Andrew Richardson, Stephen Farrelly and Phil Farnik
In 2012 an update to the Portfolio Risk Analysis (PRA) was undertaken by State Water Corporation for its 18 major dams in New South Wales. The updated portfolio level risk analysis of all the dams has taken account of the completion of major components of the 2006 dam safety upgrade program, while also incorporating continued engineering research into dam safety performance. This paper will provide an overview of the approach, the challenges faced in the process and it will highlight the innovative advances made representing industry best practice. Some future implications and directions will also be discussed.
The three main components of the PRA update in 2012 have included a significant amount of dam break hydraulic modelling including revised hydrology and flood inundation mapping delivered in-house by State Water with consultant support. The Consequence Assessment was developed with a spatial link to natural flooding and dam failure consequences by Sinclair Knight Mertz (SKM), while the third element in producing the event trees, risk analysis and PRA reports was undertaken by consultants GHD. Peer review of the PRA process and reports and additional technical review of the failure modes and event trees by a panel of industry experts provided the necessary independent input and oversight required by the NSW Dams Safety Committee.
State Water’s PRA update builds on the large body of work undertaken for and since the last PRA in 2002. The update process has applied a systematic and quantitative approach across the Portfolio that provides a robust basis for managing dam safety risk. The results of the PRA have identified further work required to investigate and assess the need for dam safety upgrade options for non-compliant dams. State Water’s investment in the PRA has produced a risk-based position on each dam in the portfolio that can be used to identify a range of measures in a revised dam safety upgrade program for the future.
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ANCOLD is an incorporated voluntary association of organisations and individual professionals with an interest in dams in Australia.