We are carrying out a project to improve dam safety at Cressbrook Dam.

Cressbrook Dam is the Toowoomba Region’s key source of drinking water, servicing over 180,000 residents.

The Cressbrook Dam Safety Improvement Project will widen the dam spillway to increase flood resilience and protect landholders downstream in the Somerset Regional Council area (Cressbrook Creek, including Toogoolawah).

The project is required as a result of the Queensland Department of Regional Development, Manufacturing and Water’s guidelines relating to acceptable flood capacity modelling under an ALARP risk-based approach.

It is the largest dam safety improvement undertaken by a Queensland local government to date and is expected to cost approximately $270 million.

In December 2023 Seymour Whyte Constructions and SMEC Australia were announced as the successful design and construction tenderer for the project.

We will now work with Seymour Whyte Constructions and SMEC Australia to establish a Project Alliance to deliver these works.

Construction will start in early 2024 and must be completed by October 2025.

For further information please contact the project team by emailing damsafetyupgrades@tr.qld.gov.au or calling 131 872.

Drone image courtesy GHD

Cressbrook Dam is located on Cressbrook Creek, approximately 15km downstream of Perseverance Dam and 35km north, north-east of Toowoomba. The dam was designed by Farr Evrat & Associates between the early 1970s and 1980, with construction completed in 1983. The reservoir first reached full supply level in May 1989. The full storage capacity of Cressbrook Dam is 81,900 ML.

The structure is a central core zoned earth-fill embankment with a concrete-lined spillway and chute on the left abutment.

Dams are long-life assets which require continual assessment, monitoring and maintenance to ensure they can provide water security for years to come. The project includes an improvement to Cressbrook Dam to ensure its long-term viability so that it can continue to: 

  • safely pass excess volumes of water during periods of extreme rainfall
  • meet modern engineering design standards
  • comply with the safety requirements set out in the Water Supply (Safety and Reliability) Act 2008 (Qld).

Dam safety is regulated by the Queensland Government's Queensland Dam Safety Management Guideline 2020 which outlines the processes and procedures dam owners need to follow.  

The project will ensure Cressbrook Dam meets all requirements under these legislative guidelines for continued safe operation.

It has been identified that an unprecedented flood event could exceed the capacity of Cressbrook Dam.

With Somerset Regional Council residents living downstream of the dam, the Department of Department of Regional Development, Manufacturing and Water has assessed the dam to be “high risk”, requiring an immediate improvement in accordance with ‘Guidelines on Safety Assessments for Referable Dams' under the Act.

The Cressbrook Dam Safety Improvement project will enable the dam to better withstand extreme rain events, ensuring it can continue to perform safely and protect downstream populations in the future.

The project is required as a result of the Queensland Department of Regional Development, Manufacturing and Water’s "As Low As Reasonably Practicable" (ALARP) principle of acceptable flood capacity modelling.

The project will widen the dam spillway to increase flood resilience and protect landholders downstream in the Somerset Regional Council area (Cressbrook Creek, including Toogoolawah).

The project will also improve dam monitoring, providing greater quality data inputs and control for downstream water operators such as SEQwater in their management of Somerset and Wivenhoe dams.

It will create local jobs during construction and encourage economic growth within Crows Nest and the broader Region.

The project is the largest dam safety improvement undertaken by a Queensland local government to date and is expected to cost approximately $270M.

Council has budgeted $270 million for 2023/24 - 2025/26 and is currently seeking external funding to meet the total project cost.

Council has budgeted approximately $270M from its Capital Works Program to fund the project in the event that external funding is not received.

Using Capital Works funding may delay the delivery of other Council projects. However, critical projects to provide essential services will still be delivered.

A financially sustainable Council is critical to ensuring the liveability of our Region now and into the future.

When Council became aware of this project it began the necessary planning. Since then, we’ve had to respond to unforeseen challenges such as significant flood events and the COVID pandemic, while we continued to work closely with the regulators to better understand the dam safety guidelines and how this will impact, not only our community, but those around us.

While we’ve been doing this detailed planning, we’ve continued to deliver critical infrastructure and essential services to our community such as new libraries, multiple sporting and community facilities, the Mt Kynoch Water Treatment Plant upgrade, Reverse Osmosis Plant for Clifton, multiple water main renewals, road upgrades for the Toowoomba Bypass and other projects that ensure the Toowoomba Region is well-positioned for future growth.

We will always do what is in the best interests of our community.

We are the first of 13 referable dams in Queensland to undertake this safety improvement project.

We understand this is important legislation required to ensure our dam can continue to perform safely and protect downstream populations in the future.

Dam safety assessments based on risk assessments have been completed at Council's other dams - Cooby and Perseverance. These assessments concluded that no improvements are required at these dams at this time. All dams in the Toowoomba Region are regularly monitored and inspected, with some additional scope being assessed at Cooby Dam as part of these inspections.

The project will widen the existing spillway and raise the dam crest level. Construction work will include:

  • improvements to access roads
  • establishment of site facilities, a construction plant and laydown areas
  • excavation of rock for spillway widening
  • excavation and stockpiling of dam wall materials
  • importation of new dam wall filter soils from offsite
  • reconstruction of the dam wall
  • construction of a concrete spillway
  • restoration of areas affected by construction activities.

Preliminary investigation works will involve geotechnical investigations including geological mapping to assess ground conditions, hydrology and constructability.

The project scope also includes:

  • investigating options for access to Cressbrook Dam, including upgrading access roads for all-weather 2WD access and determining any impact on buildings
  • finalising a project delivery model and staging
  • completing legislative, statutory and environmental approvals
  • undertaking additional technical and project delivery elements
  • completing environmental and cultural heritage investigations.

Some access roads will be repaired and/or upgraded as part of the project to improve accessibility to the construction site at Cressbrook Dam. Affected residents will be notified of construction impacts prior to the start of construction. 

Construction planning and delivery will consider seasonal weather patterns and long-range forecasts.

Early works will include construction or upgrading of access roads, water treatment and batch plant facilities.

There will be some impacts on dam access roads during construction. Early notification and appropriate traffic management will be in place on affected roads during construction.

The community will be notified of construction impacts ahead of the start of construction.

Environmental controls on the project will include control of dust.

Dam safety must not be compromised during construction. Council has engaged an experienced contractor with demonstrated techniques to ensure a flood can safely pass over the spillway during construction.

Water is one of our Region’s most precious resources and Council will ensure the project does not adversely affect water quality.

Water will be drawn from the dam approximately 1000m away from the construction area. This water will be pumped to the Mt Kynoch water treatment plant to ensure that Council consistently provides high quality drinking water to the Region.

Water is one of our Region’s most precious resources and Council will ensure the project does not adversely affect water security.

Some works on the upstream side of the spillway will be required to be carried out without water being present. Council will work with the contractor to establish if the work can be undertaken behind a temporary barrier, or if water will need to be released from the dam.

Construction may be undertaken without Council having to release any water from Cressbrook Dam.

While this critical safety improvement will reduce risks to people and property associated with extreme flood events, it will not increase the Region’s water supply. It is not feasible in our current climate to budget additional funds to deliver additional water supply.

Raw water from Cressbrook Dam is pumped to Council’s Mt Kynoch water treatment plant. This will not change as part of the project.

Construction will commence in early 2024.

The project must be completed by 1 October 2025. Some ancillary works may be required to the end of 2026.

Local businesses and suppliers will be engaged on the project where possible.

Public access to the campground, boat ramps and walking trails is expected to be maintained during construction.

The community will be advised of any disruption to recreational activities at Cressbrook Dam.

For further information contact the project team on 131 872 or damsafetyupgrades@tr.qld.gov.au