Pieter van Breda, Alison White, and Greg Carmody
Site works on the $150 million Warragamba Dam Auxiliary Spillway project commenced in March 1999 and were completed in June 2002. Successful interaction with the local community, to achieve an equitable outcome, has been a feature of the communications strategy for the project.
The Auxiliary Spillway is located close to the village of Warragamba, a township of approximately 2,000 residents. The closest residence is about 200 metres from the site. The EIS and subsequent planning documents identified key localised environmental impacts that the project would impose. The main concern of local residents, including a local action group, was the impact on their amenity during construction of the Auxiliary Spillway, particularly in relation to noise, vibration, dust and traffic.
The conditions of approval for the project included a range of communication activities, of which the formation of a Community Liaison Committee (CLC) with an independent Chairperson was a key component. When the membership of the CLC was established the Sydney Catchment Authority (SCA) and chairperson agreed that it needed to fully represent the local community – and therefore included community representatives from Warragamba and two nearby villages, the Chamber of Commerce, the local action group, the local school, local council, the dam owner (SCA) and the project manager (AWT P/L).
The establishment of the CLC has proven to be very successful. It has been the voice of the community, with responsibility to act on behalf of the community and to keep them informed of progress on the project. When issues arose during the construction, the CLC were briefed on the particular matter. The CLC was instrumental in resolving these community issues and has allowed this $150 million civil project to proceed without community attributed delays.
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J. Matthews, A. Crichton, G. Gibson
Glenmaggie Dam is a 37m high concrete gravity dam, which was constructed from 1919 to 1927. A
design review, which was carried out in line with ANCOLD Guidelines, (SMEC 1999) indicated that the dam did not meet the ANCOLD Guidelines for earthquake. This was despite the fact that the dam was stabilised in 1989 by the addition of 70 post-tensioned ground anchors. Faced with the possibility of having to perform a major upgrade to the dam, Southern Rural Water opted to undertake a more detailed assessment of the seismic loads and to carry out further analysis of the dam using the time history method. The time history method uses an accelerogram to model the forces acting on the structure throughout the earthquake and takes into account the continually changing direction of these forces. It can also be used to determine the size of any permanent
displacements caused by the earthquake, which can then be compared to the maximum allowable permanent deformation of the dam to determine if they are acceptable. The study was carried out by GHD Pty Ltd and also utilised updated seismic information for the dam site provided by the Seismology Research Centre and a geological assessment of the local faults by the URS Corporation. This paper discusses the methods used to determine the seismic loads; the techniques used in the study and the outcomes and follows the process from a dam owner’s perspective.
Water storage dams influence the lives of a large number of people. This influence may be through provision of essential water supply or risk of dam failure during sunny day or extreme flood scenarios. It is therefore imperative that these structures are managed in a responsible with a clear understanding of the associated uncertainty. In view of the large capital cost of the structures involved, this understanding is important to ensure that, where necessary,
practical and cost effective solutions are achieved. The NSW Dams Safety Committee largely regulates the management of dams in New South Wales, however, dam owners have the opportunity to display individual initiative in this process.
The Hunter Water Corporation (HWC) is a water authority based in Newcastle, New South Wales, responsible for the supply of water and wastewater services for over 470,000 people. HWC has realised, as a responsible dam owner, that safety improvements are a continuum over the life of the structure. Chichester Dam is an example of this on-going safety improvement process that is illustrated through the principle of ALARP in a risk assessment approach.
Tony McCormick, John Grimston, Robin Dawson
Project Aqua is a proposed hydroelectric and irrigation resource sharing development on the Lower Waitaki River in New Zealand’s South Island. The NZ $1 billion project aims to deliver approximately 540 MW peak power at an economically viable price, while minimising environmental and social impacts. Application of traditional hydro concepts in historical studies for the same reach has not provided an economic solution. The current proposal challenges conventional thinking in many areas with innovative concepts allowing a significantly lower cost while not sacrificing safety or flexibility.
Development of storage may involve high social and environmental impacts. No significant storage is needed for Project Aqua as the operation of existing upstream dams can be modified to provide for peaking demand and maintenance of minimum flows. The river intake offers innovative features with its very low profile structure. The concept allows a departure from the traditional barrage or dam diversion and maintains an open braid for jet boat and fish passage. This concept has proven to be a major feature in the overall project progression to the current stage.
The largest impact component of the scheme is the eight canals designed to carry 340 cumecs over 63 km through six power stations. Cuts and fills form the canals with locally derived materials used for the embankments and lining. Expensive lining has been minimised by balancing flow exchange with groundwater through the cut and fill sections.
Feasibility design has been completed and resource consents are currently being sought. This paper will cover the significant design features and impacts.
R.M. Dawson, A. Orange
Karapiro dam is the last in a line of hydro-electric dams on the Waikato River, in New Zealand’s North Island. Investigations identified a potential deficiency in parts of the dam under seismic loading. Detailed investigations and analysis narrowed the deficiency to a low strength clay seam under the concrete gravity left abutment structure. An innovative approach was taken to solving the stability problems at minimum cost, without lowering the storage lake, which would have had significant environmental and social impacts. The process of design and construction was overviewed by an international board of review.
Construction was completed in three main stages with further investigation and design refinement between. The main contract was completed over about eight months and included detailed concrete mix and pour schedule design to control stress development due to temperature gradients for the 2000 + cubic metres of mass concrete placed. While the extent of work was relatively small, the quality control, programming, and presence of a full reservoir throughout demanded a high degree of communication and co-operation between the Principal, Designer and Constructor. Despite some surprises during construction, the project was completed within budget and formed strong bonds between all those involved. This paper briefly describes the design process, and focuses on construction, from the point of view of the Owner, Constructor and the Designer.
R.I. Herweynen and A.M. Hughes
Hydro Tasmania has a number of dams which were designed and constructed in the 1950-70s
with fully grouted, post-tensioned anchors. The method used was leading edge in its day,
however, it does not achieve the cable protection of modern methods which provide two barriers
against corrosion and are monitorable. Hydro Tasmania has developed and employed an
innovative program to ascertain the integrity and remaining life of the cables and to prepare
long term management plans for its cabled dams.
An international panel was set-up to provide guidance on the overall issue, assist in developing
a sound methodology for assessing the corrosion of the anchors and advise on long-term
monitoring. To focus the efforts, Catagunya Dam was adopted as the pilot dam, as the stability
of this dam is very much dependent on the integrity of the anchors. This paper will provide a
brief overview of the project to date but will focus in detail on the main components of the
corrosion assessment of the anchors, namely:
The paper also provides a brief summary of the instrumentation installed at Catagunya Dam to
assist with the long-term monitoring of the dam.