Rod Westmore, Andrew George& Robert Wilson
A 2007 risk assessment of Hume Dam concluded that the dam did not satisfy the ANCOLD societal risk criteria for existing dams. The Spillway Southern Junction (SSJ) and its associated failure modes was one of the main contributors to the risk profile.
Upgrade works at the SSJ involved the retro-installation of additional filter and drainage materials in the 40m high embankment immediately downstream of the tower block and central core wall by installation of more than 10,000m of secant caisson drilled columns backfilled with filter and/or drainage materials.
This paper describes the design and construction issues associated with the upgrade works, the equipment and methodologies developed to achieve the principal design objectives of coverage and connectivity of filter and drainage columns, and optimisation of compaction of the backfill materials. It also describes how these requirements were met whilst minimising adverse affects such as vertical deviation, excessive vibration, subsidence of secant filter columns during construction, and clay smearing of the perimeter of individual columns.
Hume Dam Spillway Southern Junction Filter and Drainage Works
Now showing 1-12 of 45 2975:
Rory Nathan, Peter Hill
This paper provides an overview of the different simulation frameworks used for the estimation of design floods.. For small events the behaviour of many flood modifying factors is highly variable and chaotic, whereas as the magnitude of the event increases so does the organising influence of the dominant meteorologic conditions. The approach to design flood estimation will depend upon the availability of data and the exceedance probabilities of interest. The techniques can vary from frequency analysis of the data recorded at a site to rainfall-runoff modelling with design rainfall inputs derived from regional frequency analysis. For extreme floods, which are of relevance for assessing flood loadings for dams and the assessment of spillway adequacy, the stochastic (Monte Carlo) approach offers a number of advantages over the traditional deterministic approach. Although there has been significant progress in design flood estimation practice in Australia over the last couple of decades there remains many significant research and training needs.
Awoonga Dam is the sole source of water for the City of Gladstone and the heavy industries in the region. The area’s distribution reservoirs hold little more than a day’s supply. Extended water supply disruption could have severe economic impacts.
The nine large valves in the inlet tower and river outlet of the dam cannot be inspected or maintained without shutting down the entire water abstraction system. Consequentially limited maintenance has been carried out in the 25 years since the valves were installed.
Recent Dam Safety inspections carried out for the dam owner, the Gladstone Area Water Board (GAWB,) noted some deterioration of the valves and recommended that the valves should be removed, inspected and refurbished as necessary
GAWB was thus presented with a daunting challenge to refurbish valves at Awoonga Dam, as it was generally believed that their removal for refurbishment would not be possible within the time limitations imposed by the system and customer requirements.
In 2008 GAWB commissioned GHD to develop a strategy to refurbish the valves within a 12 hour shutdown period. The strategy proposed and adopted required a rigorous risk management approach and close collaboration between GAWB’s operational staff, two contractors and the consulting engineers. The work was successfully completed during 2011.
This paper discussed the strategies and processes developed and how the project planning, supervision and execution was driven by the risk management based approach. It also highlights some of the experiences and lessons learnt during the project.
2011 – Refurbishing Outlet Valves utilising Shutdown Periods
T. Mortimer, J. McNicol, P. Keefer, W. Ludlow
CS Energy’s Kogan Creek Coal Mine located in the Surat Basin in Queensland, services the 750MW coal fired, Kogan Creek Power Station. Strip mining generates large volumes of mine waste which is typically used to construct waste dumps. Recent work at the mine has focused on using mine waste to construct an ash storage facility to store ash that is piped over 5 km from the power station as a dense phase slurry. The use of mine waste to construct the ash storage facility provides significant cost and time savings, however a range of design, construction and operation issues needed to be addressed to operate a facility of this type.
This paper describes some of the key design, construction and operation considerations for the ash storage facility. Design considerations include pipeline transport through environmentally sensitive areas, addressing the stability of the embankment and the use of a partial LLDPE geomembrane lining system to reduce the risk of seepage from the storage. Construction considerations include post construction (pre ash deposition) floor treatment to reduce potential settlement. Operational considerations include ash slurry deposition, water management of the decant pond and progressive rehabilitation of the final landform.
2011 – Design, Construction and Operation of a Partially Lined, Ash Storage Facility Constructed from Mine Waste
Stuart Richardson,Tusitha Karunaratne
Goulburn-Murray Water (G-MW) manages 16 large dams across Northern Victoria. Since January 2010 after 10 years of continuous drought a number of significant and historic maximum floods were passed through some of these dams. Although these floods are not considered extreme in a dam safety context, for downstream communities they presented very real emergency situations. There has been significant community concern regarding the impact of the floods resulting in several inquiries.
G-MW has maintained and annually reviewed comprehensive Dam Safety Emergency Management Plans (DSEP) since 1997. During 2009 G-MW began developing and documenting a systemised approach to dam’s management, operation and emergency response by developing and integrating its Operations and Maintenance Manuals, Flood Incident Management Plans and Dam Safety Emergency Management Plans. The plans have been developed to align with the Australian Inter Service Incident Management System (AIIMS) which G-MW uses as its corporate incident response framework.
This paper provides an overview of the benefits of having structured and integrated manuals and response plans for managing assets, flood and extreme events. The paper also shares G-MW’s experiences in developing this integrated management approach.
Workshop paper – Karunaratne 2011 – Management of Floods in 2010 and 2011 through Goulburn-Murray Water Dams
Malcolm Barker, Toby Loxton
The Gladstone Area Water Board (GAWB) owns and operates Awoonga Dam, which is a concrete-faced rock fill embankment with a fixed crest concrete spillway on the left bank impounding a storage volume of 770,000 ML.
The current arrangement can accommodate the Probable Maximum Flood, allowing for flow over Saddles 3, 4 and 6 on the left abutment. A comprehensive study was carried out to evaluate the erosion potential downstream from Saddles 3 and 6 as well as other spillway options adjacent to the existing dam. One option was a radical approach including the removal of the Saddle Dam 3 and provision of downstream erosion protection works. This reduced the PAR and improved the overall dam flood capacity; however concerns were expressed about the environmental impact of possible erosion downstream from Saddle 3 for relatively frequent events.
A risk assessment showed that the erosion protection works downstream from the Saddle 3 or 6 were not cost effective and the preferred option for the upgrade was the closure of the Saddle Dam 3 with an auxiliary spillway created in Saddle 6,
This paper summarises the methods used and the outcomes from this study.
2011 – Awoonga Dam Acceptable Flood Capacity design – the anguish of erosion risk and implications for design