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
Now showing 1-12 of 38 2973:
Jonathon Reid, Chris Kelly, Bob Wark
One of the most important aspects in the construction of an embankment dam is to be confident that the filter materials placed meet the design intent. The design methodology for filters is now well documented.
However, all too often during construction the filter material, as placed, does not comply with the specified requirements and all parties are faced with costly decisions and delays to the works to determine correction measures and whether the work completed meets the design intent. This paper shares the knowledge gained over a number of projects the authors’ have been involved in and the methods used to improve the properties of the placed filters taking into account some of the practicalities of having these materials produced and placed in a commercial environment
Keywords: filters, specifications, manufacturing, construction, quality assurance.
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.
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.
Amanda Barrett, Mike Marley, Tariq Rahiman
The site of the Wyaralong Dam, west of Beaudesert, Queensland, has been investigated in progressive stages since 1991. The first stage of the investigation was a siting study and the second in 2006 was designed to gather sufficient geotechnical information to develop a preliminary design and provide input into the environmental approval process. The third stage of the investigation was designed to gather further information to allow the detailed design of the dam to commence. This iterative investigation approach has ensured confidence in the site geology and geotechnical model.
The site investigations have included diamond drilling, piezo-cone penetration testing, geophysics techniques, hydraulic conductivity testing, groundwater pumping tests, costean excavation, geological mapping and accompanying laboratory test programs. Investigations have been targeted to assess the foundation conditions for the proposed engineering structure and have been refined to the needs of the dam design as it has developed.
With sufficient data, a 3-dimensional geotechnical model has been developed using the computer modelling program Vulcan, to assess the position and influence of a number of key geological features observed in the site investigation. Assessment of engineering properties based on in situ and laboratory testing were then extrapolated across the site through application of the geotechnical model.
Keywords: Wyaralong Dam, geotechnical investigation, geology, 3-D Vulcan model, foundation.
Peter Cordi, Paul Fuller
Tallowa Dam was completed in 1977 at the junction of the Shoalhaven and Kangaroo Rivers in the southern highlands of NSW to provide a pumping pool for water supply transfers to Sydney. These transfers were made only during drought periods, at which time limited and fixed environmental flow releases from a low level outlet were made to the downstream Shoalhaven River. After extensive consultation with the local community the Government decided in 2006 to commence transfers earlier in the drought cycle, and release variable amounts of surface water to improve river health during transfer periods. In addition, Tallowa Dam was identified as having a significant impact on fish passage, as many species migrate to the estuary during their life cycle, and approximately 75% of the viable fish habitat was upstream of the dam. This project involved the design and construction of works to be retrofitted to the dam to address both issues. A surface water release slide gate in the spillway, a low friction coating on the spillway, and a downstream weir were constructed to release environmental flows and allow safe downstream fish passage. A new fish attraction flow outlet was drilled through the dam wall, and a fish attraction chamber and a travelling bucket fish lift was installed for upstream fish passage.
Keywords: environmental flows, fish passage, Shoalhaven River, construction.