The Koralpe hydropower scheme is a major development on the Feistritzbach tributary of the River Drau to utilize water in a 50 MW powerhouse located in the south-eastern Carinthia, Europe. The Soboth reservoir is situated 735 m higher in a narrow valley and is created by the 85 m high Feistritzbach dam which was constructed near the border of Austria and Slovenia between 1988 and 1990. This rockfill dam is the latest addition to KELAG’s more than 15 structures and is sealed by an asphaltic core. The excellent deformability and impermeability of the asphaltic core is able to follow the deformation of the compacted rock-fill material best during construction, initial filling and operation period without any seepage. The asphaltic core was placed in three 20 cm layers per day by a specially developed placing unit from a contractor. The upstream and downstream filter zone was placed at the same time with the same machine and compacted carefully by vibrating rollers. The dam is curved in plan with a radius of 650 m and contains about 1.6 million m³ rock fill material. The surface of the downstream side was built exceeding the environmental standards of the time.The most important indicator of the normal function of a dam is the behaviour of seepage. A monitoring system of seepage, piezometers, earth pressure cells and deformation has been installed. The seepage water is monitored online at seven points of the dam base and at the access tunnel to the bottom outlet valve. Geodetic measurements on and inside the dam are done once a year. Several additional pieces of surveillance equipment were installed to observe the behaviour of the asphaltic core. The paper concentrates on the design, construction and performance of the dam with the asphaltic core.
Now showing 1-12 of 59 2970:
A brief overview of dam surveillance is given from a South African perspective and more specifically the perspective of the Department of Water Affairs and Forestry (DWAF). DWAF’s Ten Commandments for the design of dam monitoring systems serve as introduction and this is followed by a summary of the design steps. The various parameters that can be measured and the South African preferences are discussed briefly followed by a synoptic description of crack and joint monitoring in South Africa. This provides the background for DWAF’s recent developments in 3-D Crack-Tilt gauges. Some of DWAF’s achievements as well as some of the blunders made by the author during the past 30 years are illustrated by means of a few case histories.
N. Vitharana, G. McNally, C. Johnson, A. Thomas, K. Dart and P. Russell
Millbrook Reservoir is an offline storage with an earthen embankment dam containing a puddle clay core and a moderately sized upstream catchment. The dam is 31m high and has a capacity of 16.5 GL when the storage water level is at the Full SupplyLevel (FSL). The reservoir is 25km NE of Adelaide on Chain of Ponds Creek, a tributary of the River Torrens. The dam was constructed during the years 1914-1918. Earthworks were carried out only during summer as the five winters during the construction period were very wet.
Dam safety reviews and geotechnical investigations, undertaken between 2001 and 2004 by SKM, showed that these winter recesses would have created weak layers, increasing the potential for piping due to the lack of a filter. This was highlighted by the large deformations which occurred at the end of construction in 1918. The spillway was assessed as able to pass a flood event with AEP of 1:1,300,000. Given the location of the dam, ANCOLD(2000b) Guidelines suggest the dam should be able to safely pass the PMF flood event. Accordingly, the dam required upgrading to modern guidelines.
The 2005 detailed design of the upgrade included the construction of a 70m wide unlined spillway, construction of filters on the downstream face of the dam with a stabilisation (weighting) fill, installation of instrumentation and seismic protection of the outlet tower. The construction of these works is currently underway.
Ensuring compliance with the Regulator’s requirements is a cornerstone consideration for any water corporation in planning its risk minimisation strategies against dam failure. With the increased focus on due diligence and corporate governance however, there are emerging themes that are of equal importance for a water corporation in planning protections against its core risks to dam safety. These considerations include:
Nerida Bartlett, David Scriven, Peter Richardson
The failure of a number of consecutive wet seasons has resulted in storage levels in Eungella Dam being at dangerously low levels such that supply could be exhausted by June 2007. Eungella Dam supplies bulk water to the Bowen Basin coal fields as well as the Collinsville power station and the Collinsville township.
The Collinsville township, power station and coal mine as well as the Newlands mines take water from the Bowen River Weir which is supplied from Eungella Dam some 95 kilometres upstream. Transmission losses of the order of 25 to 50% have been experienced for releases from Eungella Dam to Bowen River Weir.
The Eungella Dam catchment area is 142 square kilometres. Significant flows occur in the Bowen River downstream of Eungella Dam, the catchment area above Bowen River Weir being 4,520 square kilometres. The topography in the surrounding area (near Collinsville) is not suitable for dam construction.
The opportunity existed for the construction of an offstream storage adjacent to the Bowen River Weir so that the downstream flows could be captured reducing the demand on Eungella Dam thus making more water available for upstream users.
A 5,200 ML offstream storage, associated pump station and rising main was designed, constructed and filled within a period of 12 months.
Foundations at the site are highly permeable sands. Marginally suitable clay for a seal was in short supply as was suitable rock for slope protection. A fixed price budget had been set by the contributing customers.
This paper describes the hydrology, site conditions, design and construction of the project.
D.N.D. Hartford and P. A. Zielinski
With the notable exceptions of dyke safety in the Netherlands and dam safety in Australia, explicit consideration of the equity versus efficiency dilemma associated with dam safety decision-making has been virtually ignored in the past debates related to safety of dams thus leading to inconsistent judgments in the development of dam safety policies. The equity-efficiency dilemma is now being debated in Canada as part of the process of revising the Canadian Dam Safety Guidelines. This paper explains how the argument in favour of formulating the new Canadian Dam Safety Guidelines within the formal risk assessment and risk management framework is being presented. The paper then focuses on the difficulties involved in aligning the well tried and tested and generally successful traditional approach to dam safety with the relatively untried and untested risk assessment approach. While the paper does not provide a significantly different perspective (a made in Canada approach) to the role of risk assessment in dam safety management as established in Australia and as presented in ICOLD Bulletin 130 (ICOLD, 2005), it does challenge some aspects of the ways dams are classified in the emerging risk assessment frameworks for dam safety management.