2021 – A Review of Victoria’s Dam Safety Regulatory Framework
Reena Ram, Siraj Perera, Mark Pearse, John Pisaniello, Shane McGrath, Joanne Tingey-Holyoak, Peter Hill
Dam construction in Victoria commenced in the 1850s and there are over 8,000 dams currently regulated by the Department of Environment, Land, Water and Planning (DELWP). Dam ownership spans across state owned water utilities and local government authorities to privately owned hydro-electricity generators and farmers.
Victoria was one of the first states in Australia to adopt risk-informed principles in the management and regulation of dam safety. A recent review of the State’s dam safety regulatory framework included a comparative analysis of Victoria’s dam safety arrangements with other regulatory regimes within Australia and overseas, including a total of 16 jurisdictions. A similar review was conducted in 2010.
The objective of the 2019 review was to examine the effectiveness of dam safety regulation in managing dam safety risks in Victoria and to assess the extent that dam safety regulation was consistent with good practice so that improvement opportunities could be identified.
This paper discusses the processes adopted in comparing various regulatory models, identification of good international practices and opportunities to achieve improved public safety outcomes for dam owners and regulators. In particular, it outlines how the State’s journey in progressively reducing dam safety risks over the years can be further strengthened.
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Papers 2021
2021 – Terms of Reference for Technical Review Panels and their technical assurance for dam projects
Learn moreChris Nielsen, Ron Guppy, Gary Hargraves, Robert Fowden
Dam safety upgrade projects of major dams typically involve a large capital investment. It is important that expenditure decisions are based on sound criteria, both technical and non-technical. Independent peer review of technical matters plays a key role in meeting design, construction and safety objectives within practical financial constraints and assuring robust, resilient and reliable project outcomes.
An independent technical review is recommended for all dam projects.
The Queensland dam safety regulator has developed guidelines associated with technical review for dam safety projects that considers scope and limitations, expertise and governance. The guidelines are informed by literature, recent projects, a commission of inquiry, internal and external review and industry feedback. The guidelines are being implemented across major dam safety upgrade business cases through preparation of terms of reference by the Queensland Government’s business planning and implementation entities, who maintain the responsibility of providing assurance to state government projects, as well as the state’s major dam owners.
The terms of reference, supported by the underlying principles in the guidelines, provide a platform for consistent and appropriate application of technical assurance to dam projects in Queensland. Among other matters, governance is highlighted as a critical factor for success as well as clarity of the roles, responsibilities and reporting lines of all parties. The application of both guidelines and terms of reference to recent projects is discussed.
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Papers 2021
2021 – Importance of adequate characterisation of fissured clay in dam foundations, a case study
Learn moreYuqi Tan, Behrooz Ghahreman-Nejad, Keith Seddon
Inadequate geotechnical investigation and hence undetected issues within the dam foundation have been responsible for many dam failures in the past. Fissured clay in the foundation poses a significant risk to the stability of the dam if it is not adequately detected and characterised. This paper presents a framework to evaluate the strength characteristics of fissured clay and its effect on the stability and performance of an embankment dam. The strength of fissured clay can be characterised from conventional triaxial test result based on the dip angle of the fissure plane. A design chart for the strength of the fissure has been developed based on the dip angle. The stability assessment for a tailings dam indicated that the dip angle of the fissure has significant impact on the overall stability of the embankment when the angle of the fissure aligns with the angle of the critical failure plane. Both fissure strength and fissure angle should be carefully evaluated for a site where fissured clay is observed.
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Papers 2021
2021 – Paradise Dam and its present and future impact on dam projects
Learn moreChris Nielsen, Ron Guppy, Donna Dunn, David Murray
Following several years of investigations and analysis a serious safety issue with the stability of the primary spillway during major flood events was identified at Paradise Dam that required urgent risk reduction works. The response to this safety issue was significant.
The Inspector General Emergency Management conducted a review into the effectiveness of emergency response if a dam safety event were to occur, taking into consideration process and communications to manage around 40,000 population at risk, comprised mostly of residents within the city of Bundaberg.
An essential works program to reduce the risk was urgently prepared then executed effectively within a calendar year. This short timeframe required significant and novel amendments to Queensland’s laws to bypass normal legislated process for such a major project.
The Paradise Dam Commission of Inquiry was established to identify the root cause of the issues, the facts and circumstances that contributed to them and recommendations to consider for future dam projects. All recommendations from the commission were accepted by the Queensland government and, following an extensive stakeholder engagement exercise, have been implemented through changes in policy and methodology and described in published guideline revisions.
For future dam projects the lessons learnt highlighted the need for early and ongoing engagement of
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independent technical review, project governance that is cognisant of risk and the ownership and capacity to bear of that risk, the need to consider testing to confirm critical design parameters and the need for an effective regulator. The essential works program has established a precedent for the timely and appropriate application of risk reduction measures. -
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Papers 2021
2021 – Risk analysis and safety upgrade of Mangrove Creek Dam; SFAIRP assessment under Dam Safety NSW regulations
Learn moreVicent Espert, Peter Buchanan, Colleen Baker, Malcolm Barker, Mark Locke
Mangrove Creek dam is an 80 m high CFRD constructed between 1976 and 1982 for water supply to the NSW Central Coast area, and is currently operated by Central Coast Council (CCC). The dam is classified as a ‘High A’ Consequence Category dam for both Sunny Day and Flood breach in accordance with ANCOLD guidelines.Previous assessments of the dam identified that it would not be able to safely pass the ANCOLD Fallback flood capacity of the PMP flood in its current configuration. As such, the dam has been operated at a restricted full supply level for many years.
In 2020, GHD was engaged by CCC to develop a concept and detailed design to increase the spillway capacity using a standards-based approach to achieve the flood capacity fallback position. The first phases of this contract also required GHD to undertake additional investigations and analyses of various aspects of the dam and spillway to confirm the scope of works for the upgrade. During this review, it became evident that although the spillway capacity does not meet the ANCOLD fallback position, the Annual Exceedance Probability (AEP) of the existing capacity was relatively low and could potentially be deemed acceptable from a risk-based position.
A Risk Assessment was subsequently undertaken, with a SFAIRP assessment developed based on the new Dam Safety NSW guidelines. This assessment may be the first one to be completed for a major dam using the Dam Safety NSW guidelines. This paper discusses the different outcomes for a standards-based ‘Fallback’/’Simplified’ criteria and risk criteria based on DS NSW regulations, as well as the investigations developed to maintain confidence in the assessment. In addition, it describes a practical case for the application of SFAIRP criteria to a major dam.
In the case of Mangrove Creek Dam, the application of the new DS NSW Guidelines resulted in the dam being assessed as acceptable in its current state, with the FSL returned to the original design level. The outcome provided significant savings to the client, by avoiding costly upgrade works and avoiding disruption to the operation of the storage – a real success story.
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Papers 2021
2021 – Remedial Works To Lock and Weir One – It seemed like a good idea in the design office
Learn moreChristopher Dann, Chad Martin, Garry Fyfe, Nigel Rutherford
This paper presents a case study on remedial works that were undertaken at Lock and Weir One
along the River Murray, that to our knowledge are the first of their kind in Australia.
The weir structure’s left abutment is comprised of a stepped concrete structure founded on timber
piles, with timber sheet piles extending beneath the structure to cut off seepage through underlying
alluvium. A piping incident occurred at the left abutment in late 2014 and a filter blanket was
installed as an emergency response measure. A detailed review of historic construction documents
showed that there was a “missing” timber sheet pile upstream of the piping boil. Geotechnical
investigations, including piezometer installation confirmed the missing timber sheet pile was the
likely cause of the piping incident. A piping risk assessment showed the residual risk of further piping
was reasonably high.A range of remedial works was considered as permanent risk reduction works. However, these
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solutions required extensive temporary works to expose the missing timber sheet pile including a
cofferdam to access the defect and partial demolition of a recently constructed fishway structure.
An alternate Secant ‘Grout Column’ solution was developed that comprised targeted drilling and
backfill grouting to close the gap where the sheet pile was not installed and to grout an inferred void
under the abutment structure. This solution was successful at reducing seepage through the
abutment structure, as indicated by monitoring piezometers.