Armidale Dumaresq Council will shortly commence the third year of a contract for the rehabilitation of sanitary sewer pipes. In the coming four months Council’s contractor Insituform Pacific will reline around 11 kilometres of pipes, a small part of the network of 225 kilometres of pipes that carry wastewater to the Sewage Treatment Plant.
“While most of us take it for granted, a city’s sewer network plays a vital role in protecting public health and the environment,” said Mark Byrne, Council’s Utilities Technical Officer. “The first sewers were installed in Armidale in the 1930s and the system has grown significantly since then. Like all infrastructure the network requires ongoing maintenance and repair to ensure it continues to do its job properly.”
“The ground our sewer pipes were built in is affected by seasonal temperature changes and periods of drought and rain. This can cause joints in the pipes to be displaced and small breaks to open up. These faults lead to infiltration of ground water and over time tree roots can find their way in, causing blockages and overflows.”
Sewer relining contractor Insituform Pacific has been working in Armidale since early 2012, relining sections of pipe identified by Council as needing attention. They use a trenchless repair method known as a ‘cured-in-place-pipe’ or CIPP, which avoids the expense and inconvenience of having to dig up and replace pipes all over the city.
The relining process begins with a camera inspection of the existing pipe. Each section of pipe is then cleaned and any debris removed. A felt tube impregnated with a heat setting resin is winched into the pipe between the manholes at either end. The tube is then inflated with steam. This causes the resin to set, producing a new pipe within the original host pipe. Robotic cutting tools are then used to cut open connections to complete the work.
The whole process takes a couple of days from start to finish. The new pipe has a design life in excess of 50 years and since it has no joints tree roots are unable to get into gaps, minimising the chance of blockages in the future.
Insituform’s project manager Adam Podolski explained that the work would require access to manholes on some residents’ properties. “We will be contacting those residents, as well as notifying other residents living near work sites, prior to starting work”, Mr Podolski advised.