Chapter R1, Risk-Informed Decision Making
FERC Engineering Guidelines
Risk-Informed Decision Making
Chapter R1
Chapter R1, Risk-Informed Decision Making
Table of Contents
Chapter R1 Introduction to Risk-Informed Decision Making ... - 1 -
R.1.1 Introduction to Risk-Informed Decision Making Engineering Guidelines ... - 1 -
R.1.2 Risk Management of Dams ... - 2 -
R.1.3 Risk Analysis ... - 2 -
R.1.4 Risk Assessment ... - 4 -
R.1.5 Required Steps to Proceed with a RIDM Based Approach to Dam Safety ... - 4 -
Appendix A – RIDM Chapters Current and Proposed ... - 1 -
Chapter R1, Risk-Informed Decision Making - 1 - 2014 Draft
Chapter R1 Introduction to Risk-Informed Decision Making
R.1.1 Introduction to Risk-Informed Decision Making Engineering Guidelines
This chapter introduces the Risk-Informed Decision Making Engineering Guidelines (RIDM EGs) that will be used to analyze and assess the risk associated with FERC-regulated dams. For the foreseeable future the FERC will maintain both the existing, deterministic, Engineering Guidelines and these RIDM Guidelines. In the near term the RIDM Guidelines will be used on an exception basis where either a licensee may request to utilize a RIDM approach or the FERC may suggest that a RIDM approach be considered. Over time the RIDM approach may become the standard of practice with the deterministic Guidelines then being used either on an exception basis or for dams with very low consequences. In general, the RIDM EGs do not address methods for conducting stability analyses or reproduce other parts of the deterministic guidelines. The RIDM EGs focus on how to use the information from deterministic analyses along with probability-based analysis tools.
The decision-making process in RIDM is different than that used with deterministic methods. The decision-making aspects are discussed in the Risk Analysis and Risk Assessment Chapters, R24 through R28, Risk Analysis, Probability and Uncertainty, Risk Facilitation, Risk Assessment, and Consequence Assessment.
The chapters in this RIDM EG provide guidance on how to:
Clearly define the purpose and scope of the risk analysis and risk assessment
Clearly define the dam system, i.e., all parts that contribute to risk, in order to develop a risk model.
Conduct/refine the Potential Failure Mode Analysis (PFMA) to a level needed for the quantification of the risk.
Develop probabilistic (or likelihood) estimates of loading.
Estimate the probability or likelihood of dam failure given these loadings. Estimate the consequence of failure, both probable life loss and economic
losses,
Identify other consequences including possible environmental damages. Combine these estimates in a risk analysis into an estimate of the risk for
each dam.
Assess the risk at a dam to determine whether the risk is tolerable or if there is a need for risk reduction measures, including dam safety modifications. If needed, analyze risk reduction alternatives and justify potential dam
safety modifications by making the case for these actions.
Identify the urgency and priority of dam safety risk reduction actions.
Incorporate a periodic review of the analyses and assessment for each dam as part of the overall FERC Dam Safety Program.
Chapter R1, Risk-Informed Decision Making - 2 - 2014 Draft
R.1.2 Risk Management of Dams
Managing the risks associated with a dam or a portfolio of dams involves three distinct stages. These stages, each having their own purpose and function, are:
Risk Analysis (including a PFMA) Risk Assessment
Risk-Informed Decision Making
In simplistic terms qualitative or quantitative risk analysis generates numbers associated with the risk of dam failure or uncontrolled release of the reservoir. Risk assessment is the process of determining what the numbers mean. Risk-informed decision making is the process of determining what, if anything, should be done to reduce the risk and how the risk should be managed in the long-term. More technical definitions can be found in Chapter R2.
Dam safety risk management includes recurring and non-recurring activities and is the umbrella under which risk is used to inform decisions by owners and regulators. Risk communication, is also a critical part of each component of risk management. The non-recurring parts of the Risk Management process are outlined in Figure 1 below. As described above, there are three stages in the process; the PFMA, Risk Analysis and, Risk Assessment, with risk-informed decisions being included under the Risk Assessment stage of the figure. The PFMA process is detailed in Chapter R3. The Risk Analysis and Risk Assessment processes are further discussed below and in Chapters R24 and R27. The other chapters, listed in Appendix A, describe procedures for developing risk estimates including consequences.
R.1.3 Risk Analysis
Risk analysis is defined as a qualitative or quantitative procedure that identifies potential modes of failure and the conditions and events that must take place for failure to occur. A quantitative risk analysis yields a numerical estimate of the risk of adverse consequence, multiplying the probability of load times the probability of dam failure given the load times the magnitude of adverse consequence given dam failure.
Chapter R1, Risk-Informed Decision Making - 3 - 2014 Draft
Figure 1 – Flowchart of the Non-recurring Risk Management Process *Adapted from State of Victoria (2012)
Chapter R1, Risk-Informed Decision Making - 4 - 2014 Draft Quantitative Risk Analysis (QRA) is a method that has many benefits in identifying and resolving dam safety issues including:
Better understanding of the Potential Failure Modes (PFMs) Identification of previously unidentified PFMs
Consideration of a full spectrum of potential consequences (not just High, Significant, Low Hazard)
Explicit accounting of both life loss and economic consequences
Explicit accounting of the probability of failure across the full range of PFMs Explicit accounting for uncertainty in the analyses
Identifying critical systems and components
R.1.4 Risk Assessment
Risk assessment is the process of considering the quantitative or qualitative estimate of risk (the risk analysis), along with all significant related social, environmental, cost, temporal, and other factors to determine a recommended course of action to mitigate the risks or conclude that the risk is tolerable. Risk Assessment benefits include:
Identifying potential risk reduction measures if needed Focusing surveillance and monitoring programs Improving emergency action plans (EAPs)
Prioritizing resources both within a dam safety program and at a licensees’ Corporate level
Improving communication with the public and other stakeholders.
R.1.5 Required Steps to Proceed with a RIDM Based Approach to Dam Safety
To proceed with a RIDM approach to dam safety the following initial steps should be followed. These steps ensure that all parties are fully informed and that the appropriate level of expertise is applied.
1. Attendance at FERC sponsored RIDM training programs.
2. Selection of an experienced risk analysis facilitator approved by the FERC. 3. FERC staff participation in working and formal RIDM meetings.
4. Selection and use of appropriate technical consultants with experience in risk analysis and/or probabilistic hazard analyses.
5. Completion of appropriate data collection for use in a comprehensive RIDM analysis.
Chapter R1, Risk-Informed Decision Making - 5 - 2014 Draft 6. Perform an External Peer Review by an engineer with experience in RIDM
related to dams.
7. Preparation of a RIDM report signed and stamped by a Registered Professional Engineer.
Chapter R1 - 1 - 2014 Draft
Appendix A – RIDM Chapters Current and Proposed
Section A Introduction
R1 Introduction to Risk-Informed Decision Making
R2 Key Terms and Definitions
Section B How Dams Fail
R3 Potential Failure Mode Analysis R4 Development of Event Trees Section C Probabilistic Analysis
R5 Concrete Dam Analysis (Arch, Gravity, and Buttress R6 Embankment Dam Analysis (Earthfill and Rockfill)
R7 Analysis of Other Dam Types
R8 Analysis of Gates and Other Water Outlet Works
R9 Water Conveyance Systems
R10 Internal Erosion and Piping
R11 Erosion of Soil and Rock R12 Overtopping of Dams
R13 Reservoir Landslide Induced Overtopping R14 Operational Issues and SCADA Systems R15 Spillway Analysis
R16 Construction Risks
R17 Dam Safety for New Projects
Section D Determining the Probability of Loading
R18 Determining Reservoir Level Exceedance Curves
R19 Probabilistic Flood Hazard Analysis R20 Probabilistic Seismic Hazard Analysis
Section E Consequences
R21 Dam Breach Analysis
R22 Estimation of Life Safety Consequences
R23 Estimation of Economic Consequences
Section F Risk Analysis - Risk Assessment
R24 Risk Analysis
R25 Probability and Uncertainty R26 Risk Facilitation
R27 Risk Assessment
R28 Consequence Assessment
Legend
Bold Font – Posted Chapter
Italics Font – Chapter in Draft Normal Font – Future Chapter
Chapter R1 - 2 - 2014 Draft Section G Systems Analysis
R29 Systems Analysis
R30 Owner’s Dam Safety Program R31 Owner’s Annual Dam Safety Report Section H Risk Management - Risk Mitigation R32 Surveillance and Monitoring
R33 Emergency Action Plans
R34 Interim Risk Reduction Measures R35 Issue Evaluation Studies
R36 Dam Safety Modification Studies R37 Reservoir Filling Plans
Section I Other Guidelines R38 Part 12D Inspections
R39 Supporting Technical Information R40 Standard Operating Procedures
R41 Geotechnical Investigations and Studies
R42 Construction Quality Control and Inspection Programs R43 Incident Reporting
