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.
M. Shirley, P. Hill, S. Hannon, B. Abernethy, H. Griffith and S. Gatti
There is an ever increasing focus on the impact of water resource infrastructure, and particularly dams, on downstream hydrology and hence ecology. Over the last few years this focus has led to the rapd development in the philosophy and techniques for estimating the requirements of water dependent ecosystems.
This paper outlines the application of a new framework for estimating environmental water requirements which results in a range of flows, rather than a single recommended flow. Furthermore, a range of strategies for providing this water to the environment will be explored.
The paper uses the current environmental flows study on the Onkaparinga River Catchment for the Onkaparinga Catchment Water Management Board to illustrate the issues and application of the methodology. The natural hydrology of this catchment has been impacted by pumping of water from the River Murray, a major dam (Mt Bold) and the diversion of flow at Clarendon Weir. This substantial multi-disciplinary study over 3 years is estimating environmental water requirements and the strategies for providing this water to the environment.
R.A. Ayre and T. L. McGrath
The regulatory environment of Queensland’s water resources has changed significantly within the last few years as a consequence of the passing of the Water Act 2000. SunWater, as the owner of referable dams and the operator of water infrastructure, is required to observe the provisions of the new Act.
SunWater has undertaken dam failure analyses of a number of its dams in accordance with the new guidelines prepared by the Department of Natural Resources and Mines. The results of these assessments are being used as part of a portfolio risk assessment of its assets to help prioritise refurbishment activities. Aspects within the guidelines relate to various ANCOLD publications, with a focus on the consequence of failure for determining incremental hazard categories and appropriate design standards for spillway adequacy.
SunWater also operates its schemes under the provisions of Interim Resource Operation Licenses (IROLs). As part of Government’s water planning process, SunWater is required to submit proposed water management arrangements for its schemes. SunWater develops these arrangements, which include operation, water trading, and monitoring rules, to meet its business objectives and the objectives of government. With government approval, these proposed arrangements will translate to the provisions of Resource Operation Licenses when the Resource Operation Planning (ROP) process is completed.
This paper describes SunWater’s experience and approach to meeting regulatory requirements in the above areas.
H. Morrison, J. Leckie, P. Richardson, R Paton
Awoonga Dam is a 40 metre high concrete faced rockfill dam on the Boyne River near Gladstone in Central Queensland. The dam supplies domestic and industrial water to the Gladstone region and the Callide Power Station. Stage 1 will increase FSL by 10 metres to EL 40, which increases storage capacity from 289,000 ML to 777,000 ML. To provide for future industrial growth in the region, the dam design facilitates future raising up to a nominated FSL of EL 62, in a number of stages.
The project consists of:
Significant savings were realised by adopting the alliances project delivery method, resulting in completion 5 months ahead of program and more than 10% under budget.
This paper details development of the project under the alliance and outlines some of the lessons learnt.
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.
C.F. Wan, R. Fell, M.A. Foster
This paper presents the findings of experimental investigation of the rate of piping erosion of soils conducted at the University of New South Wales.
Two tests, namely the Slot Erosion Test and the Hole Erosion Test, have been developed to study the erosion characteristics of a soil. The erosion characteristics are described by the Erosion Rate Index, which indicates the rate of erosion due to fluid traction, and the Critical Shear Stress, which represents the minimum shear stress when erosion starts. Results of the two laboratory erosion tests are strongly correlated. Values of the Erosion Rate Index span from 0 to 6, indicating that two soils can differ in their rates of erosion by up to 106 times. Coarse-grained soils, in general, are less erosion-resistant than fine-grained soils. The Erosion Rate Indices of coarse-grained cohesionless soils show good correlation with the fines and clay contents, and the degree of saturation of the soils, whereas the Erosion Rate Indices of fine-grained cohesive soils show moderately good correlation with the degree of saturation. The absence of smectites and vermiculites, and apparently the presence of cementing materials, such as iron oxides, improves the erosion resistance of a fine-grained soil.
The Hole Erosion Test is proposed as a simple index test for quantifying the rate of piping erosion in a soil, and for finding the approximate Critical Shear Stress corresponding to initiation of piping erosion. Knowledge of these erosion characteristics of the core soil of an embankment dam aids assessment of the likelihood of dam failure due to piping erosion in a risk assessment process.