Trenchless technology refers to network monitoring equipment and techniques used to install, repair, or replace water infrastructure while minimising surface disruption. These techniques eliminate the need for open-cut excavation, and therefore offer environmental, social and economic benefits to government and the community.
In addition to these immediate benefits, trenchless technology often results in reduced costs. In a 2008 paper, titled ‘Cost and Risk Evaluation for Horizontal Directional Drilling versus Open Cut in an Urban Environment’, authors Neil J.A Woodroffe and Samuel T. Ariaratnam compared the costs of open-cut excavation with trenchless methods, and came to the conclusion that a trenchless approach often reduces overall construction costs in an urban environment. Additionally, trenchless technologies have been developed to reduce interruption to supply during rehabilitation works, thereby eliminating the costs associated with resident notification.
Trenchless techniques for installing new infrastructure and rehabilitating existing underground assets provide many benefits to councils, water authorities and communities. It is vital for workers within the water industry to be across trenchless methods and technologies in order to provide safer worksites for contractors, to minimise social costs to communities, and to reduce costs involved in capital works programs.
Trenchless technology is also often favoured in the water industry for its ability to reduce network water loss through novel asset management technologies. Available technologies aid asset managers to obtain the best possible data on the state of pipes, allowing for renewal of assets before failures and bursts.
It is the solution to many of the problems that Australia is facing in the near term. With an economic slowdown at home and a tight global credit market abroad, every dollar counts. Trenchless technology is no longer an expensive alternative, but instead offers many ways to do more with less.
A number of recent projects across the country have highlighted the benefits that trenchless technology can offer councils, utilities and their communities.
Going trenchless in the Sunshine State
Servicing 1687 square kilometres of the coastal city of Cairns, the Cairns Regional Council (CRC) has been adopting trenchless technology across several major projects.
With the Far North Queensland city flanking the Coral Sea to one side and the Great Dividing Range on the other, the use of trenchless technology to maintain the region’s underground infrastructure is growing, says CRC Senior Project Manager Peter Thoren.
‘Currently, the council’s Water and Waste Infrastructure branch is the primary user of trenchless technologies, which are being implemented to install new gravity and rising sewer mains, as well as water mains,’ says Thoren.
The Cairns region features a diverse range of infrastructure assets that the CRC regularly maintains, including just over 580 kilometres of stormwater pipes, 176 kilometres of stormwater open drain pipes, 2105 kilometres of water mains, and 1083 kilometres of wastewater mains.
Thoren says that major upgrades to Cairns sewer infrastructure are currently underway to meet present and future demands, including making way for an increased demand on drinking water supplies – options for which are currently being investigated and considered.
The council currently has a Core Asset Management Plan in place that covers long-term planning for the underground assets. It maps out the replacement requirements of assets, based on their age and works identified in Council’s capital works program.
As part of the plan, the council has a 10-year capital works program for installing, replacing and upgrading underground assets, which has been formulated from both external and internal investigations. The Council also undertakes a comprehensive inspection and revaluation of the drainage assets every five years, which involves physical inspections of the assets.
These programs allow for the CRC to generate plans for sewer relining, manhole refurbishment, customer meter replacement, and water main replacement programs annually.
The CRC’s application of trenchless methods across several major infrastructure projects has predominantly used pipe bursting as the primary trenchless technique.
The council has also applied directional drilling techniques in order to use a steerable head to drive and align the pipe, in addition to pipe jacking and the application of earth pressure balance tunnelling machines. CRC’s current water and wastewater infrastructure projects are all using at least one of these trenchless methods.
Thoren says that the CRC’s selection of specific trenchless techniques is dependent on each project, and that an external consultant will provide advice on the technology selection.
‘With input from our design consultant, and access to a specialist technological consultant external of the council, we’ve been able to move away from trenched solutions,’ says Thoren.
‘We’re always open to new methods and ideas, and, at present, we are gearing up for delivery of long directional drill projects throughout the Cairns City area that will need to take into account traffic, businesses and pedestrian access, and public safety; however, the impact is going to be minimal compared to what we would have been facing with a trenched project.’
Sydney pilot bore breaks records
A record-breaking pilot bore using walkover technology was recently completed as part of a series of major infrastructure upgrades in Sydney, New South Wales.
Undertaken as part of the Bargo and Buxton Wastewater Scheme – part of the Sydney Water Priority Sewer Program contract works – the 1020-metre grade-critical bore sat alongside a busy arterial road and had a deepest point of 10 metres. Adding to the challenges, the initial site layout and bore design had to be modified to accommodate existing utility services, pipeline grade requirements, and the available space next to a federally protected endangered ecological community.
Horizontal directional drilling (HDD), which involves performing a pilot bore with a drill rig connected to steel rods, and a drill head that has a locatable beacon at the front, was Sydney Water’s preferred option for use in the construction of the wastewater transfer main for the Bargo and Buxton Priority Sewerage Program.
Sydney Water Manager of Major Projects Ashley Jagoe says that HDD was assessed and chosen as the preliminary delivery technique for the project due to its ability to reduce environmental and community impacts.
‘We were better able to achieve our required design outcomes using HDD over traditional open-cut excavation,’ says Jagoe.
‘Given the relatively small diameter of the wastewater transfer pipeline, HDD provided a significant cost benefit not only in construction, but also by eliminating any restoration required between the launch and receipt points.’
Carried out by infrastructure specialist UEA, the first kilometre of the pilot bore was completed without issue and on a single battery. Just over 1020 metres of the Hawkesbury Sandstone ground matter was drilled in only 39 hours.
In total, the Bargo and Buxton projects required the creation of 17 bores of up to 1020 metres in length, with an average length of 505 metres. With a total of 8973 metres of transfer main installed via HDD, road restoration, spoil disposal and vegetation clearing was kept to an absolute minimum.
HDD was also used to avoid high points along the pipe alignment as well as environmentally sensitive and endangered ecological communities, and to minimise impacts around schools, mine sites and commercial premises.
According to UEA Project Manager Jonathan de Vos, the pilot bore operation had its fair share of challenges to overcome.
‘The major challenge for this project was the need to set up an HDD maxi rig spread on the side of a busy arterial RMS roadway,’ he says.
‘A further complexity was finding available room to internally de-bead and string out 1000 metres of high-density polyethylene (HDPE) pipe above the ground.’
De Vos says that having a very good client/contractor relationship for the duration of the project eliminated any potential delays to completion, and allowed all HDD sites to be set up and prepared well in advance of any equipment arriving.
‘All approvals and permits were received well in advance, and allowed HDD rigs and equipment to leapfrog each other as required.’
Not only was the pilot bore a significant achievement in itself, but this feat is also believed to be the longest ever completed pilot bore using walkover technology in Australasia.
Ultimately, the transfer main was completed on time and is now operational, meeting the Sydney Water Operating Licence time frames to enable both Bargo and Buxton to connect to the new wastewater system.
Trenchless bestows new life on Melbourne pipes
As part of the City of Boroondara’s ongoing drainage improvement program, rehabilitation of approximately 900 metres of brick stormwater drains recently took place in Melbourne’s inner eastern suburbs.
A number of brick-lined stormwater drains in Boroondara have been relined over the past decade, with the drains ranging in size from between 800 and 1200 millimetres, and constructed nearly 100 years ago.
Council Civil Projects Engineer Masha Patikirikorale says that a proprietary structural relining system from Water Infrastructure Group, known as the Panel Lok system, was selected from a panel of brick drain rehabilitation contractors to improve the structural integrity of the existing brick and to extend the existing drains’ service life by at least another 50 years.
‘Water Infrastructure Group uses a structural relining technique where workers enter the brick drain to carry out the relining works. This method enables them to reline sharp bends in the brick drain while maintaining a good seal between the liner and the host pipe with relative ease.’
The Panel Lok relining process involves a number of stages. First, cleaning and repair of the existing drain occurs alongside the removal of debris. Then, the design of the relining system for the brick drain is carried out, followed by manual installation of the Panel Lok system. After installation of the system, reconnection and epoxy sealing of all existing drainage inlets occurs, and the Panel Lok liner is then grouted to the host pipe.
Water Infrastructure Group Project Engineer Patrick Zemanek says that grouting between the host pipe and the liner was an important part of the company’s installation methodology, and provided long-term benefits for stormwater applications by helping to reduce maintenance issues associated with groundwater, soil and tree root ingress into conduits.
‘The PVC Panel Lok liner creates less friction than the original brick lining, so the flow capacity of the stormwater drains is also improved,’ says Zemanek.
Before and after the rehabilitation works, closed-circuit television inspections are carried out to assess the pipes’ initial condition, as well as their final post-rehabilitation state.
See it all at No-Dig 2015
The benefits that councils and utilities can gain through using trenchless technology are many and varied, with cost savings, environmental benefits, minimised urban disruptions and community satisfaction just the beginning.
This year, the Australasian trenchless industry will converge at the Gold Coast for the No-Dig Down Under conference and exhibition. Held from 8–11 September at the impressive Gold Coast Convention and Exhibition Centre, No-Dig Down Under is the 11th conference and exhibition of the Australasian Society for Trenchless Technology (ASTT).
By coming along to No-Dig Down Under, council and utility employees will learn about the cutting edge in trenchless technology and meet suppliers, manufacturers and contractors to discuss how these technologies can be used on current and upcoming projects.
The technical program will host speakers from around Australasia and the globe, who will present papers covering case studies, new and emerging technologies, challenging projects and environments, industry skills and training, risk management, and more.
The program will be supported by an exhibition hall featuring booths where contractors and suppliers from around the world will showcase their services and equipment of all shapes and sizes. This is a perfect opportunity to speak to those at the coalface of projects, and ask experts questions about upcoming projects.
No-Dig Down Under 2015 will also feature a range of social events, including opening cocktails, a canal cruise, golf day, and the prestigious ASTT Gala Dinner and Awards Evening.
The Gold Coast is the perfect venue to mix business with leisure, boasting beautiful beaches, world-class hotels and sightseeing attractions, and an expanding metropolitan city. Queensland remains one of Australia’s strongest economic states, with many mining and engineering companies in the region embracing a trenchless approach to projects.
Residents are increasingly becoming aware of the environmental, social and economic impacts of major infrastructure projects taking place in their communities, making these factors a priority for councils and utilities that are planning major works. Trenchless technology is providing effective solutions to many of the challenges that can present themselves.
Council and utility employees involved in planning major works and asset management will benefit from attending No-Dig 2015 and seeing the solutions that trenchless technology can offer firsthand. To find out more about the event or to register, visit www.nodigdownunder.com.