Retarding Basin Fundamentals (April 2013) – MODULE 1 TO 4
Retarding basins are becoming increasingly important elements in urban flood planning throughout Australia but it is evident that many basins have not been implemented in line with modern day “risk management” approaches. Accordingly, as part of its Professional Development program, and in advance of its proposed Guideline on Retarding Basins due out in 2014, the Australian National Committee on Large Dams (ANCOLD) is planning a series of seminars across Australia on Retarding Basin Fundamentals. The seminars are being provided to assist basin owners, and their professional staff and advisors, to plan, implement and operate their basins in a safe and effective manner consistent with various Government and “duty of care” obligations.
The one day seminars are being presented by leading dam safety and risk management professionals including:
Richard Rodd- dams consultant with over 40 years experience in dam and basin design, construction, operation and maintenance.
Kelly Maslin – dams consultant with over 15 years experience in dams and risk management.
Norm Himsley – dams consultant and member of NSW Dam Safety Committee with over 40 years experience in dam and basin design, construction, operation and maintenance.
Includes access to the following videos:
$60.00 - $80.00
Ben Ross, Jason Brown, Richard Rodd
Goulburn Weir was constructed in 1891 forming Lake Nagambie on the Goulburn River, approximately 8km north of Nagambie in Victoria. It is a key asset in the irrigation network diverting water to 352,000ha in Northern Victoria. The weir was remodelled between 1983 and 1987, replacing 21 overshot gates with nine radial gates. A series of 28 post tensioned bar ground anchors were installed to secure the radial gate concrete support piers to the weir’s mudstone foundations. On 8 March 2006 during routine testing of the pier bar ground anchors, failure of one anchor occurred. It posed a possible risk to pier stability. Subsequently investigations into the cause of failure and its implications was undertaken consisting of a program of data review, site investigations, metallurgical testing, geotechnical investigation, design reviews and stability assessments. It was recommended to replace the failed anchor and 10 other under performing anchors with 8 cable strand anchors at the cost of approximately $1million.
Key words: Risk, bar anchor failure, stability assessment, anchor construction.
This paper provides the insight of one practitioner into the process and application of Dam Safety Risk Assessment. The ANCOLD Guidelines on Risk Assessment provide a reasonably comprehensive outline of the key tasks involved in the risk assessment process. The intent of this paper is not to rehash the Guidelines but rather to discuss some of the practicalities of completing a dam safety risk assessment and highlight some key learning’s gained from a wide range of projects for a number of different owners.
The paper includes a brief overview of each component of the risk assessment process as well as some of the advantages and disadvantages of the various approaches to completing a risk assessment project.
2011 – Dam Safety Risk Assessment – A Practitioner’s Perspective
Technical Seminar: Safety Evaluation of Existing Dams Day 2 (March 2012) – MODULES 1 TO 4
This seminar emphasizes the importance of periodic evaluation of the safety of existing dams, and provides specific information and guidance on the visual and instrumented monitoring of the various types of dams and their appurtenant structures. Failure modes analysis is stressed as the basis for an effective and efficient monitoring program. At the conclusion of the course, attendees will have a thorough understanding of the procedures and techniques essential to carrying out meaningful dam safety evaluations and monitoring, and should be able to apply these principles to improve their own effectiveness and the effectiveness of their dam safety programs.
Kelly Maslin-dams consultant with over 15 years experience in dams and risk management.
Norm Himsley-dams consultant and member of NSW Dam Safety Committee with over 40 years experience in dam and basin design, construction, operation and maintenance.
Kristen Sih, Richard Rodd
Melbourne Water currently manages over 235 stormwater retarding basins. The process of assessing the risk posed by these assets began in 2006, and at the end of 2015 full risk assessments were completed for around 30 of the basins that were estimated to pose the highest societal risk. However, when analysing the results of these risk assessments, there was some concern that the results were inconsistent and often too conservative, given the few incipient or actual failures that had been experienced.
It was found that one of the key areas causing the conservatism was poor documentation of design and construction details, and the fact that the tools used for assessing the Potential Loss of Life (PLL) were aimed at larger storages that cause much higher depths and velocities in dambreak events than these (generally) small storages. To remedy this situation, advice was sought from specialist practitioners to develop guidance notes on the assessment of PLL and failure likelihoods for retarding basins.
On the back of these guidance notes, Melbourne Water initiated an accelerated program of assessing the risk associated with 78 retarding basins over a 6 month period. This paper describes the key recommendations from the guidance notes, compares the results of the risk assessments performed pre- and post-guidance notes and provides a summary of the portfolio risk assessment outcomes, what they mean for Melbourne Water and what the organisation intends to do to manage this risk into the future.