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.
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P.I. Hill, D. Cook, R.J. Nathan, P.A. Crowe, J.H. Green, N. Mayo
This paper describes the development of a comprehensive approach to estimating the consequences of failure of a dam. The approach considers separately the consequences in terms of potential loss of life, economic loss and damage to the environment and the development and application of the method involved professionals from a wide range of disciplines. The method has been applied to 28 dams in NSW.
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.
M. B. Barker, R.M. Holroyde, J Williams and T. Qiu
Grahamstown Dam is a major water supply source for the Newcastle area and it is proposed to raise the full supply level by 2.4m from RL 10.4m to RL 12.8m. The present spillway is inadequate to pass the PMF without overtopping of the existing embankments at the new FSL and part of the raising comprises construction of a new embankment of about 10m high with a right bank spillway upstream of the existing spillway capable of passing the PMF. The Pacific Highway is located some 600m downstream of the new spillway and a 60m wide culvert below the Pacific Highway is being constructed with capacity sufficient to pass the PMF. Significant changes were made to the feasibility design for the spillway and the Pacific Highway culvert using a labyrinth spillway and a baffle chute energy dissipator respectively. Both of these designs are uncommon and the process of finalising the designs as well as some of the problems in the use of a labyrinth spillway and the cost savings realised in the use of these designs are presented.
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.
I. R. Forster
Lyell Dam is a concrete-faced rockfill dam, located on the Coxs River, near Lithgow, NSW. The dam forms part of the Coxs River Water Supply Scheme, which supplies water to Delta Electricity’s Wallerawang and Mount Piper Power Stations. In 1994, the spillway capacity of the dam was upgraded, and the storage augmented with the addition of two 40 m long by 3.5 m high inflatable rubber dams to the spillway crest. An automatic deflation system, controlled by a programmable logic controller, was installed to provide a staged bag deflation sequence during flooding, and hence minimise the downstream impact of rubber dam operation.
Although the rubber dams and control system initially operated as designed, more recently, two uncontrolled bag deflations have occurred, which have caused flooding downstream and loss of significant storage volumes. In the first incident, a spontaneous uncontrolled deflation of the rubber dams released about 1600 ML, before the bags re-inflated automatically. An investigation revealed that the incident was most likely the result of design deficiencies in the control system. Recommendations were made for improvements to the system.
During the most recent deflation, one of the rubber dams failed by spontaneous rupture, and approximately 6000 ML of water was released from the dam. The Dam Safety Emergency Plan was activated to ensure persons at risk downstream were notified of the impending flood wave. A post- failure inspection of the ruptured bag suggested that the likely cause of failure was a manufacturing defect, which allowed air to penetrate the layers of rubber forming the bag. The rupture most likely occurred when the resulting air pocket expanded on exposure to the sun.
The paper examines the two deflation incidents in detail, and analyses the emergency response to the second incident.