Tuesday, October 16
Stephen Rigbey, P.Eng.,
SJR Consulting, Member of Oroville Independent Forensics Team (IFT)
Looking Beyond Oroville: Where do we go from here?
The Independent Forensics Team (IFT) report, published some 10 months after the Oroville spillway failure in February 2017, concluded that the failure involved a complicated interplay between physical, organizational and human factors that spanned decades. There was no one simple ‘failure mode’ or linear progression of events that led to the spillway failure and subsequent evacuation of 188,000 downstream residents. However, there were simple tell-tale signs of major unresolved issues that contributed to the failure, and these were overlooked in numerous reviews by generations of well-respected engineers.
The IFT report lays out a number of general lessons to be learned by owners, regulators and consultants. Many of these lessons are simple and self-evident, which invokes the question as to why the dam safety industry has not yet learned and applied these. Reliance on current practice without question, and considering this as ‘best practice’, has become endemic. Challenging the assumptions on which current practice is based is long overdue.
Rather than placing ever more reliance on ‘engineering judgment’ to estimate probabilities and consequences in multi-branched event and fault trees, and repeating the same failure mode development process from review to review, we need to develop new approaches to augment these current practices; approaches that include consideration of operational factors.
We also need to go back to basics, and first understand how each component of a system is supposed to work, and determine if it’s still working the way it’s supposed to. Only then can we start to investigate how the failure of each component can affect the overall system of which it is a part, and how an overall failure could progress. The roles of the CDA, and the owners, regulators and consultants which belong to the organization, must be defined in moving forward on this fundamental issue of challenging current 'best practice'.
**Presentation in English with simultaneous interpretation available