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

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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

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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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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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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

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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!

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Benefits of PFMA/Risk Approach

Instills a culture of creative thinking

Why is this important?

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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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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)