26
3 Examples of Recent Catastrophic Hydro-Dam Accidents
their lessons, while developed from their work on the Oroville water dam incident,
will apply generally to industry level practices. With regard to this present book, we
believe them to be equally applicable to industry practices for tailings dams.
Potential Failure Modes Analyses (PFMAs): The IFT recognizes that the PFMA
process is a very useful tool in helping designers and companies identify and manage
their risks. However, based on the Oroville incident investigation they believe the
current PFMA process:
• can encounter difficulties in properly characterizing hazards and related risks for
large or complex systems, including accounting for human and operational aspects
in failures;
• can demonstrate a tendency to oversimplify complex failure modes involving multiple interactions of system components by defining failure modes as a linear chain
of events;
• may not explicitly consider how broader organizational factors, such as culture
and decision-making authority and practices, can contribute to failure.
This lesson stems from the findings that the PFMA process, related to the service
spillway, failed to identify or adequately examine existing maps and borehole logs
that showed the weak quality of the strongly weathered rock in the area, did not
recognize the significant level of hazard associated with the spillways and, as a result,
did not have sufficient information for the development of adequate warning signs
and trigger mechanisms. More specific insights and recommended improvements
related to PFMAs can be found in Appendix F3 of the IFT Report.
Comprehensive Facility Reviews: This lesson derives from the finding that the
comprehensive facility reviews had failed to identify and, therefore, understand the
physical factors that led to failure of the spill way chute. The IFT Report notes
that without this information, the development of potential failure modes and the
application of the PFMA process was compromised. It was further stated that the
Oroville reviews
… have tended to focus on what has changed since the prior review, based on observations
from inspection, surveillance, monitoring, and operations during the prior five-year interval,
rather than more comprehensively reviewing long-term performance history and comparing
the original design and construction with current best practices for design and construction.
The focus of the lesson regarding comprehensive facility reviews is on the adequacy of the design and management plans in terms of judging a chance for failure
or unsatisfactory performance, the adequacy of information to make such judgments
and, if not, the need for further study or evaluation. The IFT is also of the opinion
that the reviews should be:
• thorough, taking advantage of all available information;
• critical and independent, rather than relying largely on the findings of past reviews;
• completed by people with appropriate technical expertise, experience, and qualifications to cover all aspects of design, construction, maintenance, repair, and
failure modes of the assets under consideration.
3 Examples of Recent Catastrophic Hydro-Dam Accidents
their lessons, while developed from their work on the Oroville water dam incident,
will apply generally to industry level practices. With regard to this present book, we
believe them to be equally applicable to industry practices for tailings dams.
Potential Failure Modes Analyses (PFMAs): The IFT recognizes that the PFMA
process is a very useful tool in helping designers and companies identify and manage
their risks. However, based on the Oroville incident investigation they believe the
current PFMA process:
• can encounter difficulties in properly characterizing hazards and related risks for
large or complex systems, including accounting for human and operational aspects
in failures;
• can demonstrate a tendency to oversimplify complex failure modes involving multiple interactions of system components by defining failure modes as a linear chain
of events;
• may not explicitly consider how broader organizational factors, such as culture
and decision-making authority and practices, can contribute to failure.
This lesson stems from the findings that the PFMA process, related to the service
spillway, failed to identify or adequately examine existing maps and borehole logs
that showed the weak quality of the strongly weathered rock in the area, did not
recognize the significant level of hazard associated with the spillways and, as a result,
did not have sufficient information for the development of adequate warning signs
and trigger mechanisms. More specific insights and recommended improvements
related to PFMAs can be found in Appendix F3 of the IFT Report.
Comprehensive Facility Reviews: This lesson derives from the finding that the
comprehensive facility reviews had failed to identify and, therefore, understand the
physical factors that led to failure of the spill way chute. The IFT Report notes
that without this information, the development of potential failure modes and the
application of the PFMA process was compromised. It was further stated that the
Oroville reviews
… have tended to focus on what has changed since the prior review, based on observations
from inspection, surveillance, monitoring, and operations during the prior five-year interval,
rather than more comprehensively reviewing long-term performance history and comparing
the original design and construction with current best practices for design and construction.
The focus of the lesson regarding comprehensive facility reviews is on the adequacy of the design and management plans in terms of judging a chance for failure
or unsatisfactory performance, the adequacy of information to make such judgments
and, if not, the need for further study or evaluation. The IFT is also of the opinion
that the reviews should be:
• thorough, taking advantage of all available information;
• critical and independent, rather than relying largely on the findings of past reviews;
• completed by people with appropriate technical expertise, experience, and qualifications to cover all aspects of design, construction, maintenance, repair, and
failure modes of the assets under consideration.