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.
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D. J. Dole, D. Dreverman and A. J. McLeod
The Murray-Darling Basin Commission is embarking on an ambitious project directed towards repairing the environmental damage to the River Murray, caused by a century of human intervention. Today the River Murray is one of the more highly regulated rivers in the world, with only a 27% natural annual median flow to the sea.
In April 2002 the Murray-Darling Basin Ministerial Council approved, in–principle, a program of structural works from Dartmouth Dam to the Murray Mouth, including the lower Darling downstream from the Menindee Lakes. The initial phase is estimated to cost $150 million over 7 years. At the same time the Council has authorised studies of the environmental, social and economic impacts of 3 scenarios involving recovery of 350 GL, 750 GL and 1500 GL per year from existing uses, for reallocation to the environment.
This paper describes some of the key projects in the portfolio of works under consideration, including:
The paper also outlines the extensive stakeholder consultation and community engagement processes which are fundamental to the success of the project, as well as the various means adopted to enhance the links between scientists and engineers involved in the project.
D.S. Bowles and Loren R Anderson
Starting a quarrel is like breaching a dam; so drop the matter before a dispute breaks out. Proverbs 17:14 (NIV)
An approach is summarised for presenting the outcomes of traditional engineering assessments and risk assessments to inform non-technical decision makers. The decision justification approach can be adapted to any dam owner’s unique decision context. It includes rating systems for presenting the outcomes from engineering assessments and from applying tolerable risk criteria, including ALARP. Three decision types are addressed: setting tolerable risk goals for individual dams, identifying a risk reduction pathway for a portfolio of dams, and managing residual risk on an on-going basis
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.
G.W. Ashman, C.M. Hamilton and N.J. Hall
Consideration of the need to accommodate environmental flows in the operation of major dams is a relatively new requirement in South Australia. Recognition of environmental water requirements has been promoted through the COAG water industry reforms and the State Water Resources Act. The South Australian Water Corporation is working with other Government agencies on environmental flow projects that will potentially involve three of the Corporation’s large dams. This presentation will summarise the work done to date on establishing environmental flow releases from these storages. The presentation will give the SA Water perspective on the regulatory, environmental, social and operational aspects of the environmental flow issue.
David Brett, Anton van Velden and Phil Soden
The Main Creek Tailings Dam is a 60m high earth and rockfill dam constructed during the early 1980’s to store tailings from the Savage River Mine on Tasmania’s west coast. The dam served the mine well for nearly 20 years, storing around 32 million m3 of tailings, but has required raising due to the expanded mining plans of the current operators, Australian Bulk Minerals (ABM). ABM believe that the mine could require a further 60 million m3 of tailings storage over the next twenty years at increased production levels. This could be stored in the Main Creek Dam by raising it by around 35m. In the medium term this scale of raising would be feasible using waste rock product from ongoing mining but in the short term of several years an interim solution would be required. The feasibility of upstream construction on the tailings beach was reviewed and found feasible for
a maximum 12m in 4 lifts.
Of critical concern were
The paper discusses the investigation and design phases of the dam and describes the issues arising during construction recently completed over the period January to April 2002. The use of pore pressure, shear strength changes and tailings beach movement monitoring to control construction is discussed.