Temporary Closures: Current advice
Scrivener Dam Dissipator Project
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Project Type
Asset Renewal
Design and Construction
Construction
Maintenance
Construction Start Date
2025
Completion Date
2027
Temporary Road or Lake Closures
No
Latest updates
4 April 2025
The NCA is lowering the water level of Lake Burley Griffin to support construction works for the Scrivener Dam Dissipator Strengthening Project.
The water level will be lowered by up to 250 millimetres with an additional drawdown of up to 250mm scheduled to take place in May, if required.
The water level will remain up to 500mm below normal levels until construction works for the Scrivener Dam Dissipator Strengthening Project are completed.
Project Overview
The NCA is undertaking a major strengthening project at Scrivener Dam. The project will involve strengthening work on the downstream structure of the dam – the Dissipator.
Why are we doing the project?
Scrivener Dam is a concrete gravity dam. The design and mass of the dam retains the water which forms Lake Burley Griffin. The Dam is equipped with five flood gates and three sluice gates, all of which are used to control the water level in Lake Burley Griffin.
The spillway located immediately downstream of the dam includes a dissipator structure. The dissipator is a concrete structure comprising of a horizontal concrete slab, concrete chute blocks and vertical concrete baffle blocks. The dissipator absorbs the energy of the water flowing over the flood gates and prevents potentially damaging erosion in the river channel downstream of the dam.
The dam plays a critical role in controlling the flow of water and managing the risk of floods by controlling water levels at a consistent level, that in turn protects the residents of Canberra from flooding and downstream areas from sudden fluctuations in water flows. These work s will be the most significant strengthening works completed on the dam since it was first built in 1963.
Studies commissioned by the NCA identified the need to strengthen the Scrivener Dam Dissipator. NCA worked with the University of New South Wales Water Research Laboratory (UNSW WRL), and the Dam Safety Engineers (SMEC) to design, construct and test a scale model of Scrivener Dam. The model and other investigative methods were used to ascertain how the dam and its environs function under a range of operational scenarios.
The modelling and subsequent assessments identified structural risk with the dissipator under flood conditions. There is the potential for the dissipator to be significantly damaged during a major flood event, which in turn, could lead to the failure and subsequent collapse of Scrivener Dam. The project will involve:
- Strengthening the existing horizontal concrete slab of the dissipater by installing approximately 700 new anchor points into the foundation rock of the dam (10 to 20 meters deep).
- Increasing the thickness of the horizontal concrete slab of the dissipator by half a meter.
- Reconstructing new baffle blocks to match the increased thickness of the concrete slab.
- Reinforcing the adjacent riverbanks downstream of the dam to minimise erosion that could lead to failure of the dissipater structure.
The strengthening work will ensure the ongoing safety of the dam during flood events.
Learn more about the Dam on the Scrivener Dam Attractions page.
Previous notifications
Construction Works
The $36 million project has been awarded to Seymour Whyte, following an open tender process by the National Capital Authority (NCA).
Early works for the project are expected to commence by December 2024.
Construction works on site are expected to commence in March 2025 and will be completed by mid-2027.
The level of Lake Burley Griffin will be lowered by up to 500mm for the duration of construction works on site.
NCA is working with key external stakeholders to mitigate impact to use of the lake.
Public Interest Certificate
A Public Interest Certificate has been issued. Click here to view the Public Interest Certificate.
The construction of Scrivener Dam was completed in 1963 - which is now 60 years ago. Since the dam was first constructed, the standards of construction and the body of knowledge regarding dam safety have improved. Based on several investigations and studies undertaken in recent years, the NCA has identified several structural risks with the dissipator of the dam. During flood conditions, there is a risk that the dissipator structure could fail, which in turn could cause the dam to fail. Hence, the NCA must undertake the Dissipator Strengthening project to ensure the ongoing safety of the dam.
NCA are aiming to commence works on site in early 2025 and is expected to be completed in 2027.
There are two likely community impacts, as follows:
Lowering Lake Burley Griffin – in order to effectively manage the risk for construction while working in the spillway of the dam, NCA will be lowering the level of the lake. it is planned to lower the lake by a maximum of 500mm during construction. This will be reduced as far as possible to minimise the impact to lake users.
The NCA urges all lake users to consider the impacts and potential new hazards prior to setting out onto the water.
Increased traffic on Lady Denman Drive – during construction there will be an increase in construction traffic on Lady Denman Drive. Construction traffic will enter the site on the western access road to Scrivener Dam and will cross the existing bike path adjacent to Lady Denman Drive. Traffic will be controlled during construction, however NCA urges all users to take care when navigating the area.
The NCA will continue to work with the community to understand and mitigate impacts wherever practical.
There will be no extended closures of the bike path or the bridge over the dam during construction. From time to time, we anticipate that there could be short closures to allow movement of construction vehicles, however, disruption will be kept to a minimum.
The project will involve drilling for roughly 700 new ground anchors between 10 to 20 meters deep. The process used to drill these holes will be noisy. However, the NCA has undertaken a noise and vibration impact assessment as part of the design for the project.
The study has identified that all noise generated during the project will be below ACT guidelines for the areas surrounding the dam. The NCA will monitor noise during the project and will work with stakeholders to mitigate impact during the project.
We are keen to keep the community involved and aware as to what’s happening at Scrivener Dam. Keep checking back on this website and register for project updates.