Bob Wark, Colin Bradbury, Michael Somerford and Michelle Rhodes
The Harvey Dam project is a major component of the Water Corporation’s Stirling-Harvey Redevelopment Scheme, which was developed to provide potable water to Perth. The scheme will deliver 34 GL/annum or about 10% of Perth’s supply. The project timetable was tight. The decision to proceed with the scheme, made in June 1998, required Harvey Dam to be ready to impound water by June 2002.
Construction of the Harvey Dam was complicated by the following:
These and other issues required the development of risk management strategies for the project. The construction risks were allocated within the contract to provide for an equitable sharing of risk between the Contractor and the Principal. The paper describes the development and implementation of the risk management strategies and what lessons have been learnt from the process.
Brian Walford and Ross Killick
Increasing salinity in Australian river systems is a major issue that is attracting attention from politicians, environmentalists and the wider community. The successful coexistence of mining and agriculture in the Hunter Valley has resulted in the need to tackle river salinity with a cooperative approach to not only contain salinity, but also reduce it. Mining companies have participated in the development of a tradeable emission scheme to manage the discharge of surplus saline water, resulting in the construction of mine water dams that are designed to release a large volume of saline water in 2– 3 days.
Pieter van Breda, Alison White, and Greg Carmody
Site works on the $150 million Warragamba Dam Auxiliary Spillway project commenced in March 1999 and were completed in June 2002. Successful interaction with the local community, to achieve an equitable outcome, has been a feature of the communications strategy for the project.
The Auxiliary Spillway is located close to the village of Warragamba, a township of approximately 2,000 residents. The closest residence is about 200 metres from the site. The EIS and subsequent planning documents identified key localised environmental impacts that the project would impose. The main concern of local residents, including a local action group, was the impact on their amenity during construction of the Auxiliary Spillway, particularly in relation to noise, vibration, dust and traffic.
The conditions of approval for the project included a range of communication activities, of which the formation of a Community Liaison Committee (CLC) with an independent Chairperson was a key component. When the membership of the CLC was established the Sydney Catchment Authority (SCA) and chairperson agreed that it needed to fully represent the local community – and therefore included community representatives from Warragamba and two nearby villages, the Chamber of Commerce, the local action group, the local school, local council, the dam owner (SCA) and the project manager (AWT P/L).
The establishment of the CLC has proven to be very successful. It has been the voice of the community, with responsibility to act on behalf of the community and to keep them informed of progress on the project. When issues arose during the construction, the CLC were briefed on the particular matter. The CLC was instrumental in resolving these community issues and has allowed this $150 million civil project to proceed without community attributed delays.
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.
M. Shirley, P. Hill, S. Hannon, B. Abernethy, H. Griffith and S. Gatti
There is an ever increasing focus on the impact of water resource infrastructure, and particularly dams, on downstream hydrology and hence ecology. Over the last few years this focus has led to the rapd development in the philosophy and techniques for estimating the requirements of water dependent ecosystems.
This paper outlines the application of a new framework for estimating environmental water requirements which results in a range of flows, rather than a single recommended flow. Furthermore, a range of strategies for providing this water to the environment will be explored.
The paper uses the current environmental flows study on the Onkaparinga River Catchment for the Onkaparinga Catchment Water Management Board to illustrate the issues and application of the methodology. The natural hydrology of this catchment has been impacted by pumping of water from the River Murray, a major dam (Mt Bold) and the diversion of flow at Clarendon Weir. This substantial multi-disciplinary study over 3 years is estimating environmental water requirements and the strategies for providing this water to the environment.
C.F. Wan, R. Fell, M.A. Foster
This paper presents the findings of experimental investigation of the rate of piping erosion of soils conducted at the University of New South Wales.
Two tests, namely the Slot Erosion Test and the Hole Erosion Test, have been developed to study the erosion characteristics of a soil. The erosion characteristics are described by the Erosion Rate Index, which indicates the rate of erosion due to fluid traction, and the Critical Shear Stress, which represents the minimum shear stress when erosion starts. Results of the two laboratory erosion tests are strongly correlated. Values of the Erosion Rate Index span from 0 to 6, indicating that two soils can differ in their rates of erosion by up to 106 times. Coarse-grained soils, in general, are less erosion-resistant than fine-grained soils. The Erosion Rate Indices of coarse-grained cohesionless soils show good correlation with the fines and clay contents, and the degree of saturation of the soils, whereas the Erosion Rate Indices of fine-grained cohesive soils show moderately good correlation with the degree of saturation. The absence of smectites and vermiculites, and apparently the presence of cementing materials, such as iron oxides, improves the erosion resistance of a fine-grained soil.
The Hole Erosion Test is proposed as a simple index test for quantifying the rate of piping erosion in a soil, and for finding the approximate Critical Shear Stress corresponding to initiation of piping erosion. Knowledge of these erosion characteristics of the core soil of an embankment dam aids assessment of the likelihood of dam failure due to piping erosion in a risk assessment process.