Cat McConkey, Zarmina Nasir, Rachel Caoil
The Enlarged Cotter Dam (ECD) is the first major project to be assessed and approved under the new planning regime in the Australian Capital Territory (ACT). ACTEW chose the ECD as its highest priority option in securing Canberra’s water supply for the future because of its relative economic benefit to the community, reliability of water supply, technical feasibility and comparatively low environmental impact.
The planning and construction of large dams has been reduced from a typical 10 plus years to four years in the ACT and surrounds for the ECD. Australian and International Dam design and construction has significantly developed from a time when dam approvals focused on engineering, economics and constructability to now include regulatory planning processes that seek to reconcile environmental, social and economic impacts.
This paper explores and contrasts the experience of securing approvals for the ECD in 2009 to past experiences of dam planning approvals and consultation processes.
Jared 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.
Karen Riddette, David Ho
Recent dam safety reviews of a number of Australian dams have identified that the arms of raised radial gates may be partially submerged by extreme flows which exceed the original design flood for the dam. Various design solutions have been proposed to secure and strengthen the radial gates, however an important concern is the potential for flow-induced vibration. Under extreme flood conditions, flows near the gate arms will be high-velocity, free-surface, with a steep angle of attack on the arm beams. Traditional hand calculations for computing vibrations are of limited applicability in this situation, and there is little published data available for this combination of flow conditions and arm geometry. A detailed study using CFD modelling of the potential for vibration around radial gate arms was carried out for Wyangala Dam. This paper presents the results of the validation and reveals some interesting flow patterns and vortex shedding behaviour.
Assessment of flow-induced vibration in radial gates during extreme flood
Richard 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
Gavan Hunter and Robin Fell
Earthfill embankments in Australia have been widely used in dam construction since the start of the 20th century replacing the older puddle type and concrete corewall embankment designs. Most Australian dam portfolios will have one or more of these embankment types. A key component to the dam safety assessment of these dams is understanding their deformation behaviour, in particular the assessment of the future performance of these structures as they now reach ages of 40 to 80 years or more.
This paper presents the findings of a study on the deformation behaviour of earthfill embankments. It draws on a database of 54 case studies from mainly Australia, the United States and Europe. It is a component of a broader study on the deformation behaviour of embankment dams undertaken as a research project at University of New South Wales earlier this decade.
The data presented in this paper allows dam owners and their consultants to compare the deformation behaviour of their dam to the performance of other similar earthfill dams in evaluating dam safety. Typical patterns of deformation behaviour are presented and guidance is provided on identifying trends in deformation behaviour that are assessed as “abnormal” and that may be potentially indicative of marginal stability.
Shao 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.