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Jared Deible, Richard Herweynen, Gary Dow

The foundation is an important element in the stability of any dam. Understanding the foundation and the potential failure mechanisms associated with the dam foundation is critical to developing the final dam design. This paper will discuss the challenges encountered with the foundation at the Taum Sauk Upper Reservoir Dam and the Wyaralong Dam.
The Upper Reservoir of the Taum Sauk project is a 2.3 million cubic metre roller compacted concrete (RCC) dam located near Ironton, Missouri, USA. The RCC dam was constructed in accordance with United States Federal Energy Regulatory Commission (FERC) guidelines to replace a rockfill dike that failed abruptly on December 14, 2005. Wyaralong Dam is a new RCC dam, for water supply, located on the Teviot Brook near the township of Beaudesert in south-east Queensland.
Wyaralong and Taum Sauk each had challenges associated with identifying potential failure mechanisms in the foundation and with analysing the stability of the dam for these potential failure mechanisms. The geology at the projects was very different, but challenges for each project were quantifying the amount of reliance that was placed on the rock mass at the toe of the dam, developing the shear strength parameters, and developing the associated failure mechanisms that would be analysed.
The design of Wyaralong and the rebuilt Taum Sauk Upper Reservoir, including the geometry of the dam sections, were developed based on the foundation features at each project. Foundation treatments and excavation designs were developed based on the stability analyses conducted during the design phase. These foundation treatments included removal of weak layers or defects where necessary, but features were left in place in the foundation at selected locations at each project. Where features were left in place, stability analyses concluded the dam was stable. The stability analyses at each project considered three dimensional effects along features in the foundation where appropriate.
As the foundation was uncovered during the construction phase of each project, the parameters used in the stability analysis conducted during the design phase were confirmed or adjusted. The excavation and foundation preparation activities were adjusted as necessary based on actual conditions during the construction phase.

Challenges Associated with Identifying and Analysing Potential Failure Mechanisms in Dam Foundations – Taum Sauk Upper Reservoir Dam & Wyaralong Dam Case Studies

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2010 Papers

2010 – Challenges Associated with Identifying and Analysing Potential Failure Mechanisms in Dam Foundations – Taum Sauk Upper Reservoir Dam & Wyaralong Dam Case Studies
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Jared Deible, Richard Herweynen, Gary Dow

The foundation is an important element in the stability of any dam. Understanding the foundation and the potential failure mechanisms associated with the dam foundation is critical to developing the final dam design. This paper will discuss the challenges encountered with the foundation at the Taum Sauk Upper Reservoir Dam and the Wyaralong Dam.
The Upper Reservoir of the Taum Sauk project is a 2.3 million cubic metre roller compacted concrete (RCC) dam located near Ironton, Missouri, USA. The RCC dam was constructed in accordance with United States Federal Energy Regulatory Commission (FERC) guidelines to replace a rockfill dike that failed abruptly on December 14, 2005. Wyaralong Dam is a new RCC dam, for water supply, located on the Teviot Brook near the township of Beaudesert in south-east Queensland.
Wyaralong and Taum Sauk each had challenges associated with identifying potential failure mechanisms in the foundation and with analysing the stability of the dam for these potential failure mechanisms. The geology at the projects was very different, but challenges for each project were quantifying the amount of reliance that was placed on the rock mass at the toe of the dam, developing the shear strength parameters, and developing the associated failure mechanisms that would be analysed.
The design of Wyaralong and the rebuilt Taum Sauk Upper Reservoir, including the geometry of the dam sections, were developed based on the foundation features at each project. Foundation treatments and excavation designs were developed based on the stability analyses conducted during the design phase. These foundation treatments included removal of weak layers or defects where necessary, but features were left in place in the foundation at selected locations at each project. Where features were left in place, stability analyses concluded the dam was stable. The stability analyses at each project considered three dimensional effects along features in the foundation where appropriate.
As the foundation was uncovered during the construction phase of each project, the parameters used in the stability analysis conducted during the design phase were confirmed or adjusted. The excavation and foundation preparation activities were adjusted as necessary based on actual conditions during the construction phase.

Challenges Associated with Identifying and Analysing Potential Failure Mechanisms in Dam Foundations – Taum Sauk Upper Reservoir Dam & Wyaralong Dam Case Studies
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2010 Papers

2010 – Bowen River Weir Fishway – Design and Construction
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David Scriven, Errol Beitz, Aaron Elphinstone

The Bowen River Weir is located at AMTD 94.4 km on the Bowen River, some 25 km south of Collinsville in North Queensland. The weir is part of the Bowen/Broken Rivers Water Supply Scheme and it provides a pumping pool for pipelines serving two nearby coal mining developments and a power station, and also acts as a regulator for riparian water users downstream until it meets the Burdekin River.
The weir was constructed in 1982 and incorporated a fishway towards the southern (left) bank, the design of which was based on the old “pool and weir” fish ladder type layout, typical of that era, with 48 separate cells containing partial vertical slots and baffles. This design has since been found to be ineffective for Australian native fish. In addition it was often out of service due to cells becoming filled with river sediment and debris. For these reasons it was decommissioned and made safe in late 2008 on the condition that a new fishway be constructed.
In late 2008 agreement was reached with Fisheries Queensland to install a “fish lock” type fishway at the site. This type of fishway has in recent years proved to be reliable and effective (eg. successful fish locks at Neville Hewitt and Claude Wharton Weirs). The preliminary and then final design was undertaken by SunWater (Infrastructure Development) between September 2008 and March 2009. The construction was undertaken by SunWater direct management, commencing in July 2009 and completed in late 2010.

Bowen River Weir Fishway – Design and Construction
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2010 Papers

2010 – Assessment of flow-induced vibration in radial gates during extreme flood
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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
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2010 Papers

2010 – Application of Available Climate Science to Assess the Impact of Climate Change on Spillway Adequacy
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Keirnan Fowler, Peter Hill, Phillip Jordan, Rory Nathan, Kristen Sih

Although there are considerable uncertainties in the science of climate change, there is a growing recognition of the importance of the issue. Incorporation of climate change impacts is now required in policy guidance from several government authorities and it is prudent risk management to consider the effects of climate change in planning for water resource infrastructure, including assessment and design of dam upgrades. This paper describes the potential impact of climate change on extreme flood estimates and provides a case study for Dartmouth Dam in south-eastern Australia. Three inputs to flood estimation were considered according to the projected impact of climate change; namely design rainfalls, modelled losses and initial reservoir level. The relative influence of each of these factors is explored. Rainfall and losses had a similar (and opposite) influence on results and for this dam the reservoir level prior to the flood event had the largest influence on results. This case study demonstrates that the insights of climate modellers and hydrologists need to be integrated in order to provide defensible estimates of the impact of climate change in flood hydrology studies. Credible projections of changes in design rainfall intensities are required for the full range of exceedance probabilities across Australia.

Application of Available Climate Science to Assess the Impact of Climate Change on Spillway Adequacy
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2010 Papers

2010 – Analysis and Design Challenges Associated with the Catagunya Dam Restoration Project
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Tony Harman, Richard Herweynen, Malay Ghosh

Following a number of years of investigation into the condition of the existing 1960’s post tensioned anchors at Catagunya Dam Hydro Tasmania embarked on an options study to determine the best method to restore the dam stability to acceptable limits for the long term. The required solution was intended to not only resolve the issue of anchor deterioration but also to increase the flood capacity of the dam.
Based on preliminary design work a concrete buttress solution was recommended and approved for detailed design. The preliminary design utilised a simplified, 2-dimensional, rigid body model, including crack analysis. As part of the detailed design a finite element model was developed to refine the preliminary design. However, this model did not support the simplified analysis and further non-linear finite element analysis demonstrated that the proposed passive buttress design solution was not technically feasible. The options were reconsidered and the adopted solution was to replace the original anchors with new modern anchors with a high level of corrosion protection.
The new anchors adopted are the largest post tensioned anchor loading currently used for a dam in the world. This along with the existing post-tensioned anchors and the tight geometry of the dam, which has a central spillway with a cantilevered ogee crest, provided significant challenges with the design of this dam upgrade. Some of the key design challenges included:
– Appropriate level of modeling and analysis to be able to make sound design decisions. (Hydraulic modeling and FEA).
– Congestion due to the tight geometry of the original design.
– Anchor head block detail to ensure the loads would be adequately secured and dispersed into the dam body
– Crest cantilever support to ensure that structural integrity was retained during construction and later in service. Innovative installation of carbon fibre reinforcement was used.
– Strain compatibility. It was important to ensure the structural contribution of new and old working together and that the consequences of application of new large stresses was manageable.
– Existing anchor degradation. The design needed to ensure that stability compliance was achieved for complete to zero effectiveness over time.
– Maintaining operability of dam and power station during construction.
– Achieving an effective long term maintainable solution.

This paper will present the risk associated with committing to a solution too early and the design challenges and the solutions finally developed, providing the dam industry with a valuable reference for future similar projects.

Analysis and Design Challenges Associated with the Catagunya Dam Restoration Project
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2010 Papers

2010 – Advantages gained from the use of a geomembrane waterproofing system on RCC dams: experiences from Australia
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G.L. Vaschetti, C.A. Verani, J.W. Cowland

Geomembranes are an established technique for long-term waterproofing of hydraulic structures including all types of dams, canals, tunnels and reservoirs.
Three construction projects are presented that feature unique waterproofing solutions leading to faster construction programmes and granting safer and longer service life at lower costs: The 35 m high Paradise Dam (aka Burnett River), Australia’s largest volume Roller Compacted Concrete (RCC) dam waterproofed using a PolyVinylChloride (PVC) geomembrane sandwiched between prefabricated concrete panels and the RCC itself; The 50 m high multipurpose Meander Dam in Tasmania, designed as a RCC dam of the low cementitious content type whose imperviousness is provided by a PVC geomembrane installed in exposed position and mechanically anchored to the upstream face of the dam; And the Eidsvold Weir, a 115 m long 15.45 m high RCC structure used for water supply, waterproofed using an external PVC waterstop installed on the upstream face and able to accommodate the expected movements at the joints.
The paper will outline the technical details, installation and performance of the geomembranes.

Advantages gained from the use of a geomembrane waterproofing system on RCC dams – experiences from Australia
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2010 Papers

2010 – A Unique and Holistic Approach to the Erodibility Assessment of Dam Foundations
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Richard Herweynen, Colleen Stratford

Assessing the potential for erosion of foundation rock downstream of a spillway is a problem faced on many dams, whether new or existing. The problem is made particularly difficult not only due to the uncertainty in determining the erosion potential of the rock, but also due to the variable hydrologic characteristics of flood events.

The selected spillway option for Wyaralong Dam comprises a centrally located primary spillway with a secondary spillway located on the left abutment. A stilling basin energy dissipater is provided at the toe of the primary spillway. Downstream of the secondary spillway, an apron channel will direct flows back to the stilling basin. However, for flood events larger than the 1 in 2000 AEP event, the capacity of the secondary spillway apron is exceeded and flows spill out across the left abutment of the dam towards the river channel. Erosion of this left abutment was viewed to be a potential dam safety issue, and as such, careful consideration was required during the design stage to determine the acceptability of this spillway arrangement.

In order to provide structure to a problem which often relies solely on engineering judgment, a decision process was developed, taking into consideration some of the more definable aspects of the problem. These aspects included the geological characteristics, the initial hydraulic characteristics, the flood duration, the nature of erosion should it occur and the stability of the dam. This paper describes the decision process and methodology used at Wyaralong Dam to
determine the acceptability of erosion. This paper will present the process in a way that it can be used by others in future dam projects, both new and upgrades.

A Unique and Holistic Approach to the Erodibility Assessment of Dam Foundations
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2010 Papers

2010 – A risk-based re-evaluation of reservoir operating restrictions to reduce the risk of failure from earthquake and piping
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David S. Bowles, Loren R. Anderson, Michael E. Ruthford, David C. Serafini, Sanjay S. Chauhan, Utah State University, Logan, Utah, U.S. Army Corps of Engineers, Sacramento, CA

In 2005 the Sacramento District of the US Army Corps of Engineers implemented an operating restriction to reduce the risk of an earthquake-induced failure of Success Dam, which could cause significant life loss and property damage. This paper describes an update of the 2004 risk-based evaluation of operating restrictions for Lake Success, which incorporated new information obtained by the District and enabled a re-evaluation of the level of the operating restriction and provided a basis for a possible modification of the restriction.

A RISK-BASED RE-EVALUATION OF RESERVOIR OPERATING RESTRICTIONS TO REDUCE THE RISK OF FAILURE FROM EARTHQUAKE AND PIPING
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2010 Papers

2010 – A Bi-Directional Fishlift – An Innovative Solution for Fish Passage
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Graeme Maher, Richard Herweynen, Martin Mallen-Cooper and Stuart Marshall

Increasing awareness of the environmental impact of dams means that fish passage is emerging as a critical issue for both existing and new dams in Australia.

The fish passage and outlet works for Wyaralong Dam, a new dam currently under construction, required accommodation of large ranges of head and tailwater levels. The solution that has been adopted, a bi‐directional fishlift using a single hopper with trapping for downstream fish movement occurring within the intake tower, is a world first. The solution required the innovative integration of a number of existing technologies to create a system which is necessarily complex, yet reliable and effective.

The paper incorporates discussion of the critical design constraints, the biology of fish passage, the process adopted to reach the concept solution and a description of the final design including its integration with the outlet works. A number of design issues and their solution are discussed in detail, particularly those associated with dealing with the complexity of the design constraints and how the components of the solution were integrated into a seamless design.

The paper will be of use to those involved in the process of providing fish passage on both existing and new structures that obstruct river flow.

A Bi-Directional Fishlift – An Innovative Solution for Fish Passage

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