Jack Rynn, John Pix, Garry Grant and Albert Hill
Ground motions resulting from seismic activity can cause significant damage to existing dams. For this reason, monitoring of seismic activity is an important component of a dam safety management program. Similarly, the long term gathering of data on regional seismic activity provides a sound platform for structural adequacy checks of components of existing dams under seismic loading, as well as for future dam design. In this context, the South East Queensland Water Corporation Ltd (SEQWater) and its predecessors have been monitoring earthquake activity in relation to the Wivenhoe, Somerset and North Pine Dams in South East Queensland since 1977. In 1998, SEQWater upgraded the seismic instrumentation with a digital telemetered seismic surveillance system (DTSSS) six-station network to replace the original analogue seven-station network. This state-of-the-art instrumentation was supplied and installed by Nanometrics Inc., Canada through an international tendering process. This paper presents an overview of the DTSSS, results to date and future planning for an integrated strong ground motion accelerograph network.
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David Dole and Brian Haisman
The $75 million remedial works at Hume Dam on the Murray River near Albury have been of national significance. The rehabilitation program associated with the structure itself and with its appurtenant works is now in the final steps of construction. The authors summarise this program with an emphasis not on technical details, but on decision processes. Equity in this dam is, in effect, held in equal parts by three State governments and by the Commonwealth government. At the same time, in response to the national water reform agenda, the governments have agreed upon new cost sharing arrangements that more nearly reflect the value of services to each government. The particular problems of decision-making within this evolving inter-State environment are discussed.
Lessons from experiments with application of risk analysis are discussed. Finally, the matter of adequacy of the structure for extreme floods is still under consideration. Hume Dam will presently pass the Design Flood developed in accord with Book VI (1999) of Australian Rainfall and Runoff, and the Dam Crest Flood has been estimated to have an annual exceedance probability of 1:110,000. _ Retrofitting a spillway to pass the estimated Probable Maximum Flood will double the cost of remedial works and is estimated at 10 times the cost of similar capacity built into original construction. The authors discuss the public policy elements of this pending decision.
B. A. Cole
In October 2000 ANCOLD published a history of dam technology in Australia covering the 150 years in which large dams have been constructed in this country. The paper describes how this project began, the search for authors, the way the authors tackled their tasks, the peer reviews which resulted in additional chapters being written, and the archive searches for interesting photographs to illustrate the text. All this was accomplished by dam engineers including the editor. Then follows an account of the professional publication process: sub-editing, desktop publishing, proof-reading, the preparation of an index, the cover design and the printing process. Some conclusions are drawn from this first experience of book publishing.
Michael Somerford, Michelle Northover and Steve Wilke
Western Australia’s Water Corporation is constructing the Stirling-Harvey Redevelopment Scheme, a $275 million scheme to supplement Perth’s public supply. A major component of the scheme is the construction of the Harvey Dam, a 45 metre high, earth core rockfill dam.
The main environmental issues associated with the construction of the Harvey Dam are related to construction and traffic noise, blast vibration and dust generated during the construction period. Appropriate environmental management is required to minimise noise and dust emissions because of nearby schools, town site, residences and horticultural activities.
The new reservoir will commence filling in 2002. It will inundate several private properties, farming land, an area of pine plantation and six sites of cultural and heritage significance.
This paper discusses the management and monitoring strategies associated with the construction of the new dam. It also describes the initiatives that the Water Corporation has undertaken to ensure that adverse impacts of the project on the environment are minimised.
Murray Thompson and Geoff Chenhall
The Hastings District Water Supply Augmentation Scheme [HDWS] includes a 10GL off-creek storage dam, which is currently under construction and due for completion in October 2001. The Cowarra off-creek storage dam is required to meet predicted long-term urban growth demands for water supply and to ensure protection of environmental flows in the Hastings River.
Since 1985 the Hastings Council has progressively developed a strategy for the augmentation of the water supply scheme. A very successful ongoing consultation process with both the local community and key government agencies during the planning and implementation phases of this project has highlighted a number of key issues including:
“That the impact upon aquatic flora and fauna in the Hastings River should be minimised and appropriate safeguards developed by maintaining minimum river flows to ensure that the river habitat is not adversely affected”
The subsequent HDWS Environmental Impact Statement, 1995 was one of the first in NSW to recognise the importance of environmental river flows in the assessment of the aquatic ecological effects of water supply schemes. This paper to be presented to the ANCOLD Conference on Dams will detail the investigation, planning, implementation and current construction activities associated with the Cowarra Off-Creek Storage Dam.
Mark Locke, Buddhima Indraratna, Phillip Cummins and Gamini Adikari
ABSTRACT: Australia has a large number of older embankment dams, which have been in service and performed adequately for over 50 years. However, current industry practice in embankment dam design predicts that the granular filters within these dams may not be adequate. This may require refurbishment of the dam by retro-fitting a new filter to ensure the continued safety of the structure. This paper outlines the potential problems with older embankment dam designs, and the reasons for constructing a new filter. Potential problems may include inadequate or non-existent filters, risk of failure due to earthquake, piping, or excessive foundation seepage. Design methods for granular filters are described briefly, concentrating on whether an existing filter is adequate, and the potential improvement by constructing a new filter. Construction issues for placing filters on existing dams are also discussed.
A new analytical method, developed to describe the time dependent erosion and filtration within embankment dams, is described briefly. The model predicts particle erosion, transport and retention based on fundamental fluid mechanics and geotechnical concepts. The application of this model to the design of filters for new and existing dams will be described. The predictions of such analytical modelling can give a designer a significantly clearer picture of the purpose of a granular filter, the extent of core erosion that can be expected, and the effect of retrofitting a new filter to an existing dam.