Eric J Lesleighter and Peter F Foster
The Ross River Dam was constructed in 1974 following design by the State Government, including hydraulic model testing, by SMEC. The maximum spillway discharge at that time was 1100 m3/s.Latterly, the dam and spillway have come up for a comprehensive review given that the dam is in an extreme hazard category because of its location only a short distance upstream of the city ofTownsville. The revised hydrology has produced outflow hydrographs peaking at over 4 000 m3/s –more than three and a half times the original – to be passed through the 130 ft (39.62 m) widespillway.
The paper describes the hydraulic modelling planned and carried out to determine changes needed to handle such high discharges. The modelling was to provide for the installation of radial gates and piers, and study of the water level, pressure and dissipation conditions in the dissipator for several key discharges through the range to PMF. Pressure measurements included transients, consideration of the potential for uplift of the basin floor slabs, the integrity of the walls to handle the differential loads, and, as a major consideration, the energy conditions in the flow exiting the dissipator and the integrity of the rock downstream to avoid erosion.Each of these aspects will be addressed in the paperboth from the modelling and interpretation standpoint and from the civil structural analysis standpoint, together with a description of the strengthening works required to achieve a satisfactory outcome.
Jon Williams and Chi Fai Wan
The Ross River Dam was first commissioned in 1974 and raised in 1976. The 8200 m long embankment was not fitted with chimney filters and has suffered extensive desiccation cracking since it was raised. A significant component of the dam upgrade is the retrofitting of filter zones to ensure the embankment meets current dam safety guidelines.This paper describes the process of investigation of the existing desiccation cracks and the use of Hole Erosion Tests (HET) and No Erosion Filter (NEF) tests to validate the design of the retrofitted filter.
A significant challenge in the design is to provide a cost effective solution given the 7500 m length of embankment requiring treatment. Assessment of flow rates within cracks and expected piping erosion along the cracks was used to assess the required drainage capacity. This assessment of expected flow capacity allowed the deletion of the coarse filter inthe design reducing the filter requirement from a triple filter to a single fine filter. Results of this assessment were incorporated into the Risk Assessment based design validation process
This paper sets out the principles, practices and issues relevant to the sharing of
costs for dam safety upgrades in southwest Western Australia and other locations.
? the general principles (noting that in practice multiple conditioning factors
? the practical outcomes for cost sharing in Australian jurisdictions;
? the beneficiaries of the dams, the water and the safety upgrades;
? legacy costs (including IPART’s framework and whether this can be directly
applied to the southwest);
? the Bulk Water Service Agreement;
? the question of price impacts and affordability based on surveys of farm
performance, water use and profitability; and
? the pricing impact of treating safety upgrades as if Harvey Water owned the
We examine the impact of applying economic allocation principles to this task and the
impact of other criteria such as dam safety obligations, hazards presented by a large dam,
community expectations for public safety, the broader public safety, welfare and state and
regional economic benefits reliant on dam safety, significant community costs subsidised by
irrigation customers, State Government ownership, and the effects on bulk water prices
should customers be required to fully fund the necessary dam safety upgrading.
The Tarong coal-fired power station near Kingaroy in southern Queensland discharges ash to a storage facility of 42,000 ML capacity, impounded by a 48 m high-zoned earth and rockfill dam embankment. The embankment was constructed in 1980–81. In recent years, Tarong Energy Corporation (TEC) has investigated a number of options for a new storage facility as the remaining capacity of the existing ash dam storage diminishes. TEC determined that the existing facility should be upgraded to provide additional storage capacity for the short term. At the same time, there emerged a requirement to improve the long-term seismic resistance of the embankment. Enlarging the existing spillway cut provided the material for a 400,000 m3 weighting zone and, by reducing the design flood freeboard, extended the ash disposal capacity by several years without a need to raise the embankment. Challenges included significant foundation seepage and deteriorated riprap. The paper describes the issues, risks, adopted criteria, investigation undertaken, and implementation of the upgrading works. Innovative approaches to the provision of future storage capacity are outlined.
Changes to the Regulatory and legal environment have resulted in an increased focus on the
importance of proficient management of dams. Operation and maintenance manuals are now a
Regulatory requirement in Tasmania for all but very low hazard dams and are also required to ensure that dams are managed efficiently and safely. To meet these requirements Hydro Tasmania has developed the ‘Smart’ operations and maintenance manual.
Hydro Tasmania has a large portfolio of dams and as a result requires a large number of operations and maintenance manuals. This would result in an overwhelming array of information that is subject to evolving change if the traditional approach to the manual was adopted. To overcome this burden, a controlled electronic manual was developed to enable:
• Critical operation and maintenance information to be collated with minimal effort;
• Electronic hyperlinks to key existing operation and maintenance documents, reference
materials, and portals into operational data bases; and
• A means of updating and controlling information that is subject to change.
This paper will discuss how Hydro Tasmania developed its user-friendly operation and maintenance manuals in an innovative, unique and controlled manner to ensure prudent management of dams and to comply with Regulatory change.