Here’s how one utility is dealing with ageing asbestos in water mains
As the 40,000 km of asbestos cement (AC) water pipes across Australia continue to deteriorate in the coming decades, water utilities must find safe ways to rehabilitate their assets.
While there is no evidence to suggest asbestos in pipes is a danger to drinking water, utilities need to mitigate the risks that come from replacing or upgrading the infrastructure.
The issue is most significant in Victoria, which is home to 70% of the country’s AC pipes. The situation was made more complex in 2015, when the state banned the common practice of AC pipe bursting – where a head is taken through the pipe to crack it open – because the process leaves behind asbestos fibres in the soil.
Since then, the Victorian water industry has been searching for solutions. This includes South East Water, which is dealing with 1600 km of AC pipes, or about 20% of its total water network.
Most of South East Water’s AC pipes were laid in the 1950s and 60s. Their average lifespan of 60 to 80 years means there will be a “peak of failures” in the near future, said South East Water Program Engineer Nick Stetter.
Because of this, South East Water estimates the costs of maintaining its AC pipes will increase from $10 million per year to about $40 million within the next 20 years.
“It’s inevitable the asbestos will reach the end of its life,” Stetter said.
“The aim for us is to find a range of solutions that can navigate different site constraints and best mitigate the risks.”
The utility’s main renewal technique at the moment is to ‘realign and leave’, which involves leaving the AC pipe in the ground and putting in a new one next to it.
“The issue we see with this approach is the future risk,” Stetter said.
“Even though the pipe containing asbestos isn’t being used, we still have to manage it to make sure people who dig in the area are kept safe.
“There’s also a monetary risk if regulations change and we have to remove all the asbestos we’ve abandoned in the ground.”
South East Water also practises ‘lift and re-lay’, where the AC pipe is taken out and a new main is placed in the same location.
“This removes the future liability, but it comes with a potential risk to our workers and the community, because we’re taking the asbestos out of a controlled environment and into the open where we have to dispose of it,” Stetter said.
Searching for a solution
With risks associated with both of these approaches, South East Water has been trialling new ways to rehabilitate its AC pipes. This includes developing a tool that can remove and replace the AC pipe in one operation, which Stetter will discuss during a presentation at Ozwater’19 in May.
“This removes the risk of leaving the asbestos in the ground, and it’s trenchless, so you don’t have to dig up entire roads to get to the pipe,” he said.
However, the utility knows it needs a “toolbox of technologies” to address the issue.
“Because we cover such a vast area, no one pipe is the same and the drivers that influence it being renewed are different,” Stetter said.
“South East Water also has a unique problem in that a large portion of the asbestos pipes are small in diameter … This means some of the traditional approaches, such as sliplining, aren’t appropriate.
“But in other areas we have large asbestos pipes of 300 mm, so sliplining might be appropriate. It comes back to what technology is right for the constraints.”
Informing the industry
Stetter said South East Water wants to share what it has learnt with the industry and is contributing to the Cooperative Research Centres Project (CRCP) ‘Smart Linings for Pipe and Infrastructure’.
This is a three-year program that aims to develop standards for new AC rehabilitation technologies.
“The CRCP is trying to inform decision-making around these technologies, improve the standards in Australia, and facilitate a marketplace for these technologies to be used in Australia,” Stetter said.
“It’s about gathering as much information about the different products, limitations, how they can be improved and where they can be implemented.”
Check out the full Ozwater'19 program here.