David Stephens, Phillip Jordan, Peter Hill, Tim Craig, James Woolley and Bill Hakin
As part of the design of a proposed new hydropower dam (the Alimit HPP), on the island of Luzon in the Philippines, design flood estimates have been prepared using a RORB Monte Carlo approach for events up to and including the Probable Maximum Flood. Compared with Australia, the Philippines is a relatively data sparse environment, with limited rainfall gauge records and even fewer streamflow gauging stations. As such, considerable effort was required to derive design rainfall inputs for Monte Carlo simulation, including rainfall depths as well as temporal and spatial patterns.
This project made use of a number of remotely sensed data sets, including 20 years of global half hourly gridded rainfall data from NASA and global gridded estimates of rainfall intensity-frequency-duration. As part of the project, these data sets were benchmarked against local records from Luzon as well as selected Australian data sets.
This paper sets out the process used to determine design flood estimates in the Philippines, as well as summarising the usefulness of these new data sets for potential application in data sparse regions of Australia.
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Rachel Jensen, Adam Broit, Chriselyn Kavanagh
Downstream emergency response is a critical driver in the consequences and potential life loss associated with dam flooding and failure. This response is highly varied between stakeholders, communities and the nature of the flooding or dam threat. As assessments on dam failure consequence and potential loss of life become increasingly important in understanding holistic dam risk, they are also becoming increasingly complex.
As part of a portfolio wide Comprehensive Risk Assessments, Sunwater have undertaken workshops with a wide range of stakeholders to better understand downstream emergency response and the warning timeline. The workshops have been aimed at facilitating better downstream stakeholder engagement, obtaining key data for consequence assessments and developing consistency in assumptions for potential life loss.
This paper presents the standardised methodology undertaken for warning time workshops, the outcomes for a range of downstream stakeholders and correlations between stakeholder groups which influence warning time response. These outcomes may be used by practitioners in the absence of catchment specific warning time data and provide a counterpoint to international standard warning time assumptions.
Jarrad Coffey and John Plunkett
As tailings standards continue to evolve, a greater focus is being placed on the monitoring of tailings storage facilities (TSFs). While this is a positive development for TSF safety into the future, it is only one component of the work required to implement Performance Based Risk Informed (PBRI) management. There is also a significant human element that can be aided by reducing the time spent of personnel sourcing/aggregating data and instead focussing on decision making. It is discussed in this paper how a more holistic approach to monitoring via a dashboard that displays all management data relevant to a portfolio of TSFs can be applied in parallel to risk assessment to work towards the goal of PBRI. The dashboard also facilitates review and governance activities, which are central to the Global Industry Standard on Tailings Management. An example of the dashboard utilised at Rio Tinto Iron Ore is presented to provide an example of such a system and its benefits.
T. I. Mote, N. Vitharana, L. Johnstone, and K. Illangakoon
In Australia, the consideration of faults in seismic design has been captured in recent ANCOLD Guidelines for Design of Dams and Appurtenant Structures for Earthquake. The Guidelines recommend proper characterisation of geologic setting, foundation conditions, seismotectonic setting, and identification of both active and neotectonic faults as input to the seismic design basis for dams in Australia.
A case-study is presented at the proposed Cultana Pumped Hydro Energy Storage Project in South
Australia, summarising a fault assessment in concert with reference design. The progressive assessment of a lineament to a possible active fault to ultimately a non-seismogenic fault, allowed insights in understanding active fault rupture risk and active fault implications as it pertains to siting a dam in Australia. It highlighted the need for proper characterisation of geologic setting and faults based on targeted geotechnical investigations and the challenges in phasing these with an aggressive design program. These insights are relevant to many other projects in Australia either in existence or being planned for construction.
Chris Nielsen, Irene Buckman
As individuals, we are concerned about how a risk affects us and the things we value
personally. We may be willing to live with a risk if it secures us certain benefits and if the
risk is kept low and clearly controlled. We are less tolerant of risks over which we have little
ANCOLD’s risk assessment guideline (2003) identifies an individual risk threshold as being
one where “the dam safety risk to an individual should be close to the average background
risk of the population”. This is a principle of equity, where “all individuals have
unconditional rights to certain levels of protection” (HSE, 2001). The definition of
population at risk applied to Queensland’s referable dams (DNRME, 2018), being
individuals within a residence or workplace and typically not participating in any risky
activities such as driving a vehicle or walking through flooded waters, provides further
justification of this right.
In practice addressing societal risk tolerances and duty of care considerations may result in
individual risks being substantially lower than the thresholds. This may not always be the
case and, irrespective, should not distort the purpose of the individual risk tolerance test;
the principle of equity that drives individual risk tolerability has foundations in our societal
values and is easily and widely understood as a core value. This should be succinctly
described when justifying expenditure on risky infrastructure such as dams.
This poster describes aspects to consider when selecting a threshold individual risk
tolerance. Subject to site-specific considerations of the particular age group of individuals
most at risk, the wider benefit of the dam to society and ALARP, a single threshold
individual risk tolerance of less than 10-5 per annum (or 1 in 100,000 years) would appear
The aspects described are elaborated in the revised Guidelines on Safety Standards for
Referable Dams, soon to be published on the Queensland Government website (RDMW,
Ryan Singh, Jiri Herza, James Thorp, Michael Ashley
Performance-based risk-informed decision making is an underlying principle of the Global Industry
Standard on Tailings Management (GISTM). While owners make significant efforts to align with this
principle, commonly used risk assessment and management practices in the mining industry have largely been based on the HSE principles, which consider more frequent, lower consequence incidents.
As a result, the existing risk assessment frameworks do not provide the owners with a comprehensive understanding of the risk profiles of their tailings storage facilities (TSFs). Without the understanding of a facility’s risk profile, the owners cannot appreciate how changes to their facility, processes and operational activities may impact the risk profile. A large step-change in thinking is therefore required in risk assessment practices for the owner to align their TSF management with GISTM requirements.
Beyond risk assessments, the mining industry has other valuable concepts to manage the safety of their tailings management practices, such as Critical Controls, however, commonly used risk assessment and management practices do not incorporate these concepts.
This paper explores commonly used risk assessment practices and the concepts of Critical Controls. It proposes how these concepts can be linked, with Critical Controls being embedded in the risk assessment process. The outcomes of linking these concepts result in an estimation of the effectiveness of the Critical Controls and how they can be improved to demonstrably reduce the risk presented by a TSF. A case study has been included to demonstrate the benefits of linking risk assessment with Critical Controls and how owners can readily identify deficiencies and efficiently manage the risk profiles of their facilities.