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Papers 2010
2010 – What Your Asset is Telling You – Testing and Analysis of Data
Learn moreDr Adam Butler, Robert Rigg, Glen Hobbs
The cost of maintenance is a serious problem. Preventive Maintenance is a good strategy if implemented well, but can led to unnecessary costs if items are replaced unnecessarily. Predictive maintenance can augment preventative maintenance by using real time instrumentation to monitor conditions. These techniques have been effective at recognizing the symptoms of impending machine failure
Glen Hobbs and Associates (GH&A) recently analysed pressure and displacement data from hydraulically actuated hoisting equipment of a large emergency closure fixed wheel gate. Data analysis enabled GH&A to pin-point causes of the gate malfunction. Anomalies in the data waveform corresponded to impacts and squeeze points in the system. Furthermore, comparing recent test data with older data highlighted gate deterioration over time.
Testing, analysis and trending of data enables asset managers to better predict the point at which maintenance really needs to be performed and shows that careful analysis of relevant data can help solve multi-faceted problems.
Keywords: Operations, Maintenance, Asset Management, Gates.
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Papers 2010
2010 – Water for Central Queensland – Connors River Dam and Pipeline Project
Learn moreDavid Ryan, Sean Fleming
The Connors River Dam and Pipeline Project comprises the construction of a 367,540 ML storage on the Connors River located in central Queensland and a 130 km pipeline capable of delivering annually 49,500 ML of high priority water to the rapidly expanding Central Queensland Coalfields. The dam also has the capacity to supply water for the downstream agricultural sector.
Key outcomes of SunWater’s recent business case investigations included the identification of a strategy that would deliver the project in parallel with the construction programs currently being developed by the coal mining sector, the delivery of a quality product with high certainty cost and the ability to supply water at a commercially attractive rate. Construction activity is currently scheduled to commence in mid 2011, with commissioning of the works early 2014.
The paper outlines the project details, the design features of the dam and pipeline and the contract strategy adopted in an attempt to deliver the project on time and within budget.
Keywords: Roller Compacted Concrete, Early Contractor Involvement, Design and Construction.
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Papers 2010
2010 – Using a clay cemented sandstone as RCC aggregate – a major breakthrough at Wyaralong Dam
Learn moreRichard Herweynen, Robert Montalvo, John Ager
The choice of materials used in the construction of a dam is one of the most critical decisions in the design process. Our natural behaviour as engineers is to adopt materials which have proven performance, and which conform to Australian or international standards, which sometimes causes us to overlook the specific conditions and demands of the project at hand. In an environment where the majority of concrete produced is for structural purposes, the properties of these concretes is often vastly different to those desired for mass concrete structures such as dams and spillways.
The big question at Wyaralong Dam was could onsite aggregate be used in the Roller Compacted Concrete (RCC)? The Wyaralong Dam is located in the Gatton Sandstone (early Jurassic), predominantly feldspathic to lithic‐feldspathic sandstones with a clay matrix. Early analyses and tests suggested that the Gatton Sandstone was not suitable for RCC aggregate due to a 68% wet/dry strength reduction, high water absorption (5.2 – 7.5%) and petrographic interpretation that clay content was mainly swelling clay, leading to durability concerns.
Due to significant community, safety and cost issues with importing aggregate, Wyaralong Dam Alliance (WDA), during the development of the RCC mix design for Wyaralong Dam, chose to pursue the use of onsite quarried sandstone aggregate instead of importing aggregate. Additional petrographic and XRD analyses and extensive durability tests were undertaken on cores of sandstone and RCC samples, including wet‐dry cycles, soak tests in ethylene glycol, soaks in sodium hydroxide, and heating and cooling cycles. These tests indicated that, if swelling clays are present, they do not impact the durability behavior of the RCC aggregate.
The substantial effort put into testing the sandstone aggregate has paid off for WDA. Not only have the results indicated that the RCC mix performs remarkably well in terms of durability, but the very low modulus of elasticity of the mix has provided exceptional performance in terms of thermal loading; with all the related benefits in reduced restrictions to placement schedule and cooling requirements. Onsite sandstone was not only proven to be a feasible option, it has been demonstrated that it is the best option for the project. Details of the study are provided in this paper.
Keywords: Roller Compacted Concrete (RCC), Sandstone, Aggregate, Clay, Mix, Durability
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Papers 2010
2010 – Unique Approach of an Integrated Design for a Challenging 180 Metre High Stepped Spillway
Learn moreThomas Vasconi, Mike Gowan
This paper describes the methodology adopted for the design of a 180 m-high stepped chute spillway to be constructed on a mine tailings storage facility (TSF) in Africa. This TSF dam, constructed using the “downstream method”, will be raised progressively via a series of nine lifts as mining proceeds. The first eight will be equipped with an operational spillway sized for the 1in 10,000 AEP whilst the ninth will house the closure spillway sized for the Probable Maximum Flood. The problem, common to all staged tailings dams, is how to design the spillways for such raising sequence? The very steep ridge declivity favored locating them in a unique configuration rather than the more usual separate hillside spillway on each dam abutment. The design of such spillways was challenging since it had to integrate the TSF interdependency parameters (water balance, dam raise sequence) whilst including flood routing, spillway sizing, stepped spillway design components. Challenging aspects of the design also included optimizing the costs associated with the short service life of these spillways. Furthermore, the design was undertaken in a way that the operating stepped chute could be upgraded and reused at mine closure. The design incorporates an innovative solution which allows reduction in the rock armouring quantity of up to 40% with associated cost benefits, and sustainability in terms of material usage. The lessons learnt in applying this innovative and sustainable design are useful for other sites requiring adaptive construction and short service life spillways.
Keywords: Tailings storage facility, stepped chute spillway, hydrology, hydraulics, mine water management.
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Papers 2010
2010 – U.S. Army Corps of Engineers Dam Safety and Asset Management of Mechanical /Electrical Systems for Dams
Learn moreRick W. Schultz P.E.
The Corps of Engineers Risk Management Center is undergoing a nationwide assessment of its navigation and flood control projects. Development of the methodology and tools used to determine probability of failure of mechanical and electrical systems for dams is being presented in this document. Development of the Weibull formulas for specific use in dam will be addressed along with use of fault tree analysis to determine system reliability.
Keywords: Dormant-Weibull Formula, Fault Tree, Characteristic Life of Components, Beta Shape Parameters, Inspection intervals.
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Papers 2010
2010 – TOWARDS UNDERSTANDING A KARST FOUNDATION: USE OF A THREE DIMENSIONAL FOUNDATION MODEL AT DARWIN DAM
Learn moreBrendan Sheehan, Chris Topham, Alan White, Rowenna Lagden
Darwin Dam is a 21m high embankment dam constructed on a geologically complex foundation that includes karst limestone features. The dam retains the top 15m of Lake Burbury on Tasmania’s west coast, and borders the Tasmanian Wilderness World Heritage Area. Defensive design of the dam addressed the key failure modes of piping through the complex foundations of limestone, sandstone, gravels and silts, and guarding against sinkholes forming in the limestone foundations. During construction, a comprehensive range of instruments were installed in the dam and foundation, as a long term means of monitoring this structure. A range of surveillance data has been collected since lake filling and this data, along with historic geological investigation information, was used to develop a three dimensional (3D) geological model of the dam and
foundation with phreatic profiles. The software used was a commercially available geographical information system. This tool has assisted Hydro Tasmania to better understand and manage the dam. The paper outlines the need for a 3D model, the methodology for development of the model, resources required, limitations and lessons learned. The benefits of the model, such as aiding understanding of foundation behaviour, assisting with interpretation of surveillance data, supporting decision making, and potential use during incident response are also discussed.Keywords: Three dimensional, computer model, karst foundation, geology, hydrogeology ,dam surveillance
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Papers 2010
2010 – The applications of expert rule systems in decision-making
Learn moreShao Kwan Ng
Asset management aims to ensure that assets, such as dams, are sustainable. In order to achieve this, management decisions need to be defensible and the long-term impacts of short-term decisions need to be clearly demonstrated, such that an asset operates and is maintained in an appropriate fashion and in a satisfactory condition. Expert rule systems are becoming widely recognised as powerful and elegant tools suitable for engineering and management decision-making. They are powerful, transparent and flexible tools that mimic how people make decisions, and hence provide a natural way of thinking for decision-making. This paper reviews the current usage of expert systems in asset management, and illustrates the potential of these tools, in conjunction with the available (ANCOLD) guidelines, to assist dam owners in decision-making, such as in condition evaluation and dam hazard assessment applications.
Keywords: Decision-making, expert rule systems.
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Papers 2010
2010 – Seepage Detection within Embankment Dams using Infrared Thermal Imaging
Learn moreMonique de Moel, A/Professor Jayantha Kodikara, Dr Gamini Adikari
All embankment dams have some seepage as the impounded water seeks paths of least resistance through the dam and its foundation. Seepage must, however, be controlled to prevent internal erosion of the embankment or foundation and avoid damage to surrounding structures. Embankment dams are designed to operate under controlled steady state seepage, which over time may change due to movement in the foundation and the dam, chemical actions and other forms of deterioration. Effective monitoring of seepage within embankment dams is therefore essential in regards to management of dam safety and prevention of failure.
Traditional methods of seepage monitoring have involved measurement or visual monitoring on the downstream side of the dam after the seepage has occurred. Effective, early detection of seepage in embankment dams has been difficult as it originates and develops in the subsurface. Infrared Thermal Imaging is such a technique that is non-contact, non-intrusive, simple and flexible. The analysis draws on the temperature behaviour and the heat capacity of materials within the body of the dam and consequently allows the user to identify and isolate temperature variations along the surface of interest. This paper describes the method, application and feasibility of infrared thermal imaging for the detection of seepage in earth and rockfill embankment dams. The value of this technique as an additional tool in the surveillance of dams is discussed.
Infrared thermal imaging has been in use in other fields of engineering for condition monitoring and defect detection of structures. It has shown great potential in identifying variations in surface characteristics, which may not be evident through visual inspection alone. In this paper, reliability of this technique for seepage detection in embankment dams has been analysed using 8 case studies in order to arrive at a fair understanding of the best conditions under which Infrared Thermal Imaging field inspections should be carried out. The results of field investigations undertaken at these dams suggest that Infrared Thermal Imaging is a useful and effective tool for detection of seepage and an aid in identifying seepage behaviour.
Keywords: Seepage Detection, Infrared Thermal Imaging, Dam Surveillance, Monitoring
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Papers 2010
2010 – Response and failure prevention, following the identification of a major lining defect in the Tekapo Canal, New Zealand
Learn moreJim Walker, Sergio Vallesi, Neil Sutherland, Peter Amos, Tim Mills
The Tekapo Canal is a 26km long hydropower canal owned by Meridian Energy Ltd in New Zealand. Completed in 1976, the canal is 40m wide, 7m deep and has a capacity of 120m3/s. The canal was constructed from compacted local glacial soils with a compacted silt lining sourced from till deposits.
During 2007 and 2008 the canal showed signs of leakage where it crossed over a twin barrel culvert structure. In October 2008 a diver inspection identified depressions and sinkholes on the invert of the canal above the culvert. Approximately 6m3 of silty gravel lining material had settled. Testing showed direct and rapid connections between lining defects and seepage outflows at the culvert outlet headwall. Subsequent ground penetrating radar survey confirmed the presence of voids above the culvert barrels. Diver placed filling of the defects with granular materials was immediately implemented, and a series of remedial actions over the next four months were required to arrest deterioration and enable the canal to remain operational.
The paper describes the initial response to this situation and the immediate measures taken to prevent failure. It also describes the medium term and ongoing measures implemented to maintain the safety of the canal while permanent remediation requirements are assessed. The lessons learned from this event, and their impacts on Meridian’s Dam Safety Assurance Programme (DSAP) are also discussed.
Immediate response measures included ongoing filling of lining defects with filter gravel, intensive land based and diver surveillance of the canal, planning and resourcing for emergency contingency actions in the event that a risk of breach developed. Medium term measures included arresting leakage by placing a low permeability blanket of silty gravel over the damaged area using a concrete pump, and constructing external buttresses capable of safely withstanding large discharges should deterioration of the canal structure occur.
These short and medium term remedial measures were completed with the canal full and in operation and continue to perform well 20 months later. Continuing risk mitigation measures include enhanced surveillance and monitoring (land based and using divers), localised treatment of defects, as well as ongoing monitoring and review of the Dam Safety management regime and sustained Emergency Management preparedness.
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Papers 2010
2010 – Regulating Dam Safety: How do we compare?
Learn moreKristen Sih, Peter Hill, Susan Ryan, Siraj Perera
Although ANCOLD provides guidance on good dam safety practices, in Australia it is the State and Territory Governments’ role to protect the public from dam safety incidents and in many cases these jurisdictions have legally binding regulations in place that dam owners must adhere to. This paper presents a comparative analysis of the dam safety regulations currently in place for Australian states, as well as selected international jurisdictions. The limit of applicability of the regulations, number of dams regulated, content of the regulations and powers and responsibilities of the regulator are all compared. It was found that there is a large range within each of these categories with regulatory approaches varying from light-handed and objective based, to highly prescriptive. The extent to which risk management principles are used in the regulations for each jurisdiction has also been investigated. It was found that in jurisdictions where higher hazard category dams account for a higher proportion of dams being regulated, risk analysis is included in the regulations. Finally, the ANCOLD societal risk criteria and ALARP considerations have been compared and contrasted with those from international jurisdictions and other hazardous industries.
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Papers 2010
2010 – Pukaki Canal Intake structure repairs – November 2009 – 62 hours on the slab
Learn moreJim Walker, Jamie Macgregor
The Pukaki Canal Inlet structure is a large gated culvert and stilling basin structure, it is a High PIC appurtenant structure to the Pukaki Dam, located in the Mackenzie Basin area of New Zealand’s South Island.
The 560m3/s capacity inlet structure is founded on glacial moraines. It controls flow from the178 km2 Lake Pukaki storage into the 80m wide, 22km long Pukaki/Ohau canal. It is the owner’s (Meridian Energy) most important valve, as it feeds 1550MW of hydro generation on the Waitaki River.
A risk assessment in late 2009 identified a previously unrecognised trigger for a potential failure mode for the stilling basin. Principally, ongoing erosion of the reinforced concrete base slab could lead to failure of water stops in the slab joints potentially leading to slab uplift, foundation erosion, and ultimately, catastrophic failure of the Pukaki Dam. To better define the risk to the structure, further inspection of the stilling basin was recommended.
A dewatered inspection of the stilling basin was required, as further dive inspections would not improve our understanding of structure condition. Because the stilling basin cannot be isolated from the canal, this requires dewatering the entire Pukaki/Ohau canal, presenting significant risks of damage to the canals from slumping and lining failure. A dewatered outage also has major business revenue impacts.
This paper describes how Meridian were able to take advantage of a transmission network outage, scheduled for just six days after the risk was identified, to plan, safely dewater, inspect, and rewater 22km of hydro canal, and not just to inspect the Pukaki Canal Inlet structure, but also to implement repairs to the stilling basin slab which have successfully mitigated the structure safety and operational risks. This huge undertaking involved mobilising an army of people, plant and materials, and cost over NZ$1.8m. From identifying the risk to the structure, to completing repairs took just 13 (very busy) days.
Lessons learned in the areas of dam safety and asset management are presented. As well as those contributing to the success of the project in seizing an opportunity to mitigate the identified dam safety and operational risks.
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Papers 2010
2010 – Performance of Taum Sauk Upper Reservoir Dam During Reservoir Refill
Learn moreJared Deible, John Osterle, Charles Weatherford, Tom Hollenkamp, Matt Frerking
The original rockfill dike, constructed in 1963 to form the Upper Reservoir at the Taum Sauk Pump Storage Project near Lesterville, MO failed on December 14, 2005. The Upper Reservoir has been completely rebuilt as a 2.83 million cubic yard (2.16 million cubic meters) Roller Compacted Concrete (RCC) Dam in compliance with FERC Regulations. The project is the largest RCC project constructed in the USA and is the first pumped storage project to utilize an RCC water retaining structure. The project is owned and operated by AmerenUE and consists of an Upper Reservoir and a Lower Reservoir connected by a vertical shaft, rock tunnel, and penstock. The Powerhouse has two pump-turbines with a total generation capacity of 450MW.
A refill plan was developed to monitor the performance of the dam during the first refill. Because it is a pumped storage project with no natural inflow, the reservoir level can be raised and lowered with reversible pump turbines. The refill plan includes hold points when the dam s performance will be assessed at eight reservoir levels. Monitoring of the performance of the dam is done through instrumentation readings and visual inspections. Inspections check for alignment changes, leakage, seepage, cracking, or any other unusual or changed conditions. Instrumentation monitored during the refill program includes piezometers, seepage weirs, survey monuments, and joint meters. The level control system for the project was also evaluated during the refill program. This paper summarizes the monitoring and inspections conducted during the refill and the performance of the dam during this period, and the performance of the dam during the initial period after the refill program.
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Papers 2010
2010 – Overview of Recent Dam Safety Activity on the Waikato Hydro System
Learn moreJustin Howes, Peter Amos
For many years Mighty River Power has operated an intensive Dam Safety Assurance Programme with respect to our nine large hydro assets, a unique run of river cascade system built between 1927 and 1972. From 2001 to 2007 the Arapuni Foundation Enhancement Project was a high profile activity, but there has also been much dam safety analysis and minor mitigation work that could be classified as “Business As Usual Dam Safety Activity” – this paper seeks to give a high level overview of the work carried out from 2000 to 2010. Items covered include; an overview of the hydraulic structures, their hydrological and geological setting, and the current dam safety regime. Examples of typical issues identified by the Programme are given on a structure by structure basis along the river. Seismic, Flooding, Emergency Planning, Documentation, Monitoring, Control, Electrical and Mechanical type issues are covered.
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Papers 2010
2010 – Nature-like fishways – Are they suitable for Australian conditions?
Learn moreDavid Murray
An essential criterion for any new dam project in Australia is to provide for passage of fish past the structure in both the upstream and downstream direction. In recent projects with a relatively high barrier this has been provided by mechanised systems such as locks, lifts or a combination of both.
A nature-like fishway provides for passage of fish past a barrier by applying some of the features of natural streams. The concept has been increasingly applied to fishway designs in North America and Europe. A nature-like fishway will provide variable flow depths, velocities and turbulence across its width and along its length and is constructed using natural materials to simulate the natural stream characteristics. The variable flow conditions coupled with the use of natural materials inherently result in different channel substrates that support the passage of a large range and size of fish species as well as other aquatic species. Where fish habitat has been depleted, a nature-like fishway can also supplement and enhance aquatic habitat.The performance of nature-like fishways can be difficult to quantify due the very nature of the system. However, qualitative assessments in North America are indicating that a wide range of species are using such fishways and that fish species that were previously extirpated from rivers are again migrating.
The nature-like fishway concept has been applied to in-stream structures up to four metres high in the eastern states of Australia. However, the substantial progress made with this design in North America and Europe has not as yet been applied in this country.
This paper analyses the advantages and disadvantages of nature-like fishways over mechanised systems, such as locks and lifts, and makes an assessment of the suitability of the concept to dams in Australia with relatively high walls.
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Papers 2010
2010 – Mildura Weir Denil Fishway An Innovative Fish Passage Solution for a Unique Site
Learn moreSteven Slarke, Martin Mallen-Cooper, Andrew Evans, John Prentice
As part of the Murray-Darling Basin Authority ‘Sea to Hume Dam’ program to restore fish passage along the River Murray, an innovative Denil fishway is being retrofitted into Mildura Weir (Lock 11). Due for completion in the latter half of 2010, the fishway will allow the upstream and downstream passage of medium and large sized fish past Mildura Weir, which has a difference in water levels of 3.5 metres.
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Constructed on the sloped concrete apron at the left abutment of the Dethridge weir, the Mildura Weir Denil fishway design is innovative in the River Murray. The Denil fishway is essentially separate from the existing weir, and its superstructure can be fully removed from the river during floods. The fishway can also be progressively removed during periods of rising floodwaters, maintaining operation during periods when fish migrate in particularly large numbers. The fishway represents a cost effective design, reflecting the decision to maintain the current weir structure for a further forty years, but still providing passage to a broad range of fish sizes and species. Innovative fish monitoring and carp separation facilities will be provided, shared with the other River Murray fishways. But, unique to the River Murray, viewing windows are provided to allow the public to observe fish negotiating the fishway, and to enable a better understanding of fish movement. -
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Papers 2010
2010 – Maintenance and Human Error – The Australian Dam Experience
Learn moreGlen Hobbs, Robert Rigg, Alan Hobbs, Adam Butler
Maintenance errors and associated non-conformances are becoming increasingly recognised as a source of system failures in a wide range of industries. Research in other industries has shown that errors often arise in response to local factors beyond the control of the maintainer. Various dam ‘incidents’ have been attributed to maintenance errors. In Australia we have been fortunate with few serious dam safety events. However, the dam operating and maintenance environment is changing dramatically.
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A survey of dam maintenance personnel was recently undertaken in Australia. The survey was in the form of 49 questions that asked participants to state how frequently a situation occurred. This survey format has previously been used in other industries; thus allowing a comparison of dam maintenance with other high-risk industries such as rail infrastructure, oil and gas, and airline maintenance.
A number of ‘error-producing’ conditions have been identified and survey results indicate a high level of poor procedures/documentation and supervision; highlighting the need for accurate and appropriate manuals and supervision of tasks. These and other factors are leading to instances of maintenance non-compliance, which may threaten the reliability and safety of equipment. The survey has revealed that trade training needs to be addressed. However, occupational safety issues are low; indicating a positive approach to a safe working environment. The paper also discusses the responses to specific maintenance questions relevant to the dam industry.