Thomas Ridgway, Nic Polmear, Hugh Tassell
All industries, inclusive of the dams and tailings industry use some form of monitoring and reporting to confirm items or services are functioning properly or correct. In engineering, we seek to use both manual and automated systems to both qualifiably and quantifiably define the suitability of a process or structure/item. As the dams industry continues to evolve with technology and with ongoing developments in stewardship expectations for both water dams and tailings dams the industry is beginning to move into automation of their instrumentation systems. This process has recently been undertaken at a mine in NSW with the development of both a near real-time survey monitoring and visualisation system as well as a monthly photographic assessment system. This paper will set out the process undertaken to assess the surveillance monitoring requirements for the mine, details of the design, implementation of a near real-time monitoring system and the difficulties associated with the work.
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Hench Wang, Edward Funnell, Albert Shen, Matt Scorah, Peter Hill
The use of simulation models to assess dam failure consequences has progressively advanced in Australia over the past few years. For example, it is now common for HEC-LifeSim to be used to estimate potential loss of life from the failure of large dams with large populations at risk downstream. Since its introduction to Australia, numerous presentations and papers have been provided by USACE and industry professionals that highlight the benefits of using HEC-LifeSim Version 1.0.1 for a range of different case studies.
This paper identifies some of the new features in the latest version of HEC-LifeSim that can improve the robustness and defensibility of the potential loss of life estimates for dambreak consequence assessments. The techniques that have been used to overcome these challenges are also discussed using some case studies.
The first case study demonstrates the sensitivity of the model performance and potential loss of life to changes in version and number of iterations used to simulate the life loss. This is done by comparing the differences in simulation run time and life loss between the previous and new versions of HEC-LifeSim for an example model. The second case study presents an example application of both versions of HEC-LifeSim to compare the results between one version and the other for a different dam and the final case study illustrates an improved method for interrogating the available outputs from HEC-LifeSim to provide the user with more information that otherwise could not be obtained from the default outputs.
Olle Wennstrom, Andrew White
Over the last few years tailings dams have come under increased scrutiny, partly due to two highly publicised TSF failures in South America, but also because of several other incidents in Australia and elsewhere in the world. As investors came under pressure to positively impact the projects they financed, the Global Industry Standard on Tailings Management (GISTM) was released in August 2020.
Topic 5 of GISTM, “Emergency response and long-term recovery”, comprises Principle 13: “Prepare for emergency response to tailings facility failures” and Principle 14: “Prepare for long-term recovery in the event of catastrophic failure”. The topic further introduces the term “Emergency Preparedness and Response Plan” (EPRP).
This paper explains what the term “Emergency Preparedness” means and how the owner/operator of a mine can achieve it. The paper also delivers a concept for long-term recovery planning.
Christopher 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
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.
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.
Claudia Smith, Shannon Dooland, Adam Broit, Rachel Jensen, Samantha Watt
The estimation of real consequences from dam failure that directly link to the overall likelihood of the failure is a challenging task, particularly in data sparse locations. Previous regional methods have often relied on simplistic assumptions without consideration of the true joint probability of the volume of flow in the downstream tributaries of concurrent catchments. As a result, concurrent downstream flooding directly impacting the consequence in dam break assessment scenarios may be misrepresented. More recently, the adoption of streamflow-based joint probability has become the standard, particularly where consequence estimation is used within the context of risk assessment. This paper progresses the work completed by others to establish a practical treatment method based on rainfall analysis where suitable streamflow information is unavailable. A case study is also presented where this method has improved the understanding of the risk profile associated with a coastal storage based on a better estimate of the likely flood concurrence within the storage and downstream catchments.