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Melbourne Water (MW) has historically seen dam safety management as a civil discipline and has focussed on understanding and managing the civil assets at its dam sites. The recent addition of a mechanical engineering resource to the team responsible for the dam safety management has refocused attention on the mechanical and electrical (M&E) assets and provided a more holistic asset management approach to MWs large dams.
This paper discusses the process MW has developed over the past two years to improve their understanding and management of M&E assets. It centres on key process points for how MW has prioritised the development of M&E asset management programs on the basis of an autogenous ‘asset criticality’ rating system and has utilised ANCOLD comprehensive inspections to plan and implement new inspections and tests on dam M&E assets. The two case studies of Sugarloaf and Upper Yarra Reservoirs’ outlet works demonstrate the the benefits of the process to gain operational and technical knowledge of M&E assets, strategic importance to the water supply network, identifying risks therein and reallocate significant funding to address these risks as prioritised by asset criticality.Learn more
Cameron Purss, Francisco Lopez, Steve Gray
Earthquake design of a dam and associated appurtenant structures is a key aspect of dam design in the modern era. This paper outlines the design process undertaken to address potential earthquake loading for the 32m high outlet tower to be constructed as part of the new Eurobodalla Southern Storage project on the NSW South Coast. The driver for the project is to provide increased water supply security to communities on the South Coast, an area that is currently serviced by a single reservoir and is subject to frequent water restrictions. Construction is planned to commence for the project in early 2021.
This paper presents the design methodology undertaken to meet the requirements for earthquake design and presents a novel defensive design solution to improve the reliability of the outlet works for post-earthquake operation. The Authors contend that utilising this approach in design of future outlet towers will provide a greater level of confidence in the ability to undertake intervening measures following a severe earthquake. Moreover, the technology has the potential to serve as a relatively inexpensive interim upgrade measure for existing outlet towers expected to sustain an unacceptable degree of damage under earthquake loading.Learn more
C.Johnson, D.Stephens, M.Arnold and N.Vitharana
As part of Melbourne Water’s dam safety upgrade program, emergency release capacity is being investigated at a number of dams. Recent work undertaken by the Water Resources Alliance (WRA) for Melbourne Water has highlighted the lack of current Australian guidelines for appropriate emergency release capacity. With no relevant ANCOLD Guidelines, current practice still references the 1990 USBR guidelines which relate the length of time to empty a reservoir to the hazard and risk associated with dam failure. As hazard category assessment criteria has been improved since and dam design and safety standards are more stringent, the applicability of the USBR criteria in today’s environment is under consideration.Learn more
With the prevailing climatic conditions requiring the augmentation of Melbourne’s water supplies, the Tarago Reservoir was recently brought back into service. However, the dam lacked adequate emergency and environmental release capacity, with this being critical to manage construction flood risk for a pending filter raising project. Through an analysis of recorded inflow data, it was evident the existing scour facility had insufficient capacity to handle the recorded inflows, and would not be able to maintain the reservoir at an appropriate level during the proposed works. The length of time to empty the reservoir for the existing scour facility and the preferred scour upgrade option were calculated and it was found that by providing a new 1200mm scour facility, USBR emptying times were met or exceeded. The enlarged outlet capacity was also required to meet the new environmental flow requirements for the dam.
The paper will review international guidelines, share the experience of several Australian water authorities in assigning emergency release capacity for their dams, and discuss the specific work undertaken to provide suitable emergency release capacity at Tarago Reservoir for Melbourne Water.