ANCOLD Bulletin No.114 (April 2000)
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Papers 2000
2000 – Dam Remedial Works in Western Australia
Learn moreRobert Wark, Nihal Vitharana and Michael Somerford
This paper reviews the history of dam remedial works on publicly-owned dams in Western Australia over the last 40 years. Projects have ranged from refurbishment of the facilities, through capacity upgrades to complete reconstruction. Major work has been undertaken on at least thirty dams. Most of these dams are now owned by Western Australia’s Water Corporation. The Corporation continues to undertake remedial works where necessary and now has a strategy in place for an on-going program of remedial works.
The paper outlines the scope of the work undertaken and why the work was required. The current status of the Corporation’s planning for an on-going remedial works program is also reported.
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Papers 2000
2000 – Spillway Gate Reliability
Learn moreGlen Hobbs and Danny Azavedo
Recent years have seen a growing awareness and understanding of the factors that contribute to the reliability of spillway gates and the incorporation of reliability data into overall dam risk studies.
The study of a number of spillway gate failures shows that no one component or incident leads to gate failure, but rather a combination of factors have resulted in gate failure. A rigorous reliability assessment should consider all factors, not only the equipment condition and performance but the complete system, from the receipt of data through to the actuation of the gates. It should take into account issues such as human factors, poor design, maintenance history and policy. Unfortunately one of the main hindrances to quantifying gate reliability is the lack of information on spillway gate equipment and system performance and failures.This paper considers a number of gate failures, then looks at some of the tools of reliability assessment and the role of human factors in gate reliability.
The paper then discusses a recent study of four gated dams. For this study a systems approach was adopted and human factors were considered. The results compare favourably with other similar critical structures, and show that for these well designed and maintained structures human factors are the limiting criteria in multiple gate operations. The study also shows that the probability of opening all the spillway gates at a dam improves with time (2-4 hours) during the flood operation, and it is considered that time based reliability provides a more meaningful and useful assessment of overall spillway gate reliability.
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Papers 2000
2000 – Harvey Dam Environmental Management
Learn moreMichael 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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Papers 2000
2000 – Risk Assessment and Dams – Is it Safe?
Learn moreS.G. McGrath
The use of risk analysis for dam safety is becoming more widespread. Dam owners are increasingly aware of the need for information on current and emerging practices from the world scene to determine how to proceed with the use of risk assessment. The paper summarises the findings of a Churchill Fellowship study into risk assessment for dam safety management. Dam owners, regulators and consultants from the United Kingdom, France, the Netherlands, Norway, Sweden, the United States and Canada were consulted for the study. Conclusions are drawn from the findings and recommendations made for future development.
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Papers 2000
2000 – Environmental Challenges in Constructing the Warragamba Dam Auxiliary Spillway
Learn morePieter van Breda, Peter Walton, Kate Lenertz and Tim Sheridan
The Warragamba Dam Auxiliary Spillway Project, designed to manage floodwaters up to a Probable Maximum Flood event, was approved by the NSW Minister for Urban Affairs and Planning on February 12, 1998. An Environmental Impact Statement prepared for this project predicted that noise, dust (suspended and deposited), blasting, vibration, water quality and revegetation would be the significant environmental issues requiring management throughout the construction phase.
The closest residents are approximately 200m from the construction activity. The works must not interfere with the operation of the Dam, which stores 80% of Sydney’s drinking water and the integrity of the existing infrastructure must be maintained at all times. The approved proposal was to emplace the 2.2Mm3 of spoil excavated to create the spillway in an area 25 ha by 20m high on top of a ridge on the left bank adjoining the Blue Mountains National Park. This created visual impact and rehabilitation challenges.
Although the contract for this project was primarily performance based, strict environmental clauses were incorporated to manage these priority issues. Noise and dust modelling were required from each pre-qualified Tenderer, to demonstrate capability of compliance with NSW Environment Protection Authority requirements. This formed part of the tender assessment. Criteria were also developed for revegetation, specifying numbers of endemic trees, shrubs and grasses per 400m2 of spoil emplacement in order to create a floral community similar to the existing adjacent National Park.
The implementation of these requirements and the development of a site Environmental Management Plan by the Sydney Catchment Authority, Australian Water Technologies and Abigroup Contractors, whilst maintaining productivity, has proven to be a working example of the benefits of Partnering.
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