Chas Keys and Steve Opper
As the legislated ‘combat agency’ for dealing with floods, the NSW State Emergency Service has had considerable experience in planning for flooding on the state’s rivers and in developing arrangements to help keep people safe when floods occur. This experience has been put to use over the past decade in the particular context of managing floods caused or exacerbated by dam failure. Some of the complexities of the dam-failure planning problem are explored in this paper, specifically as they relate to warning and evacuation tasks and to the issue of preparing communities for the extreme flooding which dam failure can be expected to cause. The points are made that warning is not just about mechanical alerting devices, evacuation is not restricted to commanding people to move, and public education requires a sensitive comprehension of the problems of disseminating information about rare and difficult-to-believe events.
D. J. Dole, D. Dreverman and A. J. McLeod
The Murray-Darling Basin Commission is embarking on an ambitious project directed towards repairing the environmental damage to the River Murray, caused by a century of human intervention. Today the River Murray is one of the more highly regulated rivers in the world, with only a 27% natural annual median flow to the sea.
In April 2002 the Murray-Darling Basin Ministerial Council approved, in–principle, a program of structural works from Dartmouth Dam to the Murray Mouth, including the lower Darling downstream from the Menindee Lakes. The initial phase is estimated to cost $150 million over 7 years. At the same time the Council has authorised studies of the environmental, social and economic impacts of 3 scenarios involving recovery of 350 GL, 750 GL and 1500 GL per year from existing uses, for reallocation to the environment.
This paper describes some of the key projects in the portfolio of works under consideration, including:
The paper also outlines the extensive stakeholder consultation and community engagement processes which are fundamental to the success of the project, as well as the various means adopted to enhance the links between scientists and engineers involved in the project.
David Brett, Anton van Velden and Phil Soden
The Main Creek Tailings Dam is a 60m high earth and rockfill dam constructed during the early 1980’s to store tailings from the Savage River Mine on Tasmania’s west coast. The dam served the mine well for nearly 20 years, storing around 32 million m3 of tailings, but has required raising due to the expanded mining plans of the current operators, Australian Bulk Minerals (ABM). ABM believe that the mine could require a further 60 million m3 of tailings storage over the next twenty years at increased production levels. This could be stored in the Main Creek Dam by raising it by around 35m. In the medium term this scale of raising would be feasible using waste rock product from ongoing mining but in the short term of several years an interim solution would be required. The feasibility of upstream construction on the tailings beach was reviewed and found feasible for
a maximum 12m in 4 lifts.
Of critical concern were
The paper discusses the investigation and design phases of the dam and describes the issues arising during construction recently completed over the period January to April 2002. The use of pore pressure, shear strength changes and tailings beach movement monitoring to control construction is discussed.
D.S. Bowles and Loren R Anderson
Starting a quarrel is like breaching a dam; so drop the matter before a dispute breaks out. Proverbs 17:14 (NIV)
An approach is summarised for presenting the outcomes of traditional engineering assessments and risk assessments to inform non-technical decision makers. The decision justification approach can be adapted to any dam owner’s unique decision context. It includes rating systems for presenting the outcomes from engineering assessments and from applying tolerable risk criteria, including ALARP. Three decision types are addressed: setting tolerable risk goals for individual dams, identifying a risk reduction pathway for a portfolio of dams, and managing residual risk on an on-going basis
R.A. Ayre and T. L. McGrath
The regulatory environment of Queensland’s water resources has changed significantly within the last few years as a consequence of the passing of the Water Act 2000. SunWater, as the owner of referable dams and the operator of water infrastructure, is required to observe the provisions of the new Act.
SunWater has undertaken dam failure analyses of a number of its dams in accordance with the new guidelines prepared by the Department of Natural Resources and Mines. The results of these assessments are being used as part of a portfolio risk assessment of its assets to help prioritise refurbishment activities. Aspects within the guidelines relate to various ANCOLD publications, with a focus on the consequence of failure for determining incremental hazard categories and appropriate design standards for spillway adequacy.
SunWater also operates its schemes under the provisions of Interim Resource Operation Licenses (IROLs). As part of Government’s water planning process, SunWater is required to submit proposed water management arrangements for its schemes. SunWater develops these arrangements, which include operation, water trading, and monitoring rules, to meet its business objectives and the objectives of government. With government approval, these proposed arrangements will translate to the provisions of Resource Operation Licenses when the Resource Operation Planning (ROP) process is completed.
This paper describes SunWater’s experience and approach to meeting regulatory requirements in the above areas.
Water storage dams influence the lives of a large number of people. This influence may be through provision of essential water supply or risk of dam failure during sunny day or extreme flood scenarios. It is therefore imperative that these structures are managed in a responsible with a clear understanding of the associated uncertainty. In view of the large capital cost of the structures involved, this understanding is important to ensure that, where necessary,
practical and cost effective solutions are achieved. The NSW Dams Safety Committee largely regulates the management of dams in New South Wales, however, dam owners have the opportunity to display individual initiative in this process.
The Hunter Water Corporation (HWC) is a water authority based in Newcastle, New South Wales, responsible for the supply of water and wastewater services for over 470,000 people. HWC has realised, as a responsible dam owner, that safety improvements are a continuum over the life of the structure. Chichester Dam is an example of this on-going safety improvement process that is illustrated through the principle of ALARP in a risk assessment approach.