Many of Perth’s water mains were installed from the 1890s onwards, with some sections now over 100 years old. Like anything that age, they’re starting to show wear and tear. Water Corporation’s $100 million Pipes for Perth program is replacing these pipes to avoid future bursts and leaks.
Following a water main on Wellington Street breaking three times in the space of a few weeks in 2013, Water Corporation undertook a review of its cast iron water mains throughout the Perth metropolitan area.
This review led to the decision to increase investment in water main renewals and the implementation of the Pipes for Perth program which is currently in the process of replacing 150km of water mains across the Perth metropolitan area. The program is expected to be completed in 2018.
“About 46km of water main has already been replaced or renewed as part of the project during 2017,” a Water Corporation spokesperson said.
“Work is under way in the following eleven local government authorities – Bayswater, Cambridge, Cottesloe, Fremantle, Perth, South Perth, Stirling, Subiaco, Swan, Victoria Park and Vincent.”
Planning the renewal works
The spokesperson said that Water Corporation’s planning team identifies which mains are prioritised for renewal based on the pipe’s age, material, history of faults, and the potential for disruption to the local community should the pipe fail.
“There is also a lot of preparation work contractors need to do before they can actually start digging. We need to locate all underground services, such as gas, power, telecommunication cables and existing water connections.
“Then confirm the planned alignment of the new water main is suitable – then we can start the physical replacement of the water main,” the spokesperson said.
In the past, Water Corporation generally used open trench excavation to install water mains. Now, the majority of water mains are installed using trenchless technologies such as directional drilling, which has been made possible due to the more flexible nature of polyethylene (PE) pipe.
This reduces the amount of excavation required, minimising impacts on local households and road users.
“We have also started using other trenchless technologies, such as relining. Relining can be used to renew larger distribution mains that transport large quantities of water around Perth but don’t directly supply water to customers,” the spokesperson said.
“We excavate pits above the distribution main every few hundred metres, and then pull a new liner from one pit to the next. This process is repeated at several locations along the route until the entire distribution main is relined.
“Relining work is underway along Oxford Street in Leederville and Mount Hawthorn, Walcott Street in Mount Lawley and North Perth, and Swan Street in Guildford.
“A number of local contractors have been engaged to carry out the work across the Perth metropolitan area. It is estimated that in the order of more than 400 jobs have been created as a result of this program of work.”
Engaging the community
Water Corporation has a dedicated Community Engagement Team that visit impacted businesses, and provide regular updates to the community throughout the works.
The overriding objective is to complete the project as quickly as possible while ensuring the safety of the community and contractors at all times.
This has meant contractors working seven days a week in the Perth CBD, including regular overnight work and engaging extra crews. In other areas, contractors are regularly working six days a week.
“These projects are happening in busy inner suburbs and there will be impacts on traffic, however we do all we can to minimise impacts by working closely with Main Roads WA and local governments,” the spokesperson said.
“We coordinate work with other utilities and local governments where possible to minimise disruption to the community. For example, we coordinated our water main renewal along Hay Street, West Perth to coincide with a gas main renewal being carried out with ATCO Gas.
A similar coordination of work is also taking place at Kings Square in Fremantle.”
Investing in asset renewals
The spokesperson said Water Corporation’s investment in asset renewals, including water mains, are reviewed each year, with work prioritised based on a risk-based approach to pipe replacement.
Through this approach, Water Corporation uses information on the condition and performance of water mains to determine when pipes need to be replaced, usually when they have reached the end of their useful life.
This proactive approach has resulted in Perth recording the lowest number of water main breaks in six years in 2015-16, with 12 leaks and breaks recorded per 100km of water main.
This was a 20 per cent decrease from the previous year, and is the fourth lowest out of 14 similar sized utilities across Australia. The average number of leaks and breaks for similar sized utilities was 22 breaks per 100km of water main.
Water Corporation continues to invest in the water supply scheme to minimise leaks and breaks, with $75 million invested in 2016-17 to renew water mains across the Perth metropolitan area.