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Martin Pinkham, Robin Dawson, John Grimston

Resource consents for Christchurch’s existing solid waste disposal facility at Burwood expire in May 2005 and the landfill must close. A new, state-of-the-art regional landfill is under construction at Kate Valley, which will accept solid waste from Christchurch and surrounding districts. Investigations and studies for the landfill have attracted considerable public attention, engaging public groups in discussions through resource consent hearings in 2002 and 2003.

The proposed landfill includes two embankment dams in a cascade arrangement below the landfill. The first is a 19m high sedimentation dam designed to retain silt runoff from the earthworks associated with landfill construction and operation, protecting the health of the stream and environment below the dam. The second is a 9m high dam performing dual roles of storing and supplying water for the landfill earthworks activities, and providing an additional safety buffer for silt control and containment of any accidental release of leachate at the landfill.

While the dams are relatively modest in size, they are being built to very high standards with strict peer review as a result of their association with the landfill project, and to minimise any community and environmental impacts. The design and construction of the landfill and dams is being completed using an innovative modified alliancing arrangement which provides the close working relationship that alliances are renowned for, while minimising up-front financial risk to the owner.

This paper deals with key aspects related to the landfill dams, such as community consultation and expectations, environmental impacts as well as the technical features. Construction is underway for the dams and the landfill at the time of writing of this paper.

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2005 Papers

2004 – Canterbury Regional Landfill Water Supply and Sedimentation Dams
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Martin Pinkham, Robin Dawson, John Grimston

Resource consents for Christchurch’s existing solid waste disposal facility at Burwood expire in May 2005 and the landfill must close. A new, state-of-the-art regional landfill is under construction at Kate Valley, which will accept solid waste from Christchurch and surrounding districts. Investigations and studies for the landfill have attracted considerable public attention, engaging public groups in discussions through resource consent hearings in 2002 and 2003.

The proposed landfill includes two embankment dams in a cascade arrangement below the landfill. The first is a 19m high sedimentation dam designed to retain silt runoff from the earthworks associated with landfill construction and operation, protecting the health of the stream and environment below the dam. The second is a 9m high dam performing dual roles of storing and supplying water for the landfill earthworks activities, and providing an additional safety buffer for silt control and containment of any accidental release of leachate at the landfill.

While the dams are relatively modest in size, they are being built to very high standards with strict peer review as a result of their association with the landfill project, and to minimise any community and environmental impacts. The design and construction of the landfill and dams is being completed using an innovative modified alliancing arrangement which provides the close working relationship that alliances are renowned for, while minimising up-front financial risk to the owner.

This paper deals with key aspects related to the landfill dams, such as community consultation and expectations, environmental impacts as well as the technical features. Construction is underway for the dams and the landfill at the time of writing of this paper.
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2005 Papers

2004 – Communicating Dam Safety Practices to the Community for a 60km Long Canal Hydro Development in New Zealand
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Peter D Amos, Pip Nicolson, M Grant Webby, Murray D Gillon

To obtain a resource consent to build and operate any new water resource or hydro-electric development in New Zealand, the developer is required by the Resource Management Act (RMA) to consult with the community over the effects that the development could have, including describing how public safety risks will be avoided, remedied or mitigated. The community has the opportunity to respond to the authorities issuing the resource consent and influence the conditions attached to the consent.

The proposed Project Aqua Scheme in the South Island, New Zealand, comprised a 60 km long canal system to convey 340 cumecs flow from the Waitaki River across alluvial river terraces and through a chain of six hydro-power stations before returning the water back to the river. Each section of canal between stations would have contained between 4 and 6 million m3 of water within embankments up to 20m high. A breach of any one of these canals had the potential to flood farmland, residential buildings, highways, and other infrastructure, thereby posing a safety risk to local residents together with the potential for significant economic loss.

The paper describes the methodologies that were developed and used to assess the impacts, the measures proposed to avoid, remedy or mitigate safety risks and the public reaction to the associated report that was provided for public consultation prior to abandonment of the project. The methodologies used required adaptation of dam safety and consequence assessment practices usually applied to in-river dams, and applied here to the 60 km long length of canal embankment.
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2005 Papers

2004 – The Importance of Community Consultation in Geotechnical Investigations for Project Aqua
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Don Macfarlane; Nick Eldred; Sigi Keis

Project Aqua was planned to be a major hydropower development along the lower Waitaki Valley, New Zealand. Geotechnical investigations for the project were conducted in two main stages – from the late 1970’s to mid-1980’s, and again in the period from 2002 to 2004.

Community consultation was an important part of the 2002-2004 investigations, and was a key risk management issue for Meridian Energy. The proposed scope of the work included 512 drillholes and 734 test pits spread along the 60km project corridor. All proposed drillholes and test pits were subject to the Resource Management Act 1991 and needed Resource Consent applications, which required consultation with landowners, territorial authorities, and community and cultural groups including three Maori tribes.

A number of proposed investigations could not be undertaken because the landowner would not allow land access, but over 70% of the proposed work was completed with community support.
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2005 Papers

2004 – Wai-Iti Valley Community Water Supply Augmentation Project
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John Grimston Sally Marx Robin Dawson and Peter Thomson

The Wai-iti Valley is located in the northern region of New Zealand’s South Island. Water demand during summer in the Wai-iti Valley is greater than the available supply, resulting in water allocation restrictions and pressure on in-stream habitat and uses. Further, the summer water resource in the Wai-iti Catchment is currently over-allocated. Thus, since the mid 1980s, Tasman District Council (TDC) has been unable to grant new water permits to take water from either rivers or groundwater in the Wai-iti Catchment. Existing water permit quotas have been reduced where they were not being used, but despite this agricultural, horticultural and domestic use is frequently restricted during dry years.

Recently, the need for a community solution was identified for the Wai-iti Valley area. The Wai-iti Water Augmentation Committee (comprising representatives from the local community and TDC) was set up in 1995 to find the best option for the northernmost extent of the Wai-iti valley. A feasibility study for a community dam was completed in 2001 identifying small off-river storage dams as options. The proposed scheme is located in a tributary of the Wai-iti River and is essentially a water harvesting project where winter flows in the stream would be impounded and stored, and gradually released on a regular basis back into the stream and Wai-iti River system during dry summer periods.

The paper will cover the project’s economic objectives as well as community and environmental impacts and the consenting process under the Resource Management Act. Dam construction is planned to start in October 2004.
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2005 Papers

2005 – A Contribution to Public Safety Studies – Failure Modes and Likelihood Analysis for a Tephra Dam on an Active Volcano
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Murray Gillon, Robin Fell, Harry Keys, M Foster

Volcanic eruptions at Mt Ruapehu in 1995-96 resulted in the deposition of about 7m of tephra over the rock rim overflow of Crater Lake. There is a long history of lahars (debris flows) associated with releases of water from Crater Lake. The 1995-96 eruptions emptied the lake and it has slowly been refilling from rainfall runoff and snow melt. When the lake level rises above the rock rim the tephra layer will act as a “barrier” or dam. Breaching of the barrier will release water and generate a lahar. The magnitude of the lahar flow will be a function of the lake level at the time of breaching

Extensive studies of the effects of the lahar that would be generated by the failure of the tephra barrier have been undertaken. The studies included a failure modes and likelihood analysis to provide information on the relative likelihood of failure as the lake level rises for the different failure modes applicable to this situation. The paper describes the failure modes considered and the results of the analysis.
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2005 Papers

2005 – Achieving Benefits from Instrumentation and Survey Measurements of Dam Behaviour
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John D Smart

The paper presents the recent trends in the use of instrumentation and
survey measurements at Bureau of Reclamation (Reclamation) dams. The underlying philos
ophy that has influenced those trends is presented and discussed. Based on experience at Reclamation, several factors that are considered key to the effective use of instrumentation and surveys are discussed. Several conclusions are offered.
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2005 Papers

2005 – ASSESSMENT CRITERIA FOR EMBANKMENT DAMS AND THE ROLE OF NUMERICAL MODELS
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There is a large stock of embankment dams throughout the world needing the assessment of their
safety as required by modern dam safety regulations. Due mainly to economic and site constraints
associated with potential dam upgrading work, it is imperative that a rational approach be adopted in
assessing their safety and in designing the remedial works. One of the most important criteria is the
selection of appropriate geotechnical parameters under different conditions. Predominant loading
conditions in a dam are much different from those in other structures such as bridge and building
foundations and therefore the direct adoption of traditional approaches may not always be valid. This
paper presents the various aspects of issues associated with the stability assessment of dams including
the rational selection of the parameters and numerical codes available to dan/geotechnical engineers
to assess their safety.
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2005 Papers

2005 – Assessment Criteria for Embankment Dams and the Role of Numerical Models
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N. Vitharana and S. Terzaghi

There is a large stock of embankment dams throughout the world needing the assessment of their
safety as required by modern dam safety regulations. Due mainly to economic and site constraints
associated with potential dam upgrading work, it is imperative that a rational approach be adopted in
assessing their safety and in designing the remedial works. One of the most important criteria is the
selection of appropriate geotechnical parameters under different conditions. Predominant loading
conditions in a dam are much different from those in other structures such as bridge and building
foundations and therefore the direct adoption of traditional approaches may not always be valid. This
paper presents the various aspects of issues associated with the stability assessment of dams including
the rational selection of the parameters and numerical codes available to dan/geotechnical engineers
to assess their safety.
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2005 Papers

2005 – Bellfield Outlet Tower – How to do interesting things in tight spaces
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JL Tottenham

This paper outlines how Grampians Wimmera Mallee Water (trading as GWMWater) and its consultants managed the upgrading of Bellfield dam’s 43m high, reinforced concrete dry outlet tower and discharge facilities. The upgrading included improvements to operations, the provision of safe person and materials access into the tower and its 1200 mm diameter steel penstock, anchoring the tower with post tensioned cable anchors to resist seismic loads, refurbishing a 1200 mm butterfly valve and penstock corrosion assessments and repair.

Prior to the upgrading, access to all areas was difficult and unsafe to some areas. In particular no provision had been made during the original construction for butterfly valve removal or safe access into vertical sections of the penstock. Overcoming these deficiencies required considerable survey, detailed movement planning and attention to detail.
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2005 Papers

2005 – Blowering Dam – Spillway Hydraulic Modelling
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David Ho, Karen Riddette, Michael Hogg, Jayanta Sinha and John Roberts

Blowering Dam was constructed in 1968 by the Snowy Mountains Hydro-Electric Authority, on behalf of the Water Conservation and Irrigation Commission. It is a large earth and rockfill embankment dam, approximately 112m high and 808m long, with a concrete chute spillway at the right abutment. The reservoir holds about 1,628GL of water that is mainly for irrigation and supplying an 80MW hydro-electric power station. The dam is owned and operated by State Water Corporation, NSW.

Revisions to the design flood estimate have highlighted the dam requiring an upgrade to cope with increased discharge rates. The NSW Department of Commerce has carried out feasibility studies of different upgrade options. The need to evaluate the hydraulic performance of the existing un-gated spillway was identified. Flow overtopping the chute walls can potentially erode the backfill behind the walls, and, the rockfill on the downstream toe of the embankment. Consequently, this may lead to significant damage of the spillway and may risk the safety of the dam.

Hydraulic analysis of the spillway using a 3-D computational fluid dynamics model was performed for
various flood levels to determine the discharge coefficients and the discharge rating curve. It was also required to identify whether the chute walls need raising to contain the increased discharges. These results were compared with those calculated by other “standard” methods. Such verification provided a level of confidence in the analysis results which were then used in the studies to assess available upgrade options.

In order to have further confidence in the analysis, the computed results were validated against physical test data and some limited information from an actual discharge. Further verification against established theory was conducted by modelling a supercritical flow through a contraction in an open-channel in order to see if the computation could predict the shock wave effect that was observed in physical models as well as full scale channels. A reasonably good correlation was obtained from all validating tests.

This paper presents some background of the proposed dam upgrade, potential upgrade options considered and details of the hydraulic modelling of the spillway. Some interesting flow behaviour caused by the shock wave will be highlighted.
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2005 Papers

2005 – BLOWERING DAM – SPILLWAY HYDRAULIC MODELLING
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Blowering Dam was constructed in 1968 by the Snowy Mountains Hydro-Electric Authority, on behalf of the Water Conservation and Irrigation Commission. It is a large earth and rockfill embankment dam, approximately 112m high and 808m long, with a concrete chute spillway at the right abutment. The reservoir holds about 1,628GL of water that is mainly for irrigation and supplying an 80MW hydro-electric power station. The dam is owned and operated by State Water Corporation, NSW.

Revisions to the design flood estimate have highlighted the dam requiring an upgrade to cope with increased discharge rates. The NSW Department of Commerce has carried out feasibility studies of different upgrade options. The need to evaluate the hydraulic performance of the existing un-gated spillway was identified. Flow overtopping the chute walls can potentially erode the backfill behind the walls, and, the rockfill on the downstream toe of the embankment. Consequently, this may lead to significant damage of the spillway and may risk the safety of the dam.

Hydraulic analysis of the spillway using a 3-D computational fluid dynamics model was performed for various flood levels to determine the discharge coefficients and the discharge rating curve. It was also required to identify whether the chute walls need raising to contain the increased discharges. These results were compared with those calculated by other “standard” methods. Such verification provided a level of onfidence in the analysis results which were then used in the studies to assess available upgrade options.
In order to have further confidence in the analysis, the computed results were validated against physical test data and some limited information from an actual discharge. Further verification against established theory was conducted by modelling a supercritical flow through a contraction in an open-channel in order to see if the computation could predict the shock wave effect that was observed in physical models as well as full scale channels. A reasonably good correlation was obtained from all validating tests.
This paper presents some background of the proposed dam upgrade, potential upgrade options considered and details of the hydraulic modelling of the spillway. Some interesting flow behaviour caused by the shock wave will be highlighted.
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2005 Papers

2005 – Characterisation of the Ross River Dam Foundations
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The Stage I construction of the Ross River Dam was completed in December 1973. The reservoir
reached full supply level (FSL) and then spilled in January 1974. In 1976, the left embankment was
raised to Stage II level. Spillway gates were installed in February 1978 with full supply level for
Stage 1A (FSL).
In the years following the first filling of the reservoir after the raising of FSL, salt scalding
downstream of the northern portion of the left embankment occurred. This was attributed to
foundation seepage. Investigations started in 1978 to define what remedial measures were required to ensure the safety of the left embankment. Fissured clays were first discovered in the foundations of the Ross River Dam during these investigations.
Fissures could substantially reduce the overall strength of the soil foundations. Therefore the effect of these fissures needs to be considered when evaluating the acceptable levels of reliability against embankment failure. More extensive fissuring was discovered during the current investigations and a cataloguing system was employed to characterise the foundation conditions.
A simplified layer model was adopted early on in the design but did not fully demonstrate the
complexity of the subsurface conditions. Extensive use was made of historical geological data,
current investigation data and the application of GIS systems. The resulting model more clearly
represents the foundation conditions and high degree of variability and was used in subsequent risk assessments for the upgrade design.
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2005 Papers

2005 – COMMUNITY PARTNERSHIP AND THE DELIVERY OF A MAJOR LEGACY
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The $70 million upgrade of Wivenhoe Dam is being undertaken by the Wivenhoe Alliance, in close
proximity to the town of Fernvale, Queensland. As part of the Alliance’s commitment to delivering positive outcomes for the local community, it was decided part way through the project, to commit to delivering a ‘signature’ community legacy project. The team brainstormed a range of options and a decision-making matrix was used to choose the project that would best meet its objectives.
A partnership has been formed between the Alliance, Esk Shire Council and SEQWater to deliver a
master-planned project which incorporates elements such as a community information/service facility, upgrade of Fernvale Memorial Park, streetscape enhancements, improved parking and installation of shelters along the adjacent rail trail. These major partners, together with representatives of the local community, constitute the steering committee, which oversees planning of the project.
The project aims to encourage visitors to the area, to provide improved amenity and sense of pride for the region, and in turn encourage strong relationships for SEQWater in the area in which they operate.
Due to tight time frames the partnership is managing the fund raising activities, community consultation and design processes in parallel.
This paper discusses the process by which the Alliance was able to deliver this remarkable project, within a short timeframe. It also discusses how the local community has been involved and the benefits, which have resulted.
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2005 Papers

2005 – Community Partnership and the Delivery of a Major Legacy
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Stuart Macnish, Nikki Bennett

The $70 million upgrade of Wivenhoe Dam is being undertaken by the Wivenhoe Alliance, in close
proximity to the town of Fernvale, Queensland. As part of the Alliance’s commitment to delivering positive outcomes for the local community, it was decided part way through the project, to commit to delivering a ‘signature’ community legacy project. The team brainstormed a range of options and a decision-making matrix was used to choose the project that would best meet its objectives.

A partnership has been formed between the Alliance, Esk Shire Council and SEQWater to deliver a
master-planned project which incorporates elements such as a community information/service facility,upgrade of Fernvale Memorial Park, streetscape enhancements, improved parking and installation of shelters along the adjacent rail trail. These major partners, together with representatives of the local community, constitute the steering committee, which oversees planning of the project.

The project aims to encourage visitors to the area, to provide improved amenity and sense of pride for the region, and in turn encourage strong relationships for SEQWater in the area in which they operate. Due to tight time frames the partnership is managing the fund raising activities, community consultation and design processes in parallel.

This paper discusses the process by which the Alliance was able to deliver this remarkable project, within a short timeframe. It also discusses how the local community has been involved and the benefits, which have resulted.
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2005 Papers

2005 – Dam design, Geotechnical Parameters, Numerical Codes, Hydraulic Fracturing, Seismic Analysis.
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P Maisano, M Taylor , M Barker and A Parsons

South Para Dam, completed in 1958, is located on the South Para River, 38 km north of Adelaide. The embankment is 45 m high and comprises compacted crushed phyllite with rockfill toes. The 13 m high rock fill toes are protected with three-stage filters but the remaining 32 m of embankment height has no downstream filter protection.

The South Australian Water Corporation (SA Water), the owner and operator of the dam, is considering modifications to the dam, to augment its flood mitigation role. The proposed works, while not affecting the full supply level, involve a modification to the spillway crest and raising of the embankment crest to accommodate increased flood levels. SA Water therefore commissioned a dam safety review to assess the need for any piping or overtopping protection that may be required. This was followed by concept designs to ensure that flood mitigation work is compatible with any required dam safety upgrade work.

The results of a detailed dam failure risk analysis using event trees showed that the Societal Risk for the existing dam needed to be reduced, and that the proposed spillway modifications increased the Societal Risk due to the increased risk of piping failure with higher flood levels.

The risk analysis showed that eliminating the overtopping modes of failure by raising the dam crest is not sufficient in itself to achieve the required reduction in risk. The provision of filter protection to reduce the risk of piping failure is required, but it was shown that it is not necessary to provide full height filters as the provision of filters only above full supply level would be sufficient to achieve the required reduction in risk.

The recommended upgrade works, in addition to the proposed spillway modification for flood mitigation purposes, consist of filter protection and a weighting fill above the top berm (4.4 m below FSL) to facilitate connection to a possible full height filter in the future, and a parapet wall to provide overtopping protection.The resulting cost saving compared with the installation of full height filters is in excess of $2 Million.
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2005 Papers

2005 – Dam Safety Emergency Exercise for Eildon Dam, Goulburn Weir and Waranga Basin
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Andrew Evans, Michael Cawood, Jonathon Reid

Eildon Dam, Goulburn Weir and Waranga Basin in Victoria are owned and managed by Goulburn-Murray Water (G-MW). Eildon Dam and Goulburn Weir are situated on the Goulburn River, while Waranga Basin is an offstream storage supplied from Goulburn Weir.

In November 2004 a dam safety emergency exercise involving the establishment of a central Emergency Coordination Centre at Tatura as well as Emergency Operations Centres at each of these three dam sites was conducted. The exercise presented a variety of emergency situations in stepped time increments, including earthquake, mechanical failure, a hazardous material spill and a terrorism related incident. External agencies were not involved.

The exercise was part of an ongoing G-MW program designed to test and improve dam safety emergency planning and response systems for all of G-MW’s dams and highlighted areas where procedures, situational management and communications can be enhanced.

Outcomes aimed for in G-MW’s program are improvement in Dam Safety Emergency Plans and internal communications, together with clarification of roles, responsibilities and capabilities.
The valuable experiences learned from this dam safety emergency exercise and plans for a larger scale exercise involving other emergency management agencies will be shared with others through this paper.
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