2008 – Innovative Spillway Developments in the ACT – Technical Memoire Paper
Geoff Henkel
ABSTRACT
The author has been involved in the design of a number of dams and spillways and specifically the design of several ACT lakes and ponds working either for the development authorities or as a consultant to them. This paper, a memoire, describes seven innovative spillways utilised in the ACT, five of which he was directly involved with. The use of dual spillways has been a common feature of the designs and this has been a very economic approach. As well as some use of fuseplug spillways, a labyrinth spillway and the safety of embankment overtopping, this paper may provide some useful ideas for new developments.
$15.00
Related products
-
$15.00
Papers 2008
2008 – “When is a dam not a dam?”- Design of mine tailings storage facilities for closure
Learn moreDavid Brett, Ben Hanslow. Rob Longey
Abstract: Mine tailings storages are among the largest man made structures in the world and often pose a considerable risk to the aquatic environment due to the nature of the stored materials. In particular, sulphide minerals are prone to oxidation when brought into contact with air and water. This leads to the formation of acidic conditions within the storages leading to dissolution of toxic metals, with seepage from these structures being known as Acid Rock Drainage (ARD). ARD is responsible for pollution of natural waterways in many areas of the world with some significant examples in Australia. Current practice in the mining industry is to attempt to exclude oxygen or water from tailings storages in order to prevent the oxidation process taking place. This involves capping of the storages with sophisticated soil covers or, where sufficient water is available, leaving a permanent water cover.
Mining operations have a relatively short life, usually around 5 to 10 years, although some can operate for over 100 years, as has the Mount Lyell Mine. Normal practice has been for companies to relinquish the mining lease on the cessation of mining, however governments are now realising the extent of liability involved with the “ownership” of large waste storage facilities. Bonds are placed by mining companies during operations, intended to cover the cost of “closure” of the mine. Often the major item covered by the bond is for the “closure” of the tailings storage facility. Following “closure”, the intention is that ownership of the lease, including waste storages, reverts to the State. State governments are now more aware of the potential liabilities in accepting the relinquishment of these leases and need to address the issues of their long-term management.
In Tasmania, Dam Safety legislation covers both water and also soil covered tailings storages, with the legislation requiring each type to meet various ANCOLD guidelines. In other jurisdictions this could well also be the case through common law requirements to meet common best practice. However, the current ANCOLD Guidelines are generally written around water storage dams and interpretation to include a waste storage facility is often not straightforward. As an example a tailings dam during operations with a water storage component is clearly a dam. Due to the environmental impact of failure it could well have a Significant or High-C hazard rating, which would require design for extreme floods and earthquakes. After closure, with say a soil cover and water diverted away, is it still a dam within an ANCOLD definition? Are ANCOLD guidelines relevant? The current ANCOLD (1998) Guidelines on Tailings Dam Design, Construction and Operation does not give specific guidance on these issues.
This paper explores these questions and suggests ways that ANCOLD could provide assistance with more guidance on the long term management aspect of tailings storages to assist designers, owners and regulators consider the closure phase.
Keywords: tailings, acid drainage, mine closure
Learn more -
$15.00
Papers 2008
2008 – It’s all in the planning – replacement of a valve under full reservoir head
Learn moreStuart Richardson, Peter Liepkalns, Rod Mauger
Abstract: Operations and maintenance of large dams can be complex and potentially high risk. Even on a relatively new dam like Dartmouth, Goulburn-Murray Water is regularly presented with maintenance tasks which are made very difficult because access for maintenance may not have been considered during the original design and construction of the dam.
Goulburn-Murray Water recently completed a change over of a 200mm cast iron gate valve at Dartmouth, not in itself a complex or high risk maintenance task. What made this task challenging was that the valve was subject to full reservoir head (up to 180m) with no means of isolation.
Learn more -
$15.00
Papers 2008
2008 – Management of a dwindling resource
Learn moreAndrew Shields, Dr Mark Bailey, Graeme Hannan
Abstract: In recent years, water resources have declined markedly under the effects of long-term drought and climate change. Resource planning has turned from a process of routine allocation to the specialised management of a limited and highly valued commodity. Probabilistic outlooks of water availability based on historical inflows have proven an important component of the drought communication strategies used by Goulburn-Murray Water. In turn, Goulburn-Murray Water has examined alternative means of securing additional water for its customers, including revised operating criteria and pumping from the dead storage of its dams.
With the focus on meeting essential domestic water needs and boosting irrigation supplies, Goulburn-Murray Water has used the opportunity afforded by water levels to review the capacity of its storages. The regular, but unwelcome, outcome of reduced storage capacities from these studies, and the predictions of continuing drought, present Goulburn-Murray Water and its customers with an ongoing challenge.
Keywords: water resources, allocation outlook, capacity table, dead storage, resource position
Learn more -
$15.00
Papers 2008
2008 – Towards responsible management of tailings facilities
Learn moreElizabeth Gardiner, Len Murray, David Gladwin
Abstract: The Mining Association of Canada has worked over the past 12 years to improve the management of tailings facilities. This effort began out of a realization that tailings present a major business risk to the mining industry, and that a series of major tailings failures around the world in the 1990’s were fundamentally indicative of need for improved care and management practices by tailings dam and facility owners and operators. MAC established and continues to sponsor the Tailings Working Group, which has assisted in development and publication of a three-volume set of guides to improve tailings management:
•“A Guide to the Management of Tailings Facilities”, initially published in 1998, updated edition published in 2008;
•“Developing an Operation, Maintenance and Surveillance Manual for Tailings and Water Management Facilities”, published in 2003; and
•“A Guide to Audit and Assessment of Tailings Facility Management”, published in 2008.
The three guides provide a strong message that the key to safe and environmentally responsible management of tailings is consistent application of sound engineering capability within an effective management framework.The documents are almost directly applicable to all forms of dams and are widely used for water dams. Also, because the documents are available in Spanish and French they have found wide use in International projects.
A brief comparison with published ANCOLD guidelines is provided.
Keywords: Management of tailings facilities and water dams, Operation, Maintenance and Surveillance, Auditing, risk, safety, guides
Learn more -
$15.00
Papers 2008
2008 – Design Rainfall Issues in South East Queensland
Learn moreTerry Malone
Abstract: Recent studies in SE Queensland for existing and proposed dams and other flood studies have highlighted a number of issues with respect to the design event approach in deriving and applying design rainfalls to calibrated runoff routing models.
The estimation of design rainfall depths for frequent to large events is usually done by the intensity-frequent-durations (IFD) methods outlined in Australian Rainfall and Runoff (AR&R) or CRC-Forge.
The design temporal patterns applied to these rainfall depths are critical in the estimation of design floods as are the adopted loss rates.
This paper describes the methods used to derive the design rainfall and some of the issues which arose in their application in the design event approach to assessing design floods. It uses examples at several locations in studies undertaken by SunWater and refers to similar issues encountered in other studies.
Implications for flood studies are outlined.
Keywords: design rainfall, design floods, CRC-FORGE, IFD, temporal patterns, SunWater, Queensland.
Learn more