US Army Corps of Engineers BUILDING STRONG ® Overview of Risk Approach to Manage USACE Dam and Levee Safety Program The Reality of Risk: Dam Safety in the 21 st Century Session Douglas Boyer, PE, CEG Chief, Western Division Risk Management Center Institute for Water Resources February 19, 2013
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US Army Corps of Engineers BUILDING STRONG ® Overview of Risk Approach to Manage USACE Dam and Levee Safety Program The Reality of Risk: Dam Safety in.
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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
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
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Investment Comparison
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Given
Dams needing repair – approx. 300
Annual budget - $500 M Public trust
responsibility, accountability, and transparency
Range of project benefits and value
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The Question
Which dams to work on first?
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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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Risk Assessment
What can go wrong? How can it happen? What is the likelihood? What are the consequences?
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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?
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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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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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Internal Erosion PFM Event Tree
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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
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Risk Reduction
Loss of Life, N
An
nu
al F
ailu
re P
rob
ab
ilit
y, f
Pre Remediation Post Remediation
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Cumulative Risk Reduction
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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
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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