Cressbrook Dam Safety Project Meets Compliance Standards
The Cressbrook Dam Safety Improvement Project continues to comply with the progress reporting requirements set out by the Queensland Dam Safety Regulator.
Toowoomba Region Mayor Geoff McDonald said Council regularly reports on the status of the project to the Regulator to meet various compliance requirements.
“In February, we received acknowledgement that our latest report was suitable and that the Cressbrook Dam Safety Improvement Project is progressing satisfactorily,” Mayor McDonald said.
“The design process is complex as we’re applying a risk-based design approach according to the Water Supply (Safety and Reliability) Act 2008 and the Australian National Committee on Large Dams guidelines to reduce risks to As Low As Reasonably Practicable.
“To do this, the team is diligently applying data and guidelines from various sources to arrive at a design solution that protects communities. This process includes addressing considerations such as climate change and cascade failure impacts between Perseverance, Cressbrook and Wivenhoe Dams,” he said.
Council reported to the Regulator that early geotechnical investigations to address site complexities were extended, requiring further understanding to support the design.
Council clarified with the Regulator that the construction of an endorsed design is forecast to start in the second half of 2025, with the project expected for completion at the end of 2026, weather and conditions permitting.
“The construction phase is expected to be about 18 months,” Mayor McDonald said.
Toowoomba Region Deputy Mayor and portfolio spokesperson for Strategic Water Planning and Capital Delivery, Councillor Rebecca Vonhoff, said the region had also experienced a wet summer season, followed by the impacts of ex-Tropical Cyclone Alfred, causing Perseverance Dam to spill into Cressbrook Dam. Cressbrook Dam’s current water level has exceeded 100% of its full supply level and is currently spilling.
“For some specific construction activities to occur safely, the dam needs to be at a temporary full supply level of 70 per cent.
“Last year the water levels in Cressbrook got close to where they needed to be to safely start construction. Now that the dam is spilling because of the rain we’ve had, we’re working out how all that extra water is going to impact the project.
“To get water levels down we’re going to do what we were doing last year: change how we supply water to residents so that instead of drawing from all our dams and aquifers, we’re going to mostly be pumping from Cressbrook Dam.
“Cressbrook doesn’t have a spillway like Wivenhoe or Somerset Dams that allows for large amounts of water to be released. We only have one small valve that releases water typically used to meet our legislated requirements of environmental flows. When we release water from this valve we make sure it’s done in such a way so as to minimise downstream impacts,” she said.
The safety improvement must also meet the needs of a Waterway Barrier Works permit as detailed in State Code 18 and the Fisheries Act 1994.
“Council has a good working relationship with the Regulator, and we will continue to provide them with status updates on the project. Our next status report is due by June 2025,” Cr Vonhoff said.
Clarifying timeframes has not resulted in any changes to the project’s budget as Council has worked with its partners to temporarily redeploy construction staff to other work areas outside of Council. Council continues to advocate for Federal and State funding to reduce the financial burden of the $270 million safety improvement project on ratepayers.
Preparing local roads in the Somerset Region will be completed as the construction phase gets closer. These are needed to safely and efficiently transport equipment and materials to the dam.
Improving Cressbrook Dam has been triggered by requirements of the Dam Safety Management Guideline 2020, under the Water Supply (Safety and Reliability) Act 2008, administered by the Department of Local Government, Water and Volunteers.
The Cressbrook Dam Safety Improvement Project includes widening the ungated spillway and raising the dam crest level. Cressbrook Dam will not store any more water after the improvements are constructed.
https://www.tr.qld.gov.au/about-council/news-publications/media-releases/16479-cressbrook-dam-safety-improvement-project-progressing-well-meeting-regulators-current-compliance-requirements