Redbank Creek Dam
|Reports||Redbank Creek Dam File|
|Reports- Dam Safety Emergency Plan - Redbank Dam||3 mb|
|Evaluation of Bypass Spillway Option (GHD, July 2010)||700 kb|
|Alternative Stabilisation Works (GHD, May 2010)||5 mb|
Redbank Creek Dam was constructed as water storage infrastructure for the Mudgee Town Water Supply in 1899. The dam is a 16m high concrete arch dam with a crest length of 152m and a storage capacity of approximately 180 megalitres. The dam wall is similar in size to the Rystone Dam.
Following preliminary analyses and long-term observations by the Public Works Departments back in 1984 that indicated that the dam "appeared to be behaving in a satisfactory manner" there were some uncertainties regarding concrete quality. The Department (PWD) completed a safety review of the dam which was presented to Council in June 1992. It was concluded that both the general and incremental flood hazard ratings for Redbank Creek Dam were high.
A stability analysis was completed and presented to Council by the Department of Land and Water Conservation in January 1996. The analysis examined the behaviour of the dam wall under static loadings at full supply level (FSL) and loading resulting from an inflow equivalent to a Probable Maximum Flood (PMF) event. The dam was also analysed for earthquake loadings. The report concluded that "the dam is considered to be in an unsatisfactory state even for normal loadings and the dam does not satisfy accepted design criteria". The DLWC recommended that "consideration be given to lowering the dam storage in the short term and decommissioning or strengthening the dam in the long term".
Various studies and analyses have been carried out since, culminating in a detailed design for dam stabilisation works being approved by the Dams Safety Committee, the NSW Office of Water and the Department of Environment, Climate Change and Water.
Works carried out to date include the installation of a large diameter pipe through the base of the dam and the construction of downstream erosion protection. The dam is therefore presently not capable of storing water except for short durations during large flood events (>20 years average recurrence interval) when inflows exceed the capacity of the pipe. Consequently, there is no longer a risk of a "Sunny Day" dam break event, which reduces the factor of safety requirements (e.g. there is no need to consider earthquake loadings as the dam does not normally store water).