existing sewage treatment plant

Paul Luscombe took over as Project Manager of the Facility in November 2017. Here he gives us an insight into what makes this project one of a kind.

‘The Craigieburn Transfer Hub is a rather unique system, because it has been implemented as part of a new system rather than a retro fit of an existing network to accommodate increasing flows.

In Europe and the Americas, holding and balancing facilities similar to the Hub facility are designed as a retro fit solution for much older cities and systems, where both the sewage and stormwater flows are collected in a single pipe system and are balanced in a single facility.

These facilities are typically required for single pipe systems (combined stormwater and sewage), as the peak flows are much larger than sewage only systems. In relatively young countries such as Australia, dual pipe systems are mandated and therefore flow storage and transfer facilities have not typically been required. However similar facilities have been used at the headworks of treatment plants to try and balance flows, but not further up in the network to try and reduce infrastructure size and cost. In this respect we believe Yarra Valley Water are implementing an innovative solution.

The facility is still in construction but is due to be completed in the coming months and Yarra Valley Water are keen to see this new type of asset for them in operation. March will see Yarra Valley Water and Jacobs presenting at the Australian Water Association conference
in Brisbane to share the thinking behind the strategy and the facility. We are keen to see if there are any other opportunities out there where this type of facility can be implemented to lower cost infrastructure for the community.

One of the key functional concepts of this facility is that there is no reliance on mechanical equipment to utilise the above ground storages. The storage component of the facility is designed to be gravity fed and distributed, which means the risk profile for spills is extremely low. The second key feature of the facility is that the site levels have been utilised to allow low cost above ground storage to be used rather than traditional buried concrete storages that are considerably more expensive.

Yarra Valley Water have been conservative in the implementation of this facility as it is not a typical asset. It has been elected to install an odour control facility to manage any potential odour risk, as the odour profile of the new and developing northern catchment is unknown.

The design and construction of the first stage of the facility includes significant infrastructure provisions to enable the gravity storage at the facility to easily be increased to around 100ML without any significant infrastructure other than additional tanks. 3D modelling, FEA
analysis and BIM models are relatively new in the water industry.

It was a new approach to design for many of us involved in this project, but we have found that it helped during the design process and operator training. It will no doubt help in the future with operation and maintenance activities. For Yarra Valley Water, this is a new
and exciting space in terms of asset management. To date, there has not been much in the way of 3D information in the water sector, as normally the pipeline is underground so there’s not so much interaction with the infrastructure. It’s great to be part of new developments in this space.

We’ve also worked to get progress development shots of the project by drone, from excavation and planning stages to near completion that we are at now.

We’re really proud of the role we are playing in supporting the growth and prosperity of Melbourne. The importance of water and sewage infrastructure is critically important for these new growth areas.’

The Spencer Street Sewer Redevelopment project

Catering for CBD growth

The Spencer Street Sewer Upgrade will help to facilitate the rapid residential growth that Melbourne is experiencing, working to duplicate a century old sewerage system to cope with the ever expanding population. The upgrade is stage 1 of a 4-stage plan to increase the
capacity of the sewers in Melbourne’s CBD. The works will last for up to 15 months while City West Water lays almost 700 metres of extra sewerage pipes.

The City West Water sewer duplication works in Spencer Street will be the first of four stages of major pipe upgrades to Melbourne’s CBD sewerage system.

Kate Houlden, Project Delivery Manager of Infrastructure & Delivery at City West Water talks us through the thinking behind the upgrade, presenting some eye opening statistics. Here’s how it will be done.

‘Victoria in Future (2015) forecasts growth of approximately 60,000 new apartments in the CBD over the next 35 years, with 14,000 of these apartments within the Spencer St Sewer Catchment. Considering the high impact location of the sewer, the City West Water project
team carried out a thorough process to nominate the most suitable construction methodology and delivery approach.

This included reviewing customer and stakeholder engagement strategies, CCTV camera installation to capture real time traffic conditions during construction, noise reduction controls as well as vibration and noise monitoring.

The Spencer Street Sewer will be installed using a tunnel boring machine (TBM) and the main pipeline will be DN1400 (1400mm diameter) and 600m long.

In order to lay the pipe, three main shafts along Spencer Street will be constructed. The first (which is currently underway) will act as the launch shaft for the TBM. This shaft is 13m deep and located at the intersection of Spencer Street and Lonsdale Street.

In February, construction on the second and third shafts at Bourke Street and Flinders Lane will begin.

The TBM will enter the launch shaft and tunnel along towards Flinders Lane. Each length of pipe will be lowered into the launch shaft and be used to push the TBM forward.

Once the pipeline is installed, the shafts will be used to build three large diameter maintenance holes. These will provide ongoing access to the sewer for future upkeep.

In addition to the main works, smaller maintenance holes, a smaller pipeline and connections to the existing system will also be developed.

The Spencer Street Sewer upgrade is a shining example of how City West Water is preparing for future growth within Melbourne’s CBD.

This level of growth makes it an exciting time for the sewer and plumbing industry, as we work to ensure Melbourne’s sewer catchments continue to operate efficiently and make a meaningful contribution to Melbourne’s liveability.’

Additional Statistics

Contractors to City West Water are currently employing approximately 20 personnel per month to undertake works on the Spencer Street Sewer Upgrade. This will increase to approximately 25 during the tunnelling works. This equates to an expected 45,000 person hours.

The proposed additional 14,000 apartments in the Spencer Street catchment when fully occupied will discharge enough sewage every day to cover the playing surface (17,720 sq mtrs) of the MCG to a depth of approximately 0.3 metres! Similarly, this would fill approximately
two Olympic sized swimming pools.

Annually, the volume of sewage produced would fill the MCG be to a depth of 115 metres which is 1.5 times the height of the light towers. This also equates to 776 Olympic-sized swimming pools.