Bendora Dam Spillway & Bridge Strengthening
Project Location: Bendora Dam, Namadgi National Park
Bendora Dam
Client: ActewAGL
Client’s Representative:
Superintendent: ActewAGL
Superintendent’s Representative: Robert Wilson
Project Start Date: March 2002
Description:
Bendora Dam Spillway & Bridge Strengthening.The remedial works involved allowing a maximum load of 5 tonne on the bridge, removal of lead based paint and the application of a protective coating to the existing steel bridge.
Scope of works:
- Welding stiffeners to bridge girders and installation of lateral bracing.
- Remedial work to the girder bearing supports
- Installation of galvanised steelwork supports to the cantilever deck abutments.
- Painting of steelwork
- Provision of scaffolding and temporary works
- Provision of environmental protection measures
- Protection of Canberra’s water supply
Discussion:
The remedial works at Bendora Dam posed several challenges to Guideline ACT.
- Design of access platform
- Restricted site access
- Access to underside of bridge
- Protection of the sensitive surrounding environment.
The design of the access platform included using barges with cantilever scaffold constructed upon it. Water filled tanks were used at the opposite end of the barge for ballast. Water tanks were used as they gave flexibility in the mass of the ballast, allowing the floating barge to be levelled by adding or reducing water volume.
Access to the site due to its location in the Namadgi National Park was difficult with access by narrow windy gravel roads. This made the transport of 4 huge barges to and from the site difficult. To strengthen the bridge; access was needed to the underside of the bridge deck. Load restrictions on the existing bridge ruled out the possibility of hanging scaffold from the deck. Time and flexibility restrictions together with the shape of the spillway concluded the use of scaffolding on the floating barges as the projects solutions for access to all work areas.
Despite all the work being carried out in the Bedora Dam Reserve no environmental impact was recorded due to the works. This result can be directly attributed to the environmental management system being fully implemented and monitored throughout the project. Several audits were carried out on the project, together with additional water sampling by ActewAGL, these revealed no impact on the environment.
The removal of the lead based paint was recognised as a high risk activity. The system Guideline ACT used for the removal of the lead based paint included, encapsulating the work area and vacuum filtering it to remove contaminants. The paint was removed by blasting. It was then vacuumed into 200 litre drums that were later disposed of appropriately.