Russell Paton, Peter MacTaggart, Lee Benson
The Nathan Dam project has been identified by the State Government of Queensland as a potential water supply option to facilitate future growth in central Queensland. The proposed storage is located approximately 69 km downstream of the township of Taroom and would have a storage capacity of 1,080,000 ML which would make it Queensland’s fourth largest storage.
The proposed dam arrangement includes a central concrete gated spillway section across the river in order to maximise the storage volume and limit the flood rise upstream such that flood levels at Taroom are not increased during major flood events. A high level fixed crest spillway, to assist in the passage of rare flood events, forms the right abutment portion of the dam wall. It is proposed that the bulk of the concrete sections of the dam be constructed using roller compacted concrete (RCC).
The investigations to progress Nathan Dam are complicated by the existence of the Boggomoss Snail (Adclarkia dawsonensis) within the proposed inundation area. The snail is listed as a critically endangered species under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act), and a proportion of the snail’s known population is located on a Boggomoss (the colloquial name for an artesian spring) that will be inundated should the project proceed.
SunWater has engaged Australia’s foremost expert on land snails to design a translocation process aimed at relocating the species to alternative habitat outside the inundation area. The process will seek to not only protect the snail from the dam development, but to increase both its numbers and distribution thereby reducing risks to the currently isolated population from threats such as fire and predation. It is the first time in Australia that such a trial has been attempted, and SunWater is working closely with the Federal Department of Environment, Water, Heritage and the Arts (DEWHA) to ensure that the process is consistent with their policies and guidelines.
The paper will discuss the engineering and environmental challenges of the dam and how the Environmental Impact Study process can influence the delivery of a project.
Keywords: Nathan Dam, Environment, Engineering
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Anurag Srivastava, David S. Bowles, Sanjay S. Chauhan
DAMRAE is a software tool for performing the event tree risk model computations for dam safety risk analysis. It is being applied by the US Army Corps of Engineers (USACE) and undergoing continued development and testing at Utah State University. DAMRAE is designed to overcome the limitations of existing business risk analysis software. It includes a generalized algorithm for constructing and calculating event trees. A generic project framework provides functionality for considering risk reduction alternatives or a staged implementation of risk reduction measures including obtaining estimates of their cost effectiveness of risk reduction. Evaluations against USACE tolerable risk guidelines are made. A flexible capability exists for obtaining tabular and graphical presentations of estimated risks at different levels of detail.
This paper provides an overview of the structure and capabilities of DAMRAE. It also includes an example screenshots to illustrate its capabilities. Plans for future improvements are summarized.
Keywords: Dam Safety Risk Assessment, Event Tree Analysis, Risk Reduction Measures.
Robert Fowden, Peter Allen, John McKenna
The Large Referable Farm Dam Assessment Program commenced in early 2006 after inspections identified a significant number of Queensland dams that were unknown to the Department of Environment and Resource Management (DERM) and could potentially threaten life if they were to fail. The program is unique given the number of structures under consideration and is understood to be the first widespread, systematic search for dams with a population at risk in the world. The Dam Safety (Farm Dams) team has developed many original solutions to allow the majority of investigations to be undertaken in-house, thus minimising the potentially higher cost and timeframe issues associated with obtaining external engineering and surveying support.
Keywords: Queensland, dam safety, dam failure, regulation, farm dams, surveying, modelling
Khanh (Ken) Nguyen, Peter Allen
There is community concern regarding the potential for dams to fail and threaten lives. In Queensland, the Water Supply (Security and Reliability) Act 2008 provides for the regulation of dams whose failure could cause loss of life. Other consequences of dam failure such as interruption of services, economic loss and damage to the environment would also be of paramount importance for the safety management of our dams in the current climates of change.
In 2003, the Bureau of Meteorology (BoM) revised the Probable Maximum Precipitation (PMP) estimates for both short and long durations of extreme rainfalls for northern Australia. As a consequence, the majority of cases resulted in a significant increase of extreme flood estimates for many river catchments in Queensland. Subsequent studies by the BoM have investigated the potential impact that climate change might have on PMP estimation.
This paper examines the current progress of the Queensland Spillway Upgrade Program, by discussing the current regulatory environment and identifying a number of hydrological issues which may require further investigation for Queensland conditions.
Keywords: Spillway Upgrade, Acceptable Flood Capacity, Flood Discharge Capacity.
David Brett, Bruce Brown, Imran Gillani, David Williams
This paper reports the direction of a current review of the 1999 ANCOLD Guidelines on Design, Construction and Operation of Tailings Dams. A sub-committee has been formed and has determined that the majority of the current guidelines need only minor editing but that additional attention is required to the concepts of risk and design for closure.
Major mining companies recognise that effective operation and closure of their tailings facilities are fundamental to their continued business from financial and political aspects. Risk needs to be managed throughout the life cycle of a TSF through planning, design, operation, closure and post-closure. Various methods are used to assess the “consequence category” of a TSF. This then determines design and operational criteria. Risks are identified and controls developed to limit these to acceptable levels.
The involvement in the sub-committee of representatives of the mining industry gives an industry perspective to this issue. This includes determination of acceptable risk levels and how to manage operations to achieve them.
The current ANCOLD Guidelines are very limited in terms of guidance for closure and possible abandonment of TSFs. However this area is perhaps the most critical from an economic and environmental perspective. The issues to be faced at closure and post-closure should be considered at the planning and design phases. The paper outlines some of the post closure cases that might need to be considered in design.
Keywords: guidelines, tailings dams, ANCOLD
Shane Papworth, Stuart Richardson, David Dreverman, Mel Jackson
A prominent element of the operational environment of a dam is its interaction with the community.The management of public recreational use of irrigation storages is an increasing challenge for Goulburn-Murray Water and the Murray Darling Basin Authority. The upper Murray storages have been significantly affected by the unprecedented low water resource availability which has caused an increasing conflict between the primary use of the dam to supply irrigation water and the secondary benefit of recreation and tourism use by the local communities. Many difficult management issues (media, community relations, political interest) arise from the local community, rather than just from operation of the dam itself.
An increasing awareness of the dire water resource position in recent years has coincided with an ever increasing appreciation of the environmental and social impacts of recreational use. For the storages along the Murray system, effective management is further complicated by complex agency and authority responsibilities, communities and interest groups effectively ‘in competition’ for the water resource.
To better manage these issues, ‘Land and On-Water Management Plans’ have been developed for Lake Mulwala and Lake Hume. Developing the Plans has not been without controversy, but ultimately the Plans have proved to be a simple and successful means of planning for and achieving agreed land and water management outcomes. This in turn is fostering a positive spirit of cooperation and communication with communities currently under considerable stress as a result of prolonged drought.
This paper describes the process, pitfalls and learnings to come out of the development of the Land and On-Water Management Plans.
Key words: Environment, community, irrigation dams, recreational use, planning