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Tim Donaghy

Abstract: Queensland’s regions need additional water supply infrastructure to underpin the future economic growth of the state, and secure the water supplies of existing communities in light of climate variability.

Queensland’s economy has consistently been the fastest growing of all the States for the last decade. The major component of Queensland’s growth is underpinned by resources and industry, in regional areas of the State. If the enabling infrastructure is absent, or if timeframes for development do not align with the needs of the industry, this growth will be constrained, or will go elsewhere. Future investments that support growth cannot and will not occur without certainty around the availability of future water supply.

Queensland’s regions are emerging from the worst drought in recorded history, this has revealed serious deficiencies in the resilience of our regional water supplies. For the first time in living memory, major regional centres have been forced to face the prospect of running out of water.
The Queensland Government has been proactive in identifying these issues and has responded resolutely through the release of Statewide Water Policy which supports a $451 million investment in regional water infrastructure, which aims to meet the needs of urban and rural users.

As part of this policy SunWater has been named proponent for a range of projects considered essential for Queensland’s future economic sustainability which include the Nathan Dam on the Dawson River, Water for Bowen & Proserpine Pipeline Projects, Rookwood Weir & Eden Bann Weir Raising (with RRC & GAWB), Connors River Dam & Pipelines, Nullinga Dam and Kinchant Dam Raising. SunWater is also investigating the raising of Queensland’s largest dam, Burdekin Dam. This paper will outline the need for water supply infrastructure within regional Queensland, and the challenges faced by the projects being progressed by SunWater including the technical issues, environmental sustainability and approvals, and commercial development challenges.

Keywords: Queensland, Water Supply Infrastructure, Dams

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2008 Papers

2008 – Securing water for growth in regional Queensland
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Tim Donaghy

Abstract: Queensland’s regions need additional water supply infrastructure to underpin the future economic growth of the state, and secure the water supplies of existing communities in light of climate variability.

Queensland’s economy has consistently been the fastest growing of all the States for the last decade. The major component of Queensland’s growth is underpinned by resources and industry, in regional areas of the State. If the enabling infrastructure is absent, or if timeframes for development do not align with the needs of the industry, this growth will be constrained, or will go elsewhere. Future investments that support growth cannot and will not occur without certainty around the availability of future water supply.

Queensland’s regions are emerging from the worst drought in recorded history, this has revealed serious deficiencies in the resilience of our regional water supplies. For the first time in living memory, major regional centres have been forced to face the prospect of running out of water.
The Queensland Government has been proactive in identifying these issues and has responded resolutely through the release of Statewide Water Policy which supports a $451 million investment in regional water infrastructure, which aims to meet the needs of urban and rural users.

As part of this policy SunWater has been named proponent for a range of projects considered essential for Queensland’s future economic sustainability which include the Nathan Dam on the Dawson River, Water for Bowen & Proserpine Pipeline Projects, Rookwood Weir & Eden Bann Weir Raising (with RRC & GAWB), Connors River Dam & Pipelines, Nullinga Dam and Kinchant Dam Raising. SunWater is also investigating the raising of Queensland’s largest dam, Burdekin Dam. This paper will outline the need for water supply infrastructure within regional Queensland, and the challenges faced by the projects being progressed by SunWater including the technical issues, environmental sustainability and approvals, and commercial development challenges.

Keywords: Queensland, Water Supply Infrastructure, Dams
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2008 Papers

2008 – Geotechnical risk assessment and management for hydropower development sites in the Indian Himalaya
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Robert Goldsmith

Abstract: Selection of suitable dam and associated structure sites for run-of-river hydropower projects in the Himalayan region requires a thorough assessment of the hazards and the consequences of their occurrence. Typical projects in this environment of deep ridge and ravine terrain comprise concrete gravity dams with steel flood or sluice gates. The steep abutment slopes generally require spillways to be over the dam crest and not as separate structures.

Hazards to be considered for such structures are linked mainly to geological and hydrological factors and include landslides both at the dam and in the reservoir, outwash floods from a variety of initiating causes (landslide dams or glacial melt), floods from storm events, weak or unstable foundations, seepage and pore pressures and earthquakes. Each hazard is related to a risk scenario and a matrix of events is evaluated for potential cause, consequence and impact. A measure of consequence to the project at various stages of design, construction and operation is obtained and provides a basis for preparing risk mitigation measures. Risk management plans can then be prepared using a forum process with stakeholders to achieve a satisfactory outcome.

Examples are provided from specific studies carried out for hydropower projects in the Indian Himalaya. They include a risk assessment of a floodwave overtopping a dam from debris torrent after breaching of a landslide formed dam, terrain studies and geomorphological assessment to locate landslides in dam abutments and design and construction issues relating to a project site astride a major tectonic thrust zone.

Keywords: geotechnical risk, hazard and risk matrix, risk management plan, landslides, landslide dams, hydropower dams and tunnel, Himalayas
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2008 Papers

2008 – Modelling extreme flows over a stepped spillway
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Karen Riddette, David Ho, Mike Phillips

Abstract: Stepped spillways have seen a resurgence in popularity in recent years as new research has better described flow conditions and quantified the energy dissipation capacity of this type of spillway.

While carrying out hydraulic modelling for the Hinze Dam Stage 3 upgrade project using Computational Fluid Dynamics (CFD) analysis, extensive numerical testing and validation of the CFD model for the proposed 0.8H:1V stepped spillway design was undertaken. It was found that for the expected Probable Maximum Flood (PMF) discharge, the high flow depth would result in a non-aerated, non-uniform flow, typically seen in the developing flow region just beyond the spillway crest, occurring over the entire length of the stepped spillway. To date, only limited laboratory studies have been published concerning energy losses in this particular flow regime.

This paper examines the ability of CFD modelling to compute energy dissipation and air entrainment effects in stepped spillways under extreme flow conditions. Where possible, the computed results were validated against limited published data. Some new data obtained by the CFD model is presented for energy loss in the developing flow region that has not been established before.

Keywords: stepped spillway, CFD, energy loss, developing flow.
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2008 Papers

2008 – Design considerations for upgrading SunWater’s dams for acceptable flood capacity
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Brendan Trebilco

Abstract: A number of SunWater’s dams are in the process of being upgraded to the acceptable flood capacity (AFC) to ensure the highest level of safety. The Fred Haigh Dam upgrade was completed in September 2006 and the Bjelke Petersen Dam upgrade was completed in October 2007. Borumba Dam is the latest upgrade being undertaken with construction commencing in April 2008 and is expected to be completed by December 2008. Each dam underwent a comprehensive risk assessment to identify and evaluate all risks with respect to the ANCOLD tolerability limits to ensure risks satisfied ALARP. The assessment identified the most cost effective upgrade solutions for detailed design.

The upgrade at Fred Haigh, Bjelke Petersen and Borumba Dams will enable them to pass an extreme flood equivalent to 50% of the Acceptable Flood Capacity (AFC). This is Stage 1 of a two stage upgrade to ultimately achieve 100% of the ANCOLD “Fallback” AFC which is the standard SunWater has adopted for its major dams. SunWater has prioritised spillway capacity upgrades to achieve a minimum dam portfolio standard of passing 50% Acceptable Flood Capacity inflow by 2015 and full Acceptable Flood Capacity inflow by 2025.

The most economic Stage 1 upgrade option for Fred Haigh, Bjelke Petersen and Borumba Dams was to maintain the existing spillway width and to raise the dam crest with a concrete parapet wall. For the Bjelke Petersen and Borumba Dams the spillway training wall heights were raised to allow for increased flow though the spillway. From the hydraulic model studies and flood routing a height of each different dam crest wall was obtained.

This paper will describe the different methods and considerations used for upgrading Fred Haigh, Bjelke Petersen and Borumba Dams to the 50% AFC.

Keywords: dam safety, spillway, Fred Haigh Dam, Bjelke Petersen Dam, Borumba Dam, SunWater, Queensland.
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2008 Papers

2008 – Investigations and remedial works at Drakesbrook Dam in Western Australia
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Jiri Herza, Graeme Maher, Nihal Vitharana, Megan Evers, Michael Somerford

Abstract: Drakesbrook Dam is a 17m high earthfill embankment constructed in 1931 to provide water for the Waroona Irrigation District, 80km south of Perth. The dam has a storage capacity of 2.30 GL and is classified as a “High A” hazard dam according to ANCOLD Guidelines on Dam Safety Management.

A Dam Safety Review, undertaken in 2001 identified a number of deficiencies associated with main embankment, outlet works and the main spillway requiring remedial works. Detailed design of these remedial works is currently underway. Challenging features of this project are the design of a liner for the existing curved conduit and the design of a new spillway with an usual drop-type stilling basin.

This paper presents the salient aspects of the remedial works design along with the various design and construction criteria adopted to achieve an economical design of a new spillway and outlet conduit sleeve without compromising the safety of the dam.

Keywords: remedial works, earth embankment, conduit lining, spillway replacement
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2008 Papers

2008 – Design and construction of a flood mitigation dam on the North Para River, using high-paste RCC
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Jerome Argue, Steven Slarke, Douglas Rudd

Abstract: The North Para River Flood Control Dam is an integral part of the works proposed to manage flood risk in the Gawler River, north of Adelaide. Undertaken by the Gawler River Floodplain Management Authority (GRFMA), an authority representing the six local Councils in the area, the flood storage is located on the North Para River, about 10 kms north of Gawler. Roller Compacted Concrete (RCC) was selected for the construction material, based on an assessment of the geotechnical and geological site conditions, together with advantages of reduced cost, time and structure required to pass design flood events. With an overall project cost of $16.1 million, the dam was constructed on time and well within pre-tender budget estimates.

Keywords: flood mitigation, roller compacted concrete, North Para River, construction.
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2008 Papers

2008 – Construction of the first cut-off wall by Low Headroom Cutter inside a dam tunnel in China
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Brunner Wolfgang G, Bi Arthur, Chang William, Zong Dung Feng

ABSTRACT: In the South of the Sichuan province the 240 MW Yeleh hydroelectric power project is under construction by Sichuan Nanya River Basin Hydraulic Power Development Company Limited, a state-owned enterprise, and China Gezhou Ba Water & Power Group Company Ltd.. This project sets out to develop the mountain cascade of the Nanya river, a tributary of the Dadu River, provide superior electricity and adjust flood peak and frequency. The specialist contractor Foundation Engineering Company of China Water Resource and Hydropower (FEC) was awarded the contract of foundation treatment at the right bank, which included the construction of a 75 m deep concrete cut-off wall inside a 6.0 m x 6.5 m tunnel. The requirement for 19 317 m3 cut-off wall to be constructed in permeable and very dense gravel/cobble formations and a demanding project program led FEC to adopt the BAUER Low Headroom Cutter CBC25/MBC30 in conjunction with the overlap cutter joint.

Keywords: hydroelectric project, dam, dam tunnel, cut-off wall, trench cutter
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2008 Papers

2008 – Plunge pool design at Gebidem Dam (Switzerland)
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Erik Bollaert, Nicola Bretz

Abstract: Gebidem Dam is a 122 m high double curvature arch dam situated in the canton of Wallis, Switzerland. The dam reservoir collects glacier water of the longest glacier in Europe, i.e. the Aletsch glacier (25 km length). The water is very rich in sediment. This results in huge amounts of fine sediments depositing into the reservoir. The 55 m3/s turbined by the Bitsch power station contain between 10 and 13 kg of sand, or an average of almost 40 tons per hour.

Hence, a yearly flushing is organized allowing to release about 400’000 m3 of solid material from the bottom outlets of the dam towards downstream. Moreover, the crest spillway of the dam is frequently used during summer months to release water from the reservoir, resulting in high-velocity jets impacting the downstream plunge pool. The latter consists of a series of flat concrete plates tied together by means of steel anchors and supported by a layer of underlying mass concrete.

Intensive jet impact on this concrete apron within the last 40 years has led to severe damage and, as such, replacement of the apron becomes necessary. The present paper describes the methodology applied for design of a new concrete apron. Especially the interaction between the hydrodynamic pressures exerted by overtopping jets and the steel anchorage necessary to prevent uplift of the new concrete apron is pointed out.

Keywords: scour, concrete apron design, anchorage
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2008 Papers

2008 – Thermal modelling of the mass concrete in the Hinze Dam spillway raise
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Scott Jones, David Hughes, Orville Werner

Abstract: As part of the 15 m raise of Hinze Dam, the existing 33 m high mass concrete spillway structure will be raised an additional 12.5 m. This will be achieved using conventional mass concrete placed on the top and downstream side of the existing spillway to form a new monolithic structure. Heat generated by the hydration of the cement and fly-ash will raise the peak temperature in the body of the new concrete relative to the stable and relatively uniform temperature within the existing concrete. The early, comparatively rapid volume expansion (and subsequent slow contraction) of the new concrete is externally restained along the interface and there is a potential for tensile stains to develop along the interface that are large enough to cause cracking through the body of the composite dam and potentially compromise the interface bond. The temperatures and thermal gradients induced are a function of the mix design, particularly the amount and thermal properties of cement used, and the sequencing of construction.

Two-dimensional transient coupled thermal-structural finite element (FEM) analyses were used to predict thermal deformations and stresses within the body of the spillway in the weeks and months after placement. Laboratory measured mechanical and thermal properties of the concrete and local boundary climatic data were input to the analyses. The measured adiabatic calorimeter curve showed that the fine grind and chemical composition of the local South East Queensland cement produced a rapid generation of heat which magnified potential thermal expansion issues with the early-age concrete.

Creep, shrinkage, viscous-elastic behaviour, and the increase in modulus of elasticity with age influence the degree to which expansion and contraction of the concrete are converted into stress. These variables, were either accounted for directly in the elastic FEM model, or were taken into account in the interpretation of the results.

This paper presents the assumptions, methods, and criteria used in the FEM analyses; the results of the material testing program; and the results and conclusions drawn from the analyses. A discussion on the concrete mix design trials recently completed on site is also included.

Keywords: Adiabatic Temperature, Creep, Mass Concrete, Placement Temperature, Pre-cool

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2008 Papers

2008 – Hinze Dam Stage 3 – development of the geological model and the implications for design
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Chris Chamberlain, Don Macfarlane, Geoff Eades

Abstract: The Hinze Dam Stage 3 project is a significant upgrade of the existing 63.5 m high embankment dam, located on the Nerang River in the Hinterland of the Gold Coast in South East Queensland. Construction work commenced in early 2008 and is scheduled to be complete by the end of 2010.

Investigations at the dam have been undertaken in three stages since the early 1970’s for construction of the original dam and for each of the Stage 2 and Stage 3 raises. The Stage 3 investigation program began in November 2006 and was substantially complete by March 2008. The geology of the Hinze Dam foundation has been found to be more complex than had been previously determined, particularly with regard to the geological structure, variation in weathering profile and rock strength.

Development of the Stage 3 geological model of the foundation has been an iterative process utilising documented Stage 1 and Stage 2 data and new Stage 3 data. Much of the emphasis for the Stage 3 ground investigations has been placed on the right abutment ridge and saddle dam extension where most of the Stage 3 construction will take place. Here, the geological units comprise greywacke and deformed and variably silicified greenstone, phyllite and chert. Frequent review meetings were used to present each refinement of the geological model, challenge its geological credibility, identify uncertainties with the ground conditions and adjust the investigation program.

The paper describes the development of the Stage 3 geological model, provides an outline of the broader geology of the damsite and embankment foundation and also discusses how the complicated foundation geology has driven some of the engineering solutions that are currently being constructed at the dam.

Keywords: Hinze dam, geological model, foundation geology, design solution.
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2008 Papers

2008 – Estimating construction flood risk
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Peter Hill, Phillip Jordan, Rory Nathan, Emily Payne

Abstract: There are a number of issues that need to be considered when deriving estimates of floods used to assess construction flood risk. This paper outlines the derivation of seasonal flood frequency curves and highlights the important differences in seasonality across Australia and the variation with the exceedance probability. Examples are provided as to how these seasonal frequency curves are used to estimate the construction flood risk during a particular construction activity in a safety upgrade for an existing dam or construction of a new dam. The paper also touches on the issues associated with estimating consequences for assessing construction flood risk.

Keywords: construction flood, risk, seasonal hydrology, hydrologic loading
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2008 Papers

2008 – Inelastic seismic analysis of Dartmouth Intake Tower
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Francisco Lopez, John Bosler

Abstract: A study has been undertaken to determine the structural adequacy of the Intake Tower for the Dartmouth Dam Low Level Outlet Works under the Maximum Design Earthquake (MDE). The tower is a reinforced concrete frame structure. The study included the definition of appropriate seismic inputs and nonlinear time-history analyses for different levels of ground shaking.

The behaviour of the tower was assessed in terms of material strains. The seismic acceleration-time history was applied to the model and the nonlinear analysis identified the locations in the structure which reached the following performance thresholds: cracking of core concrete, yielding of reinforcing steel, fracture of reinforcing steel and crushing of core concrete.

The results of the study showed that the tower was able to resist, without collapse, the loadings imposed by three different MDE acceleration time-histories. The predicted level of damage consisted of generalised yielding of reinforcement, formation of numerous plastic hinges at different locations in the tower and generalised spalling of cover concrete.

Overall, the structural response of the tower under the MDE events was considered satisfactory and met the performance requirement that structural collapse should not occur.

Keywords: intake tower, nonlinear, inelastic, time-history, seismic analysis.
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2008 Papers

2008 – Improving confidence in computational fluid dynamics for spillways
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Richard John Kenny

Abstract: Physical hydraulic models have traditionally provided the input to spillway design.

However, the application of Computational Fluid Dynamics (CFD) is increasing in popularity.
The reliability of CFD depends on several complex issues including the physics of the flow regime, the mathematical formulae describing the fluid flow and the solution method. CFD reliability should be confirmed for each particular application, including ogee spillways (common discharge structures on dams).

A literature review has been undertaken to determine validation techniques and the reliability of CFD related to ogee spillways. There is a great deal of information available about the aeronautical, marine, automotive and mining industries but relatively little available about ogee spillways. The degree of validation for ogee spillways was found to vary significantly and raises the question of whether better validation can be achieved. Better validation may improve confidence in CFD techniques.

A project has been undertaken through Queensland University of Technology to model a prototype scale notional 2D ogee spillway using FLUENT CFD software under steady state conditions. The project tests the sensitivity of the CFD results to various parameters. The sensitivity of the inlet mass flow rate was tested for several CFD parameters. The investigation considered:

1.The grid spacing required for geometric convergence;

2.The effect of domain extent on the computational results;

3.The influence of a boundary layer and wall roughness;

4.The importance of the choice of turbulence model; and

5.The impact of inlet turbulence assumptions.

The recommendations of the sensitivity investigations were used for validation against the United States Army Corp of Engineers (USACE) design data.

Excellent agreement was found between the CFD predictions and the USACE values.

Keywords: Computational fluid dynamics (CFD), dam, flood routing, fluent, Navier-Stokes equations, Numerical/computational modelling, Ogee spillway crest, physical model, turbulence.
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2008 Papers

2008 – Modelling procedures used for the spillway upgrade for Lake Manchester Dam
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Eric Lesleighter, Bronson McPherson, Karen Riddette, Jon Williams

Abstract: The paper describes in part the hydraulics investigations required for the major upgrade works for Lake Manchester Dam; investigations which utilised two modelling procedures. Following a brief outline of the dam rehabilitation program and works, the inadequacy of the former spillway for the revised hydrology is described. The urgency of the construction program led to the use of CFD modelling following preliminary desk studies of the hydraulics, in order to delineate certain features of the new spillway and the plunge pool area and allow the construction program to be fast-tracked. As part of the overall program to refine the spillway design, and due to the evident complexity of the flows over the spillway, physical hydraulic model studies were also carried out.

The investigations provided a very good opportunity to compare the results from two modelling approaches carried out within the same design activity. Specific results of aspects such as flow patterns, velocities, pressures, and wave action will be compared. A prominent purpose of the paper will be to acknowledge the advantages and limitations of both approaches, and seek to provide the guidelines and advice that designers and dam owners should follow and adopt to ensure the hydraulics requirements of projects are soundly engineered.

Keywords: spillways, physical modelling, numerical modelling, CFD.
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2008 Papers

2008 – Towards responsible management of tailings facilities
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Elizabeth Gardiner, Len Murray, David Gladwin

Abstract: The Mining Association of Canada has worked over the past 12 years to improve the management of tailings facilities. This effort began out of a realization that tailings present a major business risk to the mining industry, and that a series of major tailings failures around the world in the 1990’s were fundamentally indicative of need for improved care and management practices by tailings dam and facility owners and operators. MAC established and continues to sponsor the Tailings Working Group, which has assisted in development and publication of a three-volume set of guides to improve tailings management:

•“A Guide to the Management of Tailings Facilities”, initially published in 1998, updated edition published in 2008;

•“Developing an Operation, Maintenance and Surveillance Manual for Tailings and Water Management Facilities”, published in 2003; and

•“A Guide to Audit and Assessment of Tailings Facility Management”, published in 2008.
The three guides provide a strong message that the key to safe and environmentally responsible management of tailings is consistent application of sound engineering capability within an effective management framework.

The documents are almost directly applicable to all forms of dams and are widely used for water dams. Also, because the documents are available in Spanish and French they have found wide use in International projects.

A brief comparison with published ANCOLD guidelines is provided.

Keywords: Management of tailings facilities and water dams, Operation, Maintenance and Surveillance, Auditing, risk, safety, guides
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2008 Papers

2008 – Seismic hazard assessment at Hinze Dam
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Paul Somerville, Gary Gibson

Abstract: This paper describes current methods for seismic hazard analysis and their application at Hinze Dam. Although Southeastern Queensland has experienced significant earthquakes in historical time, none of them are known to have caused surface rupture, and no active faults that could be used to represent earthquake sources have been identified in the region that surrounds the site. Under these conditions, we must estimate the seismic potential of the region using historical seismicity. Two alternative approaches to modelling future earthquake occurrence based on historical seismicity have been used. The first approach is based on the AUS5 source model of ES&S (2005), which uses geological criteria to identify zones of uniform seismic potential, and then uses historical seismicity to characterize the seismic potential of each zone. The second approach, developed by Hall et al. (2007) at Risk Frontiers, is based on the spatial smoothing of historical seismicity without identifying discrete source zones. Previous work by ES&S has shown that the attenuation of strong ground motion in Southeastern Australia is fairly well represented by ground motion models developed using strong motion data from western North America. The recently developed NGA ground motion models based mainly on data from Western North America represent the local site conditions using Vs30, the shear wave velocity averaged over the top 30 metres at the site. This provides a significant advantage over previous models, which were for broad site categories such as rock or soil, and did not provide for the use of more site-specific information. The left abutment, lower tower and valley section foundation at Hinze Dam are characterized by hard unweathered rocks with shear wave velocity of 2.0 km/sec estimated from P wave velocity measurements. The right abutment of the main embankment and the saddle embankment foundation consist of extremely weathered rock, with shear wave velocity of 0.45 km/sec estimated from P wave velocity measurements. This causes the ground motion response spectra estimated for the right abutment and neighbouring foundation components to be significantly larger than for the left abutment and neighbouring foundation components, by factors of 1.4, 2.0 and 2.3 for periods of 0 (PGA), 0.5 sec and 1 sec respectively.

Keywords: seismic hazard analysis.
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