Mugga Reservoir upgrade to benefit ACT

One of the ACT’s biggest reservoirs is set to continue its important role in servicing Canberrans with potable water thanks to a raft of upgrades recently completed by Icon Water.

Canberra has a series of reservoirs that store water before it's supplied to people’s properties, and Mugga Reservoir is one of the largest, with a holding capacity of 45 million litres.

Icon Water Project Delivery Manager Andrew Blair said the Mugga Reservoir is integral to Icon Water’s service provision, as it allows for the utility to manage fluctuating demand.

“We have two water treatment plants, at Googong and Stromlo, and they provide water into our network. Mugga Reservoir works as a balancing reservoir. It helps to match the fluctuating demand for water with a relatively steady output of water from our treatment plant,” he said.

“The treatment plants have a fairly constant output, but our demand fluctuates with the daily usage patterns. Our Mugga Reservoir balances this out, helping us to manage that fluctuating demand.”

Commissioned in 1966, Mugga Reservoir was ready for an upgrade, which involved replacing the steel roof and resealing the joints.

“The roof is made of steel and the reservoir is made of concrete. The concrete structure has a longer design life than the steel roofing. It’s pretty normal for us to monitor the condition of the various components of the asset throughout its lifespan,” Blair said.

“As the roof deteriorates, there comes a point where we want to replace it to avoid any compromises to its integrity and function.

Major works

Replacing the steel roofing at Mugga Reservoir was no minor feat, with the structure being the size of a football field, Blair said.

“The roof component was really significant. It’s not a small reservoir. That involved lifting of the steel roof structure, which was recycled, and replacing the roof structure, purlins and sheeting,” Blair said.

“We have replaced the roof, but we’ve also done a lot of joint replacement too, where the concrete slabs join on the floor and the walls, using sealing bandages. This involved about 3kms of bandage to seal the joints.”

“The material used to seal the joints about 50 or 60 years ago was deteriorating, which is expected, but we have new and better products now, and so we were able to regain the water seal on the reservoir really well.”

Blair said replacing the joint seals was an important step in the process, particularly in terms of ensuring no water is lost from the reservoir unnecessarily.

“In the same way that we all have the obligation to conserve water within our homes, Icon Water also wants to conserve water as well. Due to the sheer size of Mugga Reservoir, there is a big potential for water loss. Water conservation has been a big driver for us in terms of completing the joint repairs,” he said.

“Furthermore, a leaking reservoir is financially wasteful. It makes a lot of sense for us to ensure the joints are properly sealed.”

Future improvement

With the Mugga Reservoir upgrades now complete, Icon Water is working towards upgrades at two other important sites, O’Connor Reservoir and Googong water treatment plant.

“O’Connor Reservoir is very similar to Mugga. It’s a little bit smaller, but it’s the same scope of upgrade: there’ll be a new roof and joint sealing there too,” Blair said.

Googong water treatment plant is currently upgrading its clarifiers,  a project that is about three-quarters of the way through. These clarifiers provide an important function early on in the treatment process of the water coming from Googong Dam.

Likewise, those assets were commissioned in the late 1970s, so the clarifiers were ready for renewal, with Icon Water currently replacing the steel structures within the clarifiers, Blair said.

“The steel components, being toward the end of their design life, resulted in considerable maintenance costs and some reliability risks,” he said.

“We are also infilling the square corners to allow for our circular rakes to be more effective in removing the sludge, and recoating inside of the concrete clarifiers, too.

“The works will not be increasing the capacity of the treatment plant; the main aim is to replace ageing assets that have been a big maintenance burden on the utility. The previous design had some limitations, and the upgrades will help us to maintain the asset better in future.”