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
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Conrad Ginther, Colleen Stratford
The Wyaralong Dam Alliance (WDA), a consortium of seven engineering and contracting companies, was contracted to design and construct the Wyaralong Dam, which impounds the Teviot Brook 14 km from Beaudesert in Queensland, Australia. The dam is an approximately 500 metre long, 48 metre high Roller Compacted Concrete (RCC) structure built on a foundation generally consisting of massive sandstone with intermittent conglomerate zones consisting of cemented gravels, mudclasts and sands. Geologic features of note with regard to dam stability and long term seepage at the site are dominated by downstream sloping bedding features and conglomerate zones. In addition to the bedding-related features, two predominant vertical to subvertical fracture sets exist. The condition of the vertical fractures ranges from tight and fresh at depth to highly weathered and filled with dispersive clay and gravels near the foundation surface. To provide a durable and effective long term seepage barrier for the dam, an extensive foundation cleaning and treatment operation was undertaken. This comprised drilling, blasting, and excavation of the majority of the highly weathered rock and dispersive materials supplemented by localized installation of small cut-offs and dental concrete and the construction of a double-line grout curtain installed using real time computer monitoring, the GIN methodology, and balanced, stable grout mixes.
Foundation Preparation and Seepage Barrier Installation at Wyaralong Dam Construction Project
The large flood inundating areas of Brisbane and Ipswich along the lower Brisbane River below Wivenhoe Dam in January 2011 was extensively reported by the media. An independent Commission of Inquiry was formed soon after the flood with broad terms of reference including matters related to dam operations. Prior to the Inquiry hearings and findings, reporting in the media continued and made strong allegations of blame of the flood on dam operations. The media relied on limited expertise but the articles were portrayed and subsequently re-produced by other media outlets as ‘expert’ analyses. The author’s interpretation is that media claims were misleading and damaging to the public confidence in the role of dams for flood mitigation, and this damage occurred before official Inquiry findings were available.
A brief summary is presented of now publicly available credible reports on the flood event, and a summary is also presented of the key matters and allegations reported in the media related to the dam operations. An analysis and commentary of media reporting on the flood operations of the Wivenhoe Dam is presented in the context of time and people with reference to information and expertise available to the media, and media conduct in relation to fair public interest and professional practice.
Matters of importance for objective and informed knowledge of key technical matters in relation to operation of dams, dam safety, and the inevitable extremes of nature and floods are discussed. The paper then examines the roles and possible limitations of dams engineering professionals in relation to media reporting of such matters.
This paper solely focuses on matters of media examination of the floods and dam operations, and generally does not comment on technical matters that are in the terms of reference of the Commission of Inquiry.
2011 – January 2011 Brisbane River Floods and Examination by Media of the Dam Operations
Bob Wark, Louise Thomas, Andrew Peek
Alkali Silica Reaction (ASR) has been by far the dominant cause identified in the deterioration of concrete caused by expansion of the pastes from an interaction with the aggregates. However the path to the identification of the presence of the deleterious effects of ASR is not always straightforward. In a recent example, the concrete spillway slabs and walls at South Dandalup Dam exhibited classic craze cracking symptoms of ASR. However when subjected to more detailed analysis the driving process was found to be delayed ettringite formation (DEF).
ASR and DEF are chemically different concrete deterioration mechanisms with physically similar manifestation, causing slow concrete expansion in the presence of moisture. ASR has been reported mostly in concrete structures constructed prior to the early 90’s when the DEF deterioration mechanism was not fully recognised. However it is possible that ASR and DEF can take place simultaneously and more extensive damage due to DEF could have occurred and remain undetected.
The paper will also describe a recent case using basalt aggregate for Stirling Dam in which the use of an accelerated mortar bar test gave an extreme reaction but the ASTM concrete prism expansion test gave a negative result. Further detailed petrographic examination provided the clues to the real cause.
The paper will describe the occurrence of the problems, compare the causes and outline the methods undertaken to investigate the issues. Alternative concrete mix designs, incorporating a high flyash content to replace ordinary Portland cement as the main pozzolanic material, have been investigated and successfully implemented. This paper describes the investigations undertaken to develop these alternate mixes, the resultant properties of the concrete and its resistance to deterioration.
2011 – Searching for Solutions to ASR
Roger Vreugdenhil, Peter Hill, Siraj Perera, Susan Ryan
All Australian water authorities have in place dam safety programs that seek to ensure the ongoing safety and serviceability of their dams along with the benefits they secure for the wider community. Many have progressed multiple dam safety upgrades over the past decade and embraced risk assessment as a helpful tool in prioritising upgrade investment.
The ANCOLD Guidelines on Risk Assessment (2003) have been applied across the country and, coupled with State regulation, have supported dam owner efforts in reducing risks below the ANCOLD “Limit of Tolerability”. However, it is generally acknowledged that in their current form, the ANCOLD guidelines provide limited guidance to dam owners for determining appropriate levels of risk reduction and timing of dam safety improvements. This has contributed to a range of guideline interpretations and inconsistency in subsequent dam safety investment decisions across Australia. Having achieved priority risk reduction, a number of owners are beginning to assess their dams against the ALARP principle, bringing dam safety investment within an owner’s portfolio into more direct competition with other important and urgent organisational investment decisions.
This paper outlines the outcomes of a recent study commissioned by the Victoria Department of Sustainability and Environment into risk reduction principles and the application of ALARP by a number of Australian and international dam owners and regulators, hazardous industry owners and regulators, and the interaction of ALARP with whole-of-organisation investment. The paper highlights the study process and significant points of interest regarding risk reduction principles and current application of ALARP and some options for refinement and clarity.
Towards increased clarity in the application of ALARP
Mark R. Sinclair & Richard J. Rodd
Over the last six years there have been ongoing significant developments in the design, fabrication and particularly of the corrosion protection details for high capacity ( >13,500kN MBL ) re-stressable ground anchors used to improve stability of gravity dams. These Australian based developments and the resultant specifications and details have now become the de-facto standards adopted.
The ANCOLD Register dams to have had this generation of cables installed have included; Ross River Dam, Lake Manchester Dam, Catagunya Dam, Tinaroo Falls Dam and Wellington Dam. These projects include the highest capacity permanent ground anchors installed to date worldwide. Some smaller capacity anchors installed into dams have also benefited from this technology.
The Recent Developments and Application of Large Ground Anchors for