Jemena builds, owns, operates, develops and manages approximately $A9 billion worth of gas and electricity assets in Australia.
General Manager for Gas and Water, John van Weel in talking about the Trenchless Technology used in Jemena’s recent gas projects, said “In our view such methods are often preferable to open-cut work because they minimise the impact on the environment in general and in particular in built-up areas where such methods have less impact on local residents in terms of noise and/or local traffic.”
Victoria
In Victoria, Jemena is rehabilitating parts of the Multinet Gas network, as well as being the project manager for the construction, operation and maintenance of the Multinet Gas extension programs in South Gippsland and the Yarra Ranges to meet growing demand for natural gas.
Jemena is undertaking between five to ten kilometres a year in horizontal directional drilling (HDD) and approximately 45 kilometres of pipe insertion work for the project. The program is to upgrade parts of its 9,400 kilometre gas network that delivers gas to some 660,000 homes and businesses in Melbourne’s inner, outer-eastern and south-eastern suburbs.
“Pipe insertion is the preferred method in Trenchless Technology in Victoria and it is how the majority of pipe renewal works are performed,” said Mr van Weel.
Currently Jemena is in the process of upgrading the Springvale South area, involving 16 kilometres of upgrade work. One of Jemena’s more recent HDD projects was in Mount Waverly where they constructed grid main and the drilling covered a distance of 1.2 kilometres.
New South Wales
In New South Wales, the company’s gas network provides natural gas to approximately one million customers in Sydney, Newcastle, Wollongong and more than 20 country centres – stretching
23,000 kilometres.
One of the largest HDD projects ever undertaken was the Sydney Primary Loop, a 30 kilometre pipeline linking Liverpool in Sydney’s southwest to Marrickville. The pipeline was built to improve security of gas supply and increase the capacity for long-term growth in both the eastern and the south-western regions of Sydney.
“HDD was used to overcome the challenges of laying a pipeline under rivers and in creeks without disturbing the natural environment and to minimise the impact on existing infrastructure,” Mr van Weel said.
There were a total of four HDD water crossings – Salt Pan Creek at Padstow, two crossings of the Georges River at the Casula and Hammondville and the Cooks River at Tempe. The Cooks River part of the project was interesting as it involved crossing beneath the existing secondary gas mains and the jet fuel supply to the Sydney Airport.
ACT
HDD was also used in Jemena’s project for the Canberra Airport Group (CAG). The company had to relocate a 100 metre steel gas main under the airport’s long-term car park and access roads to the airport. For this reason, an open-cut trench was not an option so under-boring over a distance of 220 metres was carried out. This project was part of the CAG reconfiguration of the airport.
Future projects
The company has started work on what will be one of its major projects in 2010 – rehabilitating the 350 mm diameter steel secondary main line between Wakehurst Parkway and Warringah in New South Wales. The line services increasing consumption loads along the length of Sydney’s northern beaches.
The Wakehurst Parkway rehabilitation project involves a cutting-edge solution requiring the insertion of high-pressure plastic pipe. Unlike previous rehabilitation projects on low and medium pressure sections of the network, where the length of the pipe inserted in each section is typically about 100 metres, the project will require inserting a 250 mm polyethylene pipe into an existing cast-iron main and then pulling it between 400 metres and one kilometre. Once in place the PV pipe will operate at a pressure of 1,050 kpa.
Jemena and HDD
Jemena has purchased a 330,000 pound HDD rig from Vermeer and this was utilised immediately on a number of their projects. Jemena’s HDD Manager Dave Warner said the drilling equipment available on the market today has transformed the quality of its projects.
Mr Warner said that proponents prefer to use HDD instead of trenching due to a number of environmental and social factors, which are attributed to the technological advances made in the industry and the improved quality of the pipe material that is used today.
“[HDD] has gone leaps and bounds in the last ten years. All the utilities are changing to polyethylene (PE) pipes, therefore making it more versatile for HDD as an option now.”
“The benefits of the PE pipe are a longer life span, and the durability of the pipe. Traditional pipes don’t have the guaranteed lifespan of what the PE pipe brings. That inherent capability of the pipe, coupled with the benefit of drilling lowers the impact to the environment.”
Mr Warner believes that as the environmental impact lessens, both the community and the proponent are kept in a positive frame of mind.
“There is less issue with community concerns and from a customer’s perspective; they don’t have as near as many complaints because you’re not digging up other people’s driveways. You’re going underneath and not disturbing them.”