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US Army Corps of Engineers
BUILDING STRONG®
Overview of Risk Approach to Manage USACE Dam and Levee Safety ProgramThe Reality of Risk: Dam Safety in the 21st Century Session
Douglas Boyer, PE, CEG
Chief, Western Division
Risk Management Center
Institute for Water Resources
February 19, 2013
BUILDING STRONG®
Corps Dam Safety Portfolio Corps owns 704 dams, Nationwide and in P.R.
► embankment = 86 %► concrete = 7 %► combination = 7 %
Project purposes include: flood control, navigation, hydropower, water supply, fish & wildlife conservation, recreation
Median height: 93 feet Mean height: 112 feet Average age: 53 years High Hazard dams: 77 % Total storage capacity: 331 Million Ac-ft
BUILDING STRONG®
Traditional Dam Safety Approach
Standard engineering analyses Conservative inputs Factor of safety “check the box” Standard design criteria
►Probable Maximum Flood (PMF)►Maximum Credible Earthquake (MCE)
Expensive designs and repairs
3
BUILDING STRONG®
Investment Comparison
BUILDING STRONG®
Given
Dams needing repair – approx. 300
Annual budget - $500 M Public trust
responsibility, accountability, and transparency
Range of project benefits and value
5
BUILDING STRONG®
The Question
Which dams to work on first?
6
BUILDING STRONG®
Risk Analysis
Provides a systematic approach to decision-making that enhances the scientific basis of USACE decisions and comprises three tasks:
Risk assessment Risk management Risk communication
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BUILDING STRONG®
Risk Assessment
What can go wrong? How can it happen? What is the likelihood? What are the consequences?
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BUILDING STRONG®
Risk Management
What is the problem? What can be done to reduce the likelihood
or severity of the risk described? What are the tradeoffs in terms of costs,
benefits, and risks among the available options both now and in the future?
What is the best way to address the described risk?
9
BUILDING STRONG®
Risk Communication
Why are we communicating? Who is our audience? What do we want to learn from our audience? What do they want to know? What do we want to get across? How will we communicate? How will we listen? How will we respond?
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BUILDING STRONG®
Answers Other Questions
Urgency of modification What to modify Extent/magnitude of modification
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Risk
Identification of potential failure modes Decomposition of failure process Qualitative or quantitative estimates of
likelihood of events Comparison of result to a standard
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BUILDING STRONG®
Internal Erosion PFM Event Tree
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BUILDING STRONG®
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
0 1 10 100 1,000 10,000 100,000
An
nu
al F
ailu
re P
rob
abili
ty, f
Loss of Life, N
Annualized Probability of Life Loss and Annual Probabiilty of Failure for Dam XYZ
Ɣ Sum of the mean risk estimates for all failure modesŶ f-N pairs
BUILDING STRONG®
Risk Reduction
Loss of Life, N
An
nu
al F
ailu
re P
rob
ab
ilit
y, f
Pre Remediation Post Remediation
BUILDING STRONG®
Cumulative Risk Reduction
BUILDING STRONG®
Traditional Process Risk InformedProcess
Em
ph
asis
of
Dam
Saf
ety
Pro
gra
m
SeepageSeismicSpillway Adequacy
Change in Dam Safety Focus
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BUILDING STRONG®
Traditional Process Risk InformedProcess
Em
ph
asis
of
Dam
Saf
ety
Pro
gra
m
SeepageSeismicSpillway Adequacy
Change in Dam Safety Focus
18
BUILDING STRONG®
Principles of Risk Informed Approaches
No simple numerical solutions – decisions are informed, not based, on risk
Risk compliments, does not replace, traditional engineering standards or experience
Credible way to treat uncertainty Periodic and Continuing Risk is integral, not “bolt on”, to our profession
BUILDING STRONG®
Benefits of PFMA/Risk Approach
Multidisciplinary Team►Civil Engineers►Other Engineers►Geologists►O&M personnel
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Wow, I never thoughtabout it that way before!
BUILDING STRONG®
Benefits of PFMA/Risk Approach
Instills a culture of creative thinking
Why is this important?
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BUILDING STRONG®
Benefits of Risk-InformedDecision-Making
Better Understanding of Potential Failure Modes Identifying Previously Unidentified Potential
Failure Modes Considering the Probability of Failure &
Consequences Comparing the Risk of Different Dams Understanding the Uncertainty in Analyses Comparing the Contribution of All Failure Modes
to the Overall Risk
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BUILDING STRONG®
Challenges Same/similar engineering
knowledge – just a different approach and focus
Training in risk concepts and principles
A tendency to focus on the “number” rather than ‘building the case’
Lack of risk experience23
BUILDING STRONG®Photograph from inundated area downstream of Teton Dam, Idaho (1976)