Andrew Evans, Michael Cawood, Jonathon Reid
Eildon Dam, Goulburn Weir and Waranga Basin in Victoria are owned and managed by Goulburn-Murray Water (G-MW). Eildon Dam and Goulburn Weir are situated on the Goulburn River, while Waranga Basin is an offstream storage supplied from Goulburn Weir.
In November 2004 a dam safety emergency exercise involving the establishment of a central Emergency Coordination Centre at Tatura as well as Emergency Operations Centres at each of these three dam sites was conducted. The exercise presented a variety of emergency situations in stepped time increments, including earthquake, mechanical failure, a hazardous material spill and a terrorism related incident. External agencies were not involved.
The exercise was part of an ongoing G-MW program designed to test and improve dam safety emergency planning and response systems for all of G-MW’s dams and highlighted areas where procedures, situational management and communications can be enhanced.
Outcomes aimed for in G-MW’s program are improvement in Dam Safety Emergency Plans and internal communications, together with clarification of roles, responsibilities and capabilities.
The valuable experiences learned from this dam safety emergency exercise and plans for a larger scale exercise involving other emergency management agencies will be shared with others through this paper.
This paper relates to the conference sub-themes of Dam Safety Upgrades – Management of
Risk and Due Diligence and Dam Construction.
Specifically, it relates to the changing willingness of governments to fund risk reduction in
dams compared with risk reduction in other areas.
The cost of dam safety upgrades is just one of a portfolio of risk reduction strategies
affecting the general community that governments are required to underwrite.
This paper examines the variation in acceptable risk standards between dam safety and
other areas. This may be explained in terms of what is acceptable to the community and the
courts. For instance, a corporation is likely to attempt to minimise its liability (which may
differ to minimising risk for the community). We also examine:
• a portfolio approach to safety expenditure and the implicit cost-benefit relationship;
• the impact of the asymmetric relationship between expenditure and absolute size of
potential loss; and
• the importance of a whole-of-government approach and reviewing apparent
inconsistencies in approach to risk.
There is an increasingly well-established literature on the value of a human life and
increasingly systematic approaches to the evaluation of risk and the setting of risk
standards. Risk standards are particularly explicit in the area of dam safety – they set limits
of tolerable risks for large-scale loss of life (eg. for existing dams, a loss of life of more than
10 persons with a probability of more than one in a ten thousand per annum is regarded as
unacceptable under the Australian guidelines).
However, there are significant contrasts in what is tolerated as acceptable risk between
different areas of government activity. To date, there appears to be no systematic evaluation
of the portfolio of risks or a common view on what is acceptable levels.
Peter Hill, Kristen Sih, Rory Nathan, Phillip Jordan
This paper presents a number of innovative hydrologic investigations undertaken for the recent detailed design of upgrades for Ross River Dam in North Queensland. A key issue for estimating extreme floods in the tropics is the estimation of flood events of long critical durations. The implication is that there is an increased focus on estimating the correct volume (not only the peakflow). This paper describes the regional analysis of flow volumes that was used to validate the estimated flood volumes.
Another issue of considerable importance is the assumed relationship between inflows and initial reservoir level. The analyses described in this paper showed that inflows are independent of reservoir levels for the more frequent events but for more extreme events they are correlated. This has important implication on how the initial reservoir level is incorporated in the hydrologic analysis. The final aspect covered by the paper is the derivation of seasonal flood frequency curves. This is particularly important given the highly seasonal nature of rainfalls in the tropics and the results are important for assessing risks during construction and scheduling the upgrade works
Steven Fox, Robert Cooper, Shane McGrath
The Project Alliance delivery model is becoming more popular within the dams industry as owners, designers and constructors seek more effective ways to deliver upgrades that are needed to meet
contemporary community expectations whilst managing the significant safety and commercial risks
typical of these projects.
The Eildon Alliance has recently completed the Eild on Dam Improvement Project on behalf of Goulburn- Murray Water. This $52 M project involved reconstruction and raising of the upper portion of the 80 m high embankment, works to strengthen the spillway chute to cope with larger flood events and refurbishment of the original 50 year old spillway mechanical equipment.
The Eildon Alliance was responsible for the detailed design, construction, commissioning and project
management of this major upgrade. To be successful, a project alliance requires
the alliance partners to adopt a cooperative approach throughout the project. This paper de
tails the benefits that this cooperation provided at Eildon, reasons for selecting the alliance project delivery model and the outcomes achieved.
John Grimston Sally Marx Robin Dawson and Peter Thomson
The Wai-iti Valley is located in the northern region of New Zealand’s South Island. Water demand during summer in the Wai-iti Valley is greater than the available supply, resulting in water allocation restrictions and pressure on in-stream habitat and uses. Further, the summer water resource in the Wai-iti Catchment is currently over-allocated. Thus, since the mid 1980s, Tasman District Council (TDC) has been unable to grant new water permits to take water from either rivers or groundwater in the Wai-iti Catchment. Existing water permit quotas have been reduced where they were not being used, but despite this agricultural, horticultural and domestic use is frequently restricted during dry years.
Recently, the need for a community solution was identified for the Wai-iti Valley area. The Wai-iti Water Augmentation Committee (comprising representatives from the local community and TDC) was set up in 1995 to find the best option for the northernmost extent of the Wai-iti valley. A feasibility study for a community dam was completed in 2001 identifying small off-river storage dams as options. The proposed scheme is located in a tributary of the Wai-iti River and is essentially a water harvesting project where winter flows in the stream would be impounded and stored, and gradually released on a regular basis back into the stream and Wai-iti River system during dry summer periods.
The paper will cover the project’s economic objectives as well as community and environmental impacts and the consenting process under the Resource Management Act. Dam construction is planned to start in October 2004.
The Ross River Dam, designed in the early seventies, does not meet current dam safety criteria for overtopping and piping within the embankment or the foundation. The dam comprises a 40m long concrete overflow spillway flanked by a central core rockfill embankment of 130 m on the right bank and 170m on the left bank with a 7620 m long left bank earth fill embankment, which has no internal filter zones for piping protection. The embankment was extensively assessed and treated forfoundation deficiencies in 1982, and further assessed in 20002002 for appropriate upgrade options.
This paper describes the process of validation of the detailed design using Risk Based Design Criteria. This process included data mining for historical performance and original design intention,
comparison of the original design against current and historical investigations and assessment of the upgrades using the large volume of data available from previous work. A design team comprising specialist hydrologists, hydrogeologists, geologists, geotechnical and dams engineers worked within a risk assessment framework at all stages of the design to ensure the design was validated using the design Validation Model. This process incorporated assessment of crest level based on flood risk and wave overtopping, review of 2D and 3D seepage models to assess piping and foundation erosion potential, assessment of fissured soils within the embankment foundation for structural stability and evaluation of spillway model testing for potential spillway failure modes.