2008 – Proposed changes to the UK Reservoir Safety Legislation to incorporate a risk based approach and the problems the UK faces into future
Dr AK Hughes
Abstract: This paper describes the way in which the UK is moving in respect of reservoir safety and outlines the legislative changes that are currently being drafted. It also identifies issues which the author thinks are important for the future of dam engineers around the world.
Keywords: safety, legislation, risk assessment
$15.00
Related products
-
$15.00
Papers 2008
2008 – Working towards design guidelines for outlet works – current practice
Learn moreMarius Jonker, Mike Taylor and Glen Hobbs
Abstract: One of the activities authorized by organizations such as ANCOLD is the development of guidelines to enhance the ability of organizations to assure that adequate dam safety programs and practices are in place.
However, due to the absence of a single recognized guideline covering the various design aspects of dam outlet works, there is currently great inconsistency in the underlying principles for design and review processes for these facilities. A single, nationally recognized “standard” would lead to greater consistency between similar project designs, facilitate more effective and consistent review of proposed designs, and result in increased potential for safer more reliable facilities.
The need for a design standard is further underscored by the fact that poorly designed and/or constructed outlet works have been identified as a significant contributor to the occurrence of embankment dam failures. The failure of critical components in the outlet works of dams, not leading to an uncontrolled release of water, is generally considered less important due to apparent lesser consequences compared with a dam failure. However, the drought experienced over the past decade in Australia has highlighted the value of water and securing it for the future. The potential impact caused by the inability of a primary storage to supply a town or city, due to a failure in the outlet works, potentially affecting thousands of people and industries, could be devastating.
This paper summarises the current state of practice with regard to outlet works for dams concerning design, construction, inspection and evaluation, as well as maintenance and renovation. It also underlines some commonly occurring deficiencies encountered at existing dams. It provides a basis for further discussions of the state of practice for these topics in order to work towards consistent and unified outlet works design guidelines for dams.
Keywords: outlet works, state of practice, design guidelines
Learn more -
$15.00
Papers 2008
2008 – Innovative Spillway Developments in the ACT – Technical Memoire Paper
Learn moreGeoff 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.
Learn more -
$15.00
Papers 2008
2008 – An overview of concrete lined stilling basin and spillway scour engineering risk assessment tool for US Army Corp of Engineers dams
Learn moreBrett J Heppermann
Abstract: As one of the main federal agencies with responsibility to build, operate, and maintain large dams in the United States, the US Army Corps of Engineers (USACE) is developing a risk based framework to better manage their portfolio of 600+ dams in terms of risk management and prioritization of funding. A key element to this effort is the development of risk-based analytical tools to evaluate primary features for applicable failure modes. These are used in conjunction with loading and consequence modules to assess the overall risk associated with the dam in terms of lives and economic damages. The focus of this paper is on the analytical tool being created for evaluating the probability of an uncontrolled reservoir release due to scour of concrete lined stilling basins and spillways.
This analysis module is broken down by potential failure modes that could initiate events that could lead to an uncontrolled release. The failure modes that are considered are Cavitation, Slab Uplift and Foundation Erosion, Ball Milling, Tunnel/Conduit Failure, Plunge Pool Erosion, Fuse Plug and Fuse Gate Failure, Hydraulic Loading and Profile, and Headcutting. Each failure mode analysis takes into account how the inlet structure, conveyance, and terminal structure is affected, if at all.
This paper gives and overview of the main characteristics of each failure mode and the methods used to quantify the risk associated with each.Keywords: risk based analytical tools, concrete scour, spillway, stilling basin, risk assessment, U.S. Army Corps of Engineers.
Learn more -
$15.00
Papers 2008
2008 – Risk assessment with uncertainty analysis for an already-initiated failure mode
Learn moreDavid S Bowles, Sanjay S Chauhan, Loren R Anderson, Terry F Glover
Abstract: A nested model is presented for considering variability and knowledge uncertainty in a dam safety risk assessment of an existing dam and interim risk-reduction alternatives (operating restrictions) during the staged implementation of a permanent structural risk reduction measure. The effects of some important aspects of natural variabilities on estimated risks are represented as cumulative distributions of probability of failure, annualised life loss, economic risk cost, and an F-N representation of life loss. Many cumulative distributions are generated to represent the effects of some important aspects of knowledge uncertainties.
An important aspect of the knowledge uncertainty is the current level of development of an already-initiated piping failure mode. Also, an approach to conditioning the system response probabilities (SRPs) for the piping failure mode on the duration of reservoir pool exceedance is included in the failure event tree risk model.
ANCOLD and Reclamation tolerable risk guidelines are evaluated at selected percentiles of variability and percentiles (levels of confidence) of knowledge uncertainty. The incremental cost-per-statistical-life saved and benefit-cost ratio for interim risk-reduction alternatives are estimated and evaluated to examine the case for more-severe levels of operating restriction than the least-severe operating restriction that is estimated to satisfy, at a selected percentile of variability and a desired level of confidence, the limit values in all of the tolerable risk guidelines that were considered.
Keywords: Dam safety, risk analysis, risk assessment, uncertainty analysis, aleatory uncertainty, epistemic uncertainty.
Learn more -
$15.00
Papers 2008
2008 – Investigations and remedial works at Drakesbrook Dam in Western Australia
Learn moreJiri Herza, Graeme Maher, Nihal Vitharana, Megan Evers, Michael Somerford
Abstract: Drakesbrook Dam is a 17m high earthfill embankment constructed in 1931 to provide water for the Waroona Irrigation District, 80km south of Perth. The dam has a storage capacity of 2.30 GL and is classified as a “High A” hazard dam according to ANCOLD Guidelines on Dam Safety Management.
A Dam Safety Review, undertaken in 2001 identified a number of deficiencies associated with main embankment, outlet works and the main spillway requiring remedial works. Detailed design of these remedial works is currently underway. Challenging features of this project are the design of a liner for the existing curved conduit and the design of a new spillway with an usual drop-type stilling basin.
This paper presents the salient aspects of the remedial works design along with the various design and construction criteria adopted to achieve an economical design of a new spillway and outlet conduit sleeve without compromising the safety of the dam.
Keywords: remedial works, earth embankment, conduit lining, spillway replacement
Learn more