Grahamstown Dam risk assessment complete

Constructed between 1956 and 1965, Grahamstown Dam is the Hunter’s largest drinking water supply dam.

A RISK assessment has found that Grahamstown Dam could be damaged in the event of an earthquake, prompting Hunter Water to immediately reduce the amount of water stored in the dam.

The risk assessment, undertaken with expert consultants and an independent expert panel, was submitted to the regulator Dams Safety NSW in early July.

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The assessment found the largest risk to the dam walls, or embankments, is an earthquake, or a series of smaller ones close to the dam.

The review estimates that the risk of this occurring to the main embankment is calculated to be a 1 in 3,500-year event, or a 0.03 percent chance of occurring in a single year.

Hunter Water Managing Director Darren Cleary said while the review found that Grahamstown Dam continues to operate safely in both normal and flood conditions, it was critical to take decisive action to reduce the immediate risk to people and nearby properties, while longer-term solutions for the dam were developed.

“In response to the report findings, we’ll be slowly reducing the amount of water in the dam over the coming weeks to lower its overall storage to around 90 percent capacity.

“This means we reduce the amount of water that could potentially be released to low-lying areas downstream of the dam’s embankments (walls) if they are damaged in the unlikely event of an earthquake.

“We’ll maintain this water level, while we proactively work through the report recommendations for additional short-term mitigation measures such as reviewing our emergency response plan, as well as developing longer-term, permanent upgrades to strengthen the dam walls.

“The safety of our community is paramount.

“I’d like to reassure our community that the dam continues to operate safely under normal conditions,” said Mr Cleary.

The assessment also found that the risks associated with earthquakes have existed since Grahamstown Dam was constructed 60 years ago.

“A detailed letter is in the mail today to residents and community members who live around Grahamstown Dam to inform them about the report findings and invite them to attend one of the drop-in information sessions we’ll be holding.

“I encourage community members to attend if they would like to find out more about the report or ask questions from our dam safety experts. We’ve also made available on our website a summary report of the findings, as well as the full version of the risk assessment,” said Mr Cleary.

For more information or to view the reports, visit www.hunterwater.com.au/grahamstown

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