Arthur Yapa, Tom Bowling and Peter Watt
Hydro Tasmania uses an electronic inclinometer to monitor the face deflections of nine of its CFRDs. The inclinometer is lowered down a steel pipe attached to the upstream face of each dam. The inclinometer was designed and constructed by the University of Tasmania and was first used on Cethana Dam when it was completed in 1972.
The success of its use on Cethana Dam lead to its use for the long term monitoring of eight subsequent CFRDs constructed by Hydro Tasmania.
After 25 years of successful operation some irregular readings of face deflection became apparent. This paper describes the investigation of the irregular readings that had been obtained, the assessment of other methods of observing concrete face deflection, and the refurbishment of the inclinometer using modern electronic components.
A. Swindon, T. Griggs, R. Herweyne and R. Fell
Cairn Curran Dam is a 44m high zoned earthfill embankment located near Bendigo in central
Victoria. The dam is owned and operated by Goulburn-Murray Water.
A risk assessment had identified that the junction between the embankment and spillway wall was a
weakness in regard to the potential for piping. Initial geotechnical investigations indicated a softened
zone adjacent to the foundation.
The conceptual upgrade design was to excavate the downstream slope and place filter material and a rockfill weighting berm. A 2-D slope stability analysis gave unacceptably low factors of safety for this excavation. The three dimensional nature of the embankment/spillway interface and excavation
geometry was identified as an important factor in the upgrade design.
A detailed geotechnical assessment was undertaken and a geotechnical model developed that
accounted for potential softened zones adjacent to the spillway wall, along the foundation, and within
A 3-D limit equilibrium slope stability program was utilised to analyse the 3-D factors of safety. The
program employed an extension of Bishop’s method of slices to a 3-D ‘method of columns’. A 3-D
finite element analysis was also undertaken to estimate likely deformations of the embankment and cut slope during construction.
The development of the geotechnical model and subsequent analysis allowed the upgrade works to be undertaken with confidence.
Dam safety emergency plans (DSEPs) are typically produced for individual dams. For owners of a large portfolio of dams, this approach creates document control difficulties, requires excessive time and effort and can lead to confusion when a single emergency affects multiple dams having individual DSEPs. Hydro Tasmania has developed a single DSEP which is applicable to its portfolio of 54 referable dams. The DSEP contains generic emergency response procedures, is applicable to a whole range of generic dam safety incidents, uses a simple colour-coded flowchart-action list format, has a two-stage emergency response, retains all necessary dam-specific information and can be easily adapted to any organisational structure. This approach was found to have benefits in document control, flexibility in the management of the emergency response and short lead time in terms of having DSEPs which cover an entire portfolio of dams.
Assessment of dam safety requires estimates of extreme rainfall together with the temporal and spatial distributions of extreme rainfall. In order to satisfy dam safety requirements for dams in the west coast of Tasmania, the Bureau of Meteorology has developed the method of storm transposition and maximisation for application in this region.
Daily, as well as continuously recorded rainfall data for all Bureau of Meteorology and Hydro Tasmania sites in western Tasmania have been analysed and the most outstanding rainfall events over one, two and three-day durations in the region have been identified. Meteorological analysis of these events reveals that the most significant rainfall events in the west coast of Tasmania are caused by the passage of fronts, which are sometimes associated with an intense extratropical cyclone, with a westerly or southwesterly airstream.
A database of isohyetal analyses of the most significant rainfall events in western Tasmania has been established. These can be used either ‘in situ’ or transposed to estimate mean catchment rainfall. Storm dewpoint temperatures for the purpose of moisture maximisation have been determined.
Cumulative and incremental three-hourly temporal distributions for sites having continuous rainfall data or three-hourly meteorological observations have been constructed and design temporal distributions of extreme rainfall have been derived.
An objective method for adjusting for differences in the topography between the storm and target locations is proposed
Sydney Catchment Authority (SCA) has been progressively enhancing its asset management capability for dams and other headworks infrastructure since 1999. A key to the development of the integrated asset management system has been the application of asset condition assessment and Failure Modes, Effects and Criticality Analysis (FMECA) across the water supply mechanical and electrical assets. This has provided vital data necessary to:
• Identify all the mechanical and electrical assets
• Update the computerised maintenance management system database (MAXIMO)
• Determine asset criticality against a range of factors
• Allow review and rationalisation of maintenance work plans
• Upgrade the System Management Plans
Asset management features as a key result area within the SCA’s Corporate Business Plan. Integrated asset management is achieved by cascading corporate outcomes, strategies, objectives and responsibilities down through divisional and team work plans to individual staff members. This paper covers a range of issues that have a bearing on the day-to-day integrity of the infrastructure required to deliver bulk raw water to the SCA’s customers.
The management of maintenance at Warragamba Dam is used as an example to demonstrate the effectiveness and practicality of the application of the contemporary asset management system.