Steve O’Brien, Christopher Dann, Gavan Hunter, Mike Schwermer
One of the principal geotechnical issues identified for the Hinze Dam Stage 3 project was the potential for internal erosion and piping within the extremely complex geology at the right abutment. A plastic concrete cut-off wall was selected as the best solution to reduce the risk of piping to acceptable levels and careful planning of this work was required to manage a range of key project risks that included complex technical challenges, potential risks to dam safety, the environment, the surrounding community as well as delivering the works on a tight construction schedule to an agreed budget value. Construction of the 220m long and up to 53m deep cut-off wall, the largest wall of this type constructed to date within Australia, was undertaken by Bauer Foundations Australia and completed in January 2009. A major key to the success of the project was the planning and risk reduction measures that were undertaken during both the design and construction phases, a summary of which is presented in this paper.
Keywords: Cutoff Wall, Plastic Concrete, Hinze Dam.
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Ben Ross, Jason Brown, Richard Rodd
Goulburn Weir was constructed in 1891 forming Lake Nagambie on the Goulburn River, approximately 8km north of Nagambie in Victoria. It is a key asset in the irrigation network diverting water to 352,000ha in Northern Victoria. The weir was remodelled between 1983 and 1987, replacing 21 overshot gates with nine radial gates. A series of 28 post tensioned bar ground anchors were installed to secure the radial gate concrete support piers to the weir’s mudstone foundations. On 8 March 2006 during routine testing of the pier bar ground anchors, failure of one anchor occurred. It posed a possible risk to pier stability. Subsequently investigations into the cause of failure and its implications was undertaken consisting of a program of data review, site investigations, metallurgical testing, geotechnical investigation, design reviews and stability assessments. It was recommended to replace the failed anchor and 10 other under performing anchors with 8 cable strand anchors at the cost of approximately $1million.
Key words: Risk, bar anchor failure, stability assessment, anchor construction.
Chi Fai Wan, Tom Haid, Jim McClain, Kelly Rodgers
The dams market in California is alive again with phenomenal growth driven by an increasing need for storage to hedge against ongoing water scarcity due to climate change and a growing demand for reliable water supplies driven by population and economic needs. To meet the region’s water supply needs the San Diego County Water Authority has launched the Emergency Storage Project (ESP), an extensive program to create a system of reservoirs, interconnected pipelines and pumping stations to provide more flexibility for water deliveries to the San Diego region, especially in the event of an emergency, such as a devastating earthquake. The Water Authority has planned for water needs in an extended drought by creating the Carryover Storage Project (CSP), which provides additional storage to capture water in wet periods for use in dry periods.
Up to 90 percent of the region’s water supply is imported by pipelines travelling hundreds of kilometres across earthquake fault lines from Northern California and the Colorado River. The major component of the fourth and final phase of the ESP is the San Vicente Dam Raise. The project includes raising the existing dam by 35 m to increase the reservoir and provide an additional 187 million m3 of water storage for the region. This will be the largest dam raise in the United States and the largest roller compacted concrete dam raise in the world. The Water Authority has contracted with Parsons/Black & Veatch Joint Venture to provide construction management services for this vital project. The dam raise is another one of the marquee water supply dams and reservoir projects that the Joint Venture members have been involved in Southern California, after successful completion of the Diamond Valley Lake for the Metropolitan Water District of Southern California and the Olivenhain Dam for Water Authority.
This paper presents a brief description of the San Vicente Dam Raise, the underlying water shortage and the emergency backup needs, and the need for carryover storage. The dam raise design has been previously presented in numerous papers and publications. Therefore, following an overview and general project description, this paper focuses on the critical role that effective construction management plays in implementation of a dam construction project of this size and complexity. Key construction management activities that are discussed in the paper include engineering design constructability reviews, independent cost estimation and scheduling, on-site laboratory management and quality control, and contractor oversight. The construction manager will be involved in this project through final design and construction over a five-year period.
Keywords: Water Scarcity, San Diego County Water Authority, Emergency Storage Project, San Vicente Dam Raise, Roller-Compacted-Concrete (RCC), Construction Management, Climate Change.
Giovanni De Cataldo
The ANCOLD Guidelines on Dam Safety Management August 2003 were formulated to ensure that dam owners adopt a responsible approach towards the safe operation and maintenance of their dams.
Is it possible to safely, responsibly and acceptably work outside the regulatory Guidelines/Requirements?
The challenge for dam owners now and into the future in meeting stringent standards, is to cost effectively manage their assets within available financial constraints whilst minimising risks and maintaining acceptable levels of safety.
With the continuing drought and suppressed storage levels in most dams, the risk to downstream communities and to the environment from dam failure is significantly reduced.
Based on various studies, investigations, internal workshops and external “Expert Panel” reviews, this paper puts forward a case for a sound and responsible risk-based approach to routine visual and surveillance monitoring frequencies at varying storage levels for “Sunny Day” conditions and compares it against traditional ANCOLD standards which are based solely on consequences.
Keywords: State Water Corporation, ANCOLD guidelines, risk-based approach, dam safety, regulator.
Robert Kingsland, Glen Burton
The management and closure of tailings dams can present mines with a trailing liability potentially extending well beyond the life of the mine. The dilemma faced by mine operators is that a tailings storage facility (TSF) is usually required to be in service up until the last product is mined and processed, but the stored tailings may be too weak to support the capping of those facilities for some years after the last tailings deposition. This paper presents the authors’ experience in the geotechnical characterisation of tailings and failure mode analysis required for tailings dams cover design, with particular reference to coal mines in the Hunter Valley. Techniques for field and laboratory determination of strength and consolidation parameters are presented. Failure modes for capping cover and displacement cover alternatives are discussed. Alternative cover techniques including strategies for improving and/or accelerating tailings strength gain are also discussed. Finally, areas needing further study are noted.
Keywords: tailings storage facilities, tailings dams, closure, capping, cover design.
M. Amghar, A. Watt, C. Thorstensen
The future effects of climate change on water resources in the southeast Queensland and other parts of Australia will depend on trends in both climatic and non-climatic factors. Evaluating these impacts is challenging because water availability, quality and streamflow are sensitive to changes in temperature and precipitation. Other important factors include increased demand for water caused by population growth, changes in the economy, development of new technologies, changes in catchment characteristics and water management decisions. In Southeast Queensland, concern for climate change has increased in recent years with research on global climate change applied to part of Southeast Queensland and it has become apparent that the region’s climate has changed in recent times. Studies have shown that Southeast Queensland’s climate has been variable over history and in the present, is experiencing continuing sea level rise, and may experience
significant climate warming. The potential effects of climate change on coastal erosion, water availability, flood control, and general water management issues have been raised and widely discussed from a variety of perspectives.
This paper presents results of an integrated economic-engineering resource assessment optimisation model of Seqwater’s water supply system illustrating the value of optimisation modelling for providing an integrated approach needed to manage a complex multipurpose water system. Overall, the approach has its own limitations, but provides useful insights on the potential for operating the current or proposed infrastructure for different future conditions.
Keywords: Brisbane Water supply, Moreton, water resource plan, optimisation, environmental flows.