Hunter Water has announced immediate measures to lower water levels in Grahamstown Dam.

The authority has responded to the findings of a comprehensive risk assessment highlighting potential earthquake-related vulnerabilities. 

The assessment, conducted in collaboration with expert consultants and an independent panel, was submitted to Dams Safety NSW earlier this month. 

The findings suggest that although Grahamstown Dam operates safely under normal and flood conditions, an earthquake could pose a significant risk. 

Hunter Water's Managing Director, Darren Cleary, emphasised the need for proactive action to mitigate risks to nearby communities. 

“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 per cent capacity,” Cleary said. 

This aims to minimise the volume of water that might be uncontrollably released if the dam were damaged by an earthquake.

The review identified the greatest threat to the dam's embankments as seismic activity, estimating a 0.03 per cent annual chance of a damaging earthquake occurring. 

Despite this low probability, Cleary has stressed the importance of caution. 

“The safety of our community is paramount. I’d like to reassure our community that the dam continues to operate safely under normal conditions,” he said.

The dam's resilience was noted during the 1989 Newcastle earthquake, which caused no significant damage, possibly due to the earthquake's location and short duration. 

However, modern geotechnical engineering and scientific monitoring have enhanced understanding of potential risks.

Hunter Water says it is implementing immediate precautionary measures while developing long-term solutions to reinforce the dam. 

“We’ll maintain this water level, while we proactively work through the report recommendations for additional short-term mitigation measures as well as developing longer-term, permanent upgrades to strengthen the dam walls,” Cleary said.

Residents and community members living around Grahamstown Dam have been notified through a detailed letter about the report findings. 

They are invited to attend information sessions to discuss the report and ask questions.