Paul W. Heinrichs & John Bosler
Spring Creek Dam is a 16m high zoned earthfill dam with a central vertical concrete core wall storing 4700 ML for Orange City Council’s water supply. It was a 14.5m high dam constructed in 1931 and in 1947 was raised by 1.0m. In 1966 after a week of heavy rain following a long dry spell, an 80m section of the downstream face slumped but the dam fortuitously survived. In 1969 the dam was re-constructed but no internal drain/filter was installed.
Following the 1994 dam surveillance report, piezometers were installed in the downstream fill. Drilling for these revealed that a substantial portion of the zone downstream of the core wall was saturated. The piezometers recorded piezometric elevations that closely and rapidly followed the reservoir level. Subsequent site investigations identified pockets of very low strength fill immediately downstream of the core wall. It was concluded that the core wall was seriously compromised and the storage level was subsequently, significantly lowered, as an interim dam safety measure.
Dambreak studies indicated the dam is a high hazard and hydrological studies found that the spillway capacity was inadequate.
This paper details the problems involved, their analyses, and the remedial measures proposed at the concept design stage. These include a chimney filter/drain, a stabilising fill combined with embankment crest raising and the construction of a 3-bay fuse plug auxiliary spillway.
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H. Morrison, J. Leckie, P. Richardson, R Paton
Awoonga Dam is a 40 metre high concrete faced rockfill dam on the Boyne River near Gladstone in Central Queensland. The dam supplies domestic and industrial water to the Gladstone region and the Callide Power Station. Stage 1 will increase FSL by 10 metres to EL 40, which increases storage capacity from 289,000 ML to 777,000 ML. To provide for future industrial growth in the region, the dam design facilitates future raising up to a nominated FSL of EL 62, in a number of stages.
The project consists of:
Significant savings were realised by adopting the alliances project delivery method, resulting in completion 5 months ahead of program and more than 10% under budget.
This paper details development of the project under the alliance and outlines some of the lessons learnt.
R.I. Herweynen and A.M. Hughes
Hydro Tasmania has a number of dams which were designed and constructed in the 1950-70s
with fully grouted, post-tensioned anchors. The method used was leading edge in its day,
however, it does not achieve the cable protection of modern methods which provide two barriers
against corrosion and are monitorable. Hydro Tasmania has developed and employed an
innovative program to ascertain the integrity and remaining life of the cables and to prepare
long term management plans for its cabled dams.
An international panel was set-up to provide guidance on the overall issue, assist in developing
a sound methodology for assessing the corrosion of the anchors and advise on long-term
monitoring. To focus the efforts, Catagunya Dam was adopted as the pilot dam, as the stability
of this dam is very much dependent on the integrity of the anchors. This paper will provide a
brief overview of the project to date but will focus in detail on the main components of the
corrosion assessment of the anchors, namely:
The paper also provides a brief summary of the instrumentation installed at Catagunya Dam to
assist with the long-term monitoring of the dam.
Bob Wark, Colin Bradbury, Michael Somerford and Michelle Rhodes
The Harvey Dam project is a major component of the Water Corporation’s Stirling-Harvey Redevelopment Scheme, which was developed to provide potable water to Perth. The scheme will deliver 34 GL/annum or about 10% of Perth’s supply. The project timetable was tight. The decision to proceed with the scheme, made in June 1998, required Harvey Dam to be ready to impound water by June 2002.
Construction of the Harvey Dam was complicated by the following:
These and other issues required the development of risk management strategies for the project. The construction risks were allocated within the contract to provide for an equitable sharing of risk between the Contractor and the Principal. The paper describes the development and implementation of the risk management strategies and what lessons have been learnt from the process.
Tim Waldron, K D Murray and Allan Crichton
The City of Hervey Bay is a growing tourist community that is located a comfortable 3½ hour drive north of Brisbane. To meet the growing water demands of the community, Wide Bay Water Corporation required the raising of its sole water supply – Lenthalls Dam.
At the time of the option study, Queensland dam owners were aware of their obligation to manage their dams to minimise adverse environmental impacts but detailed Environmental Flow Objectives were still being developed.
This required a solution for the raising of Lenthalls Dam that provided maximum flexibility while, at the same time, being cost effective.
A range of solutions and new technologies were investigated. Using a Risk Management methodology, the Crest Gate system developed in South Africa was adopted.
Subsequently, draft Environmental Flow Objectives have been set and the use of a gated system has been beneficial in meeting post-winter flow objectives.
Following the construction of the Snowy Mountains Hydro-Electric Scheme, flows in the Snowy River have been reduced to 1% of their original level at Lake Jindabyne. The Victorian, NSW and Commonwealth Governments have agreed to restore 212 gigalitres per annum (about 21% flows) to the river over a ten-year period and 28% in the longer term. The increased flows will be sourced primarily through water savings projects in Northern Victoria and NSW. This is a case study in learning how to share our precious water resources between environmental, social and economic needs.