Upon its reopening to the public in October 2013, Cotter Dam in the ACT became the tallest Roller Compacted Concrete (RCC) Dam in Australia.
Approximately one million tonnes of crushed aggregate was required to produce the 360,00m3 of RCC to build the 87m high dam. Much of the aggregate came from foundation bedrock quarried from the site itself.
The water storage capacity of the dam increased by 20 per cent, from four gigalitres to 78 gigalitres, following the work. Meanwhile, the new dam increased water storage for the ACT by 35 per cent to 277 billion litres.
It is estimated that the ACT now has enough water storage to last a generation and the threat of water restriction, which had financial ramifications for the territory, has now been removed.
The Bulk Water Alliance, collaborative venture between ACTEW Corporation, GHD, Abigroup and John Holland, delivered the Cotter Dam project.
One of the focuses of the project was to safeguard and enhance the surrounding area, particularly through environmental strategies.
Recreational space
The Cotter Dam Discovery Trail was one such initiative. The trail covers 1.4km and leads visitors along the Cotter River and around the surrounding environment. Along the route, visitors can read about Canberra’s water history and take in the views of the new dam from a 16m-wide, amphitheatre-style viewing platform.
ACTEW produced a Cotter Dam Education Kit that was distributed to schools in the ACT during the construction of the dam. Teachers were encouraged to bring their students to the Discovery Trail viewing platform to learn about the environmental, engineering and water supply aspects of the Cotter Dam enlargement, as well as the Indigenous and European heritage values of the area.
In order to build the dam safety, ACTEW had to completely close the area known as Cotter Avenue, a popular recreational area with the locals. To minimise the inconvenience as much as possible, they ran a months-long consultation program before they started building, which gave them a really clear picture of how the community felt and how we could best manage it.
“We worked with almost 1000 people through this process and one of the things they told us was that they would be ok with the closure if there was somewhere nearby with similar facilities that they could use while the dam was being built," said ACTEW Water Manager Safety and Environment Kirilly Dickson.
“So in response, we undertook a complete makeover of the nearby Casuarina Sands Recreational Area, including the development of a better, safer car park, better facilities, and more shade, barbeques and picnic tables.”
The community was keen to ensure that once construction was complete, it wanted Cotter Avenue to be returned as close as possible to its natural state.
“We even accommodated the strong nostalgia surrounding an old suspension bridge that had been a landmark of the area for decades but had been destroyed in the 2003 bushfires,” said Kirilly.
“We couldn’t build a true suspension bridge because it wouldn’t meet contemporary design safety standards, but we were able to put in a replica with the look of the past that Canberrans loved, with the safety aspects of modern design.”
Community backing was essential to the success of the project. ACTEW estimated that it had 360,000 individual interactions with the community over the course of the project. This community involvement was evident when almost 10,000 people attended the official opening of the dam in 2013.
IPWEA Sustainable Solutions in Public Works Awards
ACTEW won the Sustainable Infrastructure category and overall winner awards at IPWEA’s inaugural Sustainable Solutions in Public Works Awards for the Cotter Dam project.
ACTEW Water Manager Safety and Environment Kirilly Dickson attended the awards gala dinner in Tweed Heads to accept the top prize.
“These awards provided fantastic recognition for the excellent environmental, community, economic and cultural outcomes achieved throughout the Cotter Dam project," she said.
"Ensuring a long-lasting legacy for our community has been a key goal from the beginning of this project and one that we are extremely pleased to have recognised."
View all the winners at the Sustainable Solutions in Public Works Awards in our photo gallery from the night.