Around Australia, various utilities employ trenchless technologies to install and rehabilitate buried water and sewer network infrastructure. These technologies offer a range of benefits over traditional open-cut methods and, in recent years, have played vital roles in a number of major infrastructure projects.
The subsurface asset construction and rehabilitation techniques known as ‘trenchless technologies’ play important roles in infrastructure projects in various industries throughout Australia.
As the name implies, trenchless technologies involve minimal surface disruption compared to traditional opencut construction methods.
Types of trenchless construction include microtunnelling, horizontal directional drilling (HDD), pipe jacking and horizontal auger boring. Trenchless rehabilitation techniques include sliplining, pipe bursting, pipe lining and curedinplace pipe lining.
The water industry is one of the major users of these techniques within Australia, employing them in a range of projects to construct, maintain and rehabilitate the extensive networks of buried pipelines that provide vital sewer and water services across the country.
A number of key benefits make trenchless technology options attractive to asset owners for use in Australian water and sewer infrastructure projects.
Utilities across the country have used various trenchless construction and rehabilitation techniques for an array of different major infrastructure projects.
Prioritising sewers in sydney
Sydney Water employs trenchless technologies quite extensively across its water and sewer networks.
Paul Plowman, General Manager of Liveable City Solutions at Sydney Water, says that using trenchless solutions on projects can have many benefits to both the utility and the wider community.
Not least among these are reductions to the disruption, cost and risk associated with completing major infrastructure works.
“Sydney Water uses industry partners offering trenchless technologies widely across a range of asset rehabilitation and installation projects,” says Mr Plowman.
“In many situations trenchless technologies have provided great value for Sydney Water. The technology offers the benefit of being able to go under or around significant features in the landscape, avoiding the need to cut trenches through those features.
“This can reduce damage and disruption as well as providing the best construction risk and cost solution for our customers. Using a trenchless solution can avoid damage to a site with significant archaeological value, can avoid delays to the community when a pipe needs to cross a major rail or roadway, or could reduce the construction cost and risk associated with a tricky river crossing.”
Sydney Water’s Priority Sewerage Program, which connected many previously unsewered areas of the Sydney metropolitan region to the wastewater network, incorporated trenchless technology to great effect.
“Trenchless technologies have been used on the program to lay the many kilometres of small diameter pressure sewer networks that collect wastewater from houses. These networks run directly under the streets and private properties in the villages. Trenchless technologies often provide a costeffective solution with minimal impact to the communities we work in.
“The program has also used trenchless technologies to install the larger transfer pipelines that take the wastewater collected in the village to our treatment plants. Trenchless solutions have helped tackle the challenges presented when these pipelines need to cross major rivers, transport corridors or environmentally significant lands.”
Innovating with spray lining in Victoria
Glenn Wilson, General Manager of Infrastructure Services for Yarra Valley Water in Victoria, also believes that trenchless technology can be beneficial in many infrastructure works, often allowing projects to be completed more quickly, with fewer negative impacts to customers and at a lower cost.
“Trenchless requires minimal excavation and reduces both traffic disruption and the need for extensive traffic management, which can be expensive over an extended period of time,” says Mr Wilson.
While Mr Wilson stresses that each project should be assessed individually to determine whether trenchless techniques are appropriate, he states that, in many cases, trenchless construction is a great option for Yarra Valley Water.
“We are constantly on the lookout for ways to innovate and improve the way we currently do things. If trenchless technology can help to minimise disruption to customers and reduce costs then I would advocate its use where possible,” said Mr Wilson.
Yarra Valley Water is proactive in finding ways to incorporate innovative technologies to unlock benefits for the utility and its customers, and one of Mr Wilson’s recent projects involved trialling a new trenchless technique for spray lining water mains.
“The new spray-lining technology works by applying a quick-curing polyurea solution to the inside of the pipe. The coating is applied using a rotating applicator that moves up and down the pipe, effectively building a new pipe inside of the old one. A safe and effective solution, spray lining will reduce costs and disruption to both the local community and the environment when renewing water mains,” said Mr Wilson.
Rehabilitating a century-old sewer
According to Richard Petterson, Executive Leader of Operations and Service Delivery at Queensland Urban Utilities, trenchless technologies have frequently helped the company deliver infrastructure renewal works as quickly, safely and cost-effectively as possible.
“There’s a great need to upgrade our water and sewer systems to cater for a growing population, yet there’s also a need to deliver these works with minimal disruption to both the community and the environment.
“This is why Queensland Urban Utilities is keen to continue using trenchless technologies, especially where there’s cost efficiencies over conventional construction techniques,” said Mr Petterson.
Currently, Queensland Urban Utilities is undertaking a large project to rehabilitate Brisbane’s oldest and largest sewer pipe, the S1 Main Sewer, using trenchless methods.
“In a technique called spiral winding, a polyethylene liner – reinforced with steel ribs – is fed down the manhole and wound inside the existing concrete pipe in one continuous piece. After installation, a cement grout is injected into the lining to secure it in place,” says Mr Petterson.
Cured-in-place pipe (CIPP) is also being used to reline the curved sections of the S1 Main Sewer, and according to Mr Petterson, this embodies a great example of the benefits of trenchless technologies.
“The pipe is more than 100 years old, with diameters up to 1.5m and it lays up to eight storeys below one of the busiest roads in the state. Trenchless technology allows us to undertake this enormous task with minimal impact to the community,” he said.
“In fact, traffic flows right above the worksite with many motorists oblivious to what’s going on underneath their wheels. Compared to conventional pipe laying methods, trenchless technology is generally faster, cheaper, safer and less disruptive,” says Mr Petterson.
Extending asset lifespan in WA
Mark Leathersich, General Manager of Asset Delivery at Water Corporation, employs trenchless techniques across a diverse range of water and wastewater projects, including vital programs to rehabilitate aging assets.
“Utilising this technology allows us to extend the life of vital wastewater infrastructure by 50 to 70 years, without the need to dig up streets in urban areas to access wastewater pipes,” says Mr Leathersich.
“Trenchless technology also allows Water Corporation to minimise disruption to stakeholders and residents by removing the need to excavate land. This allows work to be completed with minimal traffic management, clearing and disruption to land.”
Completing critical crossings
According to Jim McGuire, General Manager of Commercial and Business Development at SA Water, the greatest benefits of going trenchless come into play when it comes to crossing obstacles like roads and rivers.
“Currently the many available trenchless technologies are relaying water pipes at a higher cost per metre,” he says. “However, in situations where critical crossings occur, trenchless technology has shown to be a real advantage.”
One such project was the Hawthorndene River Crossing, which involved directional drilling under Brownhill Creek.
“The project to replace a DN250 MSCL water main was located just out of the Adelaide CBD,” says Mr McGuire.
“The water main was a critical piece of infrastructure due to it being the only feed to the Hawthorndene Tank. The main had a leak, which was slowly getting worse. A material test was carried out and determined this section of main under the creek was required to be replaced.
“Due to the main’s location within a high traffic area, with a step retaining wall supporting the river bank, an open cut method was not an option. A bridge option was also not feasible due to the 100 year flood design of the creek and the risk of floating objects hitting the above-ground pipe.
“In the Hawthorndene River Crossing project, trenchless technology became the best solution, as the directional drill allowed the pipe to be installed under the river and the retaining wall. This minimised the impacts to the local community and traffic in the area. Potential issues were also deemed minimal, compared to the open-cut option,” said Mr McGuire.
A paradigm shift for construction and renewal
Mike Stokes, Program Manager at South East Water, Victoria, says that the benefits provided by trenchless technology are driving an increased uptake of these solutions for pipeline projects.
“They provide safe, low cost solutions that can be delivered quickly when used by experienced contractors in the right scenario and have limited impact on our customers and other stakeholders. They’ve become the norm, rather than the exception,” said Mr Stokes.
Trenchless technology played a vital role in South East Water’s Peninsula ECO project, which involved the installation of a 235km reticulation pressure sewer by horizontal directional drilling (HDD) on the Mornington Peninsula, from Rye to Portsea.
“The project was delivered by two contractors, Zinfra and Interflow, in 18 months of actual construction, against an original anticipated program of 30 months. HDD was selected for a number of reasons, but predominantly due to the low environmental impact and significant cost savings when compared to traditional open trench techniques.
“As an area of high environmental and cultural heritage importance, the HDD technique significantly reduced the impacts on both, while providing rapid installation in the narrow residential streets of the Peninsula with minimal surface disturbance.
“The construction impact was often so minimal and quick, home owners hadn’t even noticed the sewers had been installed. By delivering the project as one, rather than the traditional 15 year rollout, significant cost savings of $150million have been realised, resulting in this being returned to customers in the form of lower priced property connections,” says Mr Stokes
Trenchless construction is also a part of South East Water’s ongoing renewals program.
“This renewals project involves the replacement or rehabilitation of existing reticulation water and sewer assets across the South East Water region. Approximately 35km of water mains and 20km of sewers are replaced under our renewals program per year, with 98 per cent of those being completed using trenchless techniques.
“Water mains are predominantly renewed by pipe bursting, slip lining or HDD, with a very small percentage being carried out by traditional highly disruptive open trench works.”
Protecting sensitive environments
For Theo Vlachos, Acting Manager of Water and Sewer Projects at City West Water in Victoria, trenchless technologies provide the utility with an effective solution to minimise the environmental impacts of construction works.
“Trenchless technologies minimise the disruption in roads and streets where much of our renewal and rehabilitation programs are undertaken. They also allow City West Water to construct mains across creeks, rivers, roads, rail and avoid areas with flora, fauna and cultural sensitivities,” says Mr Vlachos.
Mr Vlachos believes that the uptake of trenchless technologies will continue to increase as improvements in the technology allow for a wider range of bores and soil conditions.
“City West Water has embraced trenchless technology for most of its construction activities. However, there would be further utilisation as the technology improves allowing larger bores to be implemented and boring through mixed ground conditions (clay and rock),” he says.
The triumph of trenchless
Overall, our interviewees identified a number of factors that they believe will drive further growth in the use of trenchless technologies throughout the water industry.
These included changing trends in population density and community expectations, further innovation increasing the versatility of trenchless construction techniques, and reductions in the cost of employing trenchless technology as it becomes more common.
Melbourne Water Project Manager, Andrew Moorhouse, who has overseen trenchless works including those involved in the $50 million Alphington Sewer Project, believes that the modern public is growing less tolerant of the disruption and loss of amenity associated with older pipeline installation methods such as trenching.
“There is a greater community expectation of infrastructure projects causing minimal disturbance which will drive the adoption of trenchless methods in many cases,” he says.
He believes that the main deterrent to using trenchless technology is cost, and that as the costs associated with trenchless technology reduce, the uptake of these technologies will boom.
“The pressure to drive down costs is already having increasing influence on how things are constructed in this age, and any technological improvements that reduce trenchless costs will go a long way towards making them the preferred construction method,” says Mr Moorhouse.
Meanwhile, Rex Dusting, General Manager of Infrastructure at South East Water in Victoria, believes that the uptake of trenchless technology will also be driven by changes in where new development works occur.
While open trenching is considered more acceptable in Greenfield areas with less existing infrastructure, many new developments now occur within built up areas where trenching causes unacceptable disruption.
“Times are changing as we are now seeing over 50 per cent of new development occurring within inner city areas, activity centres together with a general trend of converting single detached dwellings to multiunit developments.
“Clearly there is a significant disruption element to the community when augmenting or renewing pipe infrastructure and this is where we see the compelling case for adopting nodig technologies,” he says.
The future is trenchless
Water and sewer projects around Australia are reaping the benefits of employing trenchless technologies during infrastructure works.
Trenchless methods of construction and renewal are viewed positively throughout the industry due to their ability to enable works to take place quickly, efficiently and safely, while minimising environmental and community impacts.
This is especially vital in established urban areas as existing water and sewer infrastructure ages and requires renewal, or when these networks require augmentation to cater for an expanded population.
Due to their indisputable benefits, in coming years we can expect to see even more water and sewer infrastructure projects across Australia going trenchless.